PartB Pleasure

RINAVia Corsica, 12 - 16128 Genova - ItalyTel. +39 01053851 - Fax: +39 0105351000E-MAIL [email protected] - WEB www.rina.org

Rules for the Classification of Pleasure Yachts Effective from 1 January 2011

Part BHull and Stability

GENERAL CONDITIONSDefinitions:"Rules" in these General Conditions means the documents belowissued by the Society:- Rules for the Classification of Ships or other special units;- Complementary Rules containing the requirements for product,plant, system and other certification or containing the require-ments for the assignment of additional class notations;- Rules for the application of statutory rules, containing the rules toperform the duties delegated by Administrations;- Guides to carry out particular activities connected with Services;- Any other technical document, as for example rule variations orinterpretations.“Services” means the activities described in Article 1 below, ren-dered by the Society upon request made by or on behalf of theInterested Party.“Society” or “RINA” means RINA S.p.A. and/or all the companiesin the RINA Group which provide the Services.“Surveyor” means technical staff acting on behalf of the Society inperforming the Services.“Interested Party” means the party, other than the Society, havingan interest in or responsibility for the Ship, product, plant or sys-tem subject to classification or certification (such as the owner ofthe Ship and his representatives, the ship builder, the enginebuilder or the supplier of parts to be tested) who requests the Ser-vices or on whose behalf the Services are requested.“Owner” means the registered Owner, the ship Owner, the man-ager or any other party with the responsibility, legally or contractu-ally, to keep the ship seaworthy or in service, having particularregard to the provisions relating to the maintenance of class laiddown in Part A, Chapter 2 of the Rules for the Classification ofShips or in the corresponding rules indicated in the specific Rules.“Administration” means the Government of the State whose flagthe Ship is entitled to fly or under whose authority the Ship isauthorised to operate in the specific case."Ship" means ships, boats, craft and other special units, as forexample offshore structures, floating units and underwater craft.Article 11.1. - The purpose of the Society is, among others, the classifica-tion and certification of ships and the certification of their partsand components.The Society:- sets forth and develops Rules;- publishes the Register of Ships;- issues certificates, statements and reports based on its surveyactivities.1.2. - The Society also takes part in the implementation of nationaland international rules and standards as delegated by various Gov-ernments.1.3. – The Society carries out technical assistance activities onrequest and provides special services outside the scope of classifi-cation, which are regulated by these general conditions, unlessexpressly excluded in the particular contract.Article 22.1. - The Rules developed by the Society reflect the level of itstechnical knowledge at the time they are published. Therefore, theSociety, though committed, also through its research and develop-ment services, to continuous updating, does not guarantee theymeet state-of-the-art science and technology at the time of publi-cation or that they meet the Society's or others' subsequent techni-cal developments.2.2. - The Interested Party is required to know the Rules on thebasis of which the Services are provided. With particular referenceto Classification Services, special attention is to be given to theRules concerning class suspension, withdrawal and reinstatement.In case of doubt or inaccuracy, the Interested Party is to promptlycontact the Society for clarification. The Rules for Classification of Ships are published on the Society'swebsite: www.rina.org.2.3. - The Society exercises due care and skill: - in the selection of its Surveyors- in the performance of its Services, taking into account the level ofits technical knowledge at the time the Services are performed.2.4. - Surveys conducted by the Society include, but are not lim-ited to, visual inspection and non-destructive testing. Unless other-wise required, surveys are conducted through samplingtechniques and do not consist of comprehensive verification ormonitoring of the Ship or of the items subject to certification. Thesurveys and checks made by the Society on board ship do not nec-essarily require the constant and continuous presence of the Sur-veyor. The Society may also commission laboratory testing,underwater inspection and other checks carried out by and under

the responsibility of qualified service suppliers. Survey practicesand procedures are selected by the Society based on its experi-ence and knowledge and according to generally accepted techni-cal standards in the sector.Article 33.1. - The class assigned to a Ship, like the reports, statements, cer-tificates or any other document or information issued by the Soci-ety, reflects the opinion of the Society concerning compliance, atthe time the Service is provided, of the Ship or product subject tocertification, with the applicable Rules (given the intended use andwithin the relevant time frame).The Society is under no obligation to make statements or provideinformation about elements or facts which are not part of the spe-cific scope of the Service requested by the Interested Party or on itsbehalf.3.2. - No report, statement, notation on a plan, review, Certificateof Classification, document or information issued or given as partof the Services provided by the Society shall have any legal effector implication other than a representation that, on the basis of thechecks made by the Society, the Ship, structure, materials, equip-ment, machinery or any other item covered by such document orinformation meet the Rules. Any such document is issued solelyfor the use of the Society, its committees and clients or other dulyauthorised bodies and for no other purpose. Therefore, the Societycannot be held liable for any act made or document issued byother parties on the basis of the statements or information given bythe Society. The validity, application, meaning and interpretationof a Certificate of Classification, or any other document or infor-mation issued by the Society in connection with its Services, isgoverned by the Rules of the Society, which is the sole subjectentitled to make such interpretation. Any disagreement on techni-cal matters between the Interested Party and the Surveyor in thecarrying out of his functions shall be raised in writing as soon aspossible with the Society, which will settle any divergence of opin-ion or dispute.3.3. - The classification of a Ship, or the issuance of a certificate orother document connected with classification or certification andin general with the performance of Services by the Society shallhave the validity conferred upon it by the Rules of the Society atthe time of the assignment of class or issuance of the certificate; inno case shall it amount to a statement or warranty of seaworthi-ness, structural integrity, quality or fitness for a particular purposeor service of any Ship, structure, material, equipment or machin-ery inspected or tested by the Society.3.4. - Any document issued by the Society in relation to its activi-ties reflects the condition of the Ship or the subject of certificationor other activity at the time of the check.3.5. - The Rules, surveys and activities performed by the Society,reports, certificates and other documents issued by the Society arein no way intended to replace the duties and responsibilities ofother parties such as Governments, designers, ship builders, man-ufacturers, repairers, suppliers, contractors or sub-contractors,Owners, operators, charterers, underwriters, sellers or intendedbuyers of a Ship or other product or system surveyed.These documents and activities do not relieve such parties fromany fulfilment, warranty, responsibility, duty or obligation (also of acontractual nature) expressed or implied or in any case incumbenton them, nor do they confer on such parties any right, claim orcause of action against the Society. With particular regard to theduties of the ship Owner, the Services undertaken by the Societydo not relieve the Owner of his duty to ensure proper maintenanceof the Ship and ensure seaworthiness at all times. Likewise, theRules, surveys performed, reports, certificates and other docu-ments issued by the Society are intended neither to guarantee thebuyers of the Ship, its components or any other surveyed or certi-fied item, nor to relieve the seller of the duties arising out of thelaw or the contract, regarding the quality, commercial value orcharacteristics of the item which is the subject of transaction.In no case, therefore, shall the Society assume the obligationsincumbent upon the above-mentioned parties, even when it isconsulted in connection with matters not covered by its Rules orother documents.In consideration of the above, the Interested Party undertakes torelieve and hold harmless the Society from any third party claim,as well as from any liability in relation to the latter concerning theServices rendered.Insofar as they are not expressly provided for in these GeneralConditions, the duties and responsibilities of the Owner and Inter-ested Parties with respect to the services rendered by the Societyare described in the Rules applicable to the specific Service ren-dered.

Article 44.1. – Any request for the Society's Services shall be submitted inwriting and signed by or on behalf of the Interested Party. Such arequest will be considered irrevocable as soon as received by theSociety and shall entail acceptance by the applicant of all relevantrequirements of the Rules, including these General Conditions.Upon acceptance of the written request by the Society, a contractbetween the Society and the Interested Party is entered into, whichis regulated by the present General Conditions.4.2. – In consideration of the Services rendered by the Society, theInterested Party and the person requesting the service shall bejointly liable for the payment of the relevant fees, even if the ser-vice is not concluded for any cause not pertaining to the Society.In the latter case, the Society shall not be held liable for non-fulfil-ment or partial fulfilment of the Services requested. In the event oflate payment, interest at the legal current rate increased by 2%may be demanded.4.3. - The contract for the classification of a Ship or for other Ser-vices may be terminated and any certificates revoked at therequest of one of the parties, subject to at least 30 days' notice tobe given in writing. Failure to pay, even in part, the fees due forServices carried out by the Society will entitle the Society to imme-diately terminate the contract and suspend the Services.For every termination of the contract, the fees for the activities per-formed until the time of the termination shall be owed to the Soci-ety as well as the expenses incurred in view of activities alreadyprogrammed; this is without prejudice to the right to compensa-tion due to the Society as a consequence of the termination.With particular reference to Ship classification and certification,unless decided otherwise by the Society, termination of the con-tract implies that the assignment of class to a Ship is withheld or, ifalready assigned, that it is suspended or withdrawn; any statutorycertificates issued by the Society will be withdrawn in those caseswhere provided for by agreements between the Society and theflag State.Article 55.1. - In providing the Services, as well as other correlated infor-mation or advice, the Society, its Surveyors, servants or agentsoperate with due diligence for the proper execution of the activity.However, considering the nature of the activities performed (seeart. 2.4), it is not possible to guarantee absolute accuracy, correct-ness and completeness of any information or advice supplied.Express and implied warranties are specifically disclaimed. Therefore, except as provided for in paragraph 5.2 below, and alsoin the case of activities carried out by delegation of Governments,neither the Society nor any of its Surveyors will be liable for anyloss, damage or expense of whatever nature sustained by any per-son, in tort or in contract, derived from carrying out the Services.5.2. – Notwithstanding the provisions in paragraph 5.1 above,should any user of the Society's Services prove that he has suffereda loss or damage due to any negligent act or omission of the Soci-ety, its Surveyors, servants or agents, then the Society will paycompensation to such person for his proved loss, up to, but notexceeding, five times the amount of the fees charged for the spe-cific services, information or opinions from which the loss or dam-age derives or, if no fee has been charged, a maximum of onehundred thousand Euro. Where the fees charged are related to anumber of Services, the amount of the fees will be apportioned forthe purpose of the calculation of the maximum compensation, byreference to the estimated time involved in the performance of theService from which the damage or loss derives. Any liability forindirect or consequential loss, damage or expense is specificallyexcluded. In any case, irrespective of the amount of the feescharged, the maximum damages payable by the Society will notbe more than 1 million Euro. Payment of compensation under thisparagraph will not entail any admission of responsibility and/orliability by the Society and will be made without prejudice to thedisclaimer clause contained in paragraph 5.1 above.5.3. - Any claim for loss or damage of whatever nature by virtue ofthe provisions set forth herein shall be made to the Society in writ-ing, within the shorter of the following periods: THREE MONTHSfrom the date on which the Services were performed or THREEMONTHS from the date on which the damage was discovered.Failure to comply with the above deadline will constitute an abso-lute bar to the pursuit of such a claim against the Society.Article 66.1. - Any dispute arising from or in connection with the Rules orwith the Services of the Society, including any issues concerningresponsibility, liability or limitations of liability of the Society, willbe determined in accordance with Italian Law and settled througharbitration assigned to a board of three arbitrators who will pro-ceed in compliance with the Rules of the Chamber of National

and International Arbitration of Milan. Arbitration will take placein Genoa, Italy.6.2. - However, for disputes concerning non-payment of the feesand/or expenses due to the Society for services, the Society shallhave the right to submit any claim to the jurisdiction of the Courtsof the place where the registered or operating office of the Inter-ested Party or of the applicant who requested the Service islocated.In the case of actions taken against the Society by a third partybefore a public Court, the Society shall also have the right to sum-mon the Interested Party or the subject who requested the Servicebefore that Court, in order to be relieved and held harmlessaccording to art. 3.5 above.Article 77.1. - All plans, specifications, documents and information pro-vided by, issued by, or made known to the Society, in connectionwith the performance of its Services, will be treated as confidentialand will not be made available to any other party other than theOwner without authorisation of the Interested Party, except as pro-vided for or required by any applicable international, European ordomestic legislation, Charter or other IACS resolutions, or orderfrom a competent authority. Information about the status andvalidity of class and statutory certificates, including transfers,changes, suspensions, withdrawals of class, recommendations/conditions of class, operating conditions or restrictions issuedagainst classed ships and other related information, as may berequired, may be published on the website or released by othermeans, without the prior consent of the Interested Party.Information about the status and validity of other certificates andstatements may also be published on the website or released byother means, without the prior consent of the Interested Party.7.2. - Notwithstanding the general duty of confidentiality owed bythe Society to its clients in clause 7.1 above, the Society's clientshereby accept that the Society will participate in the IACS EarlyWarning System which requires each Classification Society to pro-vide other involved Classification Societies with relevant technicalinformation on serious hull structural and engineering systems fail-ures, as defined in the IACS Early Warning System (but not includ-ing any drawings relating to the ship which may be the specificproperty of another party), to enable such useful information to beshared and used to facilitate the proper working of the IACS EarlyWarning System. The Society will provide its clients with writtendetails of such information sent to the involved ClassificationSocieties.7.3. - In the event of transfer of class, addition of a second class orwithdrawal from a double/dual class, the Interested Party under-takes to provide or to permit the Society to provide the other Clas-sification Society with all building plans and drawings, certificates,documents and information relevant to the classed unit, includingits history file, as the other Classification Society may require forthe purpose of classification in compliance with the applicablelegislation and relative IACS Procedure. It is the Owner's duty toensure that, whenever required, the consent of the builder isobtained with regard to the provision of plans and drawings to thenew Society, either by way of appropriate stipulation in the build-ing contract or by other agreement.In the event that the ownership of the ship, product or system sub-ject to certification is transferred to a new subject, the latter shallhave the right to access all pertinent drawings, specifications, doc-uments or information issued by the Society or which has come tothe knowledge of the Society while carrying out its Services, evenif related to a period prior to transfer of ownership.Pursuant and owing to Italian legislative decree 196/2003, theInterested Party declares that it has read the information sheet con-cerning the processing of personal data published on the society'swebsite and gives its consent to such processing, also for commer-cial information purposes.Article 88.1. – Should any part of these General Conditions be declaredinvalid, this will not affect the validity of the remaining provisions.8.2. - In the event of doubts concerning the interpretation of theseGeneral Conditions, the Italian text will prevail.Article 99.1. – When the Society provides its Services to a consumer - i.e. anatural person who does not act within the scope of his businessor professional activity - the following provisions do not apply: art.3.2. (as far as the Society is solely entitled to the interpretation ofthe Rules); art. 4.2., (as far as the payment of the fees is also duefor services not concluded due to causes not attributable to theInterested Party); art. 5.1. (as far as the exclusion of liability is con-cerned); art. 5.2.; art. 5.3.; and art. 6.1. (as far as the jurisdictionof a Board of Arbitrators based in Genoa is concerned).

EXPLANATORY NOTE TO PART B

1. Reference editionThe reference edition of these Rules is the edition effec-tive from 1 January 2007.

2. Effective date of the requirements2.1 All requirements in which new or amended provi-

sions with respect to those contained in the refer-ence edition have been introduced are followed by a date shown in brackets.

The date shown in brackets is the effective date of entry into force of the requirements as amended by the last updating. The effective date of all those requirements not followed by any date shown in brackets is that of the reference edition.

2.2 Item 4 below provides a summary of the technical changes from the preceding edition. In general, this list does not include those items to which only edi-torial changes have been made not affecting the effective date of the requirements contained therein.

3. Rule Variations and CorrigendaUntil the next edition of these Rules is published, Rule Variations and/or corrigenda, as necessary, will be pub-blished on the RINA web site (www.rina.org). Except in particular cases, paper copies of Rule Variations or cor-rigenda are not issued.

4. Rule subdivision and cross-references4.1 Rule subdivision

The Rules are subdivided into five parts, from A to E.

Part A: Classification and Surveys

Part B: Hull and Stability

Part C: Machinery, Electrical Installations and Fire Protection

Part D: Materials and Welding

Part E: Additional Class Notations

Each Part consists of:• Chapters• Sections and possible Appendices• Articles• Sub-articles• Requirements

Figures (abbr. Fig) and Tables (abbr. Tab) are numbered in ascending order within each Section or Appendix.

4.2 Cross-references

Examples: Pt A, Ch 3, Sec 1, [3.2.1] or Pt A, Ch 3, App 1, [3.2.1] • Pt A means Part A

The part is indicated when it is different from the part in which the cross-reference appears. Otherwise, it is not indicated.• Ch 3 means Chapter 3

The Chapter is indicated when it is different from the chapter in which the cross-reference appears. Other-wise, it is not indicated.• Sec 1 means Section 1 (or App 1 means

Appendix 1 )

The Section (or Appendix) is indicated when it is differ-ent from the Section (or Appendix) in which the cross-reference appears. Otherwise, it is not indicated.• [3.2.1] refers to requirement 1, within sub-article 2

of article 3.

Cross-references to an entire Part or Chapter are not abbreviated as indicated in the following examples:• Part A for a cross-reference to Part A• Part A, Chapter 1 for a cross-reference to Chapter 1

of Part A.

5. Summary of amendments introduced in the edi-tion effective from 1 January 2011

Foreword

This edition of the Rules for the classification of pleasureyachts contains amendments whose effective date is 1January 2011, with the exception of some modificationsalready issued with Circular 3585/A effective from 1January 2010 and with Rule Variation PLCS/2009/02effective from 1 October 2009.

The date of entry into force of each new or amendeditem is shown in brackets after the number of the itemconcerned.

RULES FOR THE CLASSIFICATION OF PLEASURE YACHTS

Part BHull and Stability

Chapters 1 2 3 4 5 6

Chapter 1 GENERAL REQUIREMENTS

Chapter 2 STEEL HULLS

Chapter 3 ALUMINIUM HULLS

Chapter 4 REINFORCED PLASTIC HULLS

Chapter 5 WOOD HULLS

Chapter 6 STABILITY

RINA Rules for Pleasure Yachts 2011 3

CHAPTER 1GENERAL REQUIREMENTS

Section 1 General

1 Rule application 31

1.1

2 Equivalents 31

2.1

3 Direct calculations for monohull and twin hull yachts 31

3.1 Direct calculations for monohull yachts3.2 Direct calculations for twin hull yachts

4 Definitions and symbols 34

4.1 General4.2 Symbols4.3 Definitions

5 Subdivision, integrity of hull and superstructure 35

5.1 Number of watertight bulkheads5.2 Collision bulkheads5.3 Sea connections and overboard

discharge5.4 Stern and side doors below the weather deck5.5 Hatches on the weather deck5.6 Sidescuttles and windows5.7 Skylights5.8 Outer doors5.9 Drawings5.10 Ventilation5.11 Air pipes5.12 Bulwarks and guardrails or guardline5.13 Freeing ports

Section 2 Hull Outfitting

1 Rudders and steering gear 42

1.1 General1.2 Rudder stock1.3 Coupling between rudder stock and mainpiece1.4 Rudder mainpiece and blade1.5 Rudder bearings, pintles and stuffing boxes1.6 Steering gear and associated apparatus

2 Propeller shaft brackets 46

2.1 Double arm brackets2.2 Single arm brackets

3 Sailing yacht appendages and component fastenings 46

3.1 Keel connection

4 RINA Rules for Pleasure Yachts 2011

4 Stabilizer arrangements 47

4.1 General4.2 Stabilizer arrangements4.3 Stabilizing tanks

5 Thruster tunnels 48

5.1 Tunnel wall thickness5.2 Tunnel arrangement details

6 Water-jet drive ducts 48

6.1

7 Crane support arrangements 48

7.1

Section 3 Equipment

1 General 49

1.1

2 Anchors 49

2.1

3 Chain cables for anchors 49

3.1

4 Mooring lines 49

4.1

5 Windlass 49

5.1 General5.2 Working test on windlass

6 Equipment Number and equipment 50

6.1

7 Sailing yachts 50

7.1

Section 4 Non-Structural Fuel Tanks

1 General 52

1.1

2 Metallic tanks 52

2.1 General2.2 Scantlings

3 Non-metallic tanks 52

3.1 General3.2 Scantlings3.3 Tests on tanks


Section 5 Loads

1 General 54

1.1


2.1 General2.2 Definitions2.3 Symbols

3 Design acceleration 55

3.1 Vertical acceleration at LCG3.2 Transverse acceleration

4 Overall loads 55

4.1 General4.2 Longitudinal bending moment and shear force4.3 Design total vertical bending moment4.4 Transverse loads for twin hull yachts

5 Local loads 57

5.1 General5.2 Load points5.3 Design pressure for the bottom5.4 Design pressure for the side shell5.5 Design heads for decks5.6 Design heads for watertight bulkheads

Appendix 1 Side Doors and Stern Doors

1 General 64

1.1 Application1.2 Arrangement1.3 Definitions

2 Design loads 64

2.1 Side and stern doors

3 Scantlings of side doors and stern doors 64

3.1 General3.2 Plating and ordinary stiffeners3.3 Primary supporting members

4 Securing and supporting of doors 65

4.1 General4.2 Scantlings

5 Strength criteria 66

5.1 Primary supporting members and securing and supporting devices

6 Securing and locking arrangement 66

6.1 Systems for operation

7 Operating and Maintenance Manual 67

7.1 General


CHAPTER 2STEEL HULLS

Section 1 General Requirements

1 Field of application 71

1.1


2.1 Premise2.2 Definitions and symbols

3 Plans, calculations and other information to be submitted 71

3.1 3.2

4 Direct calculations 72

4.1 4.2

5 Buckling strength checks 72

5.1 Application5.2 Elastic buckling stresses of plates 5.3 Elastic buckling stresses of stiffeners5.4 Critical buckling stress

6 General rules for design 74

6.1

7 Minimum thicknesses 74

7.1

8 Plating attached to griders 75

8.1 Primary supporting members8.2 Ordinary stiffeners8.3 Special cases8.4 Calculation of section modulus

9 Corrosion protection 76

9.1 9.2 9.3

Section 2 Materials

1 General 77

1.1 Characteristics of materials1.2 Testing of materials1.3 Manufacturing processes

2 Steels for hull structure 77

2.1 Application


2.2 Information to be kept on board2.3 Material factor k2.4 Grades of steel2.5 Grades of steel for structures exposed to low air temperatures2.6 Grades of steel within refrigerated spaces

3 Steels for forging and casting 82

3.1 General3.2 Steels for forging3.3 Steels for casting

4 Other materials and products 82

4.1 General4.2 Iron cast parts

Section 3 Welding and Weld Connections

1 General 83

1.1 Application1.2 Base material1.3 Welding consumables and procedures1.4 Personnel and equipment 1.5 Documentation to be submitted1.6 Design

2 Type of connections and preparation 84

2.1 General2.2 Butt welding2.3 Fillet welding2.4 Partial and full T penetration welding 2.5 Lap-joint welding 2.6 Slot welding2.7 Plug welding

3 Specific weld connections 92

3.1 Corner joint welding3.2 Bilge keel connection3.3 Connection between propeller post and propeller shaft bossing3.4 Bar stem connections

4 Workmanship 92

4.1 Forming of plates4.2 Welding procedures and consumables4.3 Welding operations4.4 Crossing of structural elements

5 Modifications and repairs during construction 94

5.1 General5.2 Gap and weld deformations5.3 Defects5.4 Repairs on structures already welded

6 Inspections and checks 94

6.1 General 6.2 Visual and non-destructive examinations


7 End connections of ordinary stiffeners 95

7.1

8 End connections of primary supporting members 96

8.1 Bracketed end connections8.2 Bracketless end connections

9 Cut-outs and holes 96

9.1 9.2 9.3 9.4 9.5

10 Stiffening arrangement 97

10.1 10.2 10.3 10.4 10.5

11 Riveted connections 98

11.1 11.2

12 Sealed connections 98

12.1

Section 4 Longitudinal Strength

1 General 99

1.1 1.2

2 Bending stresses 99

2.1 2.2 2.3

3 Shear stresses 99

3.1

4 Calculation of the section modulus 99

4.1

Section 5 Plating


1.1

2 Keel 100

2.1 Sheet steel keel2.2 Solid keel


3 Bottom and bilge 100

3.1

4 Sheerstrake 101

4.1

5 Side 101

5.1 5.2

6 Openings in the shell plating 101

6.1 6.2 6.3

7 Local stiffeners 101

7.1 7.2 7.3

8 Cross-deck bottom plating 101

8.1

Section 6 Single Bottom

1 General 102

1.1 Scope1.2 Longitudinal structure 1.3 Transverse structure


2.1

3 Longitudinal type structure 102

3.1 Bottom longitudinals3.2 Floors3.3 Girders

4 Transverse type structures 103

4.1 Ordinary floors4.2 Centre girder4.3 Side girders

5 Constructional details 103

5.1

Section 7 Double Bottom

1 General 104

1.1

2 Minimum height 104

2.1


3 Inner bottom plating 104

3.1

4 Centre girder 104

4.1

5 Side girders 104

5.1 5.2

6 Floors 105

6.1 6.2

7 Bracket floors 105

7.1

8 Bottom and inner bottom longitudinals 105

8.1

9 Bilge keel 105

9.1 Arrangement, scantlings and connections9.2 Bilge keel connection

Section 8 Side Structures

1 General 107

1.1


2.1

3 Ordinary stiffeners 107

3.1 Transverse frames3.2 Longitudinal stiffeners

4 Reinforced beams 107

4.1 Reinforced frames4.2 Reinforced stringers

5 Frame connections 108

5.1 General

6 Scantling of brackets of frame connections 108

6.1 6.2 Lower brackets of frames

Section 9 Decks

1 General 110

1.1


2.1


3 Deck plating 110

3.1 Weather deck3.2 Lower decks

4 Stiffening and support structures for decks 110

4.1 Ordinary stiffeners4.2 Reinforced beams4.3 Pillars

Section 10 Bulkheads

1 General 112

1.1

2 Symbols 112

2.1

3 Plating 112

3.1

4 Stiffeners 112

4.1 Ordinary stiffeners4.2 Reinforced beams

5 General arrangement 112

5.1 5.2

6 Non-tight bulkheads 113

6.1 Non-tight bulkheads not acting as pillars6.2 Non-tight bulkheads acting as pillars

Section 11 Superstructures

1 General 114

1.1

2 Boundary bulkhead plating 114

2.1

3 Stiffeners 114

3.1

4 Superstructure decks 114

4.1 Plating4.2 Stiffeners


CHAPTER 3ALUMINIUM HULLS



1.1


2.1 Premise2.2 Definitions and symbols


3.1 3.2


4.1


5.1

6 Minimum thicknesses 119

6.1

Section 2 Materials, Connections and Structure Design Principles

1 Materials and connections 120

1.1 General requirements1.2 Aluminium alloy hull structures1.3 Extruded plating1.4 Tolerances1.5 Influence of welding on mechanical characteristics1.6 Material factor K for scantlings of structural members made of aluminium alloy1.7 Fillet welding1.8 Riveted connections for aluminium alloy hulls1.9 Welded connections1.10 Corrosion protection - Heterogeneous steel/aluminium alloy assembly

2 Structure design principles 124

2.1 Protection against corrosion2.2 Rounding-off

Section 3 Design Loads and Hull Scantlings

1 Design loads 125

1.1 Application

2 Hull scantlings 125

2.1


2.2 Definitions and symbols2.3 Overall strength2.4 Buckling strength of aluminium alloy structural members


1 General 132

1.1 1.2


2.1 2.2 2.3

3 Shear stresses 132

3.1

4 Calculation of the section modulus 132

4.1

Section 5 Plating


1.1

2 Keel 133

2.1 Sheet steel keel2.2 Solid keel

3 Bottom and bilge 133

3.1

4 Sheerstrake 134

4.1

5 Side 134

5.1 5.2


6.1 6.2 6.3


7.1 7.2 7.3

8 Cross deck bottom plating 134

8.1



1 General 135



2.1






5.1


1 General 137

1.1


2.1


3.1

4 Centre girder 137

4.1

5 Side girders 137

5.1 5.2

6 Floors 138

6.1 6.2

7 Bracket floors 138

7.1


8.1

9 Bilge keel 138

9.1 Arrangement, scantlings and connections9.2 Bilge keel connection



1 General 140

1.1


2.1


3.1 Transverse frames3.2 Longitudinal stiffeners



5 Frame connections 141

5.1 General

6 Scantling of brackets of frame connections 141

6.1 6.2 Lower brackets of frames

Section 9 Decks

1 General 143

1.1


2.1

3 Deck plating 143






1 General 145

1.1

2 Symbols 145

2.1

3 Plating 145

3.1

4 Stiffeners 145


5 General arrangement 145

5.1 5.2

6 Non-tight bulkheads 146

6.1 Non-tight bulkheads not acting as pillars6.2 Non-tight bulkheads acting as pillars


1 General 147

1.1


2.1

3 Stiffeners 147

3.1




CHAPTER 4REINFORCED PLASTIC HULLS



1.1


2.1 Premise2.2 Symbols2.3 Definitions


3.1 3.2


4.1


5.1 General5.2 Minimum thicknesses

6 Construction 153

6.1 Principles of building6.2 Engine exhaust6.3 Tanks for liquids

Section 2 Materials

1 General 160

1.1

2 Definitions and terminology 160

2.1

3 Materials of laminates 160

3.1 Resins3.2 Reinforcements3.3 Core materials for sandwich laminates3.4 Adhesive and sealant material3.5 Plywood3.6 Timber3.7 Repair compounds3.8 Type approval of materials

4 Mechanical properties of laminates 162

4.1 General4.2 Coefficients relative to the mechanical properties of laminates


Section 3 Construction and Quality Control

1 Shipyards or workshops 166

1.1 General1.2 Moulding shops1.3 Storage areas for materials1.4 Identification and handling of materials

2 Hull construction processes 167

2.1 General2.2 Moulds2.3 Laminating2.4 Hardening and release of laminates2.5 Defects in the laminates2.6 Checks and tests


1 General 169

1.1 1.2


2.1 2.2 2.3

3 Shear stresses 170

3.1

Section 5 External Plating

1 General 171

1.1


2.1

3 Keel 171

3.1

4 Rudder horn 171

4.1

5 Bottom plating 171

5.1

6 Sheerstrake plating and side plating 172

6.1 Sheerstrake6.2 Side plating



7.1 7.2 7.3


8.1 8.2 8.3 8.4

9 Cross-deck bottom plating 172

9.1


1 General 173



2.1






5.1



1 General 175

1.1


2.1


3.1

4 Centre girder 175

4.1

5 Side girders 176

5.1 5.2

6 Floors 176

6.1 6.2


7.1


1 General 177

1.1


2.1


3.1 3.2



Section 9 Decks

1 General 179

1.1


2.1

3 Deck plating 179






1 General 181

1.1

2 Symbols 181

2.1

3 Plating 181

3.1

4 Stiffeners 181


5 Tanks for liquids 181

5.1


1 General 182

1.1


2.1

3 Stiffeners 182

3.1




Section 12 Scantlings of Structures with Sandwich Construction

1 Premise 183

1.1

2 General 183

2.1 Laminating2.2 Vacuum bagging2.3 Constructional details

3 Symbols 183

3.1

4 Minimum thickness of the skins 184

4.1

5 Bottom 184

5.1

6 Side 184

6.1

7 Decks 185

7.1

8 Watertight bulkheads and boundary bulkheads of the superstructure 185

8.1

Section 13 Structural Adhesives

1 General 186

1.1 1.2

2 Design criteria for bonded connection 187

2.1


CHAPTER 5WOOD HULLS

Section 1 Materials

1 Suitable timber species 191

1.1

2 Timber quality 191

2.1 Planking2.2 Marine plywood and lamellar structures2.3 Certification and checks of timber quality2.4 Mechanical characteristics and structural scantlings

Section 2 Fastenings, Working and Protection of Timber

1 Fastenings 194

1.1 1.2

2 Timber working 194

2.1

3 Protection 194

3.1

Section 3 Building Methods for Planking

1 Shell planking 195

1.1 Simple skin 1.2 Double diagonal skin 1.3 Double longitudinal skin 1.4 Laminated planking in several cold-glued layers 1.5 Plywood planking 1.6 Double skin with inner plywood and outer longitudinal strakes 1.7 Fastenings and caulking 1.8 Sheathing of planking

2 Deck planking 196

2.1 Planking 2.2 Plywood 2.3 Plywood sheathed with laid deck 2.4 Longitudinal planking 2.5 Caulking


Section 4 Structural Scantlings of Sailing Yachts with or without Auxiliary Engine

1 General 200

1.1

2 Keel 200

2.1

3 Stempost and sternpost 200

3.1

4 Frames 200

4.1 Types of frames 4.2 Framing systems and scantlings

5 Floors 201

5.1 General5.2 Arrangement of floors5.3 Scantlings and fastenings

6 Beam shelves, beam clamps in way of masts, bilge stringers 203

6.1 Beam shelves6.2 Beam clamps in way of masts6.3 Bilge stringers6.4 End breasthooks

7 Beams 204

7.1 Scantlings of beams7.2 End attachments of beams7.3 Local strengthening7.4 Lower deck and associated beams

8 Planking 205

8.1 Shell planking 8.2 Deck planking8.3 Superstructures - Skylights8.4 Masts and rigging

Section 5 Structural Scantlings of Motor Yachts

1 General 212

1.1

2 Keel - stempost 212

2.1

3 Transom 212

3.1

4 Floors and frames 212

4.1 General 4.2 Bottom and side frames 4.3 Floors 4.4 Frame and beam brackets


5 Side girders and longitudinals 214

5.1

6 Beams 215

6.1

7 Beam shelves and chine stringers 215

7.1

8 Shell planking 216

8.1 Thickness of shell planking

9 Deck planking 216

9.1 Weather deck 9.2 Superstructure decks 9.3 Lower deck

Section 6 Watertight Bulkheads, Lining, Machinery Space

1 Wooden bulkheads 223

1.1

2 Steel bulkheads 223

2.1

3 Internal lining of hull and drainage 223

3.1

4 Machinery space structures 223

4.1


CHAPTER 6STABILITY

Section 1 Stability

1 General 227

1.1

2 Intact Stability Standards 227

2.1 Motor vessels2.2 Sailing vessels2.3 Element of Stability2.4 Stability Documents

Appendix 1 Inclining Test and Lightweight Check

1 General 231

1.1 Aim of the Appendix

2 Inclining weights 231

2.1

3 Pendulums 232

3.1

4 Means of communication 232

4.1

5 Documentation 232

5.1

6 Calculation of the displacement 232

6.1

7 Inclining procedure 233

7.1

8 Lightweight check 233

8.1


Appendix 2 Stability Information Booklet

1 Information to be included 234

1.1 General1.2 List of information

2 Loading conditions 234

2.1

3 Stability curve calculation 234

3.1 General3.2 Superstructures and deckhouses which may be taken into account3.3 Angle of flooding

4 Effects of free surfaces of liquids in tanks 235

4.1 General4.2 Consideration of free surface effects4.3 Categories of tanks4.4 Consumable liquids4.5 Water ballast tanks4.6 GMo and GZ curve corrections4.7 Free surface moment4.8 Small tanks4.9 Remainder of liquid


Part BHull

Chapter 1

GENERAL REQUIREMENTS

SECTION 1 GENERAL

SECTION 2 HULL OUTFITTING

SECTION 3 EQUIPMENT

SECTION 4 NON-STRUCTURAL FUEL TANKS

SECTION 5 LOADS

APPENDIX 1 SIDE DOORS AND STERN DOORS

Pt B, Ch 1, Sec 1


SECTION 1 GENERAL

1 Rule application

1.1

1.1.1 Part B of the Rules consists of five chapters andapplies to hulls of length (LH) defined in [4.2], not less than16 m and up to the length as defined in the relevant sec-tions according to the hull material and hull type intendedfor unrestricted service, which are to be classed by RINA.

Chapter 1 applies in general to all yachts, irrespective of thematerial used for the construction of the hull.

Chapter 2 contains requirements relevant to the scantlingsof hull structures of steel yachts.

Chapter 3 contains requirements relevant to the scantlingsof hull structures of aluminium alloy yachts.

Chapter 4 contains requirements relevant to the scantlingsof hull structures of yachts constructed of composite materi-als.

Chapter 5 contains requirements relevant to the scantlingsof hull structures of wooden yachts.

Yachts of unusual form, speed or proportions or of typesother than those considered in Part B will be given specialconsideration by RINA, also on the basis of equivalence cri-terion.

Yachts built using a combination of the foregoing materialsare subject to the applicable requirements of the relevantchapters. Connections between different materials will bethe subject of special consideration by RINA.

2 Equivalents

2.1

2.1.1 In examining constructional plans, RINA may takeinto account material distribution and scantlings which aredifferent from those obtained by applying these require-ments, provided that longitudinal, transversal and localstrength are equivalent to those of the relevant Rule struc-ture and that such scantlings are found satisfactory by RINAalso on the basis of direct calculations of the structuralstrength.

In particular, the structures of yachts similar in performanceto high speed craft (HSC) may have scantlings in accord-ance with RINA's "Rules for the Classification of HighSpeed Craft".

In such case, the Master is to be provided with a yacht oper-ating manual indicating the appropriate speed for each seastate.

The use of RINA's "Rules for the Classification of HighSpeed Craft" for the scantlings of the structures of the afore-mentioned yachts is to be agreed between the yard and

RINA before the submission of the drawings for approvaland the commencement of the hull.

Special structures not provided for in these Rules, such asdecks intended for the carriage of vehicles, side and sterndoors and helicopter decks, are to have scantlings inaccordance with the "Rules for the Classification of Ships".

3 Direct calculations for monohull and twin hull yachts

3.1 Direct calculations for monohull yachts

3.1.1 General Direct calculations are generally required to be carried out,at the discretion of RINA, to check the primary structures ofyachts which have unusual shapes and/or characteristics.

In addition, direct calculations are to be performed to checkthe scantlings of primary structures of yachts whenever, inthe opinion of RINA, hull shapes and structural dimensionsare such that the scantling formulae used in these Rules areno longer deemed to be effective.

By way of example, this may be the case in the followingsituations:

• elements of the primary transverse ring (beam, web andfloor) have very different cross-sectional inertia, so thatthe boundary conditions for each are not well defined;

• marked V-shapes, so that floor and web tend to degen-erate into a single element;

• complex, non-conventional geometry;

• presence of significant racking effects (yachts with manytiers of superstructure);

• structures contributing to longitudinal strength withlarge openings.

3.1.2 Loads In general, the following load conditions specified in a) tod) are to be considered.

The condition in d) is to be checked in yachts for which, inthe opinion of RINA, significant racking effects are antici-pated (yachts with many tiers of superstructure).

Depending on the loading configurations and on the struc-ture design, some load conditions as defined from points a)to d) may be less significant than others and, at the discre-tion of RINA, they may be ignored. For the same reasons itmay be necessary to consider further load conditions speci-fied by RINA in individual cases.

The vertical and transverse accelerations and the impactpressure p2 are to be calculated as stipulated in Sec 5.

For each primary supporting member, the coefficient Fa,which appears in the formula for impact pressure, is to be

Pt B, Ch 1, Sec 1


calculated as a function of the area supported by the mem-ber.

In three dimensional analyses, special attention is to bepaid to the distribution of weights and buoyancy and to thedynamic equilibrium of the yacht.

In the case of three dimensional analyses, the longitudinaldistribution of impact pressure is considered individually ineach case by RINA. In general, impact pressure is to beconsidered as acting separately on each transverse sectionof the model, the remaining sections being subject to hydro-static pressure.

a) Load condition in still waterThe following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;• outer hydrostatic load in still water.

b) Combined load condition 1The following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;• forces of inertia due to the vertical acceleration av of

the yacht, considered in a downward direction.

c) Combined load condition 2The impact pressure acting on the bottom of the yacht isto be considered.

d) Combined load condition 3The following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;• forces of inertia due to the transverse acceleration av

of the yacht.

3.1.3 Structural model The primary structures of yachts of this type may usually bemodelled with beam elements, according to criteria stipu-lated by RINA. When, however, grounds for the admissibil-ity of such model are lacking, or when the geometry of thestructures gives reason to suspect the presence of high stressconcentrations, finite element analyses are necessary.

In general, the extent of the model is to be such as to allowanalysis of the behaviour of the main structural elementsand their mutual effects.

On yachts dealt with by these Rules, the stiffness of longitu-dinal primary members (girders and stringers) is, at leastoutside the machinery space, generally negligible com-pared with the stiffness of transverse structures (beams,floors and webs), or their presence may be taken intoaccount by suitable boundary conditions. It is thereforeacceptable, in general, to examine primary members in thisarea of the hull by means of plane analyses of transverserings.

In cases where such approximation is not acceptable, themodel adopted is to be three-dimensional and is to includethe longitudinal primary members.

In cases where loads act in the transverse direction (loadcondition 3), special attention is to be devoted to the mod-elling of continuous decks and platforms. If they are of suf-ficient stiffness in the horizontal plane and are sufficiently

restrained by fore- and after-bodies, such continuous ele-ments may withstand transverse deformations of primaryrings.

In such cases, notwithstanding the provisions above, it isstill permissible to examine bidimensional rings, by simulat-ing the presence of decks and platforms with horizontalsprings according to criteria specified by RINA.

3.1.4 Boundary conditions Depending on the load conditions considered, the follow-ing boundary conditions are to be assigned:

a) Load condition in still water and combined load condi-tions 1 and 2

• horizontal and transverse restraints, in way of thecrossing point of bottom and side shells, if the anglebetween the two shells is generally less than 135°,

• horizontal and transverse restraints, in way of thekeel, if the bottom/side angle is greater than approx-imately 135°.

b) Combined load condition 3

The vertical and horizontal resultants of the loads, ingeneral other than zero, are to be balanced by introduc-ing two vertical forces and two horizontal forces at thefore and aft ends of the model, distributed on the shellsaccording to the bidimensional flow theory for shearstresses, which are equal and opposite to half the verti-cal and horizontal resultants of the loads.Where a plane model is adopted, the resultants are tobe balanced by vertical and horizontal forces, distrib-uted as specified above and acting on the plane of themodel itself.

3.1.5 Checking criteria

a) For metal structures, the stresses given by the above cal-culations are to be not greater than the following allow-able values, in N/mm2:

• bending stress:

• shear stress:

• Von Mises equivalent bending stress:

where:

K : material factor defined in Chapter 2 for steeland Chapter 3 for aluminium alloy.

f’m : coefficient depending on the material, equalto:

- 1,0, for steel structures

- 2,15, for aluminium alloy structures

fs : safety coefficient, equal to:

- 1,00, for combined load conditions

- 1,25, for load condition in still water.

The compressive values of normal stresses and shearstresses are not to exceed the values of the critical

σam170

K f'm fs⋅ ⋅----------------------=

τam90

K f'm fs⋅ ⋅----------------------=

σeq am,200

K f'm fs⋅ ⋅----------------------=

Pt B, Ch 1, Sec 1


stresses for plates and stiffeners calculated in Chapter 2and Chapter 3.In structural elements also subject to high longitudinalhull girder stresses, the allowable and critical stressesare to be reduced, in accordance with criteria specifiedby RINA.

b) For structures made of composite materials, the allowa-ble stresses are defined in Chapter 4.

3.2 Direct calculations for twin hull yachts

3.2.1 General Direct calculations are generally required to be carried out,at the discretion of RINA, to check the primary structuresand connecting structures of the two hulls which have unu-sual characteristics.

In addition, direct calculations are to be carried out tocheck the structures connecting the two hulls for yachts inwhich the structural arrangements do not allow a realisticassessment of their stress level, based on simple models andon the formulae set out in these Rules.

3.2.2 Loads In general, the following load conditions specified in a) tod) are to be considered.

The condition in a) applies to a still water static conditioncheck.

The conditions in b) and c) apply to the check of the struc-tures connecting the two hulls. The condition in c) onlyrequires checking for yachts of L > 65 m and speed V > 45knots.

The condition in d) is to be checked in yachts for which, inthe opinion of RINA, significant racking effects are expected(yachts with many tiers of superstructure).

In relation to special structure or loading configurations,should some load conditions turn out to be less significantthan others, the former may be ignored at the discretion ofRINA. By the same token, it may be necessary to considerfurther load conditions specified by RINA in individualcases.

The vertical and transverse accelerations and the impactpressure p2 are to be calculated as stipulated in Sec 5.

For each primary supporting member, the coefficient Fa,which appears in the formula for impact pressure, is to becalculated as a function of the area supported by the mem-ber.

In three-dimensional analyses, special attention is to bepaid to the distribution of weights and buoyancy and to thedynamic equilibrium of the yacht.

In the case of three-dimensional analyses, the longitudinaldistribution of impact pressure is considered individually ineach case by RINA. In general, impact pressure is to beconsidered as acting separately on each transverse sectionof the model, the remaining sections being subject to hydro-static pressure.

a) Load condition in still waterThe following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;

• outer hydrostatic load in still water.


The following are to be considered:

• forces caused by weights present, distributedaccording to the weight booklet of the yacht;

• forces of inertia due to the vertical acceleration av ofthe yacht, considered in a downward direction.

c) Combined load condition 2

The following loads are to be considered:


• forces of inertia due to the vertical acceleration av ofthe yacht, considered in a downward direction;

• the impact pressure acting hemisymmetrically onone of the halves of the hull bottom.

d) Combined load condition 3

The following loads are to be considered:


• forces of inertia due to the transverse acceleration ofthe yacht.

3.2.3 Structural model In general, the primary structures of yachts of this type areto be modelled with finite element schematisations adopt-ing a medium size mesh.

At the discretion of RINA, detailed analyses with fine meshare required for areas where stresses, calculated withmedium-mesh schematisations, exceed the allowable limitsand the type of structure gives reason to suspect the pres-ence of high stress concentrations.

In general, the extent of the model is to be such as to allowanalysis of the behaviour of the main structural elementsand their mutual effects.

On yachts dealt with by these Rules, the stiffness of longitu-dinal primary members (girders and stringers) is, at leastoutside the machinery space, generally negligible com-pared with the stiffness of transverse structures (beams,floors and webs), or their presence may be taken intoaccount by suitable boundary conditions. It is thereforeacceptable, in general, to examine primary members in thisarea of the hull by means of plane analyses of transverserings.

In cases where such approximation is not acceptable, themodel adopted is to be three-dimensional and is to includethe longitudinal primary members.

In cases where loads act in the transverse direction (loadconditions 2 and 3), special attention is to be devoted to themodelling of continuous decks and platforms. If they are ofsufficient stiffness in the horizontal plane and are suffi-ciently restrained by fore- and after-bodies, such continuouselements may withstand transverse deformations of primaryrings.

In such cases, notwithstanding the provisions above, it isstill permissible to examine bidimensional rings, by simulat-ing the presence of decks and platforms with horizontalsprings according to criteria specified by RINA.

Pt B, Ch 1, Sec 1


3.2.4 Boundary conditions Depending on the load conditions considered, the follow-ing boundary conditions are to be assigned:

a) Load condition in still water

The vertical resultant of the loads, in general other thanzero, is to be balanced by introducing two verticalforces at the fore and aft ends of the model, both distrib-uted on the shells according to the bidimensional flowtheory for shear stresses, which are equal and oppositeto half the vertical resultant of the loads.Where a plane model is adopted, the vertical resultant isto be balanced by a single force, distributed as specifiedabove and acting on the plane of the model itself.


A vertical restraint is to be imposed in way of the keel ofeach hull.

c) Combined load condition 2 and 3

The vertical and horizontal resultants of the loads, ingeneral other than zero, are to be balanced by introduc-ing two vertical forces and two horizontal forces at thefore and aft ends of the model, distributed on the shellsaccording to the bidimensional flow theory for shearstresses, which are equal and opposite to half the verti-cal and horizontal resultants of the loads.Where a plane model is adopted, the resultants are tobe balanced by vertical and horizontal forces, distrib-uted as specified above and acting on the plane of themodel itself.

3.2.5 Checking criteria

a) a) For metal structures, the stresses given by the abovecalculations are to be not greater than the followingallowable values, in N/mm2:• bending stress:

• shear stress:

• Von Mises equivalent bending stress:

where:

K : material factor defined in Chap. 2 forsteel and Chap. 3 for aluminium alloy

f’m : coefficient depending on the material,equal to:

• 1,0, for steel structures

• 2,15, for aluminium alloy structuresfs : safety coefficient, equal to:

• 1,00, for combined load conditions

• 1,25, for load condition in still water.

The compressive values of normal stresses and shearstresses are not to exceed the values of the criticalstresses for plates and stiffeners calculated in Chap.2 and Chap. 3.In structural elements also subject to high longitudi-

nal hull girder stresses, the allowable and criticalstresses are to be reduced, in accordance with crite-ria specified by RINA.

b) For structures made of composite materials, the allowa-ble stresses are defined in Chapter 4.

4 Definitions and symbols

4.1 General

4.1.1 The definitions of symbols having general validityare not normally repeated in the various Chapters, whereasthe meanings of those symbols which have specific validityare specified in the relevant Chapters.

4.2 Symbols4.2.1 LH : Hull Length, measured according to ISO 8665,

is the distance, in m, measured parallel to thestatic load waterline, from the foreside of thestem to the after side of the stern or transom,excluding projections removable parts that canbe detached in a non destructive manner andwithout affecting the structural integrity of thecraft, e.g. pulpits at either ends of the craft, plat-forms, rubbing strakes and fenders.

L : Scantling length, in m, on the full load water-line, assumed to be equal to the length on thefull load waterline with the yacht at rest;

LPP : Length between perpendiculars, is the distance,in m, measured on the full load waterline fromFP to AP.

LLL : Load Line length means 96% of the total lengthon a waterline of a ship at 85% of the leastmoulded depth measured from the top of thekeel, or the length from the fore-side of the stemto the axis of the rudder stock on that waterline,if that be greater. In ship designed with a rake ofkeel the waterline on which this is measured isto be parallel to the designed waterline.

FP : Foreword perpendicular, is the perpendicular atthe intersection of the full load waterline withthe fore side of the stem.

AP : After perpendicular, is the perpendicular at theintersection of the full load waterline with theafter side of the rudder post or to the centre ofthe rudder stock for yachts without a rudderpost.In yachts with unusual stern arrangements orwithout rudder the position of AP and the rele-vant LPP will be specially considered

B : Maximum outside breadth, in metres.D : Depth, in metres, measured vertically on the

transverse section at the middle of length L,from moulded base line to the top of the deckbeam at side on the weather deck.

D1 : Depth, in metres, measured vertically on thetransverse section at the middle of length L,from the lower side of the bar keel, if any, or of

σam170

K f'm fs⋅ ⋅----------------------=

τam90

K f'm fs⋅ ⋅----------------------=

σeq am,200

K f'm fs⋅ ⋅----------------------=

Pt B, Ch 1, Sec 1


the fixed ballast keel, if any, or of the drop keel,to the top of the deck beam at side on theweather deck.

T : Draft, in metres, measured at the middle oflength L, in metres, between the full load water-line and the lower side of the keel. In the caseof hulls with a drop or ballast keel, the lowerside of the keel is intended to mean the inter-section of the longitudinal plane of symmetrywith the continuation of the external surface ofthe hull.

T1 : Draft T, in metres, measured to the lower side -theoretically extended, if necessary, to the mid-dle of length L - of the fixed ballast keel, wherefitted, or the drop keel.

Δ : Displacement, in t, of the yacht at draught T.V : Maximum design speed, in knots, of the yacht at

displacement Δ.s : Spacing of ordinary stiffeners, in metres.S : Web frame spacing, in metres.

4.3 Definitions

4.3.1 Rule frame spacing The Rule frame spacing, sR, in m, of ordinary stiffeners isobtained as follows:

In general, spacing of transversal or longitudinal stiffeners isnot to exceed 1,2 times the Rule frame spacing.

4.3.2 SuperstructureThe superstructure is a decked structure located above theweather deck, extending from side to side of the hull orwith the side plating not inboard of the shell plating morethan 4% of the local breadth.

Superstructures may be complete, where deck and sidesextend for the whole length of the yacht, or partial, wheresides extend for a length smaller than that of the yacht, evenwhere the deck extends for the whole length of the yacht.

Superstructures may be of different tiers in relation to theirposition in respect of the weather deck.

A 1st tier superstructure is one fitted on the weather deck, a2nd tier superstructure is one fitted on the 1st tier superstruc-ture, and so on.

4.3.3 Bulkhead deck (1/1/2011)The bulkhead deck is normally the uppermost completedeck exposed to the weather and sea, which has permanentmeans of closing all openings in the weather part thereof,and below which all openings in the sides of the ship are fit-ted with permanent means of watertight closing.

4.3.4 Weather deck The weather deck is the uppermost complete weathertightdeck fitted as an integral part of the yacht 's structure andwhich is exposed to the sea and the weather.

4.3.5 DeckhouseThe deckhouse is a decked structure fitted on the weatherdeck, a superstructure deck or another deckhouse, having

limited length and a spacing between the external longitu-dinal bulkheads less than 92% of the local breadth of theyacht.

4.3.6 Weathertight

A closing appliance is considered weathertight if it isdesigned to prevent the passage of water into the yacht inany sea condition.

4.3.7 Watertight

A closing appliance is considered watertight if it is designedto prevent the passage of water in either direction under ahead of water for which the surrounding structure isdesigned.

5 Subdivision, integrity of hull and superstructure

5.1 Number of watertight bulkheads

5.1.1 All yachts are to have at least the following trans-verse watertight bulkheads:

• One collision bulkhead

• Two bulkheads forming the boundaries of the machin-ery spaces; as an alternative, the transom may beaccepted as an aft transverse bulkhead.

5.1.2 Openings in watertight bulkheads and decks (1/1/2011)

The number of openings in watertight subdivisions is to belimited to the minimum compatible with the proper work-ing of the yacht. Pipes and electrical cable may be carriedthrough watertight subdivisions provided that both watertightness and structural integrity of the bulkhead areensured by devices suitable in the opinion of RINA. Detailsrelevant to these devices and their installation on board areto be sent to RINA for approval.

In any case, when the pipe passing through the bulkhead isnon-metallic, the above device is, as a minimum, to be apipe of the same material as the bulkhead, fitted in a way torestore the structural integrity of the bullhead, having alength of 10 D, where D is the external diameter of the pipe;the length of the above pipe is not required to be more than400 mm.

Details of connection between the above device and non-metallic pipes will be the subject of special considerationby RINA.

Watertight doors are generally to be built and testedaccording to the requirements given in Pt B, Ch1, Sec 1,App.3 of the Rules for the Classification of Yachts Designedfor Commercial Use.

As a general rule, no access openings are to be fitted in thecollision bulkhead. Special consideration will be given incase of yachts with particular design only if the access ispositioned as far above the design waterline as possible andits closing appliances are watertight.

An emergency escape of maximum size 500x500 mm maybe accepted.

sR 0 350 0 005L,+,=

Pt B, Ch 1, Sec 1


5.2 Collision bulkheads

5.2.1 (1/1/2011)

A collision bulkhead is to be fitted which is to be watertightup to the bulkhead deck. This bulkhead is to be located at adistance from the forward perpendicular FP of not less than5 per cent of the length L of the yacht, and not more than 10per cent of L. In any case it is not necessary that the colli-sion bulkhead is positioned at a distance more than 2 mfrom the forward perpendicular.

5.2.2 Where any part of the ship below the waterlineextends forward of the forward perpendicular, e.g. a bul-bous bow, the distances, in metres, stipulated in [5.2.1] areto be measured from a point either:

• at the mid-length of such extension, or

• at a distance 1,5 per cent of the length L of the yacht for-ward of the forward perpendicular, or

• at a distance 3 metres forward of the forward perpen-dicular; whichever gives the smallest measurement.

5.2.3 (1/1/2011)

Where long forward superstructures are fitted, the collisionbulkhead is to be extended weathertight to the first tiersuperstructure deck.

5.2.4 (1/1/2011)

The bulkhead may have steps or recesses provided that theyare within the limits in [5.2.1] or [5.2.2].

For yachts having gross tonnage not more than 500, the partof the collision bulkhead above the water level may be fit-

ted at a distance less than 5%L from the forward perpendic-ular (but in any case not more than 300 mm from theforward perpendicular) under the following conditions (seeFig 1):

a) The lower part of the vertical collision bulkhead isformed by a step having a height from the maximumwaterline not less than 500 mm

b) The vertical lower part of the collision bulkhead indi-cated under the above point a) is fitted at a distancefrom the fore perpendicular not less than 5%L

c) The lowest limit of the collision bulkhead is positionedat least 500 mm from the stem post; such distance is tobe measured perpendicularly to the stem post profile

d) The space of the recess below the horizontal part of thebulkhead until the horizontal part of the step fitted at500 mm above the maximum waterline is filled withclosed cell high density foam

e) The Maritime Administration Rules don't containrequirements adverse to the above arrangement.

5.2.5 (1/1/2011)

RINA may, on a case-by-case basis, accept a distance fromthe collision bulkhead to the forward perpendicular greaterthan the maximum specified in [5.2.1] and [5.2.2], pro-vided that, in the event of flooding of the space forward ofthe collision bulkhead, the waterline is not below the bulk-head deck and that, taking into account the loss of stabilitydue to the free surface, compliance with the stability criteriaof Sec 6 will be guaranteed.

Figure 1 (1/1/2011)

(*) actual position of the collision bulkhead

(*)

5% L

z z

500 mm500 m

m

PhAV

Pt B, Ch 1, Sec 1


5.3 Sea connections and overboard discharge

5.3.1 Overboard discharges are to be kept to a minimumand located, as far as practicable, above the full load water-line.

In any case a metallic non-return valve is to be fitted on theside of the hull under the conditions of Pt C, Ch 1, App 1,Tab 1, Note 1.

The sea connection for the engine cooling system is to beprovided both with a grill fitted directly on the shell using alocal stiffener and with a filter after the closing valve.

The filter is to be made of metal highly resistant to corro-sion, and is to be of substantial dimensions and easy toopen.

5.3.2 All pipes leading to the sea and located under thefull load waterline are to be of adequate thickness in gen-eral metallic, sea corrosion-resistant and electrochemicallycompatible with any different materials they may be con-nected to. Joints for elbows, valves etc are to be made ofmaterial of the same composition as the pipes or, where thisis not practicable, of material which is electrochemicallycompatible.

5.3.3 Pipes for the discharge of exhaust from the enginesleading to the shell without a valve are to be made as fol-lows:

• from below the maximum waterline up to 300 mmabove the maximum water-line or to a waterline corre-sponding to a heeling angle of 7°, whichever is thegreater, the piping is to be made of corrosion resistantmaterial, galvanically compatible and resistant toexhaust products. The wall thickness pipe is to be notless than 5 mm if made of steel. If a composite materialpipe is fitted the material is to have strength equivalentto that of side laminate or bottom laminate according tothe location of the sea connection. The material is to besuitable to withstand the temperatures reached by theexhaust and in addition reference is to be made to therequirements of Pt B, Ch 4, Sec 1, [6.2];

• 300 mm or more above the maximum waterline, flexi-ble hoses compyling with the requirements of ISOStandard 13363 may be accepted;

• such hoses are to be secured by means of at least twostainless steel hose clamps at each end. The clamps areto be at least 12 mm wide and are not to be dependenton spring tension to remain fastened. The joint locationis to be readily accessible and visible at all times. Jointsfitted lower than 300 mm above the maximum water-line may be accepted provided that they remain abovethe maximum waterline and additional bilge suctionsand an alarm are fitted in the area where the joints arelocated, or a watertight compartment is provided in thearea where the joint is fitted. Where a metallic valve isfitted on the side in way of the sea connection, theexhaust pipe material is to be resistant to the exhausttemperature and non-metallic material may be acceptedfor the entire length. The non-metallic materials are tomeet the requirements in Pt C, Ch 1, App 1, Tab 1.

5.4 Stern and side doors below the weather deck

5.4.1 Side/shell doors leading to a non-watertight space

Stern and side doors fitted on yachts not more than 24 mare to meet the requirements of ISO Standard 12216 as forappliances to be fitted on area I.

5.4.2 Side/shell doors leading to internal compartment (1/1/2011)

Stern and side doors fitted on yachts more than 24 m are tobe in compliance with the following requirements:

a) All stern and side openings are to be provided with ade-quate means of closure.

The means of closure is to be watertight or weathertightdepending on the distance of the lower edge of the clo-sure from the maximum waterline.

If such distance is equal to or more than 500 mm, aweathertight means of closure may be accepted.

If the above distance is less than 500 mm a watertightmeans of closure is to be provided.

When the distance from the maximum waterline to thelower edge of the means of closure is less than 500 mm,but no essential equipment is installed in the compart-ment, and all the doors leading to internal compart-ments where essential equipment is installed are to beprovided with watertight means of closure, a weather-tight means of closure may be fitted.

When a watertight means of closure is requested, therequirements of Appendix I are to be complied with.

In addition, such watertight means are to be testedaccording to the requirements given in Pt B, Ch 1, Sec 1,App 3 of the Rules for the Classification of YachtsDesigned for Commercial Use.

b) Electrical equipment installed in the space where theaccess is provided by means of the side or stern doors isto have a degree of protection of at least IP 54.

The degree of protection of such equipment may beconsidered according to the height of installation fromthe platform and according to the means of protectionin order to avoid water spray directly reaching the elec-trical equipment.

c) In any case at the completion of the installation allwatertight and weatertight doors are to be checked by a"hose test".

The hose test is to be carried out at a minimum pressurein the hose of not less than 2,0 105 Pa, and the nozzle isto be applied at a maximum distance of 1,5 m.

The nozzle diameter is to be not less than 12 mm.

d) Stern and side doors are to be fitted with proper gaskets,and adequate securing devices.

e) The lower part of each of these openings is, in general,to be above the deepest sea going condition.

f) Doors are preferably to open outwards.

Pt B, Ch 1, Sec 1


5.4.3 DrawingsA drawing representing the structure of the side/shell doors,their locking devices and their height above the waterline isto be sent in triplicate to RINA for approval, with enclosed ageneral arrangement showing the intended use of the com-partment which the doors give access to and the machineryand/or sports craft fitted therein.

5.4.4 Other fittingsRecesses for wells, gangways, winches, platforms, etc are tobe watertight and of strength equivalent to that of the adja-cent structures. Any penetrations for electrical wiring andpiping are to ensure watertight integrity. Discharges are tobe provided to prevent the accumulation of water in thenormal foreseeable situations of transverse list and trim.

5.5 Hatches on the weather deck

5.5.1 Hatches on the weather deck and deck above are tohave a strength equivalent to that of the adjacent structuresto which they are fitted and are to be in general weather-tight. In general, hatches are to be hinged on the forwardside. Coamings above the weather deck and deck above areto be not less than the following value: Deck position 1 Deck position 2

Hatch coamings 100 mm 75 mm

Where:

Deck position 1: any position on the exposed weather deckor superstructure deck above forward of 0,25 LLL.

LLL is defined in item [4.2.1].

Deck position 2: any position on the exposed superstructuredeck or weather deck aft of 0,25 LLL.

Greater coamings may be required where closing appli-ances are not permanently attached.

5.5.2 Where the hatches may be required to be used as ameans of escape, the securing arrangements are to be oper-able from both sides.

5.5.3 (1/1/2011)Flush hatches on the weather deck are generally not to befitted. Where they are provided they are to:• be closed at sea;• be fitted in a protected location;• have at least two drains in the aft part leading over-

board;• be fitted with gaskets;• have at least 4 clips of size 600 x 600 mm;• have non-oval hinges which can be considered as clips.

For dimensions bigger than 600 x 600 mm, the acceptanceis at the discretion of RINA. Drawings representing thehatches, their position on deck, their coamings and theirsystem of closure are to be sent for approval.

In addition, hatches are, in general, to be tested accordingto the requirements given in Pt B, Ch1, Sec 1, App 3 of theRules for the Classification of Yachts Designed for Commer-cial Use.

For yachts having length LLL not more than 24 m, therequirements of ISO Standard 12216 apply. Under the

above ISO Standard, reference is to be made to the lengthLH not more than 24 m.

5.6 Sidescuttles and windows

5.6.1 GeneralFor yachts not more than 24 m the requirements of ISOSTANDARD 12216 are to be applied.

For yachts more than 24 m the following requirementsapply to sidescuttles and rectangular windows providinglight and air, located in positions which are exposed to theaction of the sea or inclement weather below and above theweather deck.

Sidescuttles and rectangular windows may be of “non-opening”, “opening” or “non-readily openable” type.

5.6.2 Zones for the determination of scantlingFor the purpose of determining the scantlings of sidescuttlesand rectangular windows, the yacht may be subdivided intozones which are defined as follows:

• Zone A: Zone between the full load waterline and a line drawnparallel to the sheer profile and having its lowest pointnot less than 500 mm or 2,5% B, whichever is greater,above the full load waterline;

• Zone B: Zone above Zone A bounded at the top by the deckfrom which the freeboard is calculated;

• Zone C: Zone corresponding to the 1st tier of superstructures andabove.

5.6.3 Scantling and arrangements of sidescuttles and rectangular windows (1/1/2009)

Sidescuttles and rectangular windows may be classified asfollows, depending on their constructional characteristics:

• (medium series) non-opening or non-readily openabletype, with deadlight: Type B;

• (light series) non-opening or opening type, withoutdeadlight: Type C.

The following requirements apply:

• in Zone A neither side-scuttles nor rectangular windowsare permitted;

• in Zone B in general only type B sidescuttles and rectan-gular windows are permitted; for yachts having grosstonnage not greater than 250, in Zone B an openableportlight type with deadlight may be fitted, providedthat in the compartments a bilge level alarm is fittedconnected to the automatic bilge pump. Alternatively,an automatic alarm for open position may be accepted.For yachts having gross tonnage greater than 250, open-able portlights with deadlight may be accepted if anautomatic alarm for open position is provided. In addi-tion, a bilge level alarm connected to the automaticbilge pumps is to be provided;

• in Zone C, even where protecting openings giving directaccess to spaces below deck, type C sidescuttles andrectangular windows are permitted.

Pt B, Ch 1, Sec 1


For the thickness of toughened glass panes of sidescuttlesand rectangular windows, having surfaces not exceeding0,16m2, and fitted below the weather deck, see Tab 1.

Table 1

For oval sidescuttles, reference is to be made to the equiva-lent surface area.

Different thickness may also be accepted on the basis of ahydraulic pressure test, performed on a mock-up represent-ative of the arrangement, the result of which confirms thatthe proposed thickness is able to ensure watertight integrityat a pressure not less than 4 times the design pressure of thehull in that zone.

Sidescuttles and rectangular windows with surfaces exceed-ing 0,16 m2 may be accepted in Zone B. Their acceptancewill be considered by RINA case by case in relation to theirnumber, type and location. The relevant drawings withdimensions of clear opening, thickness of glass and positionin respect of the deepest waterline are to be sent forapproval.

The thickness of the glass for such sidescuttles/rectangularwindows fitted below the weather deck is given by the fol-lowing formula:

where:

p : design pressure in kN/m2 computed at thelower edge of the windows but not less than 20kN/m2;

b : shorter side of the window in mm

β : 0,54 A - 0,078 A2 - 0,17

β : 0,75 for A > 3

a : long side of the window

A : ratio a/b.

Different thickness may also be accepted on the basis of ahydraulic pressure test, performed on a mock-up represent-ative of the arrangement, the result of which confirms thatthe proposed thickness is able to ensure watertight integrityat a pressure not less than 4 times the design pressure of thehull in that zone.

In any case, the thickness cannot be assumed less than 15mm.

Where sidescuttles and rectangular windows with surfaceexceeding 0,16 m2 are fitted in zone B, the constructiondetails are to be submitted to RINA; in addition, tests onmock-ups representative of the arrangement as well asdirect calculations for the zone of the side concerned mayalso be required in order to demonstrate the local structuraladequacy.

Deadlights of the fixed type are to be arranged where mon-olithic toughened glass panes are fitted.

Deadlights of the non-fixed type may be arranged whenlaminated glass panes are fitted; however, they may beomitted, at the discretion of RINA where the glass pane is ofthe laminated (shatterproof) type with a polycarbonate coreof thickness greater than 3mm.

All windows and portlights are to be hose tested after instal-lation according to RINA Rules.

5.6.4 Windows above weather deck (1/1/2009)

The required thicknesses of toughened glass panes in stand-ard rectangular windows are given in Tab 2 as a function ofthe standard sizes of clear light

Table 2

The thickness of toughened glass panes in rectangular win-dows of other sizes is given by the following formula:

where:

p : design pressure in kN/m2 to be assumed 15kN/m2 for frontal windows and 10 kN/m2 forlateral windows

b : shorter side of the window in mm

β : 0,54 A - 0,078 A2 - 0,17

β : 0,75 for A > 3

a : long side of the window

A : ratio a/b.

Clear light diameter (mm)

Thickness of toughned glass (mm)

Type B sydescuttles

(medium series)

Type C sydescuttles (light

series)

200250300350400450

88

10121215

666888

t 0 015b β p⋅,=

Nominal sizes (clear light) of rec-tangular window

(mm)

Thickness of tough-ened glass

(mm)

Total minimum number of clos-

ing appliances of opening type rec-tangular window

300x500355x500400x560450x630500x710560x800900x630

1000x7101100x800

666667889

444466688

Nota 1: Swing bolts and circular hole hinges of glass holdersof opening type rectangular windows are considered closingappliances.

t 0 005b β p⋅,=

Pt B, Ch 1, Sec 1


Different thickness may also be accepted on the basis of ahydraulic pressure test, performed on a mock-up represent-ative of the arrangement, the result of which confirms thatthe proposed thickness is able to ensure watertight integrityat a pressure not less than 4 times the design pressure.

A mock-up can be deemed representative of a set of glasspanes of the same type if they have the same thickness andthe dimensions "a" and "b" of each glass pane differ fromthose of the mock-up by not more than +/- 10%.

The thickness of toughened glass panes of windows of othershapes will be the subject of special consideration by RINAin relation to their shape.

RINA reserves the right to impose limitations on the size ofrectangular windows and require the use of glass panes ofincreased thickness in way of front bulkheads which areparticularly exposed to heavy seas.

5.6.5 Materials other than toughened glass

Materials other than toughened glass may be used for side-scuttles and windows above and below the weather deck.

The thickness of the sheets may be obtained by multiplyingthe Rule thickness for toughened glass by 1,3 in the case ofpolycarbonate sheets and 1,5 in the case of acrylic sheets.

The thickness of laminated glass is to be such that:

where:

te : equivalent thickness of the single sheet glasspane

ti : thickness of the single sheet in the laminate

n : number of sheets in the laminate.

5.7 Skylights

5.7.1 For yachts not more than 24 m, the requirements ofISO STANDARD 12216 are to be applied. For yachts morethan 24 m, skylights fitted on the weather deck may be con-sidered as fitted in zone B and therefore their thickness is tobe in accordance with item [5.6.4] or [5.6.5]. The designpressure to be assumed is 15 kN/m2 if fitted in deck position1 and 10 kN/m2 if fitted in deck position 2.

The locking devices are to be the same required for flushhatches (see item [5.5.3]).

5.8 Outer doors

5.8.1 Doors in the superstructure's side

Doors of exposed bulkheads of superstructures are to be ofadequate dimensions and construction such as to guaranteetheir weathertight integrity.

The use of FRP for doors on the weather deck other thanmachinery spaces may be accepted, providing the doors aresufficiently strong.

Where the doors may be required to be used as a means ofescape, the securing arrangements are to be operable fromboth sides.

The height of the sills of doors above the exposed deck thatgive access to compartments below the deck is to be notless than the following value:

Deck position 1 Deck position 2

Outer doors 100 mm 75 mm

Companionways 100 mm 75 mm

Doors on the weather deck to 1st tier accommodation orother spaces protecting access below may have four clips.

5.8.2 Sliding glass doors

Arrangements with sliding glass doors or glass walls aregenerally permissible only for the after end bulkhead ofsuperstructures.

The glass used is to be of the toughened type or equivalent.

The thickness may be determined using the formula in[5.6.4] assuming for P the value corresponding to 10kN/m2.

The sills of these doors are to be in accordance with therequirements set out in [5.8.1].

5.9 Drawings

5.9.1 A plan showing the position portlights, windows,skylights, external doors and glass walls is to be submitted;their dimensions and sills are to be clearly indicated.

5.10 Ventilation

5.10.1 General

Accommodation spaces are to be protected from gas orvapour fumes from machinery, exhaust and fuel systems.

Yachts are to be adequately ventilated throughout allspaces.

The machinery spaces are to be adequately ventilated so asto ensure that, when machinery therein is operating at fullpower in all weather conditions, an adequate supply of airis maintained in the spaces for the safety and the operationof the machinery, according to the Manufacturer's specifi-cation.

Ventilator openings are to be designed and position withcare, above all in exposed zones or those subject to highstress. The deck plating in way of the coamings is to be ade-quately stiffened.

The scantlings of ventilators exposed to the weather are tobe equivalent to those of the adjacent deck or bulkhead.

Ventilators are to be adequately stayed.

Ventilators which, for any reason, can be subjected to liquidpressure are to be made watertight and have scantlings suit-able for withstanding the foreseen pressure.

For yachts having gross tonnage not greater than 350, theposition of the air intake may be accepted below the

te2 ti1

2 ti2

2 … tiin

2+ +=

Pt B, Ch 1, Sec 1


weather deck, provided that the following requirements aresatisfied:

a) the minimum down flooding angle meets the minimumof the stability criteria

b) means are provided to the satisfaction of RINA in orderto guarantee the hull integrity.

c) a bilge level alarm associated with additional automaticbilge pumps is to be provided inside the compartmentswhere such ducts are fitted

d) the openings are fitted, as far as practicable, close to theweather deck and in any case are as small as possible

5.10.2 Closing appliances

All ventilator openings are to be provided with efficientweathertight closing appliances unless:

• the height of the coaming is greater than 4,5 m abovethe deck if fitted in Position 1;

• the height of the coaming is greater than 2,3 m abovethe deck if fitted in Position 2.

As a general rule, closing appliances are to be permanentlyattached to the ventilator coamings.

Ventilators are to be fitted with a suitable means of prevent-ing ingress of water and spray when open and to have suita-ble drainage arrangements leading overboard.

5.11 Air pipes

5.11.1 General

Air and sounding pipes are to comply with the requirementsof Pt C, Ch 1, Sec 9, [7].

5.11.2 Height of air pipes

The height of air pipes from the upper surface of decksexposed to the weather is to be in compliance with therequirements of Part C.

5.12 Bulwarks and guardrails or guardline

5.12.1 Stength, location and height

Bulwarks, guardrails or guardline are to be arranged onexposed decks.

Where this is not practicable, and for an area not normallyaccessed under operational conditions, they may be omit-ted and handrails are to be provided. Handrails are to meetthe requirements of ISO STANDARD 15085.

For yachts not more than 24 m the requirements of ISOSTANDARD 15085 are to be applied.

For yachts more than 24 m the requirements of ISO STAND-ARD 15085 are to be applied for the strength of the guard-line and guardrails structure.

The height of bulwarks or rails, or a combination of both, isto be not less than 600 mm. Lesser heights may be consid-ered with regard to location and hazards involved.

The maximum clearance below the lowest course of theguardline is to be 230 mm. The other courses of guardlineare to be not more than 380 mm.

The stanchions are to be spaced at not more than 2,2 m.

5.13 Freeing ports

5.13.1 (1/1/2009)

Any bulwarks or guardrails are to be provided with freeingport openings having dimensions given as follows:

• yachts having LH more than 24 m:

freeing port area area A (m2) for each side not less than

A= 0,07 l

Where:

l (m) = length of bulwark on one side, but need notexceed 0,7 LWL

The value given from the above formula is to be cor-rected for the height of the bulwarks according to thefollowing criteria.

If the bulwark height exceeds 1,2 m, the freeing portarea is to be increased by 0,004 m2 per metre of bul-wark length for each 0,1 m difference in height. Wherethe bulwark height is less than 0,9 m in height, the free-ing port area is to be decreased by the same ratio.

• Yachts having LH equal to or less than 24 m:

the requirements of ISO STANDARD 11812 are to becomplied with.

5.13.2 Freeing port arrangement

Where they exceed 230 mm in depth, freeing port openingsare to be protected by rails or bars spaced not more than230 mm apart.

The area of freeing ports is to be located for two-thirds inthe half of the well nearer the lowest point of the sheercurve.

5.13.3 Cockpits and cockpits drainage

For yachts not more than 24 m, recesses and their means fordischarge outboard are to be in compliance to ISO STAND-ARD 11812.

For yachts more than 24 m, the total area A in (m2) of themeans of discharge outboard is to be not less than the valuegiven by the formula:

A = 0,003 V

where V is the value of the well, in m3.

Pt B, Ch 1, Sec 2


SECTION 2 HULL OUTFITTING

1 Rudders and steering gear

1.1 General

1.1.1 These requirements apply to ordinary profile rudderswithout any special arrangement for increasing the rudderforce, such as fins or flaps, steering propellers, etc.

Unconventional rudders of unusual type or shape and thosewith speeds exceeding 45 knots will be the subject of spe-cial consideration by RINA.

In such cases, the scantlings of the rudder and the rudderstock will be determined by means of direct calculations tobe agreed with RINA as regards the loads and schematisa-tion.

In general, the loads will be determined either by modeltests, or by measurements taken on similar yachts, or usingrecognised theories.

The stresses in N/mm2 are not to be greater than the follow-ing:

• torsional stress = 70/e

• Von Mises equivalent stress = 120/e

as defined in [1.2.1].

The "steering gear" of a yacht means all apparatus anddevices necessary for the operation of the rudder, or equiva-lent means of manoeuvre, constituted by:

• main steering gear, designed to ensure control of theyacht at the maximum navigational speed;

• auxiliary steering gear, enabling control of the yacht inthe event of an emergency due to mechanical break-down of the components of the main steering gear.

1.2 Rudder stock

1.2.1 Rudder subject to torque onlyThe diameter DT, in mm, of rudder stocks, assumed in solidbar and subject to torque only, is given by the following for-mula:

where:

A : total rudder area, in m2 bounded by the rudder'sexternal contour including the mainpiece;

R : horizontal distance, in metres, from the centroidof area to the centreline of pintles, to be takennot less than 0,12b, where b is the width, inmetres, of the rudder, if the latter has a rectan-gular contour; for rudders with non-rectangular contours, b = A/h is to be taken, where h is therudder height, in m, in way of the centreline ofpintles mentioned above;

V : maximum design speed, in knots, of the yacht atfull load draught.

In the case of sailing yachts, with or withoutauxiliary engine, the following formula is to beused for the calculation of V:

where L is the length as defined in Sec 1;

e : 235/RS; the minimum yield stress RS is to betaken not greater than 0,7 Rm, where Rm is theminimum ultimate tensile strength of the rudderstock material.

However, the diameter DT is not to be taken lessthan 20 e1/3, in mm.

For rudder stocks made of material which ismore corrosion resistant than mild steels, alower value for diameter DT than that obtainedas above may be accepted by RINA on a case-by-case basis. In no case is such value to bereduced by more than 10%.

The diameter of rudder stocks made of compos-ite materials may be derived using the aboveformulae, taking as the value RS for the calcula-tion of e, the value of shear tensile strength ofthe composite material.

The inertia of the composite rudder stock Ic is tobe not less than Im/Em/Efc, where:

Im - the inertia of the Rule metal rudder stock

Em - the modulus of elasticity of the metal

Efc - the bending modulus of elasticity of thecomposite material.

The acceptance of rudder stocks made of com-posite material is, in any event, subject to aninspection of the fabrication procedure and,where appropriate, to comparative workingtests.

1.2.2 Rudder stocks subject to torque and bendingThe diameter DTF, in mm, of rudder stocks subject to torqueand bending, as in the case of rudders with two bearings(with solepiece) and of space rudders (see types IA, IB and IIin Fig) is to be not less than the value obtained from the for-mula:

where:

DT : diameter, in mm, of the rudder stock, as definedand calculated in [1.2.1];

K : 1,08 + 0,06 ( H / R ) for type IA or type IB rud-ders;

1,08 + 0,24 ( H / R ) for type II rudders;

DT 12 A R V2 e⋅ ⋅ ⋅( )1 3⁄=

V 2 3 L0 5,,=

DTF K DT⋅=

Pt B, Ch 1, Sec 2


H : vertical distance, in metres, from the centroid ofthe area A to the lower end of the rudder stockbearing in way of the piece.

The diameter of the rudder, required in way of the main-piece bearing, is to be extended at the upper part to at least10% of the height of the bearing or to a height equivalent to2 DTF, whichever is the greater; beyond this limit, the rudderstock diameter may be gradually tapered so as to reach thevalue of DT in way of the coupling between rudder stockand tiller.

At the lower part, the diameter DTF is to be extended as faras the coupling between the rudder stock and the main-piece; in the absence of such coupling, the diameter maybe gradually tapered below the upper edge of the rudderblade.

1.2.3 Tubular rudder stock

Where a tubular rudder stock is adopted, its inner diameterd1 and outer diameter d2, in mm, are to comply with the fol-lowing formula:

where D = DT, for rudders dealt with in [1.2.1], and D =DTF, for rudders dealt with in [1.2.2].

1.3 Coupling between rudder stock and mainpiece

1.3.1 Horizontal couplings

Horizontal flange couplings between the rudder stock andthe mainpiece when not integral are to have:

• flanges of dimensions such that the coupling bolts aredistributed on a circumference having a diameter notless than 2D or in a similar manner, where D is asdefined in [1.2.3];

• flanges of thickness not less than the diameter d of thebolts;

• bolts of diameter d, in mm, not less than 0,65 D/n0,5,where n is the number of bolts, which in no case is to beless than 4;

• bolts whose axes are at a distance not less than 1,2 dfrom the external edge of the flanges;

• bolt nuts provided with means of locking.

1.3.2 Cone couplings

Cone couplings of the shape shown in Fig 1 (with explana-tions of symbols used in a) and b) below) are to have the fol-lowing dimensions:

a) Cone coupling with hydraulic arrangements for assem-bling and disassembling the coupling

Taper:

and, in any case,:

Between the nut and rudder gudgeon a washer is to befitted having a thickness not less than 0,13 dG and anouter diameter not less than 1,3 d0 and 1,6 dG, which-ever is the greater.

b) Cone coupling without hydraulic arrangements forassembling and disassembling the couplingTaper:

and, in any case,

The dimensions of the locking nut, in both (a) and (b) above,are given purely for guidance, the determination of ade-quate scantlings being the responsibility of the Designer.

In cone couplings of type (b) above, a key is to be fitted hav-ing a cross section 0,25 DT x 0,10 DT, and keyways in boththe tapered part and the rudder gudgeon.

In cone couplings of type (a) above, the key may be omit-ted. In this case the Designer is to submit to RINA shrink-age calculations and supply all data necessary for therelevant check.

All necessary instructions for hydraulic assembly and disas-sembly of the nut, including indication of the values of allrelevant parameters, are to be available on board.

Figure 1

d24 d1

4–d2

-----------------1 3⁄

D≥

1 20⁄ d1 d0–( ) ts⁄ 1 12⁄≤ ≤

tS 1 5 d1⋅,≥

dG 0 65 d1⋅,≥

tN 0 60 dG⋅,≥

dN 1 2 d0⋅,≥

dN 1 5 dG⋅,≥

1 12⁄ d1 d0–( ) ts⁄ 1 8⁄≤ ≤

tS 1 5 d1⋅,≥

dG 0 65 d1⋅,≥

tN 0 60 dG⋅,≥

dN 1 2 d0⋅,≥

dN 1 5 dG⋅,≥

Pt B, Ch 1, Sec 2


1.4 Rudder mainpiece and blade

1.4.1 Mainpiece typesThe rudder mainpiece is formed by the stock, extended intothe blade when the coupling does not exist, or, otherwise,by a solid or tubular bar, a double T or a box structure, as inthe case of rudders with double plating.

The arms or the webs supporting the blade are to be struc-turally connected to the mainpiece.

1.4.2 Plate ruddersThe following requirements apply to rudders made of hullplates of ordinary steel; plates of other metallic material,e.g. aluminium alloy or stainless steel, are permitted; theirscantlings will be stipulated on the basis of their characteris-tics in accordance with a criterion of equivalence.

Single-plate rudders are to have:

• mainpiece with section equal, or equivalent, to that ofthe stock in way of the upper edge of the blade, gradu-ally tapered in the lower half to not less than 50%;

• plate with thickness t = 5 + 0,11 (DT - 20 ) mm, to belinearly increased with the arm spacing s, when s isgreater than 750 mm;

• horizontal arms with solid rectangular section, or equiv-alent each having, at the root, section modulus, in cm3,Z = 7 + 0,8 (DT- 20 ); for DT < 60 mm, Z = 7:cm3 is tobe taken.

Double-plate rudders are to have:

• mainpiece of section equal, or equivalent, to the sectionspecified for single-plate rudders;

• thickness t, in mm, of the plating, including that ofupper or lower closing, and vertical and horizontalwebs, given by the following formula:

where:s : spacing of the horizontal webs, in mm, to

be taken for the calculation as not greaterthan 1000;

DT : rudder stock diameter, in mm, as defined in[1.2.1];

• welded connections complying with the requirementsof Chapter 2 for steel rudders, and Chapter 3 for alumin-ium alloy rudders;

• internal surfaces protected by painting; the filling of therudder with light material of expanded type is permit-ted;

• drainage hole.

1.4.3 Rudders with blade made of glass reinforced plastics

Such rudders are to have, in particular:

• stock and mainpiece, in solid or tubular bar, made ofhull steel or light alloy, and mainpiece arms, of the samematerial, structurally connected to the mainpiece;

• blade made of a single plate or composed of two pre-formed plates, made of glass reinforced plastics, com-plying with the requirements of Chapter 4 and filledwith light material;

• mass per unit surface, m, in kg/m2, of the glass rein-forcement of the material, m = 0,6Vb, where V and bare as defined in [1.2.1]. The thickness of the plate is, inany case, to be not less than 5 mm.

1.4.4 Cast ruddersFor rudders and their stocks obtained by casting, the type ofmaterial and the relevant mechanical characteristics are tobe submitted to RINA for examination.

Castings with sharp edges and sharp section changes are tobe avoided, in particular when stock and plating are cast inone piece.

1.5 Rudder bearings, pintles and stuffing boxes

1.5.1 Rudder bearingsRudder "bearings" means:

• the bearing supporting the radial load fitted at the rud-der trunk, that at the solepiece and that in way of thestock/tiller coupling;

• a bearing, or equivalent device, carrying the verticalload, in order to support the weight of the rudder;

• rudder stop devices, designed to prevent the rudderfrom lifting as necessary.

The rudder trunk bearing height h, in mm, is to be between1,5 D and 2 D, where D is the local stock diameter asdefined in [1.2.3].

Lower values of h, but in no case less than 1,2 D, may beaccepted except in the case of spade rudders, for which h ≥1,5 D is required.

If the rudder stock is lined in way of the trunk bearing (forinstance with stainless steel brush), the lining is to be shrunkon.

Any proposed welding overlay may be accepted subject tothe use of a welding process recognised as suitable byRINA.

1.5.2 PintlesThe minimum diameter DA, in mm, of the pintles, outside ofany lining or welding, is given by the following formula:

DA = c + 0,6 D

where:

c : 1, for rudders dealt with in [1.2.1]5, in other cases;

D : rudder stock diameter as defined in [1.2.3].The height of the pintle bearing surface is to be approxi-mately 1,2 DA, but in no case less than DA.

The tapering of any truncated cone-shaped part of the pin-tle, in way of the connection to the hull, is to be 1:6 withrespect to the diameter.

For any lining or welding, the requirements of [1.5.1] apply.

1.5.3 Sealing devicesIn rudder trunks which are open to the sea, a seal or stuffingbox is to be fitted above the deepest load waterline, to pre-vent water from entering the steering gear compartment andlubricant being washed away from the rudder carrier.

t DT0 45, 0 7 s 103⁄+,( )=

Pt B, Ch 1, Sec 2


If the top of the rudder trunk is below the deepest loadwaterline, two separate seals or stuffing boxes are to be pro-vided.

1.6 Steering gear and associated apparatus

1.6.1 Premise

These requirements apply to the most commonly used typesof steering gear, which are dealt with below; any differenttypes will be specially considered by RINA in each case.

1.6.2 Types of steering gear

Remote controlled steering gear of one of the followingtypes:

• tiller; hydraulic actuator of the tiller and associated pip-ing; valves and hydraulic pump controlled by rudderwheel;

• the above apparatus, with the addition of an electricpump feeding the actuator through distributor and gyro-pilot follow-up link.

1.6.3 Steering gear of remote controlled type with rope or chain

The rudder tiller, or quadrant, is to have:

• hub of height h ≥ DT, in mm, and thickness t ≥ 0,4 DT, inmm;

• section modulus Z, in cm3, in way of the connection tothe hub, given by the following formula:

where:

DT : Rule diameter, in mm, of the rudder stock sub-ject to torque only;

a : length, in mm, of the tiller, measured from therudder stock to the point of connection of ropeor chain to the stock;

b : 0,5 DT + t, in mm.

The tiller-stock coupling is to be of the type with square sec-tion, or with cylindrical section and key, and the tiller hub isto be bolted; in particular:

• the hub bolts are to have diameter db, in mm, not lessthan the value given by the formula:

where n is the number of bolts on each side of the hub;in any case the diameter db is to be not less than 12 mm;

• the coupling key is to have rounded edges, length, inmm, equal to the hub thickness, thickness, in mm, equalto 0,17 DT and section area, in mm2, equal to 0,25 DT

2.

Alternative arrangements will be subject to special consid-eration by RINA.

1.6.4 Steering gear with hydraulic or electro-hydraulic type remote control

The parts of such steering gear are to comply with the spe-cific requirements of Part C, Chap 1, Sec 10.

Figure 2

Z 0 15DT

3

1000------------- a b–

a------------⋅ ⋅,≥

db0 4D,2n0 5,--------------=

Type IA Type IB Type II

Pt B, Ch 1, Sec 2


2 Propeller shaft brackets

2.1 Double arm brackets2.1.1 (1/1/2011)Double arm propeller shaft brackets consist of two armsforming an angle as near as practicable to 90°, and con-verging into a propeller shaft bossing.

Arms having elliptical or trapezoidal section with roundfairing are to have an area A, in mm2, at the root not lessthan that given by the following relationship:

where:dp : Rule diameter of the propeller shaft made of

steel with ultimate tensile strength Rm = 400measured inside the liner, if any, in mm,

Rma : minimum ultimate tensile strength, in N/mm2,of the material of the brackets.

The maximum thickness in way of the above section is to benot less than 0,4 dp.

Considering the diameter ( d ) of the shaft propellers calcu-lated according the formula given in Pt C, Ch 1, Sec 6,[2.2.2] or [2.2.3] as applicable taking in account the effec-tive material mechanical characteristics the boss is to havelength not more than 4 d, but in no case may a length lessthan 3 d be accepted, and thickness of 0,25 d. In any casewhen the diameter shaft propeller is calculated according PtC, Ch 1, Sec 6, [2.2.3] boss thickness is to be not less than0,35 d, d being the diameter of the propeller shaft calcu-lated according to Pt C, Ch 1, Sec 6, [2.2.4].

When the brackets are connected by means of palms, thelatter are to have thickness not less than 0,2 dp and are to beconnected to the hull by means of bolts with nuts and locknuts on the internal hull structures, which are to be suitablystiffened to the satisfaction of RINA.

The thickness of the plating in the vicinity of the connectionis to be increased by 50%.

In the case of metal hulls and brackets of the same material,the connection between bracket and hull is to be carriedout by means of welding.

The brackets are to be continuous through the plating andto be connected internally to suitable transverse or longitu-dinal structures.

The plating in way of the bracket connection is to be suita-bly increased and connected to the arm bracket with fullpenetration welding.

2.2 Single arm brackets2.2.1 (1/1/2009)Single -arm shaft brackets are to have a section modulus atship plating level, in cm3, of not less than:

where:l : length of the arm, in m, measured from the shell

plating to the centreline of the shaft boss,

n : shaft revolutions per minute,dso : Rule diameter, in mm, of the propeller shaft, for

carbon steel material,

Rma : minimum tensile strength, in N/mm2, of arms,with appropriate metallurgical temper.

Boss thickness is to be calculated as for the double armbrackets.

3 Sailing yacht appendages and com-ponent fastenings

3.1 Keel connection3.1.1 (1/1/2011)The typical ratio of the weight of external ballast to light dis-placement is generally 0,4 ÷ 0,5.

The ballast may be internal or external to the hull.

In the first case, the ballast is to be permanently secured, byclips or equivalent means, to the resistant structures of thehull (floors, frames, etc.) but in no case to the plating, onwhich it is never to bear, so as not to shift even during roll-ing or pitching.

In the second case, the connection to the hull is to beeffected by means of bolts long enough to incorporate theheight of the ballast, either wholly or in part; such bolts areto pass through the hull, with a head (or nut and lock nut) atone end and a nut and lock nut at the other, towards theinside of the hull. The surface of the ballast keel head is tobe flush with the surface of the hull, the bolt holes are to befashioned with equipment designed to achieve an almostcomplete absence of play between bolt and hole, and thelocking of the nuts is to be uniform. The nuts are to rest onplates or large washers and to be left uncovered so that theymay be easily examined.

The diameter d, in mm, at the bottom of the thread of eachkeel bolt is given by the following formula:

where:W : is the total weight of the ballast in N ;

hG : is the distance in mm, from the centroid of theballast, to the plane attachment of the ballast tothe hull ;

σR : is the minimum yield strength of the bolt mate-rial, N/mm2;

Σli : summation of the distances from the centre ofthe bolts on side of the keel to the edge of thekeel on the other side, in mm.

If there are fewer bolts on one side of the keel, Σli is to bemeasured from the centroid of the bolts on that side to theedge of the keel on the other side.

Where are fitted bolts on the longitudinal axis of the keel,Σli should be measured from the centre of the bolts to theedge of the keel.

It is to be verified that the arrangement is strong enough towithstand the grounding loads. It is assumed that the con-ventional grounding loads are the following:

A 87 5, 10 3–⋅ dP2 1600 Rma+

Rma

-----------------------------⎝ ⎠⎛ ⎞⋅=

W 30Rma

-------- 10 3– I d2××× so n dso×( )o 5,×=

d 1 60W h× G

Σ l i σR×--------------------×,=

0 5,

Pt B, Ch 1, Sec 2


a) Longitudinal grounding loads acting in the aft directionand parallel to the longitudinal hull axis. The load is tobe applied to the bottom edge of the keel

LGL = 3,1 Δ (if Lwl > 20 m)

LGL = 1,60 Δ (if Lwl < 10 m)

b) Vertical grounding load VGL, in tons, acting upward onthe bottom of the keel

VGL = 1,60 Δ

is to be verified that shear stress and primary stress dueto the load as indicated in a and b are not more than thevalue given from the following formula:

shear stress < 0,70 ηB

primary stress < 0,70 ηR

where:

Δ : is the maximum displacement of the vessel, intonnes;

ηR : is the minimum shear yield stress of the bolts mate-rial, in N/mm2.

Where direct calculations are carried out to determine thediameter of bolts, the degree of locking is to be taken intoaccount and a safety factor ≥ 3,5 in relation to the ultimatetensile strength and ≤ 2 in relation to the yield stress of thebolt material is to be applied.

3.1.2 Chain plates

The plates should be ample in size and well fastened to thestructure to distribute the loads.

Many arrangements may be adopted according to thedesign philosophy.

Basically, the following arrangement could be adopted:

a) Single strap design:

in this case the chainplates may be fitted internally orexternally and by means of bolts. In the case of internalfittings, the bolts are to have large heads; on account oftheir appearance, washers are not normally fitted on theoutside of the hull;

b) Bracket connection

in this case the chainplate is connected to a plywoodbracket by means an angle or flat bar chainplate.

The chainplate is to be bolted to the bracket. Wherepossible, the chainplates are to be bolted directly to thebulkhead. Where the chanplate and bolts penetrate, thehull or deck is to be made watertight with a flexiblesealant rather than a rigid resin, which may crack underthe strain and result in annoying leakage.

Chainplates are to be generally of mild steel, stainlesssteel, monel or aluminium. Bolts are to be galvanicallycompatible with the other materials and are to be seacorrosion-resistant.

Adequately hull reinforcement is to be provided in wayof the chainplates.

3.1.3 Component fastenings

Components can be satisfactorily fastened with bolts,screws or rivets. These fasteners are to be of a corrosion-resistant metal. Bolts, washers, backing plates and fittingsare to be of a compatible material. Where chemicallyincompatible, adequately insulation is to be provided. If thecomponents are to be fitted to a hull structure in sandwichconstruction with low density core materials, the local hullarea is to be replaced with structurally effective inserts inway of bolted connections and fittings. The inserts are to besea adequately bonded to the laminate skins and to theadjacent low density core.

Alternatively, the local area can be replaced with mono-lithic laminate of the same thickness as the sandwich lami-nate.

4 Stabilizer arrangements

4.1 General

4.1.1 The scantlings, arrangement and efficiency of stabi-liser arrangements do not fall within the scope of Classifica-tion; nevertheless, the bedplates of the various components,the supporting structures and the watertight integrity are tobe examined.

4.2 Stabilizer arrangements

4.2.1 The stabilizer fin machinery is to be supported byadequately reinforced structures.

Drawings are to be submitted for approval showing theposition, the supporting structures and the loads transmit-ted.

4.2.2 (1/1/2011)

The shell plating in way of stabilizer fins is to be adequatelyreinforced. In the case of fixed type stabiliser fins, the pas-sage to the hull and the components necessary for the oper-ation of the system, supported by adequately reinforcedstructures, are to be arranged in a watertight box with aninspection opening fitted with a watertight cover.

In metal structures, the watertight box is to be at least of thesame thickness as the adjacent shell plating. The box is tobe well stiffened. For GRP vessels, the scantling of thewatertight boxes and their stiffeners will be considered caseby case. Where it is not practical to provide a watertightbox, particularly because of the restricted inside spaces, thearrangement will be specially considered by RINA.

4.3 Stabilizing tanks

4.3.1 The tank structures are to comply with the require-ments for tank bulkheads, taking into account the maximumhead that may arise in service.

Where sloshing is foreseeable the scantlings will be the sub-ject of special consideration.

Pt B, Ch 1, Sec 2


5 Thruster tunnels

5.1 Tunnel wall thickness5.1.1 (1/1/2009)The thickness of the tunnel is to be in accordance with theManufacturer's specifications; in general, the thickness is tobe not less than:• For steel tunnels: the Rule thickness of the adjacent

plating increased by 10% (but at least 2 mm), and in anycase not less than 7 mm.

• For light alloy tunnels: the Rule thickness of the adja-cent plating increased by 10% (but at least 1 mm), andin any case not less than 8 mm.

• For composite tunnels: the Rule thickness of the adja-cent plating increased by 25%; in any case the thicknessis to be not less than 8 mm. If tunnel diameter is lessthan 300 mm, a thickness not less than the Rule thick-ness of the adjacent plating can be accepted.

5.2 Tunnel arrangement details

5.2.1 The system for connecting the tunnel to the hulldepends on the material used for the construction.

5.2.2 The thickness of the plating is to be locally increasedby 50% in way of the tunnel attachment.

5.2.3 The tunnel is to be connected to the plating bymeans of full penetration welding.

5.2.4 For tunnels in composite material, the weight of theconnecting laminate stiffener is to be equal to the weight ofthe bottom plating stiffener. The stiffener is to be arrangedon both sides of the plating laminate.Prior to the connecting lamination, the surfaces of the tun-nel and the plating concerned are to be suitably cleanedand prepared and the edges of the cuts are to be sealed withresin.

6 Water-jet drive ducts

6.1

6.1.1 The thickness of the duct is to be in accordance withthe Manufacturer's specifications and, in general, is to benot less than that of the adjacent plating.

The duct is to be adequately supported, stiffened and fullyintegrated with the hull structure.

The water-jet drive supporting structures are to be able towithstand the loads induced by the propulsion system in thefollowing conditions:

• maximum thrust ahead

• maximum thrust at the maximum lateral inclination

• maximum reverse thrust (astern speed).

The foregoing loads are to be provided by the water-jetdrive Manufacturer and adequately documented.

All hull openings are to be adequately reinforced and tohave well rounded corners.

The thickness of the plating in the vicinity of the ductentrance is to be locally increased as stated in [5.2.2].

The Manufacturer is to assess the need to arrange suitablemeans of protection at the duct opening in order to preventthe ingress of foreign bodies which may damage the inter-nal mechanism.

7 Crane support arrangements

7.1

7.1.1 Crane foundations are to be designed consideringthe worst combinations of the following loadings:

- maximum load capacity;

- the weight of the crane itself.

Insert plates are to be provided in the deck in way of thecrane foundation; in order to avoid concentration of forces,these insert plates are to have suitable dimensions (inrespect to the dimensions of the foundation), be suitablyprepared and have round corners. The thickness of theseinserts shall be in accordance with the Designer's calcula-tions.

A drawing of this arrangement with all the forces acting andthe detail of the connection to the deck is to be sent forapproval.

Pt B, Ch 1, Sec 3


SECTION 3 EQUIPMENT

1 General

1.1

1.1.1 The anchoring equipment required in 6 is intendedfor temporary mooring of a yacht within or near a harbour,or in a sheltered area.The equipment is therefore not designed to hold a yacht offfully exposed coasts in rough weather or to stop a yachtwhich is moving or drifting. In such conditions the loads onthe anchoring equipment increase to such a degree that itscomponents may be damaged or lost owing to the highenergy forces generated.The anchoring equipment required in 6 is deemed suitableto hold a yacht in good holding ground where the condi-tions are such as to avoid dragging of the anchor. In poorholding ground the holding power of the anchors will besignificantly reduced.It is assumed that under normal circumstances a yacht willuse one anchor only.

2 Anchors

2.1

2.1.1 Anchors are to be manufactured in accordance withPt D, Ch 4, Sec.1

2.1.2 The mass, per anchor, given in Tab 1 applies to "highholding power" anchors. When use is made of normal typeanchors, the mass shown in the table is to be multiplied by1,33.

When "very high holding power" anchors are used, themass of the anchors may be equal to 70% of that shown inTable 1 for stockless anchors.The actual mass of each anchor may vary by + or - 7% withrespect to that shown in Tab 1, provided that the total massof the two anchors is at least equal to the sum of the massesgiven in the Table.The first anchor is to be positioned ready for use, while thesecond may be kept on board as a spare.

3 Chain cables for anchors

3.1

3.1.1 Chain cables are to have proportions in accordancewith recognised unified standards and to be of the steelgrade given in Tab 1.

Grade 1 chain cables are generally not to be used in associ-ation with "high holding power" anchors; chain cables of atleast Grade 2 are to be used with "very high holding power"anchors.

4 Mooring lines

4.1

4.1.1 Mooring lines may be of wire, natural or syntheticfibre, or a mixture of wire and fibre.Where steel wires are used, they are to be of the flexibletype.Steel wires to be used with mooring winches, where thewire is wound on the winch drum, may be constructed withan independent metal core instead of a fibre core.The breaking loads shown in Table 1 refer to steel wires ornatural fibre ropes.Where synthetic fibre ropes are adopted, their size will bedetermined taking into account the type of material usedand the manufacturing characteristics of the rope, as well asthe different properties of such ropes in comparison withnatural fibre ropes.The equivalence between synthetic fibre ropes and naturalfibre ropes may be assessed by the following formula:

where:δ : elongation to breaking of the synthetic fibre

rope, to be assumed not less than 30%;CRS : breaking load of the synthetic fibre rope, in kN;CRM : breaking load of the natural fibre rope, in kN;Where synthetic fibre ropes are used, rope diameters under20 mm are not permitted, even though a smaller diametercould be adopted in relation to the required breaking load.

5 Windlass

5.1 General

5.1.1 Windlasses are to be power driven and suitable forthe size of chain cable and are to have the characteristicsbelow.The windlass is to be fitted in a suitable position in order toensure an easy lead of the chain cables to and through thehawse pipes; the deck in way of the windlass is to be suita-bly reinforced.A suitable stopping device is to be fitted in order to preventthe anchor from shifting due to movement of the yacht.

5.2 Working test on windlass

5.2.1 The working test of the windlass is to be carried outon board in the presence of the Surveyor.

5.2.2 The test is to demonstrate that the windlass worksadequately and has sufficient power to simultaneouslyweigh the two bower anchors (excluding the housing of theanchors in the hawse pipe) when both are suspended to55m of chain cable, in not more than 6 min.

CRS 7 4δ CRM⋅CRM

1 9⁄------------------⋅,=

Pt B, Ch 1, Sec 3


5.2.3 Where two windlasses operating separately on eachchain cable are adopted, the weighing test is to be carriedout for both, weighing an anchor suspended to 82,5m ofchain cable and verifying that the time required for theweighing (excluding the housing of the anchors in thehawse pipe) does not exceed 9 min. Where the depth ofwater in the trial area is inadequate, or the anchor cable isless than 82,5 m, suitable equivalent simulating conditionswill be considered as an alternative.

6 Equipment Number and equipment

6.1

6.1.1 All yacths are to be provided with anchors, chaincables and ropes based on their Equipment Number EN, asshown in Tab 1.

The equipment Number EN is to be calculated as follows:

where:

Δ : yacht displacement, in tonnes, as defined in Sec1

h :

a : distance, in m, from the summerload waterline amidships to theweather deck

hn : height, in m, at the centreline ofeach tier n of superstructures ordeckhouses having a breadthgreater than B/4.

A : area, in m2, in profile view, of the parts of thehull, superstructures and deckhouses above thesummer load waterline which are within thelength L of the yacht and also have a breadthgreater than B/4.

For yachts that have superstructures with the front bulkheadwith an angle of inclination aft, the equipment number canbe calculated as follows:

θn : angle of inclination with the horizontal axis aftof each front bulkhead

bn : greatest breadth, in m, of each tier n of super-structures or deckhouses having a breadthgreater than B/4.

For EN > 1060 the anchors, chain cables and ropes will bestipulated by RINA in each case.

6.1.2 When calculating h, sheer and trim are to be disre-garded, i.e. h is to be taken equal to the sum of freeboardamidships plus the height hn (at the centreline) of each tierof superstructures and deckhouses having a breadth greaterthan B/4.Where a deckhouse having a breadth greater than B/4 isabove another deckhouse with a breadth of B/4 or less, theupper deckhouse is to be included and the lower ignored.Screens or bulwarks 1,5 metres or more in height are to beregarded as parts of deckhouses when determining h and A.In determining the area A, when a bulwark is more than 1,5metres in height the area above such height is to beincluded.

6.1.3 A drawing relevant to the equipment number is to besent for approval; the drawing is also to contain informationon - geometrical elements of calculation- list of equipment;- construction and breaking load of steel wires;- material, construction, breaking load and relevant elon-

gation of synthetic ropes.

7 Sailing yachts

7.1

7.1.1 For sailing yachts (with or without auxiliary engine),the value of EN is to be calculated using the formula givenin [6.1].

EN Δ2 3⁄ 2h B 0 1A,+⋅+=

a Σhn+

EN Δ2 3⁄ 2 aB bnhn θsin n∑+⎝ ⎠⎛ ⎞ 0 1A,++=

Pt B, Ch 1, Sec 3


Table 1 (1/1/2011)

ENStockless bower

anchorsChain cables for anchors Mooring lines

A<EN<B

No. (1)Mass per anchor (kg)

Total length

(m)

Diameter (mm)

No.Length (m) (3)

Breaking load (kN)A B

Studless chain

cable (2)

Chain cables with stud

Grade U1 steel

Grade U2 steel

Grade U3 steel

507090

110130150175205240280320360400450500550600660720780840910980

7090

110130150175205240280320360400450500550600660770780840910980

1060

11122222222222222222222

100120140160180200230260310360410460520580640700770840910980

106011501260

137,5165165

192,5192,5192,5220220220

247,5247,5247,5275275275

302,5302,5302,5330330

357,5357,5357,5

1112,512,514,514,517,517,51919

20,52224-----------

-111114141616

17,517,519

20,5222224262628303032323436

---

12,512,514141616

17,517,51919

20,5222224262628283032

-----

1111

12,512,51414161617

20,520,522242424242628

22233334444444444444444

42506270747780859095

100105110110130130130130140140140140140

263135353943475155596270788698

105118126138150160173184

(1) The second anchor is intended as a spare and it is not necessary to carry it as a bower anchor provided that, in the event of theloss of the first anchor, the sheet anchor can be readily removed from its position and arranged as a bower anchor. The massrequired for each anchor can be replaced with two anchors having a total weight not less that the weight of the anchor required.In this case the two anchors are to be in place, to be used simultaneously. In addition the length of each chain line shall not beless than 70% of the total length indicated in the table

(2) The diameters refer to Grade U1 steel chain cables; where Grade U2 or U3 steel studless chain cables are used, the diametersmay be reduced guaranteeing the same breaking load as the chain cable corresponding to Grade U1.

(3) Length of each line.Note 1:At the request of the Interested Parties, at RINA's discretion, equivalent mooring equipment may be accepted.

Pt B, Ch 1, Sec 4


SECTION 4 NON-STRUCTURAL FUEL TANKS

1 General

1.1

1.1.1 The requirements of this Section apply to yachtsmore than 24 m. For yachts not more than 24m the require-ments of ISO STANDARD 10088 are to be applied.

Tanks for liquid fuel are to be designed and constructed soas to withstand, without leakage, the dynamic stresses towhich they will be subjected. They are to be fitted withinternal diaphragms, where necessary, in order to reducethe movement of liquid.

Tanks are to be arranged on special supports on the hull andsecurely fastened to them so as to withstand the stressesinduced by movement of the yacht.

Tanks are to be arranged so as to be accessible at least forexternal inspection and check of piping.

Where their dimensions permit, tanks are to include open-ings allowing at least the visual inspection of the interior.

In tanks intended to contain fuel with a flashpoint below55°C determined using the closed cup test (petrol, keroseneand similar), the above openings are to be arranged on thetop of the tank.

Such tanks are to be separated from accommodation spacesby integral gastight bulkheads. Tanks are to be arranged inadequately ventilated spaces equipped with a mechanicalair ejector.

Upon completion of construction and fitting of all the pipeconnections, tanks are to be subjected to a hydraulic pres-sure test with a head equal to that corresponding to 2 mabove the tank top or that of the overflow pipe, whichever isthe greater.

At the discretion of RINA, leak testing may be accepted asan alternative, provided that it is possible, using liquid solu-tions of proven effectiveness in the detection of air leaks, tocarry out a visual inspection of all parts of the tanks withparticular reference to pipe connections.

2 Metallic tanks

2.1 General

2.1.1 Tanks intended to contain diesel oil or gas-oil are tobe made of stainless steel, nickel copper, steel or aluminiumalloys.

Steel tanks are to be suitably protected internally and exter-nally so as to withstand the corrosive action of the salt inthe atmosphere and the fuel they are intended to contain.

The upper part of tanks is generally not to have weldededges facing upwards or be shaped so as to accumulatewater or humidity.

To this end, zinc plating may be used, except for tanksintended to contain diesel oil or gas-oil, for which internalzinc plating is not permitted.

Tanks are to be effectively earthed.

2.2 Scantlings

2.2.1 The thickness of metallic tank plating is to be not lessthan the value t, in mm, given by the following formula:

where:

s : stiffener spacing, in m;

hS : static internal design head, in m, to be assumedas the greater of the following values:

• vertical distance from the pdr (see below) toa point located 2 m above the tank top

• two-thirds of the vertical distance from thepdr to the top of overflow

K : where RS is the minimum yield stress, in

N/mm2, of the tank material. Where light alloysare employed, the value of RS to be assumed isthat corresponding to the alloy in the annealedcondition;

pdr : point of reference, intended as the lower edgeof the plate, or, for stiffeners, the centre of thearea supported by the stiffener.

In any case the thickness of the tank is to be not less than 2mm for steel and not less than 3 mm for light alloy.

The section modulus of stiffeners is to be not less than thevalue Z, in cm3, given by the formula:

where:

S : stiffener span, in m.

3 Non-metallic tanks

3.1 General

3.1.1 Fuel tanks may be made of non-metallic materials.

Mechanical tests are to be carried out on samples of thelaminate "as is" and after immersion in the fuel oil at ambi-ent temperature for a week. After immersion the mechani-cal properties of the laminate are to be not less than 80% ofthe value of the sample "as is".

For scantling calculations the mechanical characteristicsobtained by the mechanical tests are to be assumed.

t 4 s hS K⋅( )0 5,⋅ ⋅=

235RS

----------

Z 4 s S2 hS K⋅ ⋅ ⋅ ⋅=

Pt B, Ch 1, Sec 4


3.2 Scantlings

3.2.1 (1/1/2011)

The scantlings of non-metallic tanks will be specially con-sidered by RINA on the basis of the characteristics of thematerial proposed and the results of strength tests per-formed on a sample.

In general, for tanks made of composite material, the thick-ness t, in mm, of the plating and the module of stiffeners Z,in cm3, are to be not less, respectively, than the values:

where:

kof , k0 : as defined in Chapter 4;

s, S, hS : as defined in [2.2].

In any case, the thickness is to be not less than 8 mm withreinforcement not less than 30% in weight fraction.

The surface of the tanks is to be internally coated with resincapable of withstanding hydrocarbons and externallycoated with self-extinguishing resin.

The self-extinguishing characteristic is to be ascertained bya test carried out according to ASTM D635 on specimenshaving all their surface impregnated with the self-extin-guishing resin used. During such test the flame speed is notto exceed 6 cm/min.

3.3 Tests on tanks

3.3.1 GeneralPrior to their installation on board, tanks are to be subjectedto a hydraulic pressure test with a head equal to that corre-sponding to 2 m above the tank top or that of the overflowpipe, whichever is the greater.

At the discretion of RINA, leak testing may be accepted asan alternative in accordance with the conditions stipulatedin [3.3.2].

3.3.2 Leak testingLeak testing is to be carried out by applying an air pressureof 0,015 MPa.

Prior to inspection of the tightness of welding, in the case ofmetallic tanks and pipe connections, it is recommendedthat the air pressure is raised to 0,02 MPa and kept at thislevel for about 1 hour. The level may then be lowered tothe test pressure before carrying out the welding tightnesscheck of the tank and connections by means of a liquidsolution of proven effectiveness in the detection of air leaks.

The test may be supplemented by arranging a pressuregauge and checking that the reading does not vary overtime.

Leak testing is to be performed before any primer and/orcoating is applied. In the case of tanks made of compositematerial, the test is to be carried out before the surface isexternally coated with self-extinguishing resin.

t 6 s hS ko f⋅( )0 5,⋅ ⋅=

Z 15 s S2 hS K0⋅ ⋅ ⋅ ⋅=

Pt B, Ch 1, Sec 5


SECTION 5 LOADS

1 General

1.1

1.1.1 The static and dynamic design loads defined in thisSection are to be adopted in the formulae for scantlings ofhull and deck structures stipulated in Chapters 2, 3 and 4 ofPart B.

For yachts of speed exceeding 10 L0,5 knots or yachts ofunusual shape, additional information may be required inthe form of basin test results on prototypes.

Alternative methods for the determination of accelerationand loads may be taken into consideration by RINA also onthe basis of model tests or experimental values measured onsimilar yachts, or generally accepted theories.

In such case a report is to be submitted giving details of themethods used and/or tests performed.

Pressures on panels and stiffeners may be considered asuniform and equal to the value assumed in the point of ref-erence pdr as defined in [2.3].


2.1 General

2.1.1 The definitions of the following symbols are valid forall of Part B. The meanings of those symbols which havespecific validity are specified in the relevant Chapters orSections.

2.2 Definitions

2.2.1 Displacement yachtA yacht whose weight is fully supported by the hydrostaticforces.

In general, for the purposes of this Section, a displacementyacht is a craft having V / L0,5 ≤ 4.

2.2.2 Semi-planing yachtA yacht that is supported partially by the buoyancy of thewater it displaces and partially by the dynamic pressuregenerated by the bottom surface running over the water.

2.2.3 Planing yachtA yacht in which the dynamic lift generated by the bottomsurface running over the water supports the total weight ofthe yacht.

2.2.4 ChineIn hulls without a clearly visible chine, this is the point ofthe hull in which the tangent to the hull has an angle of 50°on the horizontal axis.

2.2.5 BottomThe bottom is that part of the hull between the keel and thechines.

2.2.6 Side ShellThe side shell is that part of the hull between the chine andthe highest continuous deck.

2.3 Symbols2.3.1 βx : Deadrise of the transverse section under consid-

eration.In hulls without a clearly visible deadrise, this isthe angle formed by the horizontal axis and thestraight line joining keel and chine.

PpAV : Forward perpendicular: perpendicular at theintersection of the full load waterline plane(with the yacht stationary in still water) and thefore side of the stem.

PpAD : Aft perpendicular: perpendicular at the intersec-tion of the full load waterline plane (with theyacht stationary in still water) and the aft side ofthe sternpost or transom.

pdc : Design deck, intended as the first deck abovethe full load waterline, extending for at least 0,6L and constituting an effective support for side structures.

pdr : Point of reference, intended as the lower edgeof the plating panel or the centre of the areasupported by the stiffener, depending on thecase under consideration.

Δ : Displacement, in t, of the yacht at full loaddraught T. Where unknown, to be assumedequal to 0,42 · L · B · T.

CB : Block coefficient, given by the relationship:

CS : Support contour of the yacht, in m, defined asthe transverse distance, measured along thehull, from the chines to 0,5 L. For twin hullyachts, CS is twice the distance measured alongthe single hull.

g : Acceleration of gravity = 9,81 m/s2.LCG : Longitudinal centre of gravity of the yacht;

where unknown, to be taken as located in thesection at 0,6 L from the PpAV.

aCG : Maximum design value of vertical accelerationat LCG, in g, provided by the Designer based onan assessment of the service conditions (speed,significant wave height) envisaged in the design.

V : Maximum service speed, in knots.

CBΔ

1 025L B T⋅ ⋅,-----------------------------------=

Pt B, Ch 1, Sec 5


3 Design acceleration

3.1 Vertical acceleration at LCG

3.1.1 General

The design vertical acceleration at LCG, aCG (expressed ing), is defined by the Designer and corresponds to the aver-age of the 1% highest accelerations in the most severe seaconditions expected. Generally, it is to be not less than:

where S is given by:

where:

Values of S reduced to as low as 80% of the foregoing valuemay be accepted, at the discretion of RINA, if justified onthe basis of the results of model tests or prototype tests.

The sea area to which the above mentioned value refers isdefined with reference to the significant wave height HS

which is exceeded for an average of not more than 10% ofthe year:

• Open-sea service: Hs ≥ 4,0 m;

If the design acceleration cannot be defined by theDesigner, the aCG value corresponding to the value of S cal-culated with the above-mentioned formula is to beassumed.

3.1.2 Longitudinal distribution of verticalacceleration

The longitudinal distribution of vertical acceleration alongthe hull is given by:

where:

KV : Longitudinal distribution factor, defined in Fig1, equal to 2.x/L or 0,8, whichever is thegreater, where x is the distance, in m, from thecalculation point to the aft perpendicular;

aCG : Design acceleration at LCG (see [3.1] ).

Variation of aV in the trasverse direction may generally bedisregarded.

Figure 1

3.2 Transverse acceleration

3.2.1 Transverse acceleration, to be used in direct calcula-tions for yachts with many tiers of superstructure for whichsignificant racking effects are anticipated, is defined on thebasis of model tests and full-scale measurements.

In the absence of such results, transverse acceleration, in g,at the calculation point of the yacht may be obtained from:

where:

Hsl : permissible significant wave height, in m, atspeed V

r : distance of the calculation point from:

• 0,5 D for monohull yachts

• waterline at draught T, for twin hull yachts.

4 Overall loads

4.1 General

4.1.1 Overall loads are to be used for the check of longitu-dinal strength of the yacht, as required, in relation to thematerial of the hull, in Chapters 2, 3 and 4.

4.2 Longitudinal bending moment and shear force

4.2.1 General The values of the longitudinal bending moment and shearforce are given, as a first approximation, by the formulae in[4.2.2]. For large yachts, the results of experimental tanktests may be taken into account.

If the actual distribution of weights along the yacht isknown, a more accurate calculation may be performed inaccordance with the procedure given in [4.2.3]. RINAreserves the right to require calculations to be carried outaccording to [4.2.3] whenever deemed necessary.

4.2.2 Bending moment and shear force The total bending moments Mbl,H, in hogging conditions,and Mbl,S, in sagging conditions, in kN·m, are the greater ofthose given by the formulae in a) and b) below.

For yachts of L > 100 m, only the formula in b) is generallyto be applied; the formula in a) is to be applied whendeemed necessary by RINA on the basis of the motion char-acteristics of the yacht.

The total force Tbl, in kN, is given by the formula in c)below.

a) bending moment due to still water loads, wave inducedloads and impact loads

where aCG is the vertical acceleration at the LCG,defined in [3.1].

The same value of Mbl is taken for a yacht in saggingconditions or in hogging conditions.

aCG S VL0 5,---------⋅=

S 0 65CF,=

CF 0 2, 0 6, V L0 5,⁄( )⁄[ ] 0 32,≥+=

av kv aCG⋅=

at 2 5Hsl

L-------⋅, 1 5 1 V L0 5,⁄

6-----------------+⎝ ⎠

⎛ ⎞2 r

L---⋅ ⋅+⋅=

MblH, MblS, 0 55 Δ L CB 0 7,+( ) 1 aCG+( )⋅ ⋅ ⋅ ⋅,= =

Pt B, Ch 1, Sec 5


b) bending moment due to still water loads and waveinduced loads.

where:

Ms,H : still water hogging bending moment, in kN ·m; where not supplied, the following maybe assumed for the checks:

Ms,S : still water sagging bending moment, in kN ·m; where not supplied, the following maybe assumed for the checks:

S : parameter defined in 3.1.1 to be assumed =0,21 for displacement yachts

C : 6 + 0,02 L

For the purpose of this calculation, CB may not be takenless than 0,6.

c) Total shear force

where Mbl is the greater of Mbl,H and Mbl,S calculatedaccording to a) or b) above, as applicable.

4.2.3 Bending moment and shear force taking into account the actual distribution of weights

a) The distribution of quasi-static bending moment andshear force, due to still water loads and wave inducedloads, is to be determined from the difference in weightand buoyancy distributions in sagging and hogging foreach loading condition envisaged.

b) For calculation purposes, the following values are to betaken for the design wave:

• wave length, in m:

• wave height, in m:

• wave form: sinusoidal.

c) In addition, the increase in bending moment and shearforce, due to impact loads in the forebody area, for thesagging condition only, is to be determined as specifiedbelow. For the purpose of this calculation, the hull isconsidered longitudinally subdivided into a number ofintervals, generally to be taken equal to 20. For smalleryachts, this number may be reduced to 10 if justified, atRINA's discretion, on the basis of the weight distribu-tion, the hull forms and the value of the design accelera-tion aCG.

For twin hull yachts, the following procedure is to beapplied to one of the hulls, i.e. the longitudinal distribu-tion of weight forces gi and the corresponding breadth Bi

are to be defined for one hull.The total impact, in kN, is:

where qSLi is the additional load, per length unit, inkN/m, per x/L ≥ 0,6 (see Figure 2), computed with thefollowing formula:

where:

Δxi : length of interval, in m

xi : distance, in m, from the aft perpendicular

Bi : yacht breadth, in m, at the uppermost deckin way of the coordinate xi; for twin hullyachts, Bi is the maximum breadth of onehull considered at the transverse sectionconsidered;

xi, Bi : to be measured at the centre of interval i

p0 : maximum hydrodynamic pressure, inkN/m2, calculated by the following formula:

av1 : design vertical acceleration in way of theforward perpendicular, as defined in C3.3;

G : weight force, in kN, calculated from the fol-lowing formula:

gi : weight per unit length, in kN/m, of interval i;for twin hull yachts gi is defined for one hull;

xW : distance, in m, of LCG from the midshipperpendicular, calculated by the followingformula:

r0 : radius of gyration, in m, of weight distribu-tion, calculated as follows:

normally

(guidance values)

xSL : distance, in m, from the centre of the sur-face FSL to the midship perpendicular, cal-culated from the following formula:

fSL :

MblH, MsH, 0 95 S C L2 B CB⋅ ⋅ ⋅ ⋅ ⋅,+=

MblS, MsS, 0 55 S C L2 B CB 0 7,+( )⋅ ⋅ ⋅ ⋅ ⋅,+=

MsH 85 C L2 B CB 0 7,+( )10 3–⋅ ⋅ ⋅ ⋅=

MsS 63 C L2 B CB 0 7,+( )10 3–⋅ ⋅ ⋅ ⋅=

Tt

3 1 Mbl⋅,L

----------------------=

λ L=

h L

15 L20------+

-------------------=

FSL qSLi∑ xiΔ⋅=

qSLi p0 Bi 2 π xi

L---- 0 6,–

⎝ ⎠⎛ ⎞⋅ ⋅sin⋅ ⋅=

p0av1 G r0 xW

2+( )⋅ ⋅fSL r0

2 0 5 L xSL zW–( ) xSL xW⋅–⋅ ⋅,+[ ]⋅-------------------------------------------------------------------------------------------------=

⎝ ⎠⎛ ⎞p

G gi xiΔ⋅∑=

xW

gi xiΔ xi⋅ ⋅( )∑xi xiΔ⋅( )∑

------------------------------------- 0 5 L⋅,–=

r0

gi xiΔ xi 0 5 L,–( )2⋅ ⋅[ ]∑

gi xiΔ⋅( )∑----------------------------------------------------------------

⎝ ⎠⎜ ⎟⎜ ⎟⎛ ⎞

0 5,

=

0 2 L r0 0 25 L⋅,< <⋅,

xSL1fSL

----- xiΔ xi Bi⋅ ⋅( ) 2π xi

L---- 0 6,–

⎝ ⎠⎛ ⎞⋅sin 0 5 L,–⋅∑=

xiΔ Bi⋅( ) 2π xi

L---- 0 6,–

⎝ ⎠⎛ ⎞⋅ , in m2sin⋅∑

Pt B, Ch 1, Sec 5


Figure 2

d) The resulting load distribution qsi, in k/N, for the calcu-lation of the impact induced sagging bending momentand shear force is:

• For x / L < 0,6

where:

avi : total dimensionless vertical accelerationat the interval considered, calculated bythe following formula:

ah : acceleration due to heaving motion

ap : acceleration due to pitching motion

ah e ap : are relative to g

ah :

ap :

• For x / L ≥ 0,6

e) The impact induced sagging bending moment and shearforce are to be obtained by integration of the load distri-bution qsi along the hull. They are to be added to therespective values calculated according to a) and b) inorder to obtain the total bending moment and shear dueto still water loads, wave induced loads and impactloads.

4.3 Design total vertical bending moment

4.3.1 The design total vertical bending moment Mt, in kNper m, is to be taken equal to the greater of the values indi-cated in [4.2.2] a) and b), for planing or semi-planingyachts. For displacement yachts, the value of Mt is to betaken equal to the greater of those given in [4.2.2] b).

4.4 Transverse loads for twin hull yachts

4.4.1 General

For catamarans, the hull connecting structures are to bechecked for the load conditions specified in [4.4.2] and[4.4.3] below. These load conditions are to be consideredas acting separately.

The design moments and forces given in the following para-graphs are to be used unless other values are verified bymodel tests, full-scale measurements or any other informa-tion provided by the Designer.

For yachts of length L > 65 m or speed V > 45 knots, or foryachts with structural arrangements that do not permit arealistic assessment of stress conditions based on simplemodels, the transverse loads are to be evaluated by meansof direct calculations carried out in accordance with criteriaspecified in the individual Chapters or other criteria consid-ered equivalent by RINA.

4.4.2 Transverse bending moment and shear forceThe transverse bending moment Mbt in kN·m, and shearforce Tbt, in kN, are given by:

where:

b : transverse distance, in m, between the centresof the two hulls;

aCG : vertical acceleration at LCG, defined in [3.1].

4.4.3 Transverse torsional connecting moment

The catamaran transverse torsional connecting moment, inkN.m, is given by:

where aCG is the vertical acceleration at LCG, defined in[3.1], which need not be taken greater than 1,0 g for thiscalculation.

5 Local loads

5.1 General

5.1.1 The following loads are to be considered in deter-mining the scantlings of hull structures:

• impact pressure due to slamming, if expected to occur;

• external pressure due to hydrostatic heads and waveloads;

• internal loads.

External pressure generally determines the scantlings of sideand bottom structures, whereas internal loads generallydetermine the scantlings of deck structures.

Where internal loads are caused by concentrated masses ofsignificant magnitude (e.g. tanks, machinery), the capacityof the side and bottom structures to withstand such loads isto be verified according to criteria stipulated by RINA. In

qsi qbi gi avi⋅= =

avi ah ap xi 0 5 L,–( )⋅+=

FSL

G------- r0

2 xSL xW⋅–

r02 xW

2–-----------------------------⋅

FSL

G-------

xSL xW–r0

2 xW2–

-------------------- , in m 1–⋅

qsi qbi qSLi–=

MbtΔ b aCG g⋅ ⋅ ⋅

5--------------------------------=

TbtΔ aCG g⋅ ⋅

4------------------------=

Mtt 0 125 Δ L aCG g⋅ ⋅ ⋅ ⋅,=

Pt B, Ch 1, Sec 5


such cases, the inertial effects due to acceleration of theyacht are to be taken into account.

Such verification is to disregard the simultaneous presenceof any external wave loads acting in the opposite directionto internal loads.

5.2 Load points

5.2.1 Pressure on panels and strength members is to beconsidered uniform and equal to the pressure at the follow-ing load points:

• for panels:

lower edge of the plate, for pressure due to hydrostatichead and wave load;

• for strength members:

centre of the area supported by the element.

Where the pressure diagram shows cusps or discontinuitiesalong the span of a strength member, a uniform value is tobe taken on the basis of the weighted mean value of pres-sure calculated along the length of the member.

5.3 Design pressure for the bottom

5.3.1 Planing and semi-planing yachts (1/1/2011)

The design pressure p, in kN/m2, for the scantlings of struc-tures on the bottom of the hull, plating and stiffeners is to beassumed as equal to the greater of the values p1 and p2

defined as follows:.

h0 : vertical distance, in m, from pdr to the full loadwaterline;

a : coefficient function of the longitudinal positionof pdr, equal to:

• 0,036 aft of 0,5 L

• 0,04/(CB - 0,024) in way of PpAV

• values for intermediate positions obtainedby linear interpolation;

FL : coefficient given in Fig 3 as a function of thelongitudinal position of the pdr;

F1 : coefficient function of the shape and inclinationof the hull to be taken > 0,4, given by:

where bLCG is the deadrise angle, in degrees, ofthe section in way of the LCG;

Fa : coefficient given by:

where A1 is the surface, in m2, of the platingpanel considered or the surface of the area sup-ported by the stiffener;

aV : maximum design value of vertical acceleration,in g, at the transverse section considered.

The pressure p1 is, in any case, not to be assumed as < 10D.

5.3.2 Displacement yacthsFor the purpose of the evaluation of the design pressure forthe bottom, sailing yachts with or without auxiliary engineare also included as displacement yachts.

The pressure p, in kN/m2, for the scantlings of hull struc-tures, plating and stiffeners located below the full loadwaterline is to be taken as equal to the value p1, defined asfollows:

where h0 and a are as defined in [5.3.1].

The pressure p is, in any case, not to be assumed <10 D.

5.4 Design pressure for the side shell

5.4.1 Planing or semi-planing yachts

The pressure p, in kN/m2, for the scantlings of side struc-tures, plating and associated stiffeners is to be taken asequal to the value p1, defined as follows:

The pressure p1 is, in any case, not to be assumed as < 10h1, where h1 is as defined in [5.4.2].

For the zones located forward of 0,3 L from the PpAV, thevalue p is to be not less than the value p2 defined as follows:

where:

a, h0 : as defined in [5.3.1]

C1 : coefficient given by Figure 4 as a function of theload surface A, in m2, bearing on the elementconsidered; for plating, A = 2,5s is to be taken

C2 : coefficient given by Figure 5 as a function of CB

and the longitudinal position of the elementconsidered

kV : 0,625 . L + 0,25V

α : angle formed at the point considered by the sideand the horizontal axis (see Figure 6)

γ : angle formed by the tangent at the waterline,corresponding to the draught T, taken at thepoint of intersection of the transverse section ofthe element considered, with the above water-line and the longitudinal straight line crossingthe above intersection (see Fig 7).

The value p2 may, in any case, be assumed as not greaterthan 0,5p, where p is the design pressure for the bottom asdefined in [5.3.1], calculated at the section considered.

5.4.2 Displacement yachtsFor the purpose of the evaluation of the design pressure forthe side shell, sailing yachts with or without auxiliaryengine are also included as displacement yachts.

p1 0 24L0 5,, 1h0

2T-------–⎝ ⎠

⎛ ⎞ 10 h0 a L⋅+( )⋅+⋅=

p2 15 1 aV+( ) ΔL CS⋅------------- g FL F1 Fa⋅ ⋅ ⋅ ⋅ ⋅⋅=

F150 βX–

50 βLCG–-----------------------=

Fa 0 30, 0 15, 1 43, A1 T⋅ ⋅Δ

-------------------------------⎝ ⎠⎛ ⎞log⋅–=

p1 0 24L0 5,, 1h0

2T-------–⎝ ⎠

⎛ ⎞ 10 h0 a L⋅+( )⋅+⋅=

p1 66 25, a 0 024,+( ) 0 15L, h0–( )⋅ ⋅=

p2 C1= kV( 0 6 senγ+, 90 α–( )cos⋅[ ] C2+ L0 5, sen 90 α–( ) }2⋅ ⋅ ⋅

Pt B, Ch 1, Sec 5


The design pressure p, in kN/m2, for the scantlings of sidestructures located above the full load waterline is to betaken as equal to the value p1 defined as follows:

where:

a, h0 : as defined in [5.3.1]

h1 : distance, in m, from the pdr to the straight lineof the beam of the highest continuous deck.

The pressure p1 is, in any case, not to be assumed as <10h1.

5.5 Design heads for decks

5.5.1 The design heads for the various decks are shown inTable 1.

Sheltered areas are intended to mean decks intended foraccommodation.

The design heads shown in Tab 1 assume a uniformly dis-tributed load with mass density of 0,7 t/m3 and a conse-quent load per square metre of deck, in kN/m2, equal to 6,9hd.

Where distributed loads with mass density greater or lowerthan the above are envisaged, the value h0 will be modifiedaccordingly.

In the case of decks subject to concentrated loads, thescantlings of deck structures (plating and stiffeners) will alsoneed to be checked with the aforementioned loads.

Table 1 (1/1/2011)

5.6 Design heads for watertight bulkheads

5.6.1 Subdivision bulkheads (1/1/2009)The scantlings of subdivision bulkheads, plating and associ-ated stiffeners are to be verified assuming a head hB equal tothe vertical distance, in m, from the pdr to the highest pointof the bulkhead.

5.6.2 Tank bulkheads (1/1/2009)The scantlings of tank bulkheads, plating and associatedstiffeners are to be verified assuming as hT, in m, the greaterof the following values:• vertical distance from the pdr to a point located at a

height h, in m, above the highest point of the tank givenby:

where the value of L is to be taken no less than 50 mand no greater than 80 m

• 2/3 of the vertical distance from the pdr to the top of theoverflow pipe.

p1 66 25, a 0 024,+( ) 0 15L, h0–( )⋅ ⋅=

Deck

EXPOSED WEATHER AREA SHELTERED

AREA(also partially

by deck-houses)

FWD0,075 L

fromFWD PP

AFT0,075 L

fromFWD PP

hd hd hd

Deck below pdc

- - 0,9

pdc 1,5 1,0 0,9

Decks over pdc 1,2 0,9 0,7

hT 1 0 05 L 50–( ),+[ ]=

Pt B, Ch 1, Sec 5


Figure 3

from

the

Pt B, Ch 1, Sec 5


Figure 4

Pt B, Ch 1, Sec 5


Figure 5

from

the

Pt B, Ch 1, Sec 5


Figure 6

Figure 7

TRANSVERSE SECTION CONCERNED

Pt B, Ch 1, App 1


APPENDIX 1 SIDE DOORS AND STERN DOORS

1 General

1.1 Application

1.1.1 (1/1/2009)

The requirements of this Section apply to the arrangement,strength and securing of side doors, abaft the collision bulk-head, and of stern doors leading to enclosed spaces.

1.2 Arrangement

1.2.1 (1/1/2009)

Side doors and stern doors are to be so fitted as to ensuretightness and structural integrity commensurate with theirlocation and the surrounding structure.

1.2.2 (1/1/2009)

Where the sill of any side door is below the uppermost loadline, the arrangement is considered by the Society on acase-by-case basis.

1.2.3 (1/1/2009)

Doors are preferably to open outwards.

1.3 Definitions

1.3.1 Securing device (1/1/2009)

A securing device is a device used to keep the door closedby preventing it from rotating about its hinges or about piv-oted attachments to the Yacht.

1.3.2 Supporting device (1/1/2009)

A supporting device is a device used to transmit external orinternal loads from the door to a securing device and fromthe securing device to the Yacht's structure, or a deviceother than a securing device, such as a hinge, stopper orother fixed device, which transmits loads from the door tothe Yacht's structure.

1.3.3 Locking device (1/1/2009)

A locking device is a device that locks a securing device inthe closed position.

2 Design loads

2.1 Side and stern doors

2.1.1 Design forces (1/1/2009)The design external forces FE and the design internal forcesFI to be considered for the scantlings of primary supportingmembers and securing and supporting devices of side doorsand stern doors are to be obtained, in kN, from the formu-lae in Tab 1.

3 Scantlings of side doors and stern doors

3.1 General3.1.1 (1/1/2009)The strength of side doors and stern doors is to be commen-surate with that of the surrounding structure.

3.1.2 (1/1/2009)Side doors and stern doors are to be adequately stiffenedand means are to be provided to prevent any lateral or verti-cal movement of the doors when closed.

Adequate strength is to be provided in the connections ofthe lifting/manoeuvring arms and hinges to the door struc-ture and to the Yacht's structure.

3.1.3 (1/1/2009)Shell door openings are to have well rounded corners andadequate compensation is to be arranged with web framesat sides and stringers or equivalent above and below.

3.2 Plating and ordinary stiffeners

3.2.1 Plating (1/1/2009)The thickness of the door plating is to be not less than thatobtained according to the requirements for side plating,using the door stiffener spacing.

3.2.2 Ordinary stiffeners (1/1/2009)The scantling of door ordinary stiffeners is to be not lessthan that obtained according to the requirements for theside, using the door stiffener spacing.

Pt B, Ch 1, App 1


Table 1 : Design forces (1/1/2009)

Consideration is to be given, where necessary, to differ-ences in conditions of fixity between the ends of ordinarystiffeners of doors and those of the side.

3.3 Primary supporting members3.3.1 (1/1/2009)The door ordinary stiffeners are to be supported by primarysupporting members constituting the main stiffening of thedoor.

3.3.2 (1/1/2009)The primary supporting members and the hull structure inway are to have sufficient stiffness to ensure structural integ-rity of the boundary of the door.

3.3.3 (1/1/2009)Scantlings of primary supporting members are generally tobe verified through direct calculations on the basis of thedesign loads in Tab 1 and the strength criteria given in [5].

In general, isolated beam models may be used to calculatethe loads and stresses in primary supporting members,which are to be considered as having simply supported endconnections.

4 Securing and supporting of doors

4.1 General4.1.1 (1/1/2009)Side doors and stern doors are to be fitted with adequatemeans of securing and supporting so as to be commensu-rate with the strength and stiffness of the surrounding struc-ture.

4.1.2 (1/1/2009)The number of securing and supporting devices is generallyto be the minimum practical while taking into account therequirements for redundant provision given in [4.2.3] andthe available space for adequate support in the hull struc-ture.

4.2 Scantlings

4.2.1 (1/1/2009)

Securing and supporting devices are to be adequatelydesigned so that they can withstand the reaction forceswithin the allowable stresses defined in [5].

4.2.2 (1/1/2009)

When the securing and supporting devices are equallyspaced, the distribution of the forces acting on each devicemay be obtained by dividing the total design force given in[2.1.1] by the number of the supporting devices.

For arrangements of the securing and supporting devicesdifferent from the above, a direct calculations may be nec-essary to assess the distribution of the forces acting on thedevices.

Special consideration will be given by RINA when thedimension of the opening is significant compared with thedepth of the vessel: the distribution of the forces acting onthe securing and supporting devices may need to be sup-ported by direct calculation taking into account the flexibil-ity of the hull structure and the actual position of thesupports.

4.2.3 (1/1/2009)

The arrangement of securing and supporting devices in wayof these securing devices is to be designed with redundancyso that, in the event of failure of any single securing or sup-porting device, the remaining devices are capable of with-standing the reaction forces without exceeding by morethan 20% the allowable stresses defined in [5].

4.2.4 (1/1/2009)

All load transmitting elements in the design load path, fromthe door through securing and supporting devices into theship's structure, including welded connections, are to be ofthe same strength standard as required for the securing andsupporting devices. These elements include pins, support-ing brackets and back up brackets.

Structural elements External force FE , in kN Internal force FI, in kN

Securing and supporting devices of doors opening inwards A pE + FP F0+ 10 W

Securing and supporting devices of doors opening outwards A pE F0 + 10 W + FP

Primary supporting members (1) A pE F0 + 10 W

(1) The design force to be considered for the scantlings of the primary supporting members is the greater of FE and FI. Note 1: A : Area, in m2 to be determined on the basis of the load area taking account of the direction of the pressure W : Mass of the door, in t FP : Total packing force, in kN; the packing line pressure is normally to be taken not less than 5 kN /m F0 : the greater of FC and 5A, in kN FC : Accidental force, in kN, due to loose cargoes etc., to be uniformly distributed over the area A.The aforementioned value is to be assumed considering the failure of the lashing of the objects to be carried in the space behind the doors: in such case Fc is to be assumed not less than the weight in KN of the heaviest object to be carried in the space behind the doors.However, the value of FC may be taken as zero, provided an additional structure such as an inner ramp is fitted, which is capable of protecting the door from accidental forces due to loose cargoes.pE : Design pressure for the side shell (Ch 1, Sec 1, [4]) not to be taken less than 25 kN/m2

Pt B, Ch 1, App 1


5 Strength criteria

5.1 Primary supporting members and secur-ing and supporting devices

5.1.1 Plastic reinforced structures (1/1/2009)

The allowable normal and shear stress are to be in conform-ity with the requirements stated in Ch 4, Sec 1, [4].

5.1.2 Steel structures (1/1/2009)

It is to be checked that the normal stress σ, the shear stress tand the equivalent stress σVM, induced in the primary sup-porting members and in the securing and supportingdevices of doors by the design forces defined in [2.1.1], arein compliance with the following formulae:

σ ≤ σALL

σVM = (σ2 + τ2)0,5 ≤ σVM,ALL

where:

σALL : Allowable normal stress, in N/mm2;

σALL = 120 / k;

τALL : Allowable shear stress, in N/mm2;

τALL = 80 / k;

σVM,ALL : Allowable equivalent stress, in N/mm2;

σVM,ALL = 150 / k;

k : Material factor, defined in Ch 2, Sec 2, [2.3].

5.1.3 Pins (1/1/2009)

Pins in securing and supporting devices are to be checkedfor shear stress τ and normal stress σ due to bendingmoment using the above criteria.

Where:

τ = 103 F/(2 n A) N/mm2

σ = 5,1 103 (F l /n d3) N/mm2

and:

F : design force, in KN, defined in [2.1.1];

n : number of fixed bearings supporting the pin;

A : cross-sectional area of the pin in mm2;

l : distance between two consecutive fixed bearings in mm;

d : diameter of the pin in mm.

If the radial clearance between pin and bearing and theaxial clearance between two consecutive bearings of thepins are small and l is nearly equal to d, the normal stressdue to bending moment can be disregarded.

5.1.4 Bearings (1/1/2009)

For steel to steel bearings in securing and supportingdevices, it is to be checked that the nominal bearing pres-sure.

σB, in N/mm2, is in compliance with the following formula:

σB = 0,8 ReH,B

where:

σB = 10 F/ AB

with:

F : Design force, in KN, defined in [2.1.1]

AB : Projected bearing area, in cm2

ReH,B : Yield stress, in N/mm2, of the bearing material.

For other bearing materials, the allowable bearing pressureis to be determined according to the Manufacturer's specifi-cation.

5.1.5 Bolts (1/1/2009)

The arrangement of securing and supporting devices is to besuch that threaded bolts do not carry support forces.

It is to be checked that the stress σT in way of threads ofbolts not carrying support forces is in compliance with thefollowing formula:

σT ≤ σT,ALL

where:

σT,ALL : Allowable tension in way of threads of bolts, inN/mm2;

σT,ALL = 125 / k;

k : Material factor, defined in Ch 2, Sec 2, [2.3].

6 Securing and locking arrangement

6.1 Systems for operation

6.1.1 (1/1/2009)Securing devices are to be simple to operate and easilyaccessible.

Securing devices are to be equipped with a mechanicallocking arrangement (self-locking or separate arrangement),or to be of the gravity type.

The opening and closing systems as well as securing andlocking devices are to be interlocked in such a way thatthey can only operate in the proper sequence.

6.1.2 (1/1/2009)Doors with a clear opening area equal to or greater than 10m2 are to be provided with closing devices operable from aremote control position above the freeboard deck.

This remote control is provided for the:

• closing and opening of the doors

• associated securing and locking devices.

For doors which are required to be equipped with a remotecontrol arrangement, indication of the open/closed positionof the door and the securing and locking device is to beprovided at the remote control stations.

The operating panels for operation of doors are to be inac-cessible to unauthorised persons.

A notice plate, giving instructions to the effect that all secur-ing devices are to be closed and locked before leaving har-bour, is to be placed at each operating panel and is to besupplemented by warning indicator lights.

6.1.3 (1/1/2009)

Where hydraulic securing devices are applied, the system isto be mechanically lockable in the closed position.

Pt B, Ch 1, App 1


This means that, in the event of loss of hydraulic fluid, thesecuring devices remain locked.

When in closed position, the hydraulic system for securingand locking devices is to be isolated from other hydrauliccircuits.

7 Operating and Maintenance Manual

7.1 General7.1.1 (1/1/2009)An Operating and Maintenance Manual (OMM) for the sidedoors and stern doors is to be provided on board and con-tain necessary information on:

a) special safety precautions

b) service conditions

c) maintenance.This manual is to be submitted in duplicate to the Societyfor information.

7.1.2 (1/1/2009)Documented operating procedures for closing and securingthe side and stern doors are to be kept on board and postedat an appropriate place.


Part BHull

Chapter 2

STEEL HULLS

SECTION 1 GENERAL REQUIREMENTS

SECTION 2 MATERIALS

SECTION 3 WELDING AND WELD CONNECTIONS

SECTION 4 LONGITUDINAL STRENGHT

SECTION 5 PLATING

SECTION 6 SINGLE BOTTOM

SECTION 7 DOUBLE BOTTOM

SECTION 8 SIDE STRUCTURES

SECTION 9 DECKS

SECTION 10 BULKHEADS

SECTION 11 SUPERSTRUCTURES

Pt B, Ch 2, Sec 1



1 Field of application

1.1

1.1.1 Chapter 2 applies to monohull yachts with a hullmade of steel and a length L not exceeding 120 m, withmotor or sail power with or without an auxiliary engine.

For yachts made of steel and having length L greater than120 m, reference is to be made to the Rules for the Classsifi-cation of Ships.

Multi-hulls or yachts with unusual shape, proportion andcharacteristics will be considered case by case.

In the examination of constructional plans, RINA may takeinto consideration material distribution and structural scant-lings other than those that would be obtained by applyingthese regulations, provided that structures with longitudinal,transverse and local strength not less than that of the corre-sponding Rule structure are obtained or provided that suchmaterial distribution and structural scantlings prove ade-quate, in the opinion of RINA, on the basis of direct test cal-culations of the structural strength (see Pt B, Ch1, Sec 1,para 3.1).

The structural scantlings of displacement yachts of L > 60 mmay be arranged by applying the provisions of the Rules forthe Classification of Ships.

This Chapter may also be used to check the structural scant-lings of hulls made of metals with superior mechanicalproperties, other than steel, such as titanium and its alloys.

In general the following types are considered usable in thefield of pleasure yachts:

• titanium: TiCP2, TiCP3, TiCP4;

• titanium alloys: Ti6AL4V grade 5, Ti5AL2.5Sn grade 6and Ti3AL2.5V grade 9.

For the scantlings of the plating and stiffeners, a coefficientK depending on the minimum yield strength of the materialused, is to be adopted.

The value of the minimum yield strength is, however, to benot more than 0,7 of the ultimate tensile strength of thematerial.

Higher values may be adopted, at the discretion of RINA,on condition that additional buckling strength and fatiguecalculations are carried out.

In any case use of these materials is subject to the examina-tion of the technical documentation of the manufacture ofthe material and the welding processes and tests that will beadopted.


2.1 Premise

2.1.1 The definitions and symbols in this Article are validfor all the Sections of this Chapter.

The definitions of symbols having general validity are notnormally repeated in the various Sections, whereas themeanings of those symbols which have specific validity arespecified in the relevant Sections.

2.2 Definitions and symbols

2.2.1

L : scantling length, in m, on the full load water-line, assumed to be equal to the length on thefull load waterline with the yacht at rest;

B : maximum breadth of the yacht, in m, outsideframes; in tests of the longitudinal strength oftwin hull yachts, B is to be taken as equal totwice the breadth of the single hull, measuredimmediately below the cross-deck;

D : depth of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line up to the deck beam of the upper-most continuous deck;

T : draft of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line to the full load waterline with theyacht at rest in calm water;

s : spacing of the ordinary longitudinal or trans-verse stiffener, in m;

Δ : displacement of the yacht outside frames, in t, atdraught T;

K : factor as a function of the mechanical propertiesof the steel used, as defined in Sec 2.

3 Plans, calculations and other infor-mation to be submitted

3.1

3.1.1 Table 1 lists the structural plans that are to be pre-sented in advance to RINA in triplicate, for examination andapproval when required.

The Table also indicates the information that is to be sup-plied with the plans or, in any case, submitted to RINA forthe examination of the documentation.

Pt B, Ch 2, Sec 1


For documentation purposes, copies of the following plansare also to be submitted:

- general arrangement plans;

- capacity plan;

- lines plan;

Table 1

If the INWATERSURVEY notation is to be assigned, the fol-lowing plans and information are to be submitted:

• details showing how rudder pintle and bush clearancesare to be measured and how the security of the pintlesin their sockets is to be verified with the craft afloat.

• details showing how stern bush clearances are to bemeasured with the craft afloat.

• name and characteristics of high resistance paint, forinformation only.

3.23.2.1 If a Builder for the construction of a new vessel of a stand-ard design wants to use drawings already approved for avessel similar in design and construction and classed withthe same class notation and the same navigation, the draw-ings may not be sent for approval, but the request for surveyof the vessel is to be submitted with an enclosed list ofdrawings of reference and copies of the approved drawingsare to be sent to RINA.

Attention is also to be paid to possible flag Administrationsrequirements, which may determine differences in con-struction.

It is the Builder’s responsibility to submit for approval anymodification to the approved plans prior to the commence-ment of any work.

Plan approval of standard design vessels is only valid solong as no applicable Rule changes take place. When theRules are amended, the plans are to be submitted for newapproval.

4 Direct calculations

4.1

4.1.1 As an alternative to those based on the formulae inthis Chapter, scantlings may be obtained by direct calcula-tions carried out in accordance with the provisions of Chap-ter 1 of Part B of these Rules.

Chapter 1 provides schematisations, boundary conditionsand loads to be used for direct calculations.

The scantlings are to be such as to guarantee that stress lev-els do not exceed the allowable values stipulated in theaforementioned Chapter.

4.2

4.2.1 In the case of use of materials with superior mechan-ical properties, other than steel, such as those indicated in1.1, the allowable stresses will be stipulated by RINA on thebasis of such properties and of any further fatigue testsand/or buckling checks which may be required.

5 Buckling strength checks

5.1 Application

5.1.1 Where required, the critical buckling strength ofsteel plating and stiffeners subject to compressive stresses isto be calculated as specified below.

5.2 Elastic buckling stresses of plates

5.2.1 Compressive stressThe elastic buckling strength, in N/mm2, is given by:

where:

PLANCONTAINING INFORMA-

TION RELEVANT TO:

• Midship section • main dimensions, maxi-mum operating speed V,design acceleration aCG (forplaning or semi-planingyachts)

• materials and associatedmechanical properties

• for yachts having L>50 m,if mono-hull and L> 40 m,if multi-hull, the maxi-mum still water bendingmoment is to be indicated

• displacement

• Longitudinal and trans-verse section

• Plan of the decks • openings• loads acting, if different

from Rule loads

• Shell expansion • openings

• Structure of the engineroom

• Watertight bulkheads and deep tank bulkheads

• openings• location of overflow

• Structure of stern/side door

• closing appliances

• Superstructures

• Support structure for crane

• design loads and connec-tions to the hull structures

• Rudder • materials of all compo-nents

• calculation speed

• Propeller shaft struts • material

σE 0 9 mc Et

1000 a⋅--------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=

Pt B, Ch 2, Sec 1


to compressive stress

or:

with stiffeners perpendicular to compressivestress

E : Young's modulus, in N/mm2, to be taken equalto 2,06 . 105N/mm2 for steelstructures

t : thickness of plating, in mm

a : shorter side of the plate, in m

b : longer side of the plate, in m

c : coefficient equal to:

• 1,30 when the plating is stiffened by floorsor deep girders

• 1,21 when the plating is stiffened by ordi-nary stiffeners with angle- or T-sections

• 1,10 when the plating is stiffened by ordi-nary stiffeners with bulb sections

• 1,05 when the plating is stiffened by flat barordinary stiffeners.

ψ : ratio between the smallest and largest compres-sive stresses when the stress presents a linearvariation across the plate (0<ψ <1).

5.2.2 Shear stressThe elastic buckling stress, in N/mm2, is given by:

where:

and E, t, a and b are as defined in (a) above.

5.3 Elastic buckling stresses of stiffeners

5.3.1 Column buckling without rotation of the transverse section

For the column buckling mode (perpendicular to the planeof plating) the elastic buckling stress, in N/mm2, is given by:

E : Young's modulus, in N/mm2, to be taken equalto 2,06 . 105 N/mm2 for steelstructures

Ia : moment of inertia, in cm4, of the stiffener,including plate flange

A : cross-sectional area, in cm2, of the stiffener,including plate flange

I : span, in m, of the stiffener.

5.3.2 Torsional bucklingFor the torsional mode, the elastic buckling stress, inN/mm2, is given by:

where:E, I : defined in 5.3.1 above

m : number of half-waves, given in Table 2.

Table 2

It : St. Venant moment of inertia of profile, in cm444 without plate flange, equal to:

or:

for flanged profileIp : polar moment of inertia of profile, in cm4, about

connection of stiffener to plate, equal to:

or:

IW : sectional moment of inertia of profile, in cm6,about connection of stiffener to plate, equal to:

or:

for flanged profiles.where:hW : web height, in mmtW : web thickness, in mmbf : flange width, in mmtf : flange thickness, in mm; for bulb profiles, the

mean thickness of the bulb maybe usedC : spring stiffness factor, exerted by supporting

plate, equal to:

where:t : plating thickness, in mm,s : spacing of stiffeners, in m,

mC8 4,

ψ 1 1,+--------------------= fo r p la ting with sti ffeners parallel

mC c 1ab---

⎝ ⎠⎛ ⎞

2

+⋅=2 2 1,

ψ 1 1,+-------------------- for plating⋅

τE 0 9 mt E t1000 a⋅--------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=

mt 5 34 4 ab---

2

⋅+,=

σE 0 001 EIa

A I2⋅------------⋅ ⋅,=

0<C<1 4<C<36 36<C<144 (m-1) m<C<m (m+1)

m 1 2 3 m

σEπ2 E IW⋅ ⋅104 Ip I2⋅ ⋅------------------------- m2 CK

m2-------+

⎝ ⎠⎛ ⎞ 0 385 E It

Ip

---⋅ ⋅,+⋅=

CKC I4⋅

π4 E IW⋅ ⋅---------------------- 106⋅=

hw tw3⋅

3--------------- 10 4– for flat bars⋅

13--- hw tw

3 bf tf3 1 0 63 tf

bf

----⋅,–⎝ ⎠⎛ ⎞⋅ ⋅+⋅ 10 4–⋅ ⋅

hw3 tw

3⋅3

---------------- 10 4– for f lat bars⋅

hw3 tw⋅3

--------------- hw2 bf tf⋅ ⋅+

⎝ ⎠⎛ ⎞ 10 4– for flanged profiles⋅

hw3 tw

3⋅36

---------------- 10 6– for f lat bars⋅

tf b⋅ f3 hw

2⋅12

------------------------ 10 6– for T profi les⋅

bf3 hw

2⋅12 bf hw+( )2⋅----------------------------------- tf[ bf

2 2bf hw 4hw2+⋅+( ) 3tw bf hw ] 10 6–⋅ ⋅ ⋅( )+⋅⋅

kp E t3⋅ ⋅

3s 11 33 kp hw t3⋅ ⋅ ⋅,

1000 s tw3⋅ ⋅

-----------------------------------------+⎝ ⎠⎛ ⎞⋅

-------------------------------------------------------------------- 10 3–⋅

Pt B, Ch 2, Sec 1


kp : 1 -ηp , not to be taken less than 0,

ηp : σp / σEp

σa : calculated compressive stress in the stiffenerσEp : elastic buckling stress of plating as calculated in

5.2.1.

5.3.3 Web bucklingThe elastic buckling stress, in N/mm2, is given by:

where:E : defined in 5.3.1tW, hW : defined in 5.3.2.

5.4 Critical buckling stress

5.4.1 Compressive stressThe critical buckling stress in compression, σC, for platingand stiffeners is given by:

where:ReH : minimum yield stress of steel used, in N/mm2

σE : elastic buckling stress calculated according to5.2.1 and 5.3.2.

5.4.2 Shear stressThe critical buckling shear stress τC, for plating and stiffen-ers is given by:

where:τC : 0,58 Reh

Reh : minimum yield stress of steel used, in N/mm2

τE : elastic buckling stress calculated according to5.2.2.

6 General rules for design

6.1

6.1.1 The hull scantlings required in this Chapter are ingeneral to be maintained throughout the length of the hull.

For yachts with length L greater than 50 m, reduced scant-lings may be adopted for the fore and aft zones, providedthat they are no less than those shown in Table 3.

In such case the variations between the scantlings adoptedfor the central part of the hull and those adopted for theends are to be gradual.

In the design, care is to be taken in order to avoid structuraldiscontinuities in particular in way of the ends of super-structures and of the openings on the deck or side of theyacht.

For yachts similar in performance to high speed hulls, a lon-gitudinal structure with reinforced floors, placed at a dis-tance of not more than 2 m, is required for the bottom.

Such interval is to be suitably reduced in the areas forwardof amidships subject to the forces caused by slamming.

7 Minimum thicknesses

7.1

7.1.1 The thicknesses of plating and stiffeners calculatedusing the formulae in this Chapter are to be not less than thevalues shown in Table 3.

Lesser thicknesses may be accepted provided that, in theopinion of RINA, their adequacy in terms of bucklingstrength and resistance to corrosion is demonstrated.

Where plating and stiffeners contribute to the longitudinalstrength of the yacht, their scantlings are to be such as tofulfil the requirements for yacht longitudinal strength stipu-lated in Sec 4.

σE 3 8 E tw

hw

------⎝ ⎠⎛ ⎞

2

⋅ ⋅,=

σc σE= i f σEReH

2--------≤

σc ReH 1ReH

4 σe⋅-------------–

⎝ ⎠⎛ ⎞⋅= i f σE

ReH

2-------->

τc τE= i f τEτF

2----≤

τc τF 1 τF

4 τe⋅------------–

⎝ ⎠⎛ ⎞⋅= i f τE

τF

2---->

Pt B, Ch 2, Sec 1


Table 3

8 Plating attached to griders

8.1 Primary supporting members

8.1.1 The section modulus and the moment of inertia ofprimary supporting members are to be calculated in associ-ation with an effective area AS, in cm2, of attached loadbearing plating obtained from the following:

where:

where:

Girders : primary supporting members of ordinary stiffen-ers such as deck girders, beams and webframes, side stringers, vertical and horizontalgirders of bulkheads, floors, centre and side bot-tom girders, and similar.

Ordinary stiffeners: supporting members of shell plating,decks, double bottom or tank top plating, bulk-heads, and similar.

SL : overall length of the girder, in m

bF : actual width of the load bearing plating, i.e.one-half of the sum of the spaces between par-allel stiffeners adjacent to that considered, in m

ts : mean thickness, in mm, of the attached plating

As : area of the attached plating, in cm2

ta : web thickness, in mm, in built sections

da : web depth in built sections, measured betweenthe inside of the face plate and the inside of theattached plating, in mm

8.2 Ordinary stiffeners

8.2.1 Unless otherwise stated in specific requirements, thesection modulus and the moment of inertia of the ordinarystiffeners are to be calcolated in association with an effec-tive load bearing plating having width equal to the spacingof the stiffeners and thickness equal to the mean thicknessof the attached plating.

8.3 Special cases

8.3.1 In way of fore and aft regions and, in general, wherethe web of the section is at an angle α less than 90° to theattached plating, the section modulus shall be calculatedtaking account of the inclination of the attached plating.

Where the above angle α is less than 75°, the section mod-ulus of the stiffener may be approximately calculated bymultiplying the section modulus of the web fitted at rightangles to the attached plating by cos (90 - α).

8.4 Calculation of section modulus

8.4.1 Primary supporting members

The section modulus WT, in cm3, of a built section withattached plating of area AS, in cm2, may be calculated usingthe following formula:

In cases of symmetrical sections, the section modulus maybe calculated as follows:

As a rule AS is to be greater than Ap; in this respect, thethickness of the attached plating is to be increased accord-ingly where necessary.

Aa : web area, in cm2, in built sections

bp : face plate width, in mm, in built sections

Aa : face plate area, in cm2, in built sections

In the case of members located along the edge of openings,the effective area of the attached plating is to be assumedequal to 7/10 of the value of AS calculated by assuming bF

equal to half the distance between the member consideredand its adjacent member.

MemberMinimum thickness

(mm)

Keel, bottom plating t1 = 1,35 . L1/3 . K0,5

Side plating t2 = 1,15 . L1/3 . K0,5

Open strength deck plating t3 = 1,15 . L1/3 . K0,5

Lower and enclosed deck plating t4 = t3 - 0,5

1st tier superstructure front bulkhead t5 = t4

Superstructure bulkhead t6 = t5 - 1

Watertight subdivision bulkhead t7 = t2 - 0,5

Tank bulkhead t8 = t2

Centre girder t9 = 1,75 . L1/3 . K0,5

Floors and side girders t10 = 1,30 . L1/3 . K0,5

Tubular pillars 0,03 d . K0,5 > 3,0 (1)

(1) d = diameter of the pillar, in mm

AS 10c bF tS⋅ ⋅=

for SL bF 8 : c<⁄ 0 25, SL

bF

-----⎝ ⎠⎛ ⎞ 0 016, SL

bF

-----⎝ ⎠⎛ ⎞

2

⋅–⋅=

for SL bF 8 : c≥⁄ 1=

WTAp da⋅

10----------------

tS da2⋅

6000-------------- 1

200 AS Ap–( )⋅200AS ta da⋅+-------------------------------------+

⎝ ⎠⎛ ⎞⋅+=

WTAP dA⋅

10----------------

ta d2a⋅

6000----------------+=

Pt B, Ch 2, Sec 1


9 Corrosion protection

9.1

9.1.1 All steel structures, with the exception of fuel tanks,are to be suitably protected against corrosion.

Such arrangements may consist of coating or, where appli-cable, cathodic protection.

The structures are to be clean and free from slag before thecoating is applied.

9.2

9.2.1 When a primer is used after the preparation of thesurfaces and prior to welding, as well as not impairing the

latter the composition of the primer is to be compatible withthe subsequent layers of the coating cycle.

The coating is to be applied with adequate thickness inaccordance with the Manufacturer's specifications.

9.3

9.3.1 Paint or other products containing nitrocellulose orother highly flammable substances are not to be used inmachinery or accommodation spaces.

Pt B, Ch 2, Sec 2


SECTION 2 MATERIALS

1 General

1.1 Characteristics of materials

1.1.1 The characteristics of the materials to be used in theconstruction of ships are to comply with the applicablerequirements of Part D.

1.1.2 Materials with different characteristics may beaccepted, provided their specification (manufacture, chemi-cal composition, mechanical properties, welding, etc.) issubmitted to the Society for approval.

1.2 Testing of materials

1.2.1 Materials are to be tested in compliance with theapplicable requirements of Part D.

1.3 Manufacturing processes

1.3.1 The requirements of this Section presume that weld-ing and other cold or hot manufacturing processes are car-ried out in compliance with current sound working practiceand the applicable requirements of Part D. In particular:

• parent material and welding processes are to beapproved within the limits stated for the specified typeof material for which they are intended

• specific preheating may be required before welding

• welding or other cold or hot manufacturing processesmay need to be followed by an adequate heat treatment.

2 Steels for hull structure

2.1 Application

2.1.1 Tab 1 gives the mechanical characteristics of steelscurrently used in the construction of ships.

2.1.2 Higher strength steels other than those indicated inTab 1 are considered by the Society on a case by case basis.

2.1.3 When steels with a minimum guaranteed yield stressReH other than 235 N/mm2 are used on a ship, hull scant-lings are to be determined by taking into account the mate-rial factor k defined in [2.3].

2.1.4 Characteristics of steels with specified through thick-ness properties are given in Pt D, Ch 2, Sec 1, [7].

2.2 Information to be kept on board

2.2.1 A plan is to be kept on board indicating the steeltypes and grades adopted for the hull structures. Where

steels other than those indicated in Tab 1 are used, theirmechanical and chemical properties, as well as any work-manship requirements or recommendations, are to be avail-able on board together with the above plan.

2.2.2 It is also recommended that a plan is kept on boardindicating the hull structures built in normal strength steelof grades D or E.

Table 1 : Mechanical properties of hull steels

2.3 Material factor k

2.3.1 General

Unless otherwise specified, the material factor k has the val-ues defined in Tab 2, as a function of the minimum guaran-teed yield stress ReH.

For intermediate values of ReH , k may be obtained by linearinterpolation.

Steels with a yield stress lower than 235 N/mm2 or greaterthan 390 N/mm2 are considered by the Society on a case bycase basis.

Table 2 : Material factor k

Steel gradesMinimum yield

stress ReH, in N/mm2

Ultimate minimum tensile strength Rm,

in N/mm2

A-B-D-Et ≤ 100mm

235 400 - 520

AH32-DH32-EH32t ≤ 100mmFH32t ≤ 50mm

315 440 - 590

AH36-DH36-EH36t ≤ 100mmFH36t ≤ 50mm

355 490 - 620

AH40-DH40-EH40 FH40t ≤ 50mm

390 510 - 650

Note 1:Reference in Part D: Pt D, Ch 2, Sec 1, [2]

ReH , in N/mm2 k

235 1

315 0,78

355 0,72

390 0,70

Pt B, Ch 2, Sec 2


2.4 Grades of steel

2.4.1 For the purpose of the selection of steel grades to beused for the various structural members, the latter aredivided into categories (SECONDARY, PRIMARY and SPE-CIAL), as indicated in Tab 3.

Tab 3 also specifies the classes (I, II and III) of the materialsto be used for the various categories of structural members.

2.4.2 Materials are to be of a grade not lower than thatindicated in Tab 4 depending on the material class andstructural member gross thickness.

2.4.3 For strength members not mentioned in Tab 3, gradeA/AH may generally be used.

2.4.4 In specific cases, such as [2.4.5], with regard tostress distribution along the hull girder, the classes requiredwithin 0,4L amidships may be extended beyond that zone,on a case by case basis.

2.4.5 The material classes required for the strength deckplating, the sheerstrake and the upper strake of longitudinalbulkheads within 0,4L amidships are to be maintained foran adequate length across the poop front and at the ends ofthe bridge, where fitted.

Table 3 : Application of material classes and grades (1/7/2004)

Table 4 : Material grade requirementsfor classes I, II and III

2.4.6 Rolled products used for welded attachments on hullplating, such as gutter bars and bilge keels, are to be of thesame grade as that used for the hull plating in way.

Where it is necessary to weld attachments to the sheerstrakeor stringer plate, attention is to be given to the appropriatechoice of material and design, the workmanship and weld-ing and the absence of prejudicial undercuts and notches,with particular regard to any free edges of the material.

2.4.7 In the case of grade D plates with a nominal thick-ness equal to or greater than 36 mm, or in the case of gradeDH plates with a nominal thickness equal to or greater than31 mm, the Society may, on a case by case basis, requirethe impact test to be carried out on each original “rolledunit”, where the above plates:

• either are to be placed in positions where high localstresses may occur, for instance at breaks of poop andbridge, or in way of large openings on the strength deckand on the bottom, including relevant doublings, or

• are to be subjected to considerable cold working.

Structural member categoryMaterial class or grade

Within 0,4L amidships

Outside 0,4L amidships

SECONDARY:• Longitudinal bulkhead strakes, other than that belonging to the Primary category• Deck plating exposed to weather, other than that belonging to the Primary or Special category• Side plating

I A / AH

PRIMARY:• Bottom plating (including keel plate)• Strength deck plating, excluding that belonging to the Special category• Continuous longitudinal members above strength deck• Uppermost strake in longitudinal bulkhead

II A / AH

SPECIAL:• Sheerstrake at strength deck • Stringer plate in strength deck• Deck strake at longitudinal bulkhead• Bilge strake

III II(I outside

0,6L amid-ships)

Note 1:Plating materials for sternframes, rudders, rudder horns and shaft brackets are generally to be of grades not lower than those corresponding to class II.For rudder and rudder body plates subjected to stress concentrations (e.g. in way of lower support of semi-spade rudders or at upper part of spade rudders) class III is to be applied.Note 2:Bedplates of seats for propulsion and auxiliary engines inserted in the inner bottom are to be of class I. In other cases, the steel may generally be of grade A. Different grades may be required by the Society on a case-by-case basis.

Class I II III

Gross thick-ness, in mm

NSS HSS NSS HSS NSS HSS

t ≤ 15 A AH A AH A AH

15 < t ≤ 20 A AH A AH B AH

20 < t ≤ 25 A AH B AH D DH

25 < t ≤ 30 A AH D DH D DH

30 < t ≤ 35 B AH D DH E EH

35 < t ≤ 40 B AH D DH E EH

40 < t ≤ 50 D DH E EH E EH

Note 1:“NSS” and “HSS” mean, respectively: “Normal Strength Steel” and “Higher Strength Steel”.

Pt B, Ch 2, Sec 2


2.4.8 In the case of full penetration welded joints locatedin positions where high local stresses may occur perpendic-ular to the continuous plating, the Society may, on a case bycase basis, require the use of rolled products having ade-quate ductility properties in the through thickness direction,such as to prevent the risk of lamellar tearing (Z type steel,see Part D).

2.5 Grades of steel for structures exposed to low air temperatures

2.5.1 For ships intended to operate in areas with low airtemperatures (-20°C or below), e.g. regular service duringwinter seasons to Arctic or Antarctic waters, the materials inexposed structures are to be selected based on the designtemperature tD, to be taken as defined in [2.5.2].

2.5.2 The design temperature tD is to be taken as the low-est mean daily average air temperature in the area of opera-tion, where:

Mean : Statistical mean over observation period (at least20 years)

Average : Average during one day and night

Lowest : Lowest during one year

Fig 1 illustrates the temperature definition.

For seasonally restricted service, the lowest value within theperiod of operation applies.

2.5.3 For the purpose of the selection of steel grades to beused for the structural members above the lowest ballastwaterline and exposed to air, the latter are divided into cat-

egories (SECONDARY, PRIMARY and SPECIAL), as indi-cated in Tab 5.Tab 5 also specifies the classes (I, II and III) of the materialsto be used for the various categories of structural members.

For non-exposed structures and structures below the lowestballast waterline, see [2.4].

Figure 1 : Commonly used definitions of temperatures

Table 5 : Application of material classes and grades to structures exposed to low air temperatures

Mean daily maximum temperature

Mean daily average temperature

tD = design temperature

Mean daily minimum temperature

Structural member categoryMaterial class

Within 0,4L amidships Outside 0,4L amidships

SECONDARY:Deck plating exposed to weather (in general)Side plating above TB (1)Transverse bulkheads above TB (1)

I I

PRIMARY:Strength deck plating (2)Continuous longitudinal members above strength deck Longitudinal bulkhead above TB (1)

II I

SPECIAL:Sheerstrake at strength deck Stringer plate in strength deck Deck strake at longitudinal bulkhead

III II

(1) TB is the draught in light ballast condition.(2) Plating at corners of large hatch openings to be considered on a case by case basis.

Class III or grade E/EH to be applied in positions where high local stresses may occur.Note 1:Plating materials for sternframes, rudder horns, rudders and shaft brackets are to be of grades not lower than those corre-sponding to the material classes in [2.4].

Pt B, Ch 2, Sec 2


2.5.4 Materials may not be of a lower grade than that indi-cated in Tab 6 to Tab 8 depending on the material class,structural member gross thickness and design temperaturetD.

For design temperatures tD < -55°C, materials will be spe-cially considered by the Society on a case by case basis.

2.5.5 Single strakes required to be of class III or of gradeE/EH of FH are to have breadths not less than (800+5L) mm,but not necessarily greater than 1800 mm.

2.6 Grades of steel within refrigerated spaces

2.6.1 For structural members within or adjacent to refriger-ated spaces, when the design temperature is below 0°C, thematerials are to be of grades not lower than those indicatedin Tab 9, depending on the design temperature, the struc-tural member gross thickness and its category (as defined inTab 3).

2.6.2 Unless a temperature gradient calculation is carriedout to assess the design temperature and the steel grade inthe structural members of the refrigerated spaces, the tem-peratures to be assumed are specified below:

• temperature of the space on the uninsulated side, forplating insulated on one side only, either with uninsu-lated stiffening members (i.e. fitted on the uninsulatedside of plating) or with insulated stiffening members (i.e.fitted on the insulated side of plating)

• mean value of temperatures in the adjacent spaces, forplating insulated on both sides, with insulated stiffeningmembers, when the temperature difference between theadjacent spaces is generally not greater than 10 °C(when the temperature difference between the adjacentspaces is greater than 10°C, the temperature value isstipulated by the Society on a case by case basis)

• in the case of non-refrigerated spaces adjacent to refrig-erated spaces, the temperature in the non-refrigeratedspaces is to be conventionally taken equal to 0°C.

2.6.3 Situations other than those mentioned in [2.6.1] and[2.6.2] or special arrangements will be considered by theSociety on a case by case basis.

2.6.4 Irrespective of the provisions of [2.6.1], [2.6.2] andTab 9, steel having grades lower than those required in[2.4], Tab 3 and Tab 4, in relation to the class and grossthickness of the structural member considered, may not beused.

Table 6 : Material grade requirements for class I at low temperatures

Gross thickness, in mm

-20°C / -25°C -26°C / -35°C -36°C / -45°C -46°C / -55°C

NSS HSS NSS HSS NSS HSS NSS HSS

t ≤ 10 A AH B AH D DH D DH

10 < t ≤ 15 B AH D DH D DH D DH

15 < t ≤ 20 B AH D DH D DH E EH

20 < t ≤ 25 D DH D DH D DH E EH

25 < t ≤ 30 D DH D DH E EH E EH


35 < t ≤ 45 D DH E EH E EH φ FH

45 < t ≤ 50 E EH E EH φ FH φ FH

Note 1:“NSS” and “HSS” mean, respectively, “Normal Strength Steel” and “Higher Strength Steel”.Note 2:“φ” = not applicable.

Pt B, Ch 2, Sec 2


Table 7 : Material grade requirements for class II at low temperatures

Table 8 : Material grade requirements for class III at low temperatures

Table 9 : Material grade requirements for members within or adjacent to refrigerated spaces

3 Steels for forging and casting

3.1 General

3.1.1 Mechanical and chemical properties of steels forforging and casting to be used for structural members are tocomply with the applicable requirements of Part D.

3.1.2 Steels of structural members intended to be weldedare to have mechanical and chemical properties deemedappropriate for this purpose by the Society on a case bycase basis.

3.1.3 The steels used are to be tested in accordance withthe applicable requirements of Part D.

3.2 Steels for forging

3.2.1 For the purpose of testing, which is to be carried outin accordance with the applicable provisions of Part D, theabove steels for forging are assigned to class 1 (see Pt D,Ch 2, Sec 3, [1.2]).


-20°C / -25°C -26°C / -35°C -36°C / -45°C -46°C / -55°C


t ≤ 10 B AH D DH D DH E EH




40 < t ≤ 45 E EH φ FH φ FH φ φ




-20°C / -25°C -26°C / -35°C -36°C / -45°C -46°C / -55°C


t ≤ 10 D DH D DH E EH E EH






40 < t ≤ 50 φ FH φ FH φ φ φ φ


Design tem-perature, in

°C

Gross thickness,

in mm

Structural member category

SecondaryPrimary or

Special

t ≤ 20 B / AH B / AH

-10 ≤ tD < 0 20 < t ≤ 25 B / AH D / DH

t > 25 D / DH E / EH

t ≤ 15 B / AH D / DH

-25 ≤ tD < -10 15 < t ≤ 25 D / DH E / EH

t > 25 E / EH E / EH

-40 ≤ tD < -25 t ≤ 25 D / DH E / EH

t > 25 E / EH E / EH

Pt B, Ch 2, Sec 2


3.2.2 Rolled bars may be accepted in lieu of forged prod-ucts, after consideration by the Society on a case by casebasis.

In such case, compliance with the requirements of Pt D,Ch 2, Sec 1, relevant to the quality and testing of rolledparts accepted in lieu of forged parts, may be required.

3.3 Steels for casting

3.3.1 Cast parts intended for stems, sternframes, rudders,parts of steering gear and deck machinery in general may bemade of C and C-Mn weldable steels of quality 1, havingtensile strength Rm = 400 N/mm2 or 440 N/mm2, in accord-ance with the applicable requirements of Pt D, Ch 2, Sec 4.

Items which may be subjected to high stresses may berequired to be of quality 2 steels of the above types.

3.3.2 For the purpose of testing, which is to be carried outin accordance with Pt D, Ch 2, Sec 4, [1.11], the abovesteels for casting are assigned to class 1 irrespective of theirquality.

3.3.3 The welding of cast parts to main plating contribut-ing to hull strength members is considered by the Societyon a case by case basis.

The Society may require additional properties and tests forsuch casting, in particular impact properties which areappropriate to those of the steel plating on which the castparts are to be welded and non-destructive examinations.

3.3.4 Heavily stressed cast parts of steering gear, particu-larly those intended to form a welded assembly and tillersor rotors mounted without key, are to be subjected to non-destructive examination to check their internal structure.

4 Other materials and products

4.1 General

4.1.1 Other materials and products such as parts made ofiron castings, where allowed, products made of copper andcopper alloys, rivets, anchors, chain cables, cranes, masts,derrick posts, derricks, accessories and wire ropes are gen-erally to comply with the applicable requirements of Part D.

4.1.2 The use of plastics or other special materials not cov-ered by these Rules is considered by the Society on a caseby case basis. In such cases, the Society states the require-ments for the acceptance of the materials concerned.

4.1.3 Materials used in welding processes are to complywith the applicable requirements of Part D.

4.2 Iron cast parts

4.2.1 As a rule, the use of grey iron, malleable iron orspheroidal graphite iron cast parts with combined fer-ritic/perlitic structure is allowed only to manufacture lowstressed elements of secondary importance.

4.2.2 Ordinary iron cast parts may not be used for win-dows or sidescuttles; the use of high grade iron cast parts ofa suitable type will be considered by the Society on a caseby case basis.

Pt B, Ch 2, Sec 3



1 General

1.1 Application

1.1.1 The requirements of this Section apply to the preparation,execution and inspection of welded connections in hullstructures.

The general requirements relevant to fabrication by weldingand qualification of welding procedures are given in Part D,Chapter 5. As guidance see also the indications given in the“Guide for Welding”.

The requirements relevant to the non-destructive examina-tion of welded connections are given in the Rules for carry-ing out non-destructive examination of welding.

1.1.2 Weld connections are to be executed according tothe approved plans. Any detail not specifically representedin the plans is, in any event, to comply with the applicablerequirements.

1.1.3 It is understood that welding of the various types ofsteel is to be carried out by means of welding proceduresapproved for the purpose, even though an explicit indica-tion to this effect may not appear on the approved plans.

1.1.4 The quality standard adopted by the shipyard is to besubmitted to the Society and applies to all constructionsunless otherwise specified on a case-by-case basis.

1.2 Base material

1.2.1 The requirements of this Section apply to the weld-ing of hull structural steels or aluminium alloys of the typesconsidered in Part D or other types accepted as equivalentby the Society.

1.2.2 The service temperature is intended to be the ambi-ent temperature, unless otherwise stated.

1.3 Welding consumables and procedures

1.3.1 Approval of welding consumables and procedures

Welding consumables and welding procedures adopted areto be approved by the Society.

The requirements for the approval of welding consumablesare given in Pt D, Ch 5, Sec 2.

The requirements for the approval of welding proceduresfor the individual users are given in Pt D, Ch 5, Sec 4 andPt D, Ch 5, Sec 5.

The approval of the welding procedure is not required inthe case of manual metal arc welding with approved cov-

ered electrodes, except in the case of one side welding onrefractory backing (ceramic).

1.3.2 Consumables

For welding of hull structural steels, the minimum consuma-ble grades to be adopted are specified in Tab 1 dependingon the steel grade.

For welding of other materials, the consumables indicatedin the welding procedures to be approved are consideredby the Society on a case by case basis.

Table 1 : Consumable grades

1.3.3 Electrodes for manual welding

Basic covered electrodes are to be used for the welding ofstructural members made in higher strength steels and irre-spective of the steel type.

Non-basic covered electrodes are generally allowed formanual fillet welding of structural members of moderatethickness (gross thickness less than 25 mm) made in normalstrength steels.

Steel grade

Consumable minimum grade

Butt welding, partial and full T penetration welding

Fillet welding

A 1 1

B - D 2

E 3

AH32 - AH36DH32 - DH36

2Y 2Y

EH32 - EH36 3Y

FH32 - FH36 4Y

AH40 2Y40 2Y40

DH40 - EH40 3Y40

FH40 4Y40

Note 1:Welding consumables approved for welding higher strength steels (Y) may be used in lieu of those approved for welding normal strength steels having the same or a lower grade; welding consumables approved in grade Y40 may be used in lieu of those approved in grade Y having the same or a lower grade.Note 2:In the case of welded connections between two hull struc-tural steels of different grades, as regards strength or notch toughness, welding consumables appropriate to one or the other steel are to be adopted.

Pt B, Ch 2, Sec 3


1.4 Personnel and equipment

1.4.1 WeldersManual and semi-automatic welding is to be performed bywelders certified by the Society in accordance with recog-nised standards (see Pt D, Ch 5, Sec 1, [2.2.3] and Pt D,Ch 5, Sec 1, [2.2.5]); the welders are to be employed withinthe limits of their respective approval.

1.4.2 Automatic welding operatorsPersonnel manning automatic welding machines andequipment are to be competent and sufficiently trained.

1.4.3 OrganisationThe internal organisation of the shipyard is to be such as toensure compliance in full with the requirements in [1.4.1]and [1.4.2] and to provide assistance for and inspection ofwelding personnel, as necessary, by means of a suitablenumber of competent supervisors.

1.4.4 NDE operators Non-destructive tests are to be carried out by qualified per-sonnel, certified by the Society, or by recognised bodies incompliance with appropriate standards.

The qualifications are to be appropriate to the specificapplications.

1.4.5 Technical equipment and facilitiesThe welding equipment is to be appropriate to the adoptedwelding procedures, of adequate output power and such asto provide for stability of the arc in the different weldingpositions.

In particular, the welding equipment for special weldingprocedures is to be provided with adequate and duly cali-brated measuring instruments, enabling easy and accuratereading, and adequate devices for easy regulation and regu-lar feed.

Manual electrodes, wires and fluxes are to be stocked insuitable locations so as to ensure their preservation in goodcondition.

1.5 Documentation to be submitted

1.5.1 The structural plans to be submitted for approval,according to Ch 2, Sec 1, are to contain the necessary datarelevant to the fabrication by welding of the structures anditems represented. Any detail not clearly represented in theplans is, in any event, to comply with the applicable Rulerequirements.

For important structures, the main sequences of prefabrica-tion, assembly and welding and non-destructive examina-tion planned are also to be represented in the plans.

1.5.2 A plan showing the location of the various steeltypes is to be submitted at least for outer shell, deck andbulkhead structures.

1.6 Design

1.6.1 General For the various structural details typical of welded construc-tion in shipbuilding and not dealt with in this Section, the

rules of good practice, recognised standards and past expe-rience are to apply as agreed by the Society.

1.6.2 Plate orientationThe plates of the shell and strength deck are generally to bearranged with their length in the fore-aft direction. Possibleexceptions to the above will be considered by the Societyon a case by case basis; tests as deemed necessary (forexample, transverse impact tests) may be required by theSociety.

1.6.3 Overall arrangement Particular consideration is to be given to the overall arrange-ment and structural details of highly stressed parts of thehull.

Special attention is to be given to the above details in theplan approval stage.

1.6.4 Prefabrication sequences Prefabrication sequences are to be arranged so as to facili-tate positioning and assembling as far as possible.

The amount of welding to be performed on board is to belimited to a minimum and restricted to easily accessibleconnections.

1.6.5 Distance between weldsWelds located too close to one another are to be avoided.The minimum distance between two adjacent welds is con-sidered on a case by case basis, taking into account thelevel of stresses acting on the connected elements.

In general, the distance between two adjacent butts in thesame strake of shell or deck plating is to be greater than twoframe spaces.

2 Type of connections and preparation

2.1 General

2.1.1 The type of connection and the edge preparation areto be appropriate to the welding procedure adopted, thestructural elements to be connected and the stresses towhich they are subjected.

2.2 Butt welding

2.2.1 General In general, butt connections of plating are to be full penetra-tion, welded on both sides except where special proceduresor specific techniques, considered equivalent by the Soci-ety, are adopted.

Connections different from the above may be accepted bythe Society on a case by case basis; in such cases, the rele-vant detail and workmanship specifications are to beapproved.

2.2.2 Welding of plates with different thicknesses In the case of welding of plates with a difference in grossthickness equal to or greater than:

• 3 mm, if the thinner plate has a gross thickness equal toor less than 10 mm

Pt B, Ch 2, Sec 3


• 4 mm, if the thinner plate has a gross thickness greaterthan 10 mm,

a taper having a length of not less than 4 times the differ-ence in gross thickness is to be adopted for connections ofplating perpendicular to the direction of main stresses. Forconnections of plating parallel to the direction of mainstresses, the taper length may be reduced to 3 times the dif-ference in gross thickness.

When the difference in thickness is less than the above val-ues, it may be accommodated in the weld transitionbetween plates.

2.2.3 Edge preparation, root gap Typical edge preparations and gaps are indicated in the“Guide for welding”.

The acceptable root gap is to be in accordance with theadopted welding procedure and relevant bevel preparation.

2.2.4 Butt welding on permanent backingButt welding on permanent backing, i.e. butt weldingassembly of two plates backed by the flange or the faceplate of a stiffener, may be accepted where back welding isnot feasible or in specific cases deemed acceptable by theSociety.

The type of bevel and the gap between the members to beassembled are to be such as to ensure a proper penetrationof the weld on its backing and an adequate connection tothe stiffener as required.

2.2.5 Section, bulbs and flat bars When lengths of longitudinals of the shell plating andstrength deck within 0,6 L amidships, or elements in generalsubject to high stresses, are to be connected together bybutt joints, these are to be full penetration. Other solutionsmay be adopted if deemed acceptable by the Society on acase by case basis.

2.3 Fillet welding

2.3.1 GeneralIn general, ordinary fillet welding (without bevel) may beadopted for T connections of the various simple and com-posite structural elements, where they are subjected to lowstresses (in general not exceeding 30 N/mm2) and adequateprecautions are taken to prevent the possibility of local lam-inations of the element against which the T web is welded.

Where this is not the case, partial or full T penetration weld-ing according to [2.4] is to be adopted.

2.3.2 Fillet welding typesFillet welding may be of the following types:

• continuous fillet welding, where the weld is constitutedby a continuous fillet on each side of the abutting plate(see [2.3.3])

• intermittent fillet welding, which may be subdivided(see [2.3.4]) into:

- chain welding

- scallop welding

- staggered welding.

2.3.3 Continuous fillet weldingContinuous fillet welding is to be adopted:• for watertight connections• for connections of brackets, lugs and scallops • at the ends of connections for a length of at least 75mm

• where intermittent welding is not allowed, according to[2.3.4].

Continuous fillet welding may also be adopted in lieu ofintermittent welding wherever deemed suitable, and it isrecommended where the spacing p, calculated accordingto [2.3.4], is low.

2.3.4 Intermittent weldingThe spacing p and the length d, in mm, of an intermittentweld, shown in:• Fig 1, for chain welding

• Fig 2, for scallop welding• Fig 3, for staggered welding

are to be such that:

where the coefficient ϕ is defined in Tab 2 and Tab 3 for thedifferent types of intermittent welding, depending on thetype and location of the connection.

In general, staggered welding is not allowed for connec-tions subjected to high alternate stresses.

In addition, the following limitations are to be compliedwith:

• chain welding (see Fig 1):d ≥ 75 mmp-d ≤ 200 mm

Figure 1 : Intermittent chain welding

• scallop welding (see Fig 2): d ≥ 75 mm

p-d ≤ 150 mm v ≤ 0,25b, without being greater than 75 mm

Figure 2 : Intermittent scallop welding

• staggered welding (see Fig 3):d ≥ 75 mm

pd--- ϕ≤

Pt B, Ch 2, Sec 3


p-2d ≤ 300 mm

p ≤ 2d for connections subjected to high alternatestresses.

Figure 3 : Intermittent staggered welding

2.3.5 Throat thickness of fillet weld T connections The throat thickness of fillet weld T connections is to beobtained, in mm, from the following formula:

where:

wF : Welding factor, defined in Tab 2 for the varioushull structural connections; for connections ofprimary supporting members belonging to sin-gle-skin structures and not mentioned in Tab 2,wF is defined in Tab 3;

t : Actual gross thickness, in mm, of the structuralelement which constitutes the web of the T con-nection

p, d : Spacing and length, in mm, of an intermittentweld, defined in [2.3.4].

Figure 4 : Continuous fillet weldingbetween cut-outs

For continuous fillet welds, p/d is to be taken equal to 1.

In no case may the throat thickness be less than:• 3,0 mm, where the gross thickness of the thinner plate

is less than 6 mm • 3,5 mm, otherwise.

The throat thickness may be required by the Society to beincreased, depending on the results of structural analyses.

The leg length of fillet weld T connections is to be not lessthan 1,4 times the required throat thickness.

2.3.6 Weld dimensions in a specific caseWhere intermittent fillet welding is adopted with: • length d = 75 mm• throat thickness tT specified in Tab 4 depending on the

thickness t defined in [2.3.5]

the weld spacing may be taken equal to the value p1

defined in Tab 2. The values of p1 in Tab 2 may be usedwhen 8 ≤ t ≤ 16 mm.

For thicknesses t less than 8 mm, the values of p1 may beincreased, with respect to those in Tab 2, by:• 10 mm for chain or scallop welding• 20 mm for staggered welding

without exceeding the limits in [2.3.4].

For thicknesses t greater than 16 mm, the values of p1 are tobe reduced, with respect to those in Tab 2, by:• 10 mm for chain or scallop welding• 20 mm for staggered welding.

Figure 5 : Intermittent scallop fillet weldingbetween cut-outs

tT wFtpd---=

Throatthickness a

λε

Throatthickness a

λ1 λ2 λ3 λ=∑(λi)ε

Pt B, Ch 2, Sec 3


Table 2 : Welding factors wF and coefficient ϕ for the various hull structural connections

Hull areaConnection

wF (1)ϕ (2) (3) p1, in mm (see

[2.3.6]) (3)of to CH SC ST

General, unless other-wise speci-fied in the

table

watertight plates boundaries 0,35

webs of ordinary stiff-eners

plating 0,13 3,5 3,0 4,6 ST 260

face plate of fabricated stiff-eners

at ends (4) 0,13

elsewhere 0,13 3,5 3,0 4,6 ST 260

Bottom and double bot-

tom

longitudinal ordinary stiffeners

bottom and inner bottom plating 0,13 3,5 3,0 4,6 ST 260

centre girder keel 0,25 1,8 1,8 CH/SC 130

inner bottom plating 0,20 2,2 2,2 CH/SC 160

side girders bottom and inner bottom plating 0,13 3,5 3,0 4,6 ST 260

floors (interrupted girders) 0,20 2,2 CH 160

floors bottom and inner bottom plating

in general 0,13 3,5 3,0 4,6 ST 260

at ends (20% of span) for longitudinally framed double bot-tom

0,25 1,8 CH 130

inner bottom plating in way of brackets of primary supporting members

0,25 1,8 CH 130

girders (interrupted floors) 0,20 2,2 CH 160

partial side girders floors 0,25 1,8 CH 130

web stiffeners floor and girder webs 0,13 3,5 3,0 4,6 ST 260

Side ordinary stiffeners side and plating 0,13 3,5 3,0 4,6 ST 260

Deck strength deck side plating Partial penetration welding

non-watertight decks side plating 0,20 2,2 CH 160

ordinary stiffeners and intercostal girders

deck plating 0,13 3,5 3,0 4,6 ST 260

hatch coamings deck plating in general 0,35

at corners of hatch-ways for 15% of the hatch length

0,45

web stiffeners coaming webs 0,13 3,5 3,0 4,6 ST 260

Bulkheads watertight bulkhead structures

boundaries 0,35

non-watertight bulk-head structures

boundaries wash bulkheads 0,20 2,2 2,2 CH/SC 160

others 0,13 3,5 3,0 4,6 ST 260

ordinary stiffeners bulkhead plating

in general (5) 0,13 3,5 3,0 4,6 ST 260

at ends (25% of span), where no end brackets are fitted

0,35

Structures located for-ward of 0,75 L from the AE

(6)

bottom longitudinal ordinary stiffeners

bottom plating 0,20 2,2 CH 160

floors and girders bottom and inner bottom plating 0,25 1,8 CH 130

side frames in panting area

side plating 0,20 2,2 CH 160

webs of side girders in single side skin struc-tures

side plating and face plate

A< 65 cm2 (7) 0,25 1,8 1,8 CH/SC 130

A ≥ 65 cm2 (7) See Tab 3

Pt B, Ch 2, Sec 3


After peak (6) internal structures each other 0,20

side ordinary stiffeners side plating 0,20

floors bottom and inner bottom plating 0,20

Machinery space (6)

centre girder keel and inner bottom plating

in way of main engine foundations

0,45

in way of seating of auxiliary machinery and boilers

0,35

elsewhere 0,25 1,8 1,8 CH/SC 130

side girders bottom and inner bottom plating

in way of main engine foundations

0,45


0,35


floors (except in way of main engine foundations)

bottom and inner bottom plating


0,35


floors in way of main engine foundations

bottom plating 0,35

foundation plates 0,45

floors centre girder single bottom 0,45

double bottom 0,25 1,8 1,8 CH/SC 130

Superstruc-tures and

deckhouses

external bulkheads deck in general 0,35

engine and boiler casings at corners of openings (15% of opening length)

0,45

internal bulkheads deck 0,13 3,5 3,0 4,6 ST 260

ordinary stiffeners external and internal bulkhead plating 0,13 3,5 3,0 4,6 ST 260

Pillars elements composing the pillar section

each other (fabricated pillars) 0,13

pillars deck pillars in compres-sion

0,35

pillars in tension Full penetration welding

Ventilators coamings deck 0,35

Hull areaConnection

wF (1)ϕ (2) (3) p1, in mm (see

[2.3.6]) (3)of to CH SC ST

Pt B, Ch 2, Sec 3


2.3.7 Throat thickness of welds between cut-outs The throat thickness of the welds between the cut-outs inprimary supporting member webs for the passage of ordi-nary stiffeners is to be not less than the value obtained, inmm, from the following formula:

where:tT : Throat thickness defined in [2.3.5] ε, λ : Dimensions, in mm, to be taken as shown in:

• Fig 4, for continuous welding• Fig 5, for intermittent scallop welding.

2.3.8 Throat thickness of welds connecting ordinary stiffeners with primary supporting members

The throat thickness of fillet welds connecting ordinary stiff-eners and collar plates, if any, to the web of primary sup-

porting members is to be not less than 0,35tW, where tW isthe web gross thickness, in mm.

Where primary supporting member web stiffeners arewelded to ordinary stiffener face plates, in certain cases theSociety may require the above throat thickness to beobtained, in mm, from the following formula:

where:

pS, pW : Still water and wave pressure, respectively, inkN/m2, acting on the ordinary stiffener, definedin Ch 7, Sec 2, [3.3.2]

b,c,d,u,v: Main dimensions, in mm, of the cut-out shownin Fig 6.

Rudders webs in general each other 0,20 2,2 SC 160

plating in general 0,20 2,2 SC 160

top and bottom plates of rudder plat-ing

0,35

solid parts or rudder stock According to Ch 10, Sec 1, [7.4] or Ch 10, Sec 1, [7.5]

horizontal and vertical webs directly con-nected to solid parts

each other 0,45

plating 0,35

(1) In connections for which wF ≥ 0,35, continuous fillet welding is to be adopted. (2) For coefficient ϕ, see [2.3.4]. In connections for which no ϕ value is specified for a certain type of intermittent welding, such

type is not permitted and continuous welding is to be adopted.(3) CH = chain welding, SC = scallop welding, ST = staggered welding.(4) Ends of ordinary stiffeners means the area extended 75 mm from the span ends. Where end brackets are fitted, ends means the

area extended in way of brackets and at least 50 mm beyond the bracket toes. (5) In tanks intended for the carriage of ballast or fresh water, continuous welding with wF = 0,35 is to be adopted.(6) For connections not mentioned, the requirements for the central part apply.(7) A is the face plate sectional area of the side girders, in cm2.

Hull areaConnection

wF (1)ϕ (2) (3) p1, in mm (see

[2.3.6]) (3)of to CH SC ST

tTC tTελ---=

tT

4 pS pW+( )sl 1 s2l------–

⎝ ⎠⎛ ⎞

u v c 0 2d,+b 0 2d,+----------------------

⎝ ⎠⎛ ⎞+

-------------------------------------------------------=

Pt B, Ch 2, Sec 3


Table 3 : Welding factors wF and coefficient ϕ for connections of primary supporting members

Figure 6 : End connection of ordinary stiffenerDimensions of the cut-out

Table 4 : Required throat thickness

Primary support-ing member

ConnectionwF (1)

ϕ (2) (3) p1, in mm (see [2.3.6]) (3)of to CH SC ST

General (4) web, where A < 65 cm2

plating andface plate

at ends 0,20


web,where A ≥ 65 cm2

plating 0,35

face plate at ends 0,35


end brackets face plate 0,35

In tanks, whereA < 65 cm2 (5)

web plating at ends 0,25


face plate at ends 0,20



In tanks, whereA ≥ 65 cm2

web plating at ends 0,45

elsewhere 0,35

face plate 0,35


(1) In connections for which wF ≥ 0,35, continuous fillet welding is to be adopted. (2) For coefficient ϕ, see [2.3.4]. In connections for which no ϕ value is specified for a certain type of intermittent welding, such

type is not permitted.(3) CH = chain welding, SC = scallop welding, ST = staggered welding. (4) For cantilever deck beams, continuous welding is to be adopted.(5) For primary supporting members in tanks intended for the carriage of ballast or fresh water, continuous welding is to be

adopted.Note 1:A is the face plate sectional area of the primary supporting member, in cm2. Note 2:Ends of primary supporting members means the area extended 20% of the span from the span ends. Where end brackets are fitted, ends means the area extended in way of brackets and at least 100 mm beyond the bracket toes.

c

u vd

c b

t, in mm tT, in mm t, in mm tT, in mm

6 3,0 17 7,0

8 3,5 18 7,0

9 4,0 19 7,5

10 4,5 20 7,5

11 5,0 21 8,5

12 5,5 22 8,5

13 6,0 23 9,0

14 6,0 24 9,0

15 6,5 25 10,0

16 6,5 26 10,0

Pt B, Ch 2, Sec 3


2.3.9 Throat thickness of deep penetration fillet welding

When fillet welding is carried out with automatic weldingprocedures, the throat thickness required in [2.3.5] may bereduced up to 15%, depending on the properties of theelectrodes and consumables. However, this reduction maynot be greater than 1,5 mm.

The same reduction applies also for semi-automatic proce-dures where the welding is carried out in the downhandposition.

2.4 Partial and full T penetration welding

2.4.1 General

Partial or full T penetration welding is to be adopted forconnections subjected to high stresses for which fillet weld-ing is considered unacceptable by the Society.

Typical edge preparations are indicated in:

• for partial penetration welds: Fig 7 and Fig 8, in whichf, in mm, is to be taken between 3 mm and t/3, and αbetween 45° and 60°

• for full penetration welds: Fig 9 and Fig 10, in which f,in mm, is to be taken between 0 and 3 mm, and αbetween 45° and 60°

Back gouging is generally required for full penetrationwelds.

2.4.2 Lamellar tearing

Precautions are to be taken in order to avoid lamellar tears,which may be associated with:

• cold cracking when performing T connections betweenplates of considerable thickness or high restraint

• large fillet welding and full penetration welding onhigher strength steels.

2.5 Lap-joint welding

2.5.1 General

Lap-joint welding may be adopted for:

• peripheral connection of doublers

• internal structural elements subjected to very lowstresses.

Elsewhere, lap-joint welding may be allowed by the Societyon a case by case basis, if deemed necessary under specificconditions.

Continuous welding is generally to be adopted.

2.5.2 Gap

The surfaces of lap-joints are to be in sufficiently close con-tact.

2.5.3 Dimensions

The dimensions of the lap-joint are to be specified and areconsidered on a case by case basis. Typical details are givenin the “Guide for welding”.

Figure 7 : Partial penetration weld

Figure 8 : Partial penetration weld

Figure 9 : Full penetration weld

Figure 10 : Full penetration weld

T

f

� �

T

f

�

T

f

��

T

f

�

Pt B, Ch 2, Sec 3


2.6 Slot welding

2.6.1 General

Slot welding may be adopted in very specific cases subjectto the special agreement of the Society, (e.g. for doublers).

In general, slot welding of doublers on the outer shell andstrength deck is not permitted within 0,6L amidships.Beyond this zone, slot welding may be accepted by theSociety on a case by case basis.

Slot welding is, in general, permitted only where stresses actin a predominant direction. Slot welds are, as far as possi-ble, to be aligned in this direction.

2.6.2 Dimensions

Slot welds are to be of appropriate shape (in general oval)and dimensions, depending on the plate thickness, and maynot be completely filled by the weld.

Typical dimensions of the slot weld and the throat thicknessof the fillet weld are given in the “Guide for welding”.

The distance between two consecutive slot welds is to benot greater than a value which is defined on a case by casebasis taking into account:

- the transverse spacing between adjacent slot weld lines

- the stresses acting in the connected plates

- the structural arrangement below the connected plates.

2.7 Plug welding

2.7.1 Plug welding may be adopted only when acceptedby the Society on a case by case basis, according to specifi-cally defined criteria. Typical details are given in the “Guidefor welding”.

3 Specific weld connections

3.1 Corner joint welding

3.1.1 Corner joint welding, as adopted in some cases atthe corners of tanks, performed with ordinary fillet welds, ispermitted provided the welds are continuous and of therequired size for the whole length on both sides of the joint.

3.1.2 Alternative solutions to corner joint welding may beconsidered by the Society on a case by case basis.

3.2 Bilge keel connection

3.2.1 The intermediate flat, through which the bilge keel isconnected to the shell according to Ch 2, Sec 7, [9], is to bewelded as a shell doubler by continuous fillet welds.

The butt welds of the doubler and bilge keel are to be fullpenetration and shifted from the shell butts.

The butt welds of the bilge plating and those of the doublersare to be flush in way of crossing, respectively, with thedoubler and with the bilge keel.

3.3 Connection between propeller post and propeller shaft bossing

3.3.1 Fabricated propeller posts are to be welded with fullpenetration welding to the propeller shaft bossing.

3.4 Bar stem connections

3.4.1 The bar stem is to be welded to the bar keel gener-ally with butt welding.

The shell plating is also to be welded directly to the barstem with butt welding.

4 Workmanship

4.1 Forming of plates

4.1.1 Hot or cold forming is to be performed according tothe requirements of recognised standards or those acceptedby the Society on a case by case basis depending on thematerial grade and rate of deformation.

Recommendations for cold and hot forming are given in the“Guide for welding”.

4.2 Welding procedures and consumables

4.2.1 The various welding procedures and consumablesare to be used within the limits of their approval and inaccordance with the conditions of use specified in therespective approval documents.

4.3 Welding operations

4.3.1 Weather protection

Adequate protection from the weather is to be provided toparts being welded; in any event, such parts are to be dry.

In welding procedures using bare, cored or coated wireswith gas shielding, the welding is to be carried out inweather protected conditions, so as to ensure that the gasoutflow from the nozzle is not disturbed by winds anddraughts.

4.3.2 Butt connection edge preparation

The edge preparation is to be of the required geometry andcorrectly performed. In particular, if edge preparation is car-ried out by flame, it is to be free from cracks or other detri-mental notches.

Recommendations for edge preparation are given in the“Guide for welding”.

4.3.3 Surface condition

The surfaces to be welded are to be free from rust, moistureand other substances, such as mill scale, slag caused byoxygen cutting, grease or paint, which may produce defectsin the welds.

Effective means of cleaning are to be adopted particularly inconnections with special welding procedures; flame ormechanical cleaning may be required.

Pt B, Ch 2, Sec 3


The presence of a shop primer may be accepted, provided ithas been approved by the Society.

Shop primers are to be approved by the Society for a spe-cific type and thickness according to Pt D, Ch 5, Sec 3.

4.3.4 Assembling and gap

The setting appliances and system to be used for positioningare to ensure adequate tightening adjustment and an appro-priate gap of the parts to be welded, while allowing maxi-mum freedom for shrinkage to prevent cracks or otherdefects due to excessive restraint.

The gap between the edges is to comply with the requiredtolerances or, when not specified, it is to be in accordancewith normal good practice.

4.3.5 Gap in fillet weld T connections

In fillet weld T connections, a gap g, as shown in Fig 11, notgreater than 2 mm may be accepted without increasing thethroat thickness calculated according to [2.3.5] to [2.3.9],as applicable.

In the case of a gap greater than 2 mm, the above throatthickness is to be increased accordingly as specified inSec 2 for some special connections of various ship types.Recommendations are also given in the “Guide for weld-ing”.

In any event, the gap g may not exceed 4 mm.

Figure 11 : Gap in fillet weld T connections

4.3.6 Plate misalignment in butt connections

The misalignment m, measured as shown in Fig 12,between plates with the same gross thickness t is to be lessthan 0,15t, without being greater than 3 mm, where t is thegross thickness of the thinner abutting plate.

4.3.7 Misalignment in cruciform connections

The misalignment m in cruciform connections, measuredon the median lines as shown in Fig 13, is to be less than:

• t/2, in general, where t is the gross thickness of the thin-ner abutting plate

• the values specified in Sec 2 for some special connec-tions of various ship types.

The Society may require lower misalignment to be adoptedfor cruciform connections subjected to high stresses.

Figure 12 : Plate misalignment in butt connections

Figure 13 : Misalignment in cruciform connections

4.3.8 Assembling of aluminium alloy parts

When welding aluminium alloy parts, particular care is tobe taken so as to:

• reduce as far as possible restraint from welding shrink-age, by adopting assembling and tack welding proce-dures suitable for this purpose

• keep possible deformations within the allowable limits.

4.3.9 Preheating and interpass temperatures

Suitable preheating, to be maintained during welding, andslow cooling may be required by the Society on a case bycase basis.

Pt B, Ch 2, Sec 3


4.3.10 Welding sequences

Welding sequences and direction of welding are to bedetermined so as to minimise deformations and preventdefects in the welded connection.

All main connections are generally to be completed beforethe ship is afloat.

Departures from the above provision may be accepted bythe Society on a case by case basis, taking into account anydetailed information on the size and position of welds andthe stresses on the zones concerned, both during shiplaunching and with the ship afloat.

4.3.11 Interpass cleaning

After each run, the slag is to be removed by means of achipping hammer and a metal brush; the same precaution isto be taken when an interrupted weld is resumed or twowelds are to be connected.

4.3.12 Stress relieving

It is recommended and in some cases it may be requiredthat special structures subject to high stresses, having com-plex shapes and involving welding of elements of consider-able thickness (such as rudder spades and stern frames), areprefabricated in parts of adequate size and stress-relieved inthe furnace, before final assembly, at a temperature withinthe range 550°C ÷ 620°C, as appropriate for the type ofsteel.

4.4 Crossing of structural elements

4.4.1 In the case of T crossing of structural elements (oneelement continuous, the other physically interrupted at thecrossing) when it is essential to achieve structural continuitythrough the continuous element (continuity obtained bymeans of the welded connections at the crossing), particularcare is to be devoted to obtaining the correspondence of theinterrupted elements on both sides of the continuous ele-ment. Suitable systems for checking such correspondenceare to be adopted.

5 Modifications and repairs during construction

5.1 General

5.1.1 Deviations in the joint preparation and other speci-fied requirements, in excess of the permitted tolerances andfound during construction, are to be repaired as agreed withthe Society on a case by case basis.

5.2 Gap and weld deformations

5.2.1 When the gap exceeds the required values, weldingby building up or repairs are to be authorised by the Soci-ety’s Surveyor.

Recommendations for repairing gap and weld deformationsnot complying with the required standards are given in the“Guide for welding”.

5.3 Defects

5.3.1 Defects and imperfections on the materials andwelded connections found during construction are to beevaluated for possible acceptance on the basis of the appli-cable requirements of the Society.

Where the limits of acceptance are exceeded, the defectivematerial and welds are to be discarded or repaired, asdeemed appropriate by the Surveyor on a case by casebasis.

When any serious or systematic defect is detected either inthe welded connections or in the base material, the Manu-facturer is required to promptly inform the Surveyor andsubmit the repair proposal.

The Surveyor may require destructive or non-destructiveexaminations to be carried out for initial identification ofthe defects found and, in the event that repairs are under-taken, for verification of their satisfactory completion.

5.4 Repairs on structures already welded

5.4.1 In the case of repairs involving the replacement ofmaterial already welded on the hull, the procedures to beadopted are to be agreed with the Society on a case by casebasis, considering these modifications as repairs of the in-service ship’s hull.

6 Inspections and checks

6.1 General

6.1.1 Materials, workmanship, structures and welded con-nections are to be subjected, at the beginning of the work,during construction and after completion, to inspectionssuitable to check compliance with the applicable require-ments, approved plans and standards.

6.1.2 The Manufacturer is to make available to the Sur-veyor a list of the manual welders and welding operatorsand their respective qualifications.

The Manufacturer's internal organisation is responsible forensuring that welders and operators are not employedunder improper conditions or beyond the limits of theirrespective qualifications and that welding procedures areadopted within the approved limits and under the appropri-ate operating conditions.

6.1.3 The Manufacturer is responsible for ensuring that theoperating conditions, welding procedures and work sched-ule are in accordance with the applicable requirements,approved plans and recognised good welding practice.

6.2 Visual and non-destructive examina-tions

6.2.1 After completion of the welding operation and work-shop inspection, the structure is to be presented to the Sur-veyor for visual examination at a suitable stage offabrication.

As far as possible, the results of non-destructive examina-tions are to be submitted.

Pt B, Ch 2, Sec 3


6.2.2 Non-destructive examinations are to be carried outwith appropriate methods and techniques suitable for theindividual applications, to be agreed with the Surveyor on acase by case basis.

6.2.3 Radiographic examinations are to be carried out onthe welded connections of the hull in accordance with theSociety’s requirements, the approved plans and the Sur-veyor’s instructions.

6.2.4 The Society may allow radiographic examinations tobe partially replaced by ultrasonic examinations.

6.2.5 When the visual or non-destructive examinationsreveal the presence of unacceptable defects, the relevantconnection is to be repaired to sound metal for an extentand according to a procedure agreed with the Surveyor. Therepaired zone is then to be submitted to non-destructiveexamination, using a method at least as effective as thatadopted the first time and deemed suitable by the Surveyorto verify that the repair is satisfactory.

Additional examinations may be required by the Surveyoron a case by case basis.

6.2.6 Ultrasonic and magnetic particle examinations mayalso be required by the Surveyor in specific cases to verifythe quality of the base material.

7 End connections of ordinary stiffen-ers

7.1

7.1.1 Where ordinary stiffeners are continuous throughprimary supporting members, they are to be connected tothe web plating so as to ensure proper transmission ofloads, e.g. by means of one of the connection details shownin Fig 6 to Fig 9.

Connection details other than those shown in Fig 6 to Fig 9may be considered by RINA on a case by case basis.

Figure 14 : End connection of ordinary stiffener with-out collar plate

Figure 15 : End connection of ordinary stiffener with collar plate

Figure 16 : End connection of ordinary stiffener with one large collar plate

Figure 17 : End connection of ordinary stiffener with two large collar plates

In all the above connections, the radius of the all the scal-lops in the primary member around the stiffener is to be atleast 20mm.

The extension of the collar plate above the primary memberis to be at least 3 t, where t is the thickness of the collarplate.

7.1.2 Where ordinary stiffeners are cut at primary support-ing members, brackets are to be fitted to ensure the struc-tural continuity. The net thickness of brackets is to be not less than that ofordinary stiffeners. Brackets with net thickness, in mm, lessthan 15Lb, where Lb is the length, in m, of the free edge ofthe end bracket, are to be flanged or stiffened by a weldedface plate. The net sectional area, in cm2, of the flangededge or face plate is to be at least equal to 10Lb .

7.1.3 Where necessary, RINA may require backing brack-ets to be fitted, as shown in Fig 10, in order to improve thefatigue strength of the connection.

Pt B, Ch 2, Sec 3


Figure 18 : End connection of ordinary stiffener with backing bracket

8 End connections of primary support-ing members

8.1 Bracketed end connections

8.1.1 Arm lengths of end brackets are to be equal, as far aspracticable.

As a general rule, the height of end brackets is to be not lessthan that of the primary supporting member.

8.1.2 The thickness of the end bracket web is generally tobe not less than that of the primary supporting memberweb.

8.1.3 The scantlings of end brackets are generally to besuch that the net section modulus of the primary supportingmember with end brackets is not less than that of the pri-mary supporting member at mid-span.

8.1.4 The width, in mm, of the face plate of end brackets isto be not less than 50(Lb+1), where Lb is the length, in m, ofthe free edge of the end bracket.

Moreover, the net thickness of the face plate is to be not lessthan that of the bracket web.

8.1.5 Stiffening of end brackets is to be designed such thatit provides adequate buckling web stability.

As guidance, the following prescriptions may be applied:

• where the length Lb is greater than 1,5 m, the web of thebracket is to be stiffened;

• the net sectional area, in cm2, of web stiffeners is to benot less than 16,5l, where l is the span, in m, of the stiff-ener;

• tripping flat bars are to be fitted to prevent lateral buck-ling of web stiffeners. Where the width of the symmetri-cal face plate is greater than 400 mm, additionalbacking brackets are to be fitted.

8.2 Bracketless end connections

8.2.1 As a general rule, in the case of bracketless crossingbetween primary supporting members (see Fig 11), the

thickness of the common part of the web is to be not lessthan the value obtained, in mm, from the following formula:

where:

w : the lesser of w1 and w 2,MAX

w1 : gross section modulus, in cm3, of member 1

w 2,MAX: the greater value, in cm3, of the gross section mod-uli of members 2 and 3

Ω : Area, in cm2, of the common part of members 1, 2 and3.

In the absence of one of members 2 and 3 shown in Fig 11,the value of the relevant gross section modulus is to betaken equal to zero.

8.2.2 In no case may the thickness calculated according to4.2.1 be less than the smallest web net thickness of themembers forming the crossing.

8.2.3 In general, the continuity of the face plates is to beensured.

Figure 19 : Bracketless end connections of primary supporting members

9 Cut-outs and holes

9.1

9.1.1 Cut-outs for the passage of ordinary stiffeners are tobe as small as possible and well rounded with smoothedges.

In general, the depth of cut-outs is to be not greater than50% of the depth of the primary supporting member.

9.2

9.2.1 Where openings such as lightening holes are cut inprimary supporting members, they are to be equidistantfrom the face plate and corners of cut-outs and, in general,their height is to be not greater than 20% of the web height.

t 15,75WΩ------=

Ω

Member 3

Member 1

Member 2

Pt B, Ch 2, Sec 3


9.3

9.3.1 Openings may not be fitted in way of toes of endbrackets.

9.4

9.4.1 Over half of the span of primary supporting mem-bers, the length of openings is to be not greater than the dis-tance between adjacent openings.

At the ends of the span, the length of openings is to be notgreater than 25% of the distance between adjacent open-ings.

9.5

9.5.1 The cut-out is to be reinforced to one of the solutionsshown in Fig. 20 to Fig. 22:

• continuous face plate (Solution 1): see Fig 20

• straight face plate (Solution 2): see Fig 21

• compensation of the opening (Solution 3): see Fig 22

• combination of the above solutions.

Other arrangements may be accepted provided they aresupported by direct calculations submitted to RINA forreview.

Figure 20 : Stiffening of large openings in primary supporting members - Solution 1

Figure 21 : Stiffening of large openings in primary supporting members - Solution 2

Figure 22 : Stiffening of large openings in primary supporting members - Solution 3 (inserted plate)

10 Stiffening arrangement

10.1

10.1.1 Webs of primary supporting members are generallyto be stiffened where the height, in mm, is greater than100t, where t is the web net thickness, in mm, of the pri-mary supporting member.In general, the web stiffeners of primary supporting mem-bers are to be spaced not more than 110t apart.

10.2

10.2.1 As a general rule, tripping brackets (see Fig 23)welded to the face plate may be fitted:at every fourth spacing of ordinary stiffeners, withoutexceeding 4 m• at the toe of end brackets• at rounded face plates• in way of cross ties• in way of concentrated loads.

Where the width of the symmetrical face plate is greaterthan 400 mm, backing brackets are to be fitted in way of thetripping brackets.

10.3

10.3.1 In general, the width of the primary supportingmember face plate is to be not less than one tenth of thedepth of the web, where tripping brackets are spaced asspecified in 6.2.

10.4

10.4.1 The arm length of tripping brackets is to be not lessthan the greater of the following values, in m:

where:

b : Height, in m, of tripping brackets, shown in Fig 23

st : Spacing, in m, of tripping brackets

t : Net thickness, in mm, of tripping brackets.

It is recommended that the bracket toe should be designedas shown in Fig 23.

t t

d 0,38b=

d 0,85b st

t---=

Pt B, Ch 2, Sec 3


10.5

10.5.1 Tripping brackets with a net thickness, in mm, lessthan 15Lb are to be flanged or stiffened by a welded faceplate.

Figure 23 : Primary supporting member: web stiffener in way of ordinary stiffener

11 Riveted connections

11.1

11.1.1 When riveted connections are employed, themechanical properties of the rivets are to be indicated on

the plans.RINA may, at its discretion, require shear, tensile and com-pression tests to be carried out on representative specimensof riveted connections.

11.2

11.2.1 When rivets are used to connect materials of differ-ent types, precautions are to be taken against electrolyticcorrosion.Whenever possible, the arrangements are to be such as toenable inspection in service without the need to removecoverings, etc.

12 Sealed connections

12.1

12.1.1 Where a sealing product is used to ensure airtightor watertight integrity, product information is to be submit-ted together with evidence of its previous successful use.

Pt B, Ch 2, Sec 4


SECTION 4 LONGITUDINAL STRENGTH

1 General

1.1

1.1.1 The structural scantlings prescribed in Chapter 2 arealso intended for the purposes of the longitudinal strengthof a yacht of length having L not exceeding 50 m for mono-hull yachts or 40 m for catamarans and openings on thestrength deck of limited size.

For yachts of greater length and/or openings of size greaterthan the breadth B of the hull and extending for a consider-able part of the length of the yacht, calculation of longitudi-nal strength is required.

1.2

1.2.1 To this end, longitudinal strength calculations are tobe carried out considering the load and ballast conditionsfor both departure and arrival.

2 Bending stresses

2.1

2.1.1 In addition to satisfying the minimum requirementsstipulated in the individual Sections of this Chapter, thescantlings of members contributing to the longitudinalstrength of monohull yachts and catamarans are to achievea section modulus of the midship section at the bottom andthe deck such as to guarantee stresses not exceeding theallowable values.

Therefore:

where:

Wf, Wp : section modulus at the bottom and the deck,respectively, of the transverse section, in m3

MT : design total vertical bending moment defined inChap.1, Sec 5.

f : 0,80 for planing yachts

f : 0,72 for displacement yachts

σs : mimimum yield stress of the material, inN/mm2.

2.2

2.2.1 The compressive value of normal stresses is not toexceed the value of the critical stresses for plates and stiff-eners calculated in Sec 1, [5].

2.3

2.3.1 The moment of inertia J of the midship section, inm4, is to be not less than the value given by the followingformulae.

For planing yachts:

For displacement yachts:

3 Shear stresses

3.1

3.1.1 The shear stresses in every position along the lengthL are not to exceed the allowable values; in particular.

where:

Tt : total shear in kN defined in Chapter 1

σs, f : defined in 2

At : actual shear area of the transverse section, inm2, to be calculated considering the net area ofside plating and of any longitudinal bulkheads excluding openings.

4 Calculation of the section modulus

4.1

4.1.1 In the calculation of the modulus and inertia of themidship section, all the continuous members, plating andlongitudinal stiffeners are generally to be included, pro-vided that they extend for at least 0,4 L amidships.

σ f f σs N mm2⁄⋅≤

σp f σs N mm2⁄⋅≤

σ fMT

1000 Wf

----------------------- N mm2⁄=

σpMT

1000 Wp

------------------------ N mm2⁄=

J 5 32,= M 10 6–⋅ ⋅

J 5 90,= M 10 6–⋅ ⋅

Tt

At

----- 10 3– f σs⋅≤⋅

Pt B, Ch 2, Sec 5


SECTION 5 PLATING


1.1

1.1.1 s : spacing of ordinary longitudinal or transverse

stiffener, in mp : scantling pressure, in kN/m2, given in Chap.1,

Sec. 5K : factor defined in Sec. 2.

2 Keel

2.1 Sheet steel keel

2.1.1 The keel plating is to have a width bCH, in mm,throughout the length of the yacht, not less than the valueobtained by the following equation:

and a thickness not less than that of the adjacent bottomplating increased by 2 mm.

2.2 Solid keel

2.2.1 The height and thickness of the keel, throughout thelength of the yacht, are to be not less than the values hCH

and tCH, in mm, calculated with the following equations:

Lesser heights and thicknesses may be accepted providedthat the effective area of the section is not less than that ofthe Rule section.

Lesser heights and thicknesses may also be acceptable if acentre girder is placed in connection with the solid keel.

The garboard strakes connected to the keel are each to havea width not less than 750 mm and a thickness not less thanthat of the bottom plating increased by 10%.

3 Bottom and bilge

3.1

3.1.1 Bottom plating is the plating up to the chine or to theupper turn of the bilge.

The thickness of the bottom plating and the bilge is to benot less than the greater of the values t1 and t2, in mm, cal-culated with the following formulae:

where:

k1 : 0,11, assuming p=p1

: 0,07, assuming p=p2.

ka : coefficient as a function of the ratio S/s given inTable 1 below where S is the greater dimensionof the plating, in m.

k2 : curvature correction factor given by 1-(h/s) to betaken not less than 0,7 where h is the distance,in mm, measured perpendicularly from thechord s to the highest point of the arc of platingbetween the two supports (see Figure 1).

The thickness of the plating of the bilge is, in any event, tobe taken as not less than the greater of the thicknesses of thebottom and side.

Sheet steel of plating connected to the stem or to the stern-post or in way of the propeller shaft struts is to have a thick-ness, in mm, not less than the value te given by:

and, in any event, equal to the thickness of the bottomincreased by 50%.

Table 1

bCH 4 5, L 600+⋅=

hCH 1 5, L 100+⋅=

tCH 0 35, L 6+⋅( ) K0 5,⋅=

S/s Ka

1 17,5

1,2 19,6

1,4 20,9

1,6 21,6

1,8 22,1

2,0 22,3

>2 22,4

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 8 s T K⋅( )0 5,⋅ ⋅=

te 0 05, L 6+⋅( ) K0 5,⋅=

Pt B, Ch 2, Sec 5


Figure 1

4 Sheerstrake

4.1

4.1.1 In yachts having L > 50 a sheerstrake plate of heighth, in mm, not less than 0,025 L and thickness not less thanthe greater of the values of the plating of the side and thestringer plate is to be fitted.

In the case of sidescuttles or windows or other openingsarranged on the sheerstrake plate, the thickness is to beincreased sufficiently as necessary in order to compensatesuch openings.

In way of the ends of the bridge, the thickness of the sheer-strake is to be adequately increased.

5 Side

5.1

5.1.1 The thickness of side plating is to be not less than thegreater of the values t1 and t2, in mm, calculated with thefollowing formulae:

where k1, k2 and ka are as defined in 3.1.

5.2

5.2.1 The thickness of the transom is to be no less than thatrequired for the bottom, for the part below the waterline, orfor the side, for the part above the waterline.

In the event of water-jet drive systems, the thickness of thetransom will be the subject of special consideration.

6 Openings in the shell plating

6.1

6.1.1 Sea intakes and other openings are to be wellrounded at the corners and located, as far as possible, out-side the bilge strakes and the keel. Arrangements are to besuch as to ensure continuity of strength in way of openings.

An increase in the thickness of the local plating may berequired where the openings are of unusual dimensions.

6.2

6.2.1 Openings in the curved zone of the bilge strakes maybe accepted where the former are elliptical or fitted withequivalent arrangements to minimise the stress concentra-tion effects. In any event, such openings are to be locatedwell clear of welded connections.

6.3

6.3.1 The internal walls of sea intakes are to have externalplating thickness increased by 1 mm, but not less than 6mm.

7 Local stiffeners

7.1

7.1.1 The thickness of plating determined with the forego-ing formulae is to be increased locally, generally by at least50%, in way of the stem, propeller shaft struts, rudder hornor trunk, stabilisers, anchor recesses, etc.

7.2

7.2.1 Where the aft end is shaped such that the bottomplating aft has a large flat area, RINA may require the localplating to be increased and/or reinforced with the fitting ofadditional stiffeners.

7.3

7.3.1 The thickness of plating is to be locally increased inway of inner or outer permanent ballast arrangements.

The thickness is to be not less than 1,25 that of the adjacentplating but no greater than that of the keel.

8 Cross-deck bottom plating

8.1

8.1.1 The thickness is to be taken, the stiffener spacing sbeing equal, no less than that of the side plating.

Where the gap between the bottom and the waterline is sosmall that local wave impact phenomena are anticipated,an increase in thickness and/or additional internal stiffenersmay be required.

h

S

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 6 5, s T K⋅( )0 5,⋅ ⋅=

Pt B, Ch 2, Sec 6



1 General

1.1 Scope

1.1.1 This Section stipulates the criteria for the structuralscantlings of a single bottom, which may be of either longi-tudinal or transverse type.

1.2 Longitudinal structure

1.2.1 The longitudinal type structure is made up of ordi-nary reinforcements placed longitudinally, supported byfloors. The floors may be supported by girders, which in turn maybe supported by transverse bulkheads, or by the sides of thehull.

1.2.2 A centre girder is to be fitted. Where the breadth of the floors exceeds 6 m, sufficient sidegirders are to be fitted so that the distance between themand the centre girder or the side does not exceed 3 m.

1.2.3 The bottom of the engine room is to be reinforcedwith a suitable web floor consisting of floors and girders;the latter are to extend beyond the engine room for a suita-ble length and are to be connected to any existing girders inother areas.

1.2.4 Additional bottom stiffeners are to be fitted in way ofthe propeller shaft struts, the rudder and the ballast keel.

1.3 Transverse structure

1.3.1 The transverse framing consists of ordinary stiffenersarranged transversally (floors) and placed at each frame sup-ported by girders, which in turn are supported by transversebulkheads or reinforced floors.


1.3.3 In way of the propeller shaft struts, the rudder hornand the ballast keel, additional floors are to be fitted withsufficiently increased scantlings.

1.3.4 The bottom of the engine room is to be reinforcedwith a suitable web floor consisting of floors and girders;the latter are to be fitted as a continuation of the existinggirders outside the engine room.

1.3.5 Floors of increased scantlings are to be fitted in wayof reinforced frames at the sides and reinforced beams onthe weather deck. Any intermediate floors are to be ade-quately connected to the ends.


2.1

2.1.1

s : spacing of ordinary longitudinal or transversestiffeners, in m;

p : scantling pressure, in kN/m2, given in Chap. 1

K : coefficient defined in Sec. 2 of this Chapter.

3 Longitudinal type structure

3.1 Bottom longitudinals

3.1.1 The section modulus of longitudinal stiffeners is tobe not less than the value Z, in cm3, calculated with the fol-lowing formula:

where:

k1 : 0,83 assuming p=p1

: 0,36 assuming p=p2

S : conventional span of the longitudinal stiffener,in m, equal to the distance between floors.

The bottom longitudinal stiffeners are preferably to be con-tinual through the transverse members. Where they are tobe interrupted in way of a transverse watertight bulkhead,brackets are to be provided at the ends.

3.2 Floors

3.2.1 The section modulus of the floors at the centreline ofthe span S is to be not less than the value ZM, in cm3, calcu-lated with the following formula.

where:

k1 : defined in 3.1

b : half the distance, in m, between the two floorsadjacent to that concerned

S : conventional floor span equal to the distance, inm, between the two supporting members (sides,girders, keel with a dead rise edge > 12°).

In the case of a keel with a dead rise edge < 12° but > 8°,the span S is always to be calculated considering the dis-tance between girders or sides; the modulus ZM may, how-ever, be reduced by 40%.

If a side girder is fitted on each side with a height equal tothe local height of the floor, the modulus may be reducedby a further 10%.

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

ZM k1 b S2 K p⋅ ⋅ ⋅ ⋅=

Pt B, Ch 2, Sec 6


3.3 Girders

3.3.1 Centre girder

When the girder forms a support for the floor, the sectionmodulus is to be not less than the value ZPC, in cm3, calcu-lated with the following formula:

where:

k1 : defined in 3.1

bPC : half the distance, in m, between the two sidegirders if supporting or equal to B/2 in theabsence of supporting side girders

S : conventional girder span equal to the distance,in m, between the two supporting members(transverse bulkheads, floors).

Whenever the centre girder does not form a support for thefloors, the section modulus is to be not less than the valueZPC, in cm3, calculated with the following formula:

where:

k1 : defined in 3.1

b’PC : half the distance, in m, between the two sidegirders if present or equal to B/2 in the absenceof side girders

S : distance between the floors.

3.3.2 Side girders

When the side girder forms a support for the floor, the sec-tion modulus is to be not less than the value ZPL, in cm3,calculated with the following formula:

where:

k1 : defined in 3.1.

bPL : half the distance, in m, between the two adja-cent girders or between the side and the girderconcerned


Whenever the side girder does not form a support for thefloors, the section modulus is to be not less than the valueZPL, in cm3, calculated with the following formula:

where:

k1 : defined in 3.1

b’PL : half the distance, in m, between the two adja-cent girders or between the side and the adja-cent girder


4 Transverse type structures

4.1 Ordinary floors

4.1.1 The section modulus for ordinary floors is to be notless than the value Z, in cm3, calculated with the followingformula:

where:

k1 : defined in 3.1

S : conventional span in m, of the floor equal to thedistance between the members which support it(girders, sides).

4.2 Centre girder

4.2.1 The section modulus of the centre girder is to be notless than the value ZPC, in cm3, calculated with the follow-ing formula:

where:


: 0,75 assuming p=p2.


S : conventional span of the centre girder, equal tothe distance, in m, between the two supportingmembers (transverse bulkheads, floors).

4.3 Side girders

4.3.1 The section modulus is to be not less than the valueZPL, in cm3, calculated with the following formula:

where:

k1 : defined in 4.2

bPL : half the distance, in m, between the two adja-cent girders or between the side and the girderadjacent to that concerned

S : conventional girder span equal to the distance,in m, between the two members which supportit (transverse bulkheads, floors).

5 Constructional details

5.1

5.1.1 The centre girder and side girders are to be con-nected to the stiffeners of the transom by means of suitablefittings.

The face plate of the girders may be gradually reduced toreach the dimensions of that of the transom stiffeners.

ZPC k1 bPC S2 K p⋅ ⋅ ⋅ ⋅=

ZPC k1 bPC′ S2 K p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL S2 K p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL′ S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=



Pt B, Ch 2, Sec 7



1 General

1.1

1.1.1 This Section stipulates the criteria for the structuralscantlings of a double bottom, which may be of either lon-gitudinal or transverse type. The longitudinal type structure is made up of ordinary rein-forcements placed longitudinally, supported by floors.

The fitting of a double bottom with longitudinal framing isrecommended for planing and semi-planing yachts.

1.1.2 The fitting of a double bottom extending from thecollision bulkhead to the forward bulkhead in the machin-ery space, or as near thereto as practicable, is requested foryachts of L > 50 m. On yachts of L > 61 m a double bottom is to be fitted, as faras practicable, outside the machinery space extending for-ward to the collision bulkhead and aft to the after peakbulkhead.

On yachts of L > 76 m the double bottom is to extend, as faras this is practicable, throughout the length of the yacht.

The double bottom is to extend transversally to the side soas to protect the bottom in the bilge area, as far as possible.

1.1.3 The dimensions of the double bottom, and in partic-ular the height, are to be such as to allow access for inspec-tion and maintenance. In floors and in side girders, manholes are to be provided inorder to guarantee that all parts of the double bottom canbe inspected at least visually.

The height of manholes is generally to be not greater thanhalf the local height in the double bottom. When manholeswith greater height are fitted, the free edge is to be rein-forced by a flat iron bar or other equally effective reinforce-ments are to be arranged.

Manholes are not to be placed in the continuous centregirder, or in floors and side girders below pillars, except inspecial cases at the discretion of RINA.

1.1.4 Openings are to be provided in floors and girders inorder to ensure down-flow of air and liquids in every part ofthe double bottom. Holes for the passage of air are to be arranged as close aspossible to the top and those for the passage of liquids asclose as possible to the bottom.

Bilge wells placed in the inner bottom are to be watertightand limited as far as possible in height and are to have wallsand bottom of thickness not less than that prescribed forinner bottom plating.

In zones where the double bottom varies in height or isinterrupted, tapering of the structures is to be adopted inorder to avoid discontinuities.

2 Minimum height

2.1

2.1.1 The height of the double bottom is to be sufficient toallow access to all areas and, in way of the centre girder, isto be not less than the value hDF, in mm, obtained from thefollowing formula:

The height of the double bottom is in any event to be notless than 700 mm. For yachts less than 50 m in length, RINAmay accept reduced height.

3 Inner bottom plating

3.1

3.1.1 The thickness of the inner bottom plating is to be notless than the value t1, in mm,calculated with the followingformula:

where:s : spacing of the ordinary stiffeners, in m.For yachts of length L < 50 m, the thickness is to be main-tained throughout the length of the hull.

For yachts of length L > 50 m, the thickness may be gradu-ally reduced outside 0,4 L amidships so as to reach a valueno less than 0,9 t1 at the ends.

Where the inner bottom forms the top of a tank intended forliquid cargoes, the thickness of the top is also to complywith the provisions of Sec.10.

4 Centre girder

4.1

4.1.1 A centre girder is to be fitted, as far as this is practi-cable, throughout the length of the hull. The thickness of the centre girder is to be not less than thefollowing value tpc, in mm:

5 Side girders

5.1

5.1.1 Where the breadth of the floors does not exceed 6m, side girders need not be fitted.

Where the breadth of the floors exceeds 6 m, side girdersare to be arranged with thickness equal to that of the floors.

hdf 28B 32 T 10+( )+=

t1 0 04L, 5s 1+ +( )k0 5,=

tp c 0 008hdf, 2+( )k0 5,=

Pt B, Ch 2, Sec 7


A sufficient number of side girders are to be fitted so that thedistance between them, or between one such girder and thecentre girder or the side, does not exceed 3 m.

The side girders are to be extended as far forward and aft aspracticable and are, as a rule, to terminate on a transversebulkhead or on a floor or other transverse structure of ade-quate strength.

5.2

5.2.1 Where additional girders are foreseen in way of thebedplates of engines, they are to be integrated into thestructures of the yacht and extended as far forward and aftas practicable.

Girders of height no less than that of the floors are to be fit-ted under the bedplates of main engines.

Engine foundation bolts are to be arranged, as far as practi-cable, in close proximity to girders and floors.

Where this is not possible, transverse brackets are to be fit-ted.

6 Floors

6.1

6.1.1 The thickness of floors tm, in mm, is to be not lessthan the following value:

Watertight floors are also to have thickness not less thanthat required in Sec.10 for tank bulkheads.

6.2

6.2.1 When the height of a floor exceeds 900 mm, verticalstiffeners are to be arranged.

In any event, solid floors or equivalent structures are to bearranged in longitudinally framed double bottoms in the fol-lowing locations:

• under bulkheads and pillars

• outside the machinery space at an interval no greaterthan 2 m

• in the machinery space under the bedplates of mainengines

• in way of variations in height of the double bottom.

Solid floors are to be arranged in transversely framed dou-ble bottoms in the following locations:


• in the machinery space at every frame

• in way of variations in height of the double bottom

• outside the machinery space at 2 m intervals.

7 Bracket floors

7.1

7.1.1 At each frame between solid floors, bracket floorsconsisting of a frame connected to the bottom plating and areverse frame connected to the inner bottom plating are tobe arranged and attached to the centre girder and the mar-gin plate by means of flanged brackets with a width offlange not less than 1/10 of the double bottom depth.

The frame section modulus Zc, in cm3, is to be not lessthan:

where:



S : frame span, in m, equal to the distance betweenthe mid-spans of the brackets connecting theframe/reverse frame.

The reverse frame section modulus is to be not less than85% of the frame section modulus.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the frame and reverse frame sectionmoduli are to be no less than those required for tank stiffen-ers as stated in Sec.10.

8 Bottom and inner bottom longitudi-nals

8.1

8.1.1 The section modulus of bottom stiffeners is to be noless than that required for single bottom longitudinals stipu-lated in Sec.6.

The section modulus of inner bottom stiffeners is to be noless than 85% of the section modulus of bottom longitudi-nals.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the section modulus of longitudinals isto be no less than that required for tank stiffeners as statedin Sec.10.

9 Bilge keel

9.1 Arrangement, scantlings and connec-tions

9.1.1 ArrangementWhere installed, bilge keels may not be welded directly onthe shell plating. An intermediate flat, or doubler, isrequired on the shell plating.

The ends of the bilge keel are to be sniped at an angle of15° or rounded with large radius. They are to be located inway of a transverse bilge stiffener. The ends of the interme-diate flat are to be sniped at an angle of 15°.

The arrangement shown in Fig 1 is recommended.

tm 0 008hdf, 0 5,+( )k0 5,=

Zc k1 s S2 p K⋅ ⋅ ⋅ ⋅=

Pt B, Ch 2, Sec 7


Figure 1 : bilge keel arrangement

The arrangement shown in Fig 2 may also be accepted

Figure 2 : bilge keel arrangement

9.1.2 MaterialsThe bilge keel and the intermediate flat are to be made ofsteel with the same yield stress and grade as that of the bilgestrake.

9.1.3 ScantlingsThe net thickness of the intermediate flat is to be equal tothat of the bilge strake. However, this thickness may gener-ally not be greater than 15 mm.


9.2.1 The intermediate flat, through which the bilge keel isconnected to the shell, is to be welded as a shell doubler bycontinuous fillet welds.The butt welds of the doubler and bilge keel are to be fullpenetration and shifted from the shell butts.


Pt B, Ch 2, Sec 8



1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof the reinforcement structures of the side, which may be oflongitudinal or transverse type.

The longitudinal type structure consists of ordinary stiffenersplaced longitudinally supported by reinforced frames, gen-erally spaced not more than 2 m apart, or by transversebulkheads.

The transverse type structure is made up of ordinary rein-forcements placed vertically (frames), which may be sup-ported by reinforced stringers, by decks, by flats or by thebottom structures.

Reinforced frames are to be provided in way of the mast andthe ballast keel, in sailing yachts, in the machinery spaceand in general in way of large openings on the weatherdeck.


2.1

2.1.1


p : scantling pressure, in kN/m2, defined in Part B,Chap. 1, Sec. 5;

K : factor defined in Sec. 2 of this Chapter.

3 Ordinary stiffeners

3.1 Transverse frames

3.1.1 The section modulus of the frames is to be not lessthan the value Z, in cm3, calculated with the following for-mula:

where:



S : conventional frame span, in m, equal to thedistance between the supporting members.

The ordinary frames are to be well connected to the ele-ments which support them, in general made up of a beamand a floor.

3.2 Longitudinal stiffeners

3.2.1 The section modulus of the side longitudinals is to benot less than the value Z, in cm3, calculated with the fol-lowing formula:

The section modulus of the frames is to be not less than thevalue Z, in cm3, calculated with the following formula:

where:



S : conventional span of the longitudinal, in m,equal to the distance between the supportingmembers, in general made up of reinforced fra-mes or transverse bulkheads.

4 Reinforced beams

4.1 Reinforced frames

4.1.1 The section modulus of the reinforced frames is tobe not less than the value Z, in cm3, calculated with the fol-lowing formula:

where:

k1 : 1 assuming p=p1

: 0,7 assuming p=p2

KCR : 0,9 for reinforced frames which support ordi-nary longitudinal stiffeners, or reinforced string-ers;

: 0,4 for reinforced frames which do not supportordinary stiffeners;

s : spacing, in m, between the reinforced frames orhalf the distance between the reinforced framesand the transverse bulkhead adjacent to theframe concerned;

S : conventional span, in m, equal to the distancebetween the members which support the rein-forced frame.

4.2 Reinforced stringers

4.2.1 The section modulus of the reinforced stringers is tobe not less than the value Z, in cm3,calculated with the fol-lowing formula:

where:

k1 : defined in 4.1

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 KCR s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=

Z k1 KCR′ s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=

Pt B, Ch 2, Sec 8


K’CR : • 0,9 for reinforced stringers which supportordinary vertical stiffeners (frames);

• 0,4 for reinforced stringers which do notsupport ordinary vertical stiffeners;

s : spacing,in m, between the reinforced stringersor 0,5 D in the absence of reinforced stringersor decks;

S : conventional span, in m, equal to the distancebetween the members which support thestringer, in general made up of transverse bulk-heads or reinforced frames.

5 Frame connections

5.1 General

5.1.1 End connections of frames are to be bracketed.

5.1.2 ‘Tweendeck frames are to be bracketed to the deck atthe top and welded or bracketed at the bottom.In the case of bulb profiles, a bracket may be required to befitted at the bottom.

5.1.3 Brackets are normally connected to frames by lapwelds. The length of overlap is to be not less than the depthof frames.

6 Scantling of brackets of frame con-nections

6.1

6.1.1 As a general rule, for yachts of length greater than50m, the following scantlings may be adopted:

6.1.2 Upper brackets of framesThe arm length of upper brackets connecting frames to deckbeams is to be not less than the value obtained, in mm,from the following formula:

where:

φ: coefficient equal to:• for unflanged brackets:

φ = 48• for flanged brackets:

φ = 43,5

w : required section modulus of the stiffener, in cm3, givenin [ 6.1.2] and [ 6.3.3] and depending on the type of con-nection,

t : bracket net thickness, in mm.

6.1.3 For connections of perpendicular stiffeners locatedin the same plane (see Fig 1) or connections of stiffenerslocated in perpendicular planes (see Fig 2), the requiredsection modulus is to be taken equal to:

where w1 and w2 are the required section moduli of stiffen-ers, as shown in Fig 1 and Fig 2.

6.1.4 For connections of frames to deck beams (see Fig 3),the required section modulus is to be taken equal to:

• for bracket "A":

• for bracket "B":

where w1 , w'1 and w2 are the required section moduli ofstiffeners, as shown in Fig 3.

Figure 1 : Connections of perpendicular stiffeners in the same plane

Figure 2 : Connections of stiffeners located in per-pendicular planes

d φ w 30+t

-----------------=

w w2= if w2 w1≤

w w1= if w2 w1>

wA w1= if w2 w1≤

wB w'1= butneed not be greater then w1

w2

w1

d

d

w2

w1

d

d

theoriticalbracket

actualbracket

Pt B, Ch 2, Sec 8


Figure 3 : Connections of frames to deck beams

6.2 Lower brackets of frames

6.2.1 In general, frames are to be bracketed to the innerbottom or to the face plate of floors as shown in Fig 4.

Figure 4 : Lower brackets of frames

6.2.2 The arm lengths d1 and d2 of lower brackets offrames are to be not less than the value obtained, in mm,from the following formula:

where:

φ: coefficient equal to:• for unflanged brackets:

φ = 50• for flanged brackets:

φ = 45

w : required section modulus of the frame, in cm3,

t : bracket thickness, in mm.

6.2.3 Where the bracket thickness, in mm, is less than15Lb , where Lb is the length, in m, of the bracket free edge,the free edge of the bracket is to be flanged or stiffened by awelded face plate.

The sectional area, in cm2, of the flange or the face plate isto be not less than 10Lb.

w2

w1

dA

w'1

dA

dB

d B

h'1

h'1

A

B

d1

d2

h

2 h

1,5

h

75

75

d φ w 30+t

-----------------=

Pt B, Ch 2, Sec 9


SECTION 9 DECKS

1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof decks, plating and reinforcing or supporting structures.

The reinforcing and supporting structures of decks consist ofordinary reinforcements, beams or longitudinal stringers,laid transversally or longitudinally, supported by lines ofshoring made up of systems of girders and/or reinforcedbeams, which in turn are supported by pillars or by trans-verse or longitudinal bulkheads.

Reinforced beams together with reinforced frames are to beplaced in way of the mast in sailing yachts.

In sailing yachts with the mast resting on the deck or on thedeckhouse, a pillar or bulkhead is to be arranged in way ofthe mast base.


2.1

2.1.1

pdc : calculation deck, meaning the first deck abovethe full load waterline, extending for at least 0,6L and constituting an efficient support for thestructural elements of the side; in theory, it is toextend for the whole length of the yacht;

s : spacing of ordinary transverse or longitudinalstiffeners, in m;

h : scantling height, in m, the value of which isgiven in Part B, Chap 1, Sec 5;

K : factor defined in Sec 2.

3 Deck plating

3.1 Weather deck

3.1.1 The thickness of the weather deck plating, consider-ing that said deck is also a strength deck, is to be not lessthan the value t, in mm, calculated with the following for-mula:

In yachts having L>50 m, a stringer plate is to be fitted withwidth b, in m, not less than 0,025 L and thickness t, in mm,not less than the value given by the formula:

The stringer plate of increased thickness may be waived ifthe thickness adopted for the deck is greater than Rulethickness.

3.2 Lower decks


Where the deck is a tank top, the thickness of the deck is, inany event, to be not less than the value calculated with theformulae given in Sec.10 for tank bulkhead plating.

4 Stiffening and support structures for decks


4.1.1 The section modulus of the ordinary stiffeners ofboth longitudinal and transverse (beams) type is to be notless than the value Z, in cm3, calculated with the followingformula:

where:

C1 : 1,44 for weather deck longitudinals

: 0,63 for lower deck longitudinals

: 0,56 for beams. S : conventional span, in m, equal to the distance

between the two supporting members.

4.2 Reinforced beams

4.2.1 The section modulus for girders and for ordinaryreinforced beams is to be not less than the value Z, in cm3,calculated with the following equation:

where:

b : average width of the strip of deck resting on thebeam, in m. In the calculation of b any open-ings are to be considered as non-existent

S : conventional span of the reinforced beam, in m,equal to the distance between the two support-ing members (pillars, other reinforced beams,bulkheads).

4.3 Pillars

4.3.1 Pillars are, in general, to be made of tubes. In tanksintended for liquid cargoes, open section pillars are to befitted.The section area of pillars is to be not less than the value A,in cm2, given by the formula:

t 1 9, s L K⋅( )0 5,⋅ ⋅=

t 2 4, s L K⋅( )0 5,⋅ ⋅=

t 1 15, s L K⋅( )0 5,⋅ ⋅=

Z 7 5, C1 s S2 K h⋅ ⋅ ⋅ ⋅ ⋅=

Z 4 75, b S2 K h⋅ ⋅ ⋅ ⋅=

Pt B, Ch 2, Sec 9


where:

Q : load resting on the pillar, in kN, calculated withthe following formula:

where:

A : area of the part of the deck restingon the pillar, in m2.

h : scantling height, defined in [2.1.1].

λ : the ratio between the pillar length and the mini-mum radius of gyration of the pillar cross-sec-tion.

4.3.2 Pillar connectionsHeads and heels of pillars are to be attached to the sur-rounding structure by means of brackets and insert plates sothat the loads are well distributed.

Insert plates may be replaced by doubling plates, except inthe case of pillars which may also work under tension, suchas those in tanks.

In general, the thickness of doubling plates is to be not lessthan 1,5 times the thickness of the pillar.

Pillars are to be attached at their heads and heels by contin-uous welding.

Pillars are to be connected to the inner bottom at the inter-section of girders and floors.

Where pillars connected to the inner bottom are not locatedin way of intersections of floors and girders, partial floors orgirders or equivalent structures suitable to support the pil-lars are to be arranged.

A Q12 5, 0 045λ,–---------------------------------------=

Q 6 87, A h⋅ ⋅=

Pt B, Ch 2, Sec 10



1 General

1.1

1.1.1 The number and position of watertight bulkheadsare, in general, to be in accordance with the provisions ofChapter 1 of Part B.

“Tanks" means the structural tanks that are part of the hulland intended to contain liquids (water, fuel oil or lube oil).

In order to contain fuel oil with a flashpoint ≤ 55° C, the useof independent metal tanks is required as stated in Chapter1 of Part B.

Tanks, complete with all pipe connections, are to be sub-jected to a hydraulic pressure test with a head above thetank top equal to h, as defined in Chap. 1, Sec. 5, or to theoverflow pipe, whichever is the greater.

At the discretion of RINA, leak testing with an air pressureof 0,15 bar may be accepted as an alternative, provided thatit is possible, using liquid solutions of proven effectivenessin the detection of air leaks, to carry out a visual inspectionof all parts of the tanks with particular reference to pipeconnections.

2 Symbols

2.1

2.1.1

s : spacing between the stiffeners, in m

S : conventional span, equal to the distance, in m,between the members that support the stiffenerconcerned

hs, ho : as defined in Part B, Chap. 1, Sec. 5

K : as defined in Chap. 2, Sec. 2.

3 Plating

3.1

3.1.1 The watertight bulkhead plating is to have a thick-ness not less than the value tS in mm, calculated with thefollowing formula:

The coefficient k1 and the scantling height h have the valuesindicated in Table 1.

Table 1 (1/1/2009)

4 Stiffeners


4.1.1 The section modulus of ordinary stiffeners is to benot less than the value Z, in cm3, calculated with the fol-lowing formula:

The values of the coefficient c and of the scantling height hare those indicated in Table 2.


4.2.1 The horizontal webs of bulkheads with ordinary ver-tical stiffeners and reinforced stiffeners in the bulkheadswith ordinary horizontal stiffeners are to have a sectionmodulus not less than the value Z, in cm3, calculated withthe following formula:

C1 : 6, for subdivision bulkheads

: 10, for tank bulkheads

b : width, in m, of the zone of bulkhead resting onthe horizontal web or on the reinforced stiffener

h : scantling height indicated in Table 2.

Table 2 (1/1/2009)

5 General arrangement

5.1

5.1.1 The structural continuity of the bulkhead verticaland horizontal primary supporting members with the sur-rounding supporting structures is to be carefully ensured.

tS k1 s h K⋅( )0 5,⋅ ⋅=

Bulkhead k1 h (m)

Collision bulkhead 4,35 hB

Watertight bulkhead 3,8 hB

Deep tank bulkhead 4,25 hT

Bulkhead h (m) c

Collision bulkhead hB 0,78

Watertight bulkhead hB 0,63

Deep tank bulkhead hT 1

Z 7 5, s S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=

Z C1 b S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=

Pt B, Ch 2, Sec 10


5.2

5.2.1 Where vertical stiffeners are cut in way of watertightdoors, reinforced stiffeners are to be fitted on each side ofthe door and suitably overlapped; cross-bars are to be pro-vided to support the interrupted stiffeners.

6 Non-tight bulkheads

6.1 Non-tight bulkheads not acting as pillars

6.1.1 Non-tight bulkheads not acting as pillars are to beprovided with vertical stiffeners with a maximum spacingequal to:• 0,9 m, for transverse bulkheads• two frame spacings, with a maximum of 1,5 m, for lon-

gitudinal bulkheads.

6.2 Non-tight bulkheads acting as pillars

6.2.1 Non-tight bulkheads acting as pillars are to be pro-vided with vertical stiffeners with a maximum spacing equalto:• two frame spaces, when the frame spacing does not

exceed 0,75 m,• one frame spaces, when the frame spacing is greater

than 0,75 m.

Pt B, Ch 2, Sec 11



1 General

1.1

1.1.1 First tier superstructures or deckhouses are intendedas those situated on the uppermost exposed continuousdeck of the yacht, second tier superstructures or deckhousesare those above, and so on.

Where the distance from the hypothetical freeboard deck tothe full load waterline exceeds the freeboard that can hypo-thetically be assigned to the yacht the reference deck for thedetermination of the superstructure tier may be the deckbelow the one specified above, see Ch 1, Sec 1, [4.3.2].

When there is no access from inside superstructures anddeckhouses to 'tweendecks below, reduced scantlings withrespect to those stipulated in this Section may be acceptedat the discretion of RINA.

2 Boundary bulkhead plating

2.1

2.1.1 The thickness of the boundary bulkheads is to be notless than the value t, in mm, calculated with the followingformula:


h : conventional scantling height, in m, the value ofwhich is to be taken not less than the value indi-cated in Table 1.

K : factor defined in Chap. 2, Sec. 2.

In any event, the thickness t is to be not less than the valuesshown in Chap. 2, Sec. 1, Table 2.

Table 1

3 Stiffeners

3.1

3.1.1 (1/1/2011)

The stiffeners of the boundary bulkheads are to have a sec-tion modulus not less than the value Z, in cm3, calculatedwith the following formula:

where:

h : conventional scantling height, in m, defined in2

K : factor defined in Ch 2, Sec 2

s : spacing of the stiffeners, in m

S : span of the stiffeners, equal to the distance, inm, between the members supporting the stiff-ener concerned.

4 Superstructure decks

4.1 Plating

4.1.1 (1/1/2011)

The superstructure deck plating is to be not less than thevalue t, in mm, calculated with the following formula:

where:


K : factor defined in Ch 2, Sec 2

h : conventional scantling height, in m, defined in[2.1].

4.2 Stiffeners

4.2.1 (1/1/2011)

The section modulus Z, in cm3, of both the longitudinal andtransverse ordinary deck stiffeners is to be not less than thevalue calculated with the following formula:

where:

S : conventional span of the stiffener, equal to thedistance, in m, between the supporting mem-bers

s, h : as defined in [2.1].

Reinforced beams (beams, stringers) and ordinary pillars areto have scantlings as stated in Sec 9.

Type of bulkhead h (m)

1st tier front 1,5

2nd tier front 1,0

Other bulkheads wherever situated 1,0

t 3 s K h⋅( )0 5,⋅ ⋅=

Z 5 5, s S2 h K⋅ ⋅ ⋅ ⋅=

t 4 3, s K h⋅( )0,⋅ ⋅=

Z 5 5, s S2 h K⋅ ⋅ ⋅ ⋅=


Part BHull

Chapter 3

ALUMINIUM HULLS


SECTION 2 MATERIALS



SECTION 5 PLATING




SECTION 9 DECKS



Pt B, Ch 3, Sec 1




1.1

1.1.1 Chapter 3 applies to monohull yachts with a hullmade of aluminium alloy and a length L not exceeding 90m, with motor or sail power with or without an auxiliaryengine. Multi-hulls or hulls with a greater length will be consideredcase by case.

In the examination of constructional plans, RINA may takeinto consideration material distribution and structural scant-lings other than those that would be obtained by applyingthese regulations, provided that structures with longitudinal,transverse and local strength not less than that of the corre-sponding Rule structure are obtained or provided that suchmaterial distribution and structural scantlings prove ade-quate in the opinion of RINA, on the basis of direct test cal-culations of the structural strength.

The formulae indicated in this Chapter are based on use ofan aluminium alloy having yield strength, in the weldedcondition, Rp 0,2 = 110 N/mm2 (corresponding to a perma-nent elongation of 0,2%).

The scantlings of structures made with light alloys havingdifferent values of yield strength are obtained taking intoaccount coefficient K as defined in Section 2.


2.1 Premise

2.1.1 The definitions and symbols in this Article are validfor all the Sections of this Chapter. The definitions of symbols having general validity are notnormally repeated in the various Sections, whereas themeanings of those symbols which have specific validity arespecified in the relevant Sections.


2.2.1 L : scantling length, in m, on the full load water-

line, assumed to be equal to the length on thefull load waterline with the yacht at rest;

B : maximum breadth of the yacht, in m, outsideframes; in tests of the longitudinal strength oftwin hull yachts, B is to be taken as equal totwice the breadth of the single hull, measuredimmediately below the cross-deck;

D : depth of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line up to the deck beam of the upper-most continuous deck;

T : draft of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line to the full load waterline with theyacht at rest in calm water;

s : spacing of the ordinary longitudinal or tran-sverse stiffener, in m;

Δ : displacement of the yacht outside frames, in t,at draught T;

K : factor as a function of the mechanical proper-ties of the aluminium alloy used, as defined inSec. 2.


3.1

3.1.1 Table 1 lists the structural plans that are to be pre-sented in advance to RINA in triplicate, for examinationand approval when required.

The Table also indicates the information that is to be sup-plied with the plans or, in any case, submitted to RINA forthe examination of the documentation.

For documentation purposes, copies of the following planare also to be submitted:


- capacity plan;

- lines plan;

Pt B, Ch 3, Sec 1


Table 1

If the INWATERSURVEY notation is to be assigned, the fol-lowing plans and information are to be submitted:• details showing how rudder pintle and bush clearances

are to be measured and how the security of the pintlesin their sockets is to be verified with the craft afloat.



3.2

3.2.1 If a Builder for the construction of a new vessel of astandard design wants to use drawings already approved for

a vessel similar in design and construction and classed withthe same class notation and the same navigation, the draw-ings may not be sent for approval, but the request for surveyof the vessel is to be submitted with an enclosed list ofdrawings reference and copies of the approved drawingsare to be sent to RINA.

Attention is also to be paid to possible flag Administartionsrequirements, which may determine differences in con-struction.



4 Direct calculations

4.1

4.1.1 When deemed necessary by RINA, direct calcula-tions of the hull structural scantlings are to be carried out,on the basis of the most advanced calculation techinques.When performing direct calculations the load specified inChap 1, Sec 5 are generally to be applied. Where, in thecase of ships of special design for which, in the opinion ofRINA, these requirements are deemed inappropriate, loadscalculated according to other criteria are to be adopted.


5.1


For yachts with length L greater than 50 m, reduced scant-lings may be adopted for the fore and aft zones, providedthat, with particular regard to plating, they are no less thanthose shown in Table 2.



For yachts similar in performance to high speed craft, a lon-gitudinal structure with reinforced floors, placed at adistance of not more than 2 m, is required for the bottom.

Such interval is to be suitably reduced in the areas forwardof amidships subject to the forces caused by slamming.

PLANCONTAINING INFORMATION

RELEVANT TO:

• Midship section • main dimensions, maximumoperating speed V, designacceleration aCG (for planingor semi-planing yachts)

• materials and associatedmechanical properties

• for yachts with L > 40 m, ifmulti-hull, or L > 50 m, ifmono-hull, state the maxi-mum vertical bendingmoment in still water

• displacement

• longitudinal and trasversal section

• Plan of the decks • openings• loads acting, if different

from Rule loads

• Plating development • openings

• Structure of the engineroom

• Watertight bulkheadsand deep tankbulkheads

• openings• location of air outlets

• Structure of stern/side door

• closing appliances

• Superstructures • openings• location of overflow

• Support structure for crane

• design loads and connec-tions to the hull structures

• Rudder • materials of all components• calculation speed

• Propeller shaft struts • material

Pt B, Ch 3, Sec 1


6 Minimum thicknesses

6.1

6.1.1 In general, the thicknesses of plating stiffeners andcores of reinforced beams are to be not less than the mini-mum values shown in Table 2. Lesser thicknesses may be accepted provided that, in theopinion of RINA, their adequacy in terms of bucklingstrength and resistance to corrosion is demonstrated.

Where plating and stiffeners contribute to the longitudinalstrength of the yacht, their scantlings are to be such as tofulfil the requirements for yacht longitudinal strength stipu-lated in Sec. 4.

Table 2

MemberMinimum thickness

(mm)

Keel, bottom plating t1 = 1,75 . L1/3 . K0,5

Side plating t2 = 1,50 . L1/3 . K0,5

Open strength deck plating t3 = 1,50 . L1/3 . K0,5

Lower and enclosed deck plating t4 = t3 - 0,5

1st tier superstructure front bulk-head

t5 = t1

Superstructure bulkhead t6 = t5 - 1,5

Watertight subdivision bulkhead t7 = t2 - 0,5

Tank bulkhead t8 = t2

Centre girder t9 = 2,3 . L1/3 . K0,5

Floors and side girders t10 = 1,70 . L1/3 . K0,5

Tubular pillars t11 = 0,05 d (1)

(1) d = diameter of the pillar, in mm

Pt B, Ch 3, Sec 2


SECTION 2 MATERIALS, CONNECTIONS AND STRUCTURE

DESIGN PRINCIPLES

1 Materials and connections

1.1 General requirements

1.1.1 Materials to be used in hull and equipment construc-tion, in delivery condition, are to comply with theserequirements or with specific requirements applicable toindividual cases; they are to be tested in compliance withthe applicable provisions. Quality and testing requirementsfor materials covered here are outlined in the relevant RINARules.These requirements presume that welding and other cold orhot manufacturing processes are carried out in compliancewith current sound working practice and the relevant RINAprovisions. The latter, in particular, may include require-ments concerning welding operations and techniques andother manufacturing processes (e.g., specific preheatingbefore welding and/or welding or other cold or hot manu-

facturing processes followed by an appropriate heat treat-ment).

Welding processes are to be approved for the specified typeof material for which they are intended and with limits andconditions as stated in the applicable RINA requirements.

1.2 Aluminium alloy hull structures

1.2.1 The designation of aluminium alloys used here com-plies with the numerical designation used in RRIAD (Regis-tration Record of International Alloy Designation).

The characteristics of aluminium alloys to be used in theconstruction of aluminium craft are to comply with the rele-vant requirements of RINA Rules.

As a rule, series 5000 aluminium-magnesium alloys (seeTab 1) or series 6000 aluminium-magnesium-silicon alloys(see Tab 2) are to be used.

Table 1 (1/1/2011)

SERIES 5000 WROUGHT ALUMINIUM ALLOYS FOR WELDED CONSTRUCTION(Rolled products: Plates and Sections)

Guaranteed mechanical characteristics (1)

Alloy (2)

Temper (3)

Dimensionsin mm

Minimum guaranteed yield stress

Rp 0,2 at 0,2%N/mm2

Minimum guaranteed tensile strength Rm

N/mm2

5083 (Plates)

0 or H111t ≤ 6 t > 6

125115

275 275

5083 (Sections)

0 or H111 All thicknesses 110 270

5086 (Plates)


5086 (Sections)


5754 0 or H111t ≤ 6t > 6

8070

190 190

5454 0 or H111 All thicknesses 85 215

5454 F All thicknesses 100 210

(1) The guaranteed mechanical characteristics in this Table correspond to general standard values. For more information, refer to the minimum values guaranteed by the product supplier.

(2) Other grades or tempers may be considered, subject to RINA’s agreement.(3) 0 : annealed

H111: roller levelled after annealingF: as fabricated.

(4) See [1.5.1].

Pt B, Ch 3, Sec 2


Table 2 (1/1/2011)

The use of series 6000 alloys or extruded plates, for partswhich are exposed to sea water atmosphere, will be consid-ered in each separate case by RINA, also taking intoaccount the protective coating applied.

The list of aluminium alloys given in Tab 1 and Tab 2 is notexhaustive. Other aluminium alloys may be considered,provided the specification (manufacture, chemical compo-sition, temper, mechanical properties, welding, etc.) and thescope of application are submitted to RINA for review.

In the case of welded structures, alloys and welding proc-esses are to be compatible and appropriate, to the satisfac-tion of RINA and in compliance with the relevant Rules.

For forgings or castings, requirements for chemical compo-sition and mechanical properties will be defined in eachseparate case by RINA.

In the case of structures subjected to low service tempera-tures or intended for other particular applications, the alloysto be employed will be defined in each separate case byRINA, which will state the acceptability requirements andconditions.

Unless otherwise specified, Young’s modulus for aluminiumalloys is equal to 70000 N/mm2 and Poisson’s ratio equal to0,33.

1.3 Extruded plating

1.3.1 Extrusions with built-in plating and stiffeners,referred to as extruded plating, may be used.

In general, the application is limited to decks and deck-houses. Other uses may be permitted at the discretion ofRINA.

Extruded plating is preferably to be oriented so that the stiff-eners are parallel to the direction of main stresses.

Connections between extruded plating and primary mem-bers are to be given special attention.

1.4 Tolerances

1.4.1 The under-thickness tolerances of plates and rolledsections are to be in accordance with Tab 3.The under-thickness tolerances of extruded plating are to bein accordance with Tab 4.

The responsibility for maintaining the required toleranceslies with the Manufacturer, who is also to inspect the sur-face condition.

1.5 Influence of welding on mechanical characteristics

1.5.1 Welding heat input lowers locally the mechanicalstrength of aluminium alloys hardened by work hardening(series 5000 other than condition 0 or H111) or by heattreatment (series 6000).

Consequently, where necessary, a drop in mechanical char-acteristics of welded structures is to be considered in theheat-affected zone, with respect to the mechanical charac-teristics of the parent material.

The heat-affected zone may be taken to extend 25 mm oneach side of the weld axis.

Aluminium alloys of series 5000 in 0 condition (annealed)or in H111 condition (annealed flattened) are not subject toa drop in mechanical strength in the welded areas.

SERIES 6000 WROUGHT ALUMINIUM ALLOYS FOR WELDED CONSTRUCTION(Rolled products: Plates and Sections)

Guaranteed mechanical characteristics (1)

Alloy (2)

Temper (3)

Dimensionsin mm

Minimum guaranteed yield stress

Rp 0,2 a 0,2%N/mm2

Minimum guaranteed tensile strength Rm

N/mm2

6005 A (Open Sections)

T5 or T6t ≤ 6

6< t ≤ 10 10 < t ≤ 25

225215200

270260 250

6005 A (Closed Sections)

T5 or T6t ≤ 6

6< t ≤ 25 215200

255250

6061 (Sections)

T6 t ≤ 25 240 260

6082(Sections)

T6 t ≤ 15 250 290

(1) The guaranteed mechanical characteristics in this table correspond to general standard values. For more information, refer to the minimum values guaranteed by the product supplier.

(2) Other grades or tempers may be considered, subject to RINA’s agreement.(3) T5 : artificially aged

T6 : solution heat treated and artificially aged.

Pt B, Ch 3, Sec 2


Aluminium alloys of series 5000 other than condition 0 orH111 are subject to a drop in mechanical strength in thewelded areas. The mechanical characteristics to considerare, normally, those of condition 0 or H111. Highermechanical characteristics may be taken into account, pro-vided they are duly justified.

Aluminium alloys of series 6000 are subject to a drop inmechanical strength in the vicinity of the welded areas. Themechanical characteristics to be considered are, normally,to be indicated by the supplier.

Table 3

Table 4

1.6 Material factor K for scantlings of struc-tural members made of aluminium alloy

1.6.1 (1/1/2011)

The value of the material factor K to be introduced into for-mulae for checking scantlings of structural members, givenin this Chapter and the various Appendices, is determinedby the following equation:

where:

Rp0,2 : is the minimum guaranteed yield stress, inN/mm2, of the parent material in delivery condi-tion

R’p0,2 : is the minimum guaranteed yield stress, inN/mm2, of metal in welded condition, i.e.:

• condition 0 or H111 for series 5000 alloys(see [1.5])

• to be indicated by the supplier for series6000 alloys (see [1.5]).

η : is the joint coefficient for the welded assembly,corresponding to the aluminium alloy consid-ered, given in Tab 5 (for series 5000 other thancondition 0 or H11, and series 6000 to be cal-culated by knowing R'p0,2)

β : is the coefficient of metallurgical efficiency,having the same physical mean of η. WhenR’p0,2 is not available, coefficient η is to be takenequal β, given in Tab 6

For welded constructions in hardened aluminium alloys(series 5000 other than condition 0 or H111 and series6000), greater characteristics than those in annealed orwelded condition may be considered, provided that weldedconnections are located in areas where stress levels areacceptable for the alloy considered in annealed or weldedcondition.

In the case of welding of two different aluminium alloys, thematerial factor K to be considered for the scantlings ofwelds is to be the greater material factor of the aluminiumalloys of the assembly.

Table 5 : Joint coefficient for aluminum alloys (1/1/2011)

Table 6 : Aluminum alloys Metallurgical efficiency coefficient ß (1/1/2011)

1.7 Fillet welding

1.7.1 The effective length, in mm, of the weld beads isgiven by:

where d is the actual length, in mm, of the weld bead.

As-built thickness t, in mm

Under-thickness tolerance, in mm

t ≤ 8 0,3

8< t ≤ 12 0,5

12< t ≤ 20 0,7

t > 20 1

As-built thickness t, in mm

Under-thickness tolerance, in mm

t ≤ 6 0,3

6< t ≤ 10 0,4

K 110

η Rp 0 2,⋅--------------------=

Aluminium alloys η

Alloys without work-hardening treatment (series 5000 in annealed condition 0 or annealed flattened condition H111)

1

Alloys hardened by work harden-ing (series 5000 other than condi-tion 0 or H111)

R’p 0,2/Rp 0,2

Alloys hardened by heat treatment (series 6000)

R’p 0,2/Rp 0,2

(1) When no information is available, coefficient η is to be taken equal to the metallurgical efficiency coeffi-cient ß defined in Tab 6.

Note 1:R’p0,2 : minimum guaranteed yield stress, in N/mm2, of

metal in welded condition.

Aluminium alloysTemper

conditionGross thickness,

in mmβ

6005 A(Open sections)

T5 or T6 t ≤ 6 0.45

t > 6 0,40

6005 A(Closed sections)

T5 or T6 All 0,50

6061 (Sections) T6 All 0,53

6082 (Sections) T6 All 0,45

de d 20–=

Pt B, Ch 3, Sec 2


1.8 Riveted connections for aluminium alloy hulls

1.8.1 Use of rivets for connecting structures is limited, inprinciple, only to members which do not contribute to theoverall strength of the hull. Exceptions are to be supportedby experimental evidence or good in-service performance.

The conditions for riveted connection acceptability are tobe individually stated in each particular case, depending onthe type of member to be connected and the rivet material.

Whenever riveted connections are to be employed, adetailed plan, illustrating the process as well as the dimen-sions and location of rivets and holes, together with themechanical and metallurgical properties of the rivets, is tobe submitted for approval.

RINA may, at its discretion, require tension, compressionand shear tests to be carried out on specimens of rivetedconnections constructed under the same conditions as dur-ing actual hull construction, to be witnessed by a RINA Sur-veyor.

RINA reserves the right to accept the results of tests per-formed by recognised bodies or other Societies.

1.9 Welded connections

1.9.1 General requirementsFor welding, the requirements Chap 2, Sec 3 apply. In par-ticular, these provisions make the adoption of welding pro-cedures dependent on their previous qualification by RINA.In addition, individual builders are to hold an authorisationby RINA to use these procedures, employing welders quali-fied by RINA.

1.9.2 Accessibility and edge preparation For correct execution of welded joints, sufficient accessibil-ity is necessary, depending on the welding process adoptedand the welding position.

Edge cutting, to be carried out in general by machining, isto be regular and without burrs or cuts.

The structural parts to be welded as well as those adjacent,even if they have been previously pickled, are to be cleanedcarefully before welding, using suitable mechanical means,such as stainless steel wire brushes, so as to eliminateoxides, grease or other foreign bodies which could give riseto welding defects.

Edge preparation, alignment of joints, spot-welding meth-ods and root chipping are to be appropriate to the type ofjoint and welding position, and comply with RINA require-ments for the welding procedures adopted.

1.9.3 InspectionsInspections of welded connections by RINA Surveyors are,in general, those specified in (a) to (e) below. The extent ofinspection will be defined by RINA on a case by case basis.

a) Inspection of base materials for compliance with therequirements in this Article and of structures with theapproved plans.

b) Inspection of the use and application conditions ofwelding procedures for compliance with those

approved and verification that qualified welders areemployed.

c) Visual examination of edge preparations, root chippingand execution of welds in way of structural connec-tions.

d) Examination of radiographs of welded joints (radio-graphing is to be performed, if necessary, depending onthe extent of the examinations), and inspection of per-formance of the ultrasonic or magnetic particle exami-nations which may be required.

e) Inspection of any repairs, to be performed with proce-dures and inspection methods at the discretion of theRINA Surveyor.

Irrespective of the extent of such inspections, it is theresponsibility of the builder to ensure that the manufactur-ing procedures, processes and sequences are in compliancewith the relevant RINA requirements, approved plans andsound working practice. For this purpose, the shipyard is tohave its own production control organization.

1.9.4 Welding processes for light alloysIn general, the welding of the hull structures is to be per-formed with the MIG (metal-arc inert gas) and TIG (tung-sten-arc inert gas) processes using welding consumablesrecognized as suitable for the base material to be used.Welding processes and filler materials other than thoseabove will be individually considered by RINA at the timeof approval of welding procedures.

For authorisation to use welding procedures in production,the following details are to be stated:

a) grade and temper of parent and filler materials

b) weld execution procedures: type of joint (e.g. butt-joint,fillet joint); edge preparation (e.g. thicknesses, bevelling,right angle edges); welding position (e.g. flat, vertical,horizontal) and other parameters (e.g. voltage, amper-age, gas flow capacity)

c) welding conditions (e.g. cleaning procedures of edgesto be welded, protection from environmental atmos-phere)

d) special operating requirements for butt-joints, for exam-ple for plating: welding to be started and completed onend pieces outside the joint, back chipping, arrange-ments for repairs consequent to possible arc restarts

e) type and extent of controls during production.

1.10 Corrosion protection - Heterogeneous steel/aluminium alloy assembly

1.10.1 Connections between aluminium alloy parts, andbetween aluminium alloy and steel parts, if any, are to beprotected against corrosion by means of coatings applied bysuitable procedures agreed by RINA.

In any case, any direct contact between steel and alumin-ium alloy is to be avoided (e.g. by means of zinc or cad-mium plating of the steel parts and application of a suitablecoating on the corresponding light alloy parts).

Any heterogeneous jointing system is subject to RINA’sagreement.

Pt B, Ch 3, Sec 2


The use of transition joints made of aluminium/steel-cladplates or profiles is subject to RINA’s agreement.

Transition joints are to be type approved.

Qualifications tests for welding procedures are to be carriedout for each joint configuration.

2 Structure design principles

2.1 Protection against corrosion

2.1.1 Scantlings stipulated in Sec 3 and Sec 4 assume thatthe materials used are chosen and protected in such a waythat the strength lost by corrosion is negligible.

2.1.2 The shipyard is to give RINA a document specifyingall the arrangements made to protect the material against

corrosion at the construction stage: coating types, numberand thickness of layers, surface preparation, applicationconditions, control after completion, anodic protection, etc.

2.1.3 This document is also to include maintenancearrangements to be made in service to restore and maintainthe efficiency of this protection, whatever the reasons for itsweakening, and whether or not incidental.

All such maintenance operations are to be listed in a bookshown to the RINA Surveyor in charge upon request.

2.2 Rounding-off

2.2.1 Values for thickness as obtained from formulae are tobe rounded off to the nearest standard value, without such areduction exceeding 3 per cent.

Pt B, Ch 3, Sec 3


SECTION 3 DESIGN LOADS AND HULL SCANTLINGS

1 Design loads

1.1 Application

1.1.1 The requirements in Ch 1, Sec 5, [3], Ch 1, Sec 5,[4], and Ch 1, Sec 5, [5] apply.

2 Hull scantlings

2.1

2.1.1 This Article stipulates requirements for the scantlingsof hull structures (plating, stiffeners, primary supportingmembers). The loads acting on such structures are to be cal-culated in accordance with Ch 1, Sec 5.

In general, for craft with length L > 65 m or speed V > 45knots, the scantlings of transverse structures are to be veri-fied also by direct calculations carried out in accordancewith Ch 3, Sec 1, [4].

For all other craft, RINA may, at its discretion and as analternative to the requirements of this Article, accept scant-lings for transverse structures of the hull based on direct cal-culations in accordance with Ch 3, Sec 1, [4].


2.2.1 “Rule bracket” - A bracket with arms equal to I/8, lbeing the span of the connected stiffener. Where the bracketconnects two different types of stiffeners (frame and beam,bulkhead web and longitudinal stiffener, etc.), the value of lis to be that of the member with the greater span, or accord-ing to criteria specified by RINA.

t : thickness, in mm, of plating and deck panels;

Z : section modulus, in cm3, of stiffeners and pri-mary supporting members;

s : spacing of stiffeners, in m, measured along theplating;

l : overall span of stiffeners, in m, i.e. the distancebetween the supporting elements at the ends ofthe stiffeners (see Fig 4);

S : conventional scantling span of primary support-ing members, in m, to be taken as given in theexamples in Fig 5. Special consideration is to begiven to conditions different from those shown.In no case is S to be less than 1,1 S0, S0 beingthe distance between the internal ends of theconventional brackets as indicated in Fig 5 or, ifthere are no brackets, between the ends of themembers;

b : actual surface width of the load bearing on pri-mary supporting members; for usual arrange-ments b = 0,5 · (l1 + l2), where l1 and l2 are the

spans of stiffeners supported by the primary sup-porting member;

p : design pressure, in kN/m2, calculated as definedin Ch 1, Sec 5, [5];

σam : permissible normal stress, in N/mm2;

τam : permissible shear stress, in N/mm2;

K : material factor defined in Sec 2, [1.6];

e : σp / σbl, ratio between permissible and actualhull girder longitudinal bending stresses (see[2.4]);

σp : maximum admissible stress, in N/mm2, asdefined in [2.4.1];

σbl : longitudinal bending stress, in N/mm2, asdefined in [2.4.1];

μ :

, which is not to be taken greater than 1,0.

2.3 Overall strength

2.3.1 Longitudinal strengthIn general, the scantlings resulting from local strength cal-culations in this Article are such as to ensure adequate lon-gitudinal strength of the hull girder for the craft.

Specific longitudinal strength calculations are to be carriedaccording to the requirements of Sec 4.

2.3.2 Transverse strength of twin-hull craftThe equivalent Von Mises stresses obtained for load condi-tions in Ch 1, Sec 5, [4.4.2] and Ch 1, Sec 5, [4.4.3] are notto exceed 75/K N/mm2.

The compressive values of normal stresses and the shearstresses are not to exceed the values of critical stresses forplates and stiffeners calculated according to [2.5].

In general, the bottom of the cross-deck is to be constitutedby continuous plating for its entire longitudinal and trans-verse extension. Alternative solutions may, however, beexamined by RINA on the basis of considerations pertainingto the height of the cross-deck above the waterline and tothe motion characteristics of the craft.

In the special case of twin hull craft, when the structureconnecting both hulls is formed by a deck with single plat-ing stiffened by n reinforced beams, the normal and shearstresses in the beams for the load condition in Ch 1, Sec 5,[4.4.3] can be calculated as indicated in [2.4.3].

For craft with L > 65 m or speed V > 45 knots, or for thosecraft whose structural arrangements do not permit a realisticassessment of stress conditions based on simple models, thetransverse strength is to be checked by means of direct cal-culations carried out in accordance with the criteria speci-fied in Ch 3, Sec 1, [4].

1 1 0 5 sl---

⎝ ⎠⎛ ⎞⋅,–,

⎝ ⎠⎛ ⎞

0 5,

Pt B, Ch 3, Sec 3


2.3.3 Transverse strength in the special case of twin-hull craft when the structure connecting both hulls is formed by a deck with single plate stiffened by n reinforced beams

See Fig 6; G is the centre of the stiffnesses ri of the n beams.Its position is defined by:

where:a : the abscissa, in m, of the centre G with respect

to an arbitrarily chosen origin 0 ri

, in N/m

Ei : Young’s modulus, in N/mm2, of the beam iIi : bending inertia, in, in m4, of the beam iSi : span, in m, of the beam i between the inner

faces of the hullsxi : abscissa, in m, of the beam i with respect to the

origin 0.If Fi, in N, is the force taken over by the beam i, the deflec-tion yi, in m, of the hull in way of the beam i, is:

di : xi - a, abscissa, in m, of the beam i in relation toG

ω : rotation angle, in rad, of one hull in relation tothe other around a transverse axis passingthrough G.

Considering that the transverse torsional moment (see Ch 1,Sec 3, [3.2.3])

the formula for ω may be obtained as follows:

As Mtt, ri and di are known, and ω thus deduced, the forceFi, in N, the bending moment Mi, in N · m, and the corre-sponding normal and shear stresses can be evaluated ineach beam:

Note 1: Beams calculated by the above method are assumed to befixed in each hull as beams in way of bulkheads inside hulls. Forthis hypothesis to be correct, the beams are to extend over thewhole breadth of both hulls and their stiffness is to be kept thesame over the entire span inside and outside the hulls.

ari xi⋅∑

ri∑--------------------=

ri : 12 Ei Ii⋅ ⋅Si

3----------------------- 106⋅

yiFi Si

3 10 6–⋅ ⋅12 Ei Ii⋅ ⋅

-------------------------------Fi

ri

---- di ω⋅= = =

M tt Fi di 10 3–⋅ ⋅∑=

ω M tt

ri di2⋅∑

--------------------- 103⋅=

Fi ω ri di⋅ ⋅=

Mi Fi Si 2⁄⋅=

Pt B, Ch 3, Sec 3


Figure 1 : Examples of conventional spans of ordinary stiffeners

Pt B, Ch 3, Sec 3


Figure 2 : Examples of conventional spans of primary supporting members

Ap = area of girder face plate

a1 = area of bracket face plate

a1 0,5 Ap

Pt B, Ch 3, Sec 3


Figure 3

2.4 Buckling strength of aluminium alloy structural members

2.4.1 ApplicationThese requirements apply to aluminium alloy plates andstiffeners subjected to compressive loads, to calculate theirbuckling strength.

2.4.2 Elastic buckling stresses of platesa) Compressive stress

The elastic buckling stress, in N/mm2, is given by:

where:m : coefficient equal to:

σE 0 9 mc εt

1000 a⋅---------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=

1 γ2+( )2 for uniform compression ψ( ) 1;=

Pt B, Ch 3, Sec 3


m1 :

t : plate thickness, in mm,E : Young’s modulus, in N/mm2, to be taken

equal to 0,7 · 105 N/mm2;a : shorter side of plate, in m;c : unloaded side of plate, in m;d : loaded side of plate, in m;Ψ : ratio between smallest and largest compres-

sive stress in the case of linear variationacross the panel (0 ≤ Ψ ≤ 1);

γ : , to be not greater than 1;

γ1 :

ε : coefficient equal to:- 1, for edge d stiffened by a flat bar or

bulb section, and γ ≥ 1- 1,1, for edge d stiffened by angle- or T-

section, and γ ≥ 1- 1,1, for edge d stiffened by flat bar or

bulb section, and γ < 1- 1,25, for edge d stiffened by angle- or T-

section, and γ < 1b) Shear stress

The elastic buckling stress, in N/mm2, is given by:

where:mt :

E, t and a are given in (a)b : longer side of plate, in m.

2.4.3 Critical buckling stressa) Compressive stress

The critical buckling stress, in N/mm2, is given by:

where:Rp0,2 : minimum guaranteed yield stress of alumin-

ium alloy used, in N/mm2, in delivery con-dition

σE : elastic buckling stress calculated accordingto [2.5.2], (a) above.

b) Shear stress


where:

τF :

Rp0,2 : minimum guaranteed yield stress of alumin-ium alloy used, in N/mm2, in delivery con-dition

τE : elastic buckling stress calculated accordingto [2.5.2], (b).

2.4.4 Axially loaded stiffenersa) Elastic flexural buckling stress

The elastic flexural buckling stress, in N/mm2, is givenby:

where:r : gyration radius, in mm,

l : moment of inertia of the stiffener, in cm4,calculated with a plate flange of width equalto φ

φ : smaller of:800 · a200 · c

S : area of the cross-section of the stiffener, incm2, excluding attached plating

m : coefficient depending on boundary condi-tions:

- 1, for a stiffener simply supported atboth ends,

- 2, for a stiffener simply supported at oneend and fixed at the other end,

- 4, for a stiffener fixed at both ends.

b) Local elastic buckling stresses

The local elastic buckling stresses, in N/mm2, are givenby:- for flat bars:

- built-up stiffeners with symmetrical flange:

where:

hw : web height, in mm,

tw : web thickness, in mm,bf : flange width, in mm,

tf : flange thickness, in mm.

1γγ1

---- m1 1–( ) , for compression-bending stress+

0 ψ 1), if γ γ1<( )≤ ≤( )

2 1,1 1, ψ+-------------------- 1 γ2+( )2 , for compression-bending stress⋅

0 ψ 1≤ ≤( ) if γ γ1≥

2 1,1 1 ψ+,-------------------- 1 γ1

2+( )2⋅

cd---

4 1 1 ψ+,0 7,

--------------------–⎝ ⎠⎛ ⎞

0 5,

1–

3--------------------------------------------------

⎝ ⎠⎜ ⎟⎜ ⎟⎜ ⎟⎛ ⎞

0 5,

τE 0 9 m t E t1000 a⋅---------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=

5 34 4 ab---

⎝ ⎠⎛ ⎞

2

⋅+,

σc σE= if σE

Rp0 2,

2------------≤

σc Rp 0 2, 1Rp 0 2,

4 σE⋅-------------–

⎝ ⎠⎛ ⎞⋅= if σE

Rp 0 2,

2------------>

τc τE= if τEτF

2----≤

τc τF 1 τF

4 τE⋅------------–

⎝ ⎠⎛ ⎞⋅= if τE

τF

2---->

Rp0 2,

30 5,------------

σE 69 1 r1000 c⋅---------------------

⎝ ⎠⎛ ⎞

2

m 104⋅ ⋅ ⋅,=

10I

S φ t 10 2–⋅ ⋅+-----------------------------------

⎝ ⎠⎛ ⎞

0 5,

σE 55 tw

hw

------⎝ ⎠⎛ ⎞

2

103⋅ ⋅=

σE 27tw

hw

------⎝ ⎠⎛ ⎞

2

104 web⋅ ⋅=

σE 11 tf

bf

----⎝ ⎠⎛ ⎞

2

104 flange⋅ ⋅=

Pt B, Ch 3, Sec 3


c) Critical buckling stress


where:

Rp0,2 : minimum guaranteed yield stress of alumin-ium alloy used, in N/mm2, in delivery con-ditions

η : joint coefficient for the welded assembly,defined in Sec 2, [1.6]

σE : either overall elastic buckling stress or localelastic buckling stress calculated accordingto (a) and (b) above, whichever is the lesser.

σc σE= i f σEη Rp0 2,⋅

2--------------------≤

σc η Rp0 2, 1η Rp0 2,⋅

4 σE⋅--------------------–

⎝ ⎠⎛ ⎞⋅ ⋅= if σE

η Rp 0 2,⋅2

-------------------->

Pt B, Ch 3, Sec 4



1 General

1.1

1.1.1 The structural scantlings prescribed in Chapter 3 arealso intended for the purposes of the longitudinal strengthof a yacht having length L not exceeding 45 m for mono-hull or 40 m for catamarans and openings on the strengthdeck of limited size.

For yachts of greater length and/or openings of size greaterthan the breadth B of the hull and extending for a consider-able part of the length of the yacht, calculation of the longi-tudinal strength is required.

1.2


2 Bending stresses

2.1

2.1.1 In addition to satisfying the minimum requirementsstipulated in the individual Chapters of these Rules, thescantlings of members contributing to the longitudinalstrength of monohull yachts and catamarans are to achievea section modulus of the midship section at the bottom andthe deck such as to guarantee stresses not exceeding theallowable values.

Therefore:

where:

Wf, Wp : section modulus at the bottom and the deck,respectively, of the transverse section, in m3

MT : design total vertical bending moment defined inChap. 1, Sec. 5.



σs : minimum yield stress of the material, in N/mm2.

2.2

2.2.1 The compressive value of normal stresses is not toexceed the value of the critical stresses for plates and stiff-eners calculated in Chap 3, Sec 3, [2.4.2].

2.3

2.3.1 The moment of inertia J of the midship section, inm4, is to be not less than the value given by the followingformulae:

J = 16 . MT . 10-6 for planing yachts

J = 18 . MT . 10-6 for displacement yachts.

3 Shear stresses

3.1

3.1.1 The shear stresses in every position along the lengthL are not to exceed the allowable values; in particular:

where:

Tt : total shear stress in kN defined in Chap. 1, Sec.5

σs, f : defined in 2

At : actual shear of the transverse section, in m2, tobe calculated considering the net area of sideplating and of any longitudinal bulkheadsexcluding openings.

4 Calculation of the section modulus

4.1

4.1.1 In the calculation of the modulus and inertia of themidship section, all the continuous members, plating andlongitudinal stiffeners are generally to be included, pro-vided that they extend for at least 0,4 L amidships.

σ f f σs N mm2⁄⋅≤

σp f σs N mm2⁄⋅≤

σ fMT

1000 Wf

----------------------- N mm2⁄=

σpMT

1000 Wp

------------------------ N mm2⁄=

Tt

At

----- 10 3– f σs⋅≤⋅

Pt B, Ch 3, Sec 5


SECTION 5 PLATING


1.1

1.1.1

s : spacing of ordinary longitudinal or transversestiffener, in m;

p : scantling pressure, in kN/m2, given in Chap. 1,Sec. 5;


2 Keel

2.1 Sheet steel keel

2.1.1 The keel plating is to have a length bCH, in mm,throughout the length of the yacht, not less than the valueobtained by the following equation:

and a thickness not less than that of the adjacent bottomplating increased by 2 mm.

2.2 Solid keel

2.2.1 The height and thickness of the keel, throughout thelength of the yacht, are to be not less than the values hCH

and tCH, in mm, calculated with the following equations:

Lesser heights and thicknesses may be accepted providedthat the effective area of the section is not less than that ofthe Rule section.

Lesser heights and thicknesses may also be acceptable if acentre girder is placed in connection with the solid keel.

The garboard strakes connected to the keel are each to havea width not less than 750 mm and a thickness not less thanthat of the bottom plating increased by 10%.

3 Bottom and bilge

3.1

3.1.1 Bottom plating is the plating up to the chine or to theupper turn of the bilge.

The thickness of the bottom plating and the bilge is to benot less than the greater of the values t1 and t2, in mm, cal-culated with the following formulae:

where:

k1 : 0,15, assuming p=p1

: 0,10, assuming p=p2.

ka : coefficient as a function of the ratio S/s given inTable 1 below where S is the greater dimensionof the plating, in m.

k2 : curvature correction factor given by 1-h/s to betaken not less than 0,7, where h is the distance,in mm, measured perpendicularly from thechord s to the highest point of the arc of platingbetween the two supports (see Figure 1).

Figure 1


Sheet steel of plating connected to the stem or to the stern-post or in way of the propeller shaft struts is to have a thick-ness, in mm, not less than the value te given by:

and, in any event, equal to the thickness of the bottomincreased by 50%.

bCH 4 5, L 600+⋅=

hCH 1 5, L 100+⋅=

tCH 0 35, L 6+⋅( ) K0 5,⋅=

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 11 s T K⋅( )0 5,⋅ ⋅=

h

S

te 1 3, 0 05, L 6+⋅( ) K0 5,⋅ ⋅=

Pt B, Ch 3, Sec 5


Table 1

4 Sheerstrake

4.1

4.1.1 In yachts having L> 50 m, a sheerstrake plate ofheight h, in mm, not less than 0,025 L and thickness not lessthan the greater of the values of the plating of the side andthe stringer plate is to be fitted.

In the case of sidescuttles or windows or other openingsarranged on the sheerstrake plate, the thickness is to beincreased sufficiently as necessary in order to compensatesuch openings.

In way of the ends of the bridge, the thickness of the sheer-strake is to be adequately increased.

5 Side

5.1


where k1, k2 and ka are as defined in 3.1.

5.2

5.2.1 The thickness of the transom is to be no less than thatrequired for the bottom, for the part below the waterline, orfor the side, for the part above the waterline.

In the event of water-jet drive systems, the thickness of thetransom will be the subject of special consideration.


6.1


6.2

6.2.1 Openings in the curved zone of the bilge strakes maybe accepted where the former are elliptical or fitted withequivalent arrangements to minimise the stress concentra-tion effects. In any event, such openings are to be locatedwell clear of welded connections.

6.3


7 Local stiffeners

7.1

7.1.1 The thickness of plating determined with the forego-ing formulae is to be increased locally, generally by at least50%, in way of the stem, propeller shaft struts, rudder hornor trunk, stabilisers, anchor recesses, etc.

7.2


7.3

7.3.1 The thickness of plating is to be locally increased inway of inner or outer permanent ballast arrangements. The thickness is to be not less than 1,25 that of the adjacentplating but no greater than that of the keel.

8 Cross deck bottom plating

8.1

8.1.1 The thickness is to be taken, the stiffener spacing sbeing equal, no less than that of the side plating. Where the gap between the bottom and the waterline isreduced so that local wave impact phenomena are antici-pated, an increase in thickness and/or additional internalstiffeners may be required.

S/s Ka

1 17,5

1,2 19,6

1,4 20,9

1,6 21,6

1,8 22,1

2,0 22,3

>2 22,4

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 10 s T K⋅( )0 5,⋅ ⋅=

Pt B, Ch 3, Sec 6



1 General

1.1 Scope



1.2.1 The longitudinal type structure is made up of ordi-nary reinforcements placed longitudinally, supported byfloors. The floors may be supported by girders, which in turn maybe supported by transverse bulkheads, or by the sides of thehull.







1.3.3 In way of the propeller shaft struts, the rudder hornand the ballast keel, additional floors are to be fitted withsufficiently increased scantlings.

1.3.4 The bottom of the engine room is to be reinforcedwith a suitable web floor consisting of floors and girders;the latter are to be fitted as a continuation of the existinggirders outside the engine room.

1.3.5 Floors are to be fitted in way of reinforced frames atthe sides and reinforced beams on the weather deck. Anyintermediate floors are to be adequately connected to theends.


2.1

2.1.1


p : scantling pressure, in kN/m2, given in Chap. 1;

K : coefficient defined in Sec 2 of this Chapter.



3.1.1 The section modulus of longitudinal stringers is to benot less than the value Z, in cm2, calculated with the fol-lowing formula:

where:


: 0,7 assuming p=p2


The bottom longitudinal stringers are preferably to be con-tinual through the transverse members. Where they are tobe interrupted in way of a transverse watertight bulkhead,brackets are to be provided at the ends.

3.2 Floors


where:




In the case of a keel with a dead rise edge ≤12° but > 8° thespan S is always to be calculated considering the distancebetween girders or sides; the modulus ZM may, however, bereduced by 40%.


Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

ZM k1 b S2 K p⋅ ⋅ ⋅ ⋅=

Pt B, Ch 3, Sec 6


3.3 Girders

3.3.1 Centre girder


where:


bPC : half the distance, in m, between the two sidegirders if supporting or equal to B/2 in theabsence of side girders



where:


b’PC : half the distance, in m, between the two sidegirders if present or equal to B/2in the absenceof side girders


3.3.2 Side girders


where:

k1 : defined in 3.1

bPL : half the distance, in m, between the two adja-cent girders or between the side and the girderconcerned



where:

k1 : defined in 3.1


S : distance between the floors, in m.


4.1 Ordinary floors


where:

k1 : defined in 3.1


4.2 Centre girder


where:

k1 : 2,32 assuming p= p1

: 1,43 assuming p= p2

KPC : half the distance, in m, between the two sidegirders if supporting or equal to B/2 in theabsence of supporting side girders


4.3 Side girders


where:

k1 : defined in 3.1




5.1


The face plate of the girders may be gradually reduced toreach the dimensions of that of the transom stiffeners.


ZPC k1 bPC′ S2 K p⋅ ⋅ ⋅ ⋅=


ZPL k1 bPL′ S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=



Pt B, Ch 3, Sec 7



1 General

1.1

1.1.1 This Section stipulates the criteria for the structuralscantlings of a double bottom, which may be of either lon-gitudinal or transverse type. The longitudinal type structure is made up of ordinary rein-forcements placed longitudinally, supported by floors.


1.1.2 The fitting of a double bottom extending from thecollision bulkhead to the forward bulkhead in the machin-ery space, or as near thereto as practicable, is requested foryachts of L > 50 m. On yachts of L > 61 m a double bottom is to be fitted out-side the machinery space extending, as far as possible, for-ward to the collision bulkhead and aft to the after peakbulkhead.

On yachts of L > 76 m the double bottom is to extend, as faras possible, throughout the length of the yacht.

The double bottom is to extend transversally to the side soas to protect the bottom in the bilge area, as far as possible.

1.1.3 The dimensions of the double bottom, and in partic-ular the height, are to be such as to allow access for inspec-tion and maintenance. In floors and in side girders, manholes are to be provided inorder to guarantee that all parts of the double bottom canbe inspected at least visually.



1.1.4 Openings are to be provided in floors and girders inorder to ensure down-flow of air and liquids in every part ofthe double bottom. Holes for the passage of air are to be arranged as close aspossible to the top and those for the passage of liquids asclose as possible to the bottom.



2 Minimum height

2.1

2.1.1 The height of the double bottom is to be sufficient toallow access to all areas and, in way of the centre girder, isto be not less than the value hDF, in mm, obtained from thefollowing formula:

The height of the double bottom is, in any event, to be notless than 700 mm. For yachts less than 50 m in length RINAmay accept reduced height.


3.1

3.1.1 The thickness of the inner bottom plating is to be notless than the value t1, in mm, calculated with the followingformula:

where:s : spacing of the ordinary stiffeners, in m.

For yachts of length L < 50 m, the thickness is to be main-tained throughout the length of the hull.


Where the inner bottom forms the top of a tank intended forliquid cargoes, the thickness of the top is also to complywith the provisions of Sec. 10.

4 Centre girder

4.1

4.1.1 A centre girder is to be fitted, as far as this is practi-cable, throughout the length of the hull. The thickness of the centre girder is to be not less than thefollowing value tpc, in mm:

5 Side girders

5.1



hdf 28B 32 T 10+( )+=

t1 1 4 0 04L, 5s 1+ +( )k,=

tpc 1 4 0 008,( hdf 2 )+, k⋅=

Pt B, Ch 3, Sec 7




5.2





6 Floors

6.1

6.1.1 The thickness of floors tm, in mm, is to be not lessthan the following value:

Watertight floors are also to have thickness not less thanthat required in Sec. 10 for tank bulkheads.

6.2

6.2.1 When the height of a floor exceeds 900 mm, verticalstiffeners are to be arranged.

In any event, solid floors or equivalent structures are to bearranged in longitudinally framed double bottoms in the fol-lowing locations.

• under buklheads and pillars

• outside the machinery space at an interval no greaterthan 2 m

• in the machinery space under the bedplates of mainengines

• in way of variations in height of the double bottom.

Solid floors are to be arranged in transversely framed dou-ble bottoms in the following locations:


• in the machinery space at every frame

• in way of variations in height of the double bottom

• outside the machinery space at 2 m intervals.

7 Bracket floors

7.1

7.1.1 At each frame between solid floors, bracket floorsconsisting of a frame connected to the bottom plating and areverse frame connected to the inner bottom plating are tobe arranged and attached to the centre girder and the mar-gin plate by means of flanged brackets with a width offlange not less than 1/10 of the double bottom depth.

The frame section modulus Zc, in cm3, is to be not lessthan:

where:



S : frame span, in m, equal to the distance betweenthe mid-spans of the brackets connecting theframe/reverse frame.

The reverse frame section modulus is to be not less than85% of the frame section modulus.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the frame and reverse frame sectionmoduli are to be no less than those required for tank stiffen-ers as stated in Sec. 10.


8.1

8.1.1 The section modulus of bottom stiffeners is to be noless than that required for single bottom longitudinals stipu-lated in Sec. 6.

The section modulus of inner bottom stiffeners is to be noless than 85% of the section modulus of bottom longitudi-nals.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the section modulus of longitudinals isto be no less than that required for tank stiffeners as statedin Sec. 10.

9 Bilge keel

9.1 Arrangement, scantlings and connec-tions

9.1.1 ArrangementWhere installed, bilge keels may not be welded directly onthe shell plating. An intermediate flat, or doubler, isrequired on the shell plating.

The ends of the bilge keel are to be sniped at an angle of15° or rounded with large radius. They are to be located inway of a transverse bilge stiffener. The ends of the interme-diate flat are to be sniped at an angle of 15°.

The arrangement shown in Fig 1 is recommended.

tm 0 008hdf, 0 5,+=

Zc k1 s S2 p K⋅ ⋅ ⋅ ⋅=

Pt B, Ch 3, Sec 7


Figure 1 : Bilge keel arrangement

The arrangement shown in Fig 2 may also be accepted.

9.1.2 Materials

The bilge keel and the intermediate flat are to be made ofthe same alloy as that of the bilge strake.

9.1.3 Scantlings

The net thickness of the intermediate flat is to be equal tothat of the bilge strake. However, this thickness may gener-ally not be greater than 15 mm.

Figure 2 : Bilge keel arrangement


9.2.1 The intermediate flat, through which the bilge keel isconnected to the shell, is to be welded as a shell doubler bycontinuous fillet welds.

The butt welds of the doubler and bilge keel are to be fullpenetration and shifted from the shell butts.


Pt B, Ch 3, Sec 8



1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof the reinforcement structures of the side, which may be oflongitudinal or transverse type.





2.1

2.1.1


p : scantling pressure, in kN/m2, defined in Part B,Chap. 1, Sec. 5 ;



3.1 Transverse frames


where:


: 1 assuming p=p2



3.2 Longitudinal stiffeners


where:k1 : 1,6 assuming p=p1

: 0,7 assuming p=p2


4 Reinforced beams


4.1.1 The section modulus of the reinforced frames is to benot less than the value calculated with the following for-mula:

where:k1 : 1 assuming p=p1

: 0,7 assuming p=p2



s : spacing between the reinforced frames or halfthe distance between the reinforced frames andthe transverse bulkhead adjacent to the frameconcerned;



4.2.1 The section modulus of the reinforced stringers is tobe not less than the value calculated with the following for-mula:

where:k1 : defined in 4.1KCR : 1,92 for reinforced stringers which support ordi-

nary vertical stiffeners (frames); : 0,86 for reinforced stringers which do not sup-

port ordinary vertical stiffeners;

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 KCR s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=

Z k1 KCR′ s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=

Pt B, Ch 3, Sec 8


s : spacing between the reinforced stringers or 0,5D in the absence of other reinforced stringers ordecks;


5 Frame connections

5.1 General

5.1.1 End connections of frames are to be bracketed.

5.1.2 'Tweendeck frames are to be bracketed to the deck atthe top and welded or bracketed at the bottom to the deck.

In the case of bulb profiles, a bracket may be required to befitted at the bottom.

5.1.3 Brackets are normally connected to frames by lapwelds. The length of overlap is to be not less than the depthof frames.

6 Scantling of brackets of frame con-nections

6.1

6.1.1 As a general rule, for yachts of length greater than 50m, the following scantlings may be adopted.

6.1.2 Upper brackets of frames

The arm length of upper brackets connecting frames to deckbeams is to be not less than the value obtained, in mm,from the following formula:

where:

ϕ : coefficient equal to:

• for unflanged brackets:

ϕ = 48

• for flanged brackets:

ϕ = 43,5

w : required net section modulus of the stiffener, incm3, given in [6.1.3] and [6.1.4] and dependingon the type of connection,


6.1.3 For connections of perpendicular stiffeners locatedin the same plane (see Fig 1) or connections of stiffenerslocated in perpendicular planes (see Fig 2), the requiredsection modulus is to be taken equal to:

where w1 and w2 are the required net section moduli ofstiffeners, as shown in Fig 1 and Fig 2.

6.1.4 For connections of frames to deck beams (see Fig 3),the required section modulus is to be taken equal to:

• for bracket “A”:

• for bracket “B”:

wB = w’1 but need not be greater than w1

where w1 , w’1 and w2 are the required net section moduliof stiffeners, as shown in Fig 3.

Figure 1 : Connections of perpendicular stiffenersin the same plane

Figure 2 : Connections of stiffeners locatedin perpendicular planes

d ϕ w 30+t

-----------------=

w w2 if w2 w1≤=

w w1 if w2 w1>=

wA w1 if w2 w1≤=

wA w2 if w2 w1>=

w2

w1

d

d

w2

w1

d

d

theoreticalbracket

actualbracket

Pt B, Ch 3, Sec 8


Figure 3 : Connections of frames to deck beams

6.2 Lower brackets of frames

6.2.1 In general, frames are to be bracketed to the innerbottom or to the face plate of floors as shown in Fig 4.

Figure 4 : Lower brackets of main frames

6.2.2 The arm lengths d1 and d2 of lower brackets offrames are to be not less than the value obtained, in mm,from the following formula:

where:ϕ : coefficient equal to:

• for unflanged brackets:ϕ = 50

• for flanged brackets:ϕ = 45

w : required net section modulus of the frame, incm3,


6.2.3 Where the bracket thickness, in mm, is less than15Lb , where Lb is the length, in m, of the bracket free edge,the free edge of the bracket is to be flanged or stiffened by awelded face plate.

The sectional area, in cm2, of the flange or the face plate isto be not less than 10Lb.

w2

w1

dA

w'1

dA

dB

d B

h'1

h'1

A

B

d1

d2

h

2 h

1,5

h

75

75

d ϕ w 30+t

-----------------=

Pt B, Ch 3, Sec 9


SECTION 9 DECKS

1 General

1.1

1.1.1 This Section lays down the criteria and formulae forthe scantlings of decks, plating and reinforcing or support-ing structures. The reinforcing and supporting structures of decks consist ofordinary reinforcements, beams or longitudinal stringers,laid transversally or longitudinally, supported by lines ofshoring made up of systems of girders and/or reinforcedbeams, which in turn are supported by pillars or by trans-verse or longitudinal bulkheads.




2.1

2.1.1



h : scantling height, in m, the value of which isgiven in Part B, Chap. 1, Sec. 5;


3 Deck plating

3.1 Weather deck


In yachts having L > 50 m, a stringer plate is to be fitted withwidth b, in m, not less than 0,025 L and thickness t, in mm,not less than the value given by the formula:

The stringer plate of increased thickness may be waived ifthe thickness adopted for the deck is greater than Rulethickness.

3.2 Lower decks

3.2.1 The thickness of decks below the weather deckintended for accommodation spaces is to be not less thanthe value calculated with the formula:




4.1.1 The section modulus of the ordinary stiffeners ofboth longitudinal and transverse (beams) type is to be notless than the value Z, in cm3, calculated with the followingequation:

where:

C1 : 1,44 for weather deck longitudinals

: 0,63 for lower deck longitudinals: 0,56 for beams.



where:



4.3 Pillars

4.3.1 Pillars are, in general, to be made of tubes. In tanksintended for liquid cargoes, open section pillars are to befitted.

The section area of pillars is to be not less than the value A,in cm2, given by the formula:

where:

t 2 5, s L K⋅( )0 5,⋅ ⋅=

t 3 1, s L K⋅( )0 5,⋅ ⋅=

t 1 5, s L K⋅( )0 5,⋅ ⋅=

Z 7 5, C1 s S2 K h⋅ ⋅ ⋅ ⋅ ⋅=

Z 9 b S2 K h⋅ ⋅ ⋅ ⋅=

A 1 6Q,12 5, 0 045λ,–---------------------------------------=

Pt B, Ch 3, Sec 9


Q : load resting on the pillar, in kN, calculated withthe following formula:

where:A : area of the part of the deck resting

on the pillar, in m2

h : scantling height, defined in 2.1.1

λ : the ratio between the pillar length and the mini-mum radius of gyration of the pillar cross-sec-tion.

4.3.2 Pillar connectionsHeads and heels of pillars are to be attached to the sur-rounding structure by means of brackets and insert plates sothat the loads are well distributed.

Insert plates may be replaced by doubling plates, except inthe case of pillars which may also work under tension, suchas those in tanks.

In general, the net thickness of doubling plates is to be notless than 1,5 times the net thickness of the pillar.

Pillars are to be attached at their heads and heels by contin-uous welding.

Pillars are to be connected to the inner bottom at the inter-section of girders and floors.

Where pillars connected to the inner bottom are not locatedin way of intersections of floors and girders, partial floors orgirders or equivalent structures suitable to support the pil-lars are to be arranged.

Q 6 87, A h⋅ ⋅=

Pt B, Ch 3, Sec 10



1 General

1.1

1.1.1 The number and position of watertight bulkheadsare, in general, to be in accordance with the provisions ofChap 1, Sec 1.

"Tanks" means the structural tanks that are part of the hulland intended to contain liquids (water, fuel oil or lube oil).

In order to contain fuel oil with a flashpoint ≤ 55° C, the useof independent metal tanks is required as stated in Chapter1 of Part B.


At the discretion of RINA, leak testing with an air pressureof 0,15 bar may be accepted as an alternative, provided thatit is possible, using liquid solutions of proven effectivenessin the detection of air leaks, to carry out a visual inspectionof all parts of the tanks with particular reference to pipeconnections.

2 Symbols

2.1

2.1.1



hS, h0 : as defined in Part B, Chap. 1, Sec. 5

K : as defined in Chap. 2, Sec. 2.

3 Plating

3.1


The coefficient k1 and the scantling height h have the valuesindicated in Table 1.

Table 1 (1/1/2009)

4 Stiffeners



The values of the coefficient c and of the scantling height hare those indicated in Table 2.


4.2.1 The horizontal webs of bulkheads with ordinary ver-tical stiffeners and reinforced stiffeners in the bulkheadswith ordinary horizontal stiffeners are to have a sectionmodulus not less than the value Z, in cm 3, calculated withthe following formula:

where:

C1 : 11,4 for watertight bulkheads

: 19 for deep tank bulkheads


h : scantling height indicated in Table 2.

Table 2 (1/1/2009)

5 General arrangement

5.1

5.1.1 The structural continuity of the bulkhead vertical andhorizontal primary supporting members with the surround-ing supporting structures is to be carefully ensured.

tS k1 s h K⋅( )0 5,⋅ ⋅=

Bulkhead k1 h (m)




Bulkhead h (m) c




Z 14 s S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=

Z C1 b S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=

Pt B, Ch 3, Sec 10


5.2

5.2.1 Where vertical stiffeners are cut in way of watertightdoors, reinforced stiffeners are to be fitted on each side ofthe door and suitably overlapped; cross-bars are to be pro-vided to support the interrupted stiffeners.

6 Non-tight bulkheads

6.1 Non-tight bulkheads not acting as pillars

6.1.1 Non-tight bulkheads not acting as pillars are to beprovided with vertical stiffeners with a maximum spacingequal to:• 0,9 m, for transverse bulkheads• two frame spaces, with a maximum of 1,5 m, for longi-

tudinal bulkheads.

6.2 Non-tight bulkheads acting as pillars

6.2.1 Non-tight bulkheads acting as pillars are to be pro-vided with vertical stiffeners with a maximum spacing equalto:• two frame spaces, when the frame spacing does not

exceed 0,75 m,• one frame space, when the frame spacing is greater than

0,75 m.

Pt B, Ch 3, Sec 11



1 General

1.1


Where the distance from the hypothetical freeboard deck tothe full load waterline exceeds the freeboard that can hypo-thetically be assigned to the yacht, the reference deck forthe determination of the superstructure tier may be the deckbelow the one specified above (see Ch 1, Sec 1, [4.3.5]).



2.1



h : conventional scantling height, in m, the value ofwhich is to be taken not less than the value indi-cated in Table 1.

K : factor defined in Chap. 2, Sec. 2.

In any event, the thickness t is to be not less than the valuesshown in Chap. 2, Sec. 1, Table 2.

Table 1

3 Stiffeners

3.1

3.1.1 The stiffeners of the boundary bulkheads are to havea section modulus not less than the value Z, in cm3, calcu-lated with the following formula:

where:

h : conventional scantling height, in m, defined in2

K : factor defined in Chap. 2, Sec. 2


S : span of the stiffeners, equal to the distance, inm, between the members supporting the stiff-ener concerned.


4.1 Plating

4.1.1 The superstructure deck plating is to be not less thanthe value t, in mm, calculated with the following formula:

where:


K : factor defined in Chap. 3, Sec. 2

h : conventional scantling height, in m, defined in2.1.

4.2 Stiffeners

4.2.1 The section modulus Z, in cm3, of both the longitudi-nal and transverse ordinary deck stiffeners is to be not lessthan the value calculated with the following formula:

where:

S : conventional span of the stiffener, equal to thedistance, in m, between the supporting mem-bers

s, h : as defined in 2.1.

Reinforced beams (beams, stringers) and ordinary pillars areto have scantlings as stated in Sec. 9.


1st tier front 1,5

2nd tier front 1,0


t 3 9, s K h⋅( )0 5,⋅ ⋅=

Z 6 5, s S2 h K⋅ ⋅ ⋅ ⋅=

t 3 9, s K h⋅( )0 5,⋅ ⋅=

Z 6 5, s S2 h K⋅ ⋅ ⋅ ⋅=


Part BHull

Chapter 4

REINFORCED PLASTIC HULLS


SECTION 2 MATERIALS

SECTION 3 CONSTRUCTION AND QUALITY CONTROL


SECTION 5 EXTERNAL PLATING




SECTION 9 DECKS



SECTION 12 SCANTLINGS OF STRUCTURES WITH SANDWICH CONSTRUCTION

Pt B, Ch 4, Sec 1




1.1

1.1.1 Chapter 4 applies to monohull yachts with a hullmade of composite materials and a length L not exceeding60 m, with motor or sail power with or without an auxiliaryengine.

Multi-hulls or hulls with a greater length will be consideredcase by case.

In the examination of constructional plans, RINA may takeinto consideration material distribution and structural scant-lings other than those that would be obtained by applyingthese regulations, provided that structures with longitudinal,transverse and local strength not less than that of the corre-sponding Rule structure are obtained or provided that suchmaterial distribution and structural scantlings prove ade-quate, in the opinion of RINA, on the basis of direct test cal-culations of the structural strength. (See Pt B, Ch 1, Sec 1,par. 3.1)


2.1 Premise

2.1.1 The definitions and symbols in this Article are validfor all the Sections of this Chapter.

The definitions of symbols having general validity are notnormally repeated in the various Sections, whereas themeanings of those symbols which have specific validity arespecified in the relevant Sections.

2.2 Symbols

2.2.1

γr : density of the resin; standard value 1,2 g/cm3;

γv : density of the fibres; standard value for glassfibres 2,56 g/cm3;

p : mass per area of the reinforcement of a singlelayer, in g/m2;

q : total mass per area of a single layer of the lami-nate, in g/m2;

gc : p/q = content of reinforcement in the layer; forlaminates in glass fibre the most frequent maxi-mum values of gc are the following, taking intoaccount that reinforcements are to be "wet" bythe resin matrix and compacted therein: 0,34for reinforcements in mat or cut filaments, 0,5for reinforcements in woven roving or cloth;

P : total mass per area of reinforcements in the lam-inate, in g/m2;

Q : total mass per area of the laminate, in gm2,excluding the surface coating of resin;

Gc : P/Q = content of reinforcement in the laminate;for laminates with glass fibre reinforcements thevalue of GC is to be not less than 0,30;

ti : thickness of a single layer of the laminate, inmm. In the case of glass reinforcements suchthickness is given by:

p being expressed in kg/m2;

tF : Σti = total thickness of the laminate.

2.3 Definitions

2.3.1

Reinforced plastic : a composite material consistingmainly of two components, amatrix of thermosetting resin andof fibre reinforcements, producedas a laminate through moulding;

Reinforcements : reinforcements are made up of aninert resistant material matrix ofthermosetting resin and of fibrereinforcements, encapsulated inthe matrix (resin) to increase itsresistance and rigidity. The rein-forcements usually consist ofglass fibres or other materials,such as aramid or carbon typefibres;

Single-skin laminate : reinforced plastic material with,in general, the shape of a flat orcurved plate, or moulded.

Sandwich laminate : material composed of two single-skin laminates, structurally con-nected by the interposition of acore of light material.


3.1

3.1.1 Plans with the scantlings, the layout and the majorstructures of the hull are to be submitted to RINA for exami-nation sufficiently in advance of commencement of thelaminating of the hull.

ti 0 33p 2 56,gc

------------- 1 36,–⎝ ⎠⎛ ⎞,=

Pt B, Ch 4, Sec 1


The plans are to indicate the scantlings and the minimummechanical properties of the laminates as well as the per-centage in mass of the reinforcement in the laminate.

In general, the following plans are to be sent for examina-tion in triplicate.

• the midship section and the transverse sections with themain dimensions of the construction shown and, forconstructions with an engine, the design speed and thedesign acceleration aCG;

• longitudinal & transverse section and relevant typicalconnection details;

• deck plan;

• construction of the bottom, floors, girders;

• double bottom;

• lamination schedule;

• watertight and subdivision bulkheads;

• superstructures;

• engine and auxiliary foundations.

• structure of stern/side door and relevant closing appli-ances;

• support structure for crane with design loads;

The above-mentioned plans are also to contain the relativelamination details, the percentage, in mass, of the reinforce-ment, the type of resin, core materials characteristics, thesandwich construction process and the type of structuraladhesive used (if any). In the case of reinforcements otherthan glass, the minimum mechanical properties of the lami-nate are to be indicated.

A list of all materials used in the construction, including thecommercial name and the relevant characteristics of eachcomponent such as gel coat, resin, fibre reinforcement, corematerial, fire-retardant additives or resins, adhesive, corebonding materials, details of the process of sandwich con-struction and details of the materials used for grantingreserve of buoyancy (and method of installation), is to besent with the initial submission of the plans and a copy ofthis list is to be provided to the attending Surveyor.The above list of drawings is for guidance purposes only; inparticular, the same plan may be relative to one or more ofthe subjects indicated.

For documentation purposes, copies of the following plansare also to be submitted:


- capacity plan;

- lines plan;

If the INWATERSURVEY notation is to be assigned, the fol-lowing plans and information are to be submitted:

• details showing how rudder pintle and bush clearancesare to be measured and how the security of the pintlesin their sockets is to be verified with the craft afloat.



3.2

3.2.1 If a Builder for the construction of a new vessel of astandard design wants to use drawings already approved fora vessel similar in design and construction and classed withthe same class notation and the same navigation, the draw-ings may not be sent for approval, but the request of surveyof the vessel ois to be submitted with an enclosed list ofdrawings of refernce and copies of the approved drawingsare to be sent to RINA.Attention is also to be paid to possible flag Administartionsrequirements, which may determine differences in con-struction.



4 Direct calculations 4.1 4.1.1 As an alternative to those based on the formulae inthis Chapter, scantlings may be obtained by direct calcula-tions carried out in accordance with the provisions ofChap. 1, Sec. 1 of these Rules. Chapter 1 provides schematisations, boundary conditionsand loads to be used for direct calculations.The scantlings of the various structures are to be such as toguarantee that stress levels do not exceed the allowable val-ues stipulated in Table 1. The values in column 1 are to beused for the load condition in still water, while those in col-umn 2 apply to dynamic loads.

Table 1

MemberAllowable stresses

1 2

Keel, bottom plating 0,4 σ 0, 8 σ

Side plating 0,4 σ 0,8 σ

Deck plating 0,4 σ 0,8 σ

Bottom longitudinals 0,6 σt 0,9 σt

Side longitudinals 0,5 σt 0,9 σt

Deck longitudinals 0,5 σt 0, 9 σt

Floors and girders 0,4 σt 0,8 σt

Frames and reinforced side stringers 0,4 σt 0,8 σt

Reinforced beams and deck girders 0,4 σt 0,8 σt

Note 1:σ(N/mm2): the ultimate bending strength for single-skin

laminates; the lesser of the ultimate tensilestrength and the ultimate compressive strengthfor sandwich type laminates. In this case theshear stress in the core is to be no greater than0,5 Rt, where Rt is the ultimate shear strength ofthe core material;

σt(N/mm2): the ultimate tensile strength of the laminate.

Pt B, Ch 4, Sec 1



5.1 General


For yachts with length L greater than 30 m, reduced scant-lings may be adopted for the fore and aft zones.



For high speed hulls, a longitudinal structure with rein-forced floors, placed at a distance of not more than 2 m, isrequired for the bottom.

Such spacing is to be suitably reduced in the areas forwardof amidships subject to the forces caused by slamming.

5.2 Minimum thicknesses

5.2.1 The thicknesses of the laminates of the various mem-bers calculated using the formulae in this Chapter are to benot less than the values, in mm, in Table 2.

Table 2

The minimum values shown are required for laminates con-sisting of polyester resins and glass fibre reinforcements.

For laminates made using reinforcements of fibres otherthan glass (carbon and/or aramid, glass and aramid), lowerminimum thicknesses than those given in Table 2 may beaccepted on the basis of the principle of equivalence.

In such case, however, the thickness adopted is to be ade-quate in terms of buckling strength.

This thickness is, in any case, to be submitted to RINA forapproval.

6 Construction

6.1 Principles of building

6.1.1 DefinitionsThe stiffeners with the lowest spacing are defined in thisChapter as ordinary stiffeners.

Depending on the direction of ordinary stiffeners, a struc-ture is made of one of the following systems:

- longitudinal framing,

- transverse framing.

Ordinary stiffeners are supported by structural members,defined as primary stiffeners, such as:

- keelsons or floors,

- stringers or web frames,

- reinforced beams or deck stringers.

6.1.2 General provisionsThe purpose of this item [6.1.2] is to give some recom-mended structural details. However, they do not constitutea requirement; different details may be proposed by build-ers and agreed upon by RINA, provided that builders givejustifications, to be defined in each special case.

Arrangements are to be made to ensure the continuity oflongitudinal strength:

• in areas with change of stiffener framing,

• in areas with large change of strength,

• at connections of ordinary and primary stiffeners.

Arrangements are to be made to ensure the continuity oftransverse strength in way of connections between hulls ofcatamarans and axial structure.

Structure discontinuities and rigid points are to be avoided;when the strength of a structure element is reduced by thepresence of an attachment or an opening, proper compen-sation is to be provided.

Openings are to be avoided in highly stressed areas, in par-ticular at ends of primary stiffeners, and for webs of primarystiffeners in way of pillars.

If necessary, the shape of openings is to be designed toreduce stress concentration.

In any case, the corners of openings are to be rounded.

Connections of the various parts of a hull, as well as attach-ment of reinforcing parts or hull accessories, can be madeby moulding on the spot, by bonding separately moulded,or by mechanical connections.

Bulkheads and other important reinforcing elements are tobe connected to the adjacent structure by corner joints (seeFig 1) on both sides, or equivalent joints.

The mass per m2 of the corner joints is to be at least 50% ofthe mass of the lighter of the two elements to be fitted, andat least 900 g/m2 of mat or its equivalent.

MemberSingle-skin laminate

Sandwichlaminate (1)

Keel, bottom plating 5,5 4,5/3,5

Side plating 5 4/3

Inner bottom plating 5 4,5/3,5

Strength deck plating 4 3/2

Lower deck plating 3 2/2

Subdivision bulkhead plating

2,5 2/2

Tank bulkhead plating 4,5 4/3

Side superstructures 2,5 2/2

Front superstructures 3 2,5/2,5

Girders-floors - 2/2

Any stiffeners - 2 (2)

(1) The first value refers to the external skin, the secondrefers to the internal skin

(2) Intended to refer to the thickness of the layers encapsu-lating the core

Pt B, Ch 4, Sec 1


The width of the layers of the corner joints is to be workedout according to the principle given in Fig 1.

The connection of the various parts of the hull, as well asconnection of reinforcing members to the hull, can bemade by adhesives, subject to special examination byRINA.

6.1.3 Plates

The edges of the reinforcements of one layer are not to bejuxtaposed but to overlap by at least 50 mm; these overlapsare to be offset between various successive layers.

Prefabricated laminates are fitted by overlapping the layers,preferably with chamfering of edges to be connected.

The thickness at the joint is to be at least 15% higher thanthe usual thickness.

Changes of thickness for a single-skin laminate are to bemade as gradually as possible and over a width which is, ingeneral, not to be less than thirty times the difference inthickness, as shown in Fig 2.

The connection between a single-skin laminate and a sand-wich laminate is to be carried out as gradually as possibleover a width which is, in general, not to be less than threetimes the thickness of the sandwich core, as shown inFig 3.

a) Deck-side shell connection

This connection is to be designed both for the bendingstress shown in Fig 4, caused by vertical loads on deckand horizontal loads of seawater, and for the shear stresscaused by the longitudinal bending.

In general, the connection is to avoid possible looseningdue to local bending, and ensure longitudinal continu-ity. Its thickness is to be sufficient to keep shear stressesacceptable.

Fig 5 to Fig 8 give examples of deck-side shell connec-tions.

b) Bulkhead-hull connection

In some cases, this connection is needed to distributethe local load due to the bulkhead over a sufficientlength of hull. Fig 9 and Fig 10 give possible solutions.The scantlings of bonding angles are determinedaccording to the loads acting upon the connections.

The builder is to pay special attention to connectionsbetween bulkheads of integrated tanks and structuralmembers.

c) Passages through hull

Passages of metal elements through the hull, especiallyat the level of the rudder stock, shaft brackets, shaft line,etc., are to be strongly built, in particular when sub-jected to alternating loads.

Passages through hull are to be reinforced by means of aplate and counterplate connected to each other.

d) Passages through watertight bulkheads

The continuous omega or rectangle stiffeners at a pas-sage through a watertight bulkhead are to be watertightin way of the bulkhead.

e) Openings in deck

The corners of deck openings are to be rounded in orderto reduce local stress concentrations as much as possi-ble, and the thickness of the deck is to be increased tomaintain the stress at a level similar to the mean stresson the deck.

The reinforcement is to be made from a material identi-cal to that of the deck.

6.1.4 Stiffeners

Primary stiffeners are to ensure structural continuity.

Abrupt changes in web height, flange breadth and cross-sectional area of web and flange are to be avoided.

In general, at the intersection of two stiffeners of unequalsizes (longitudinals with web-frames, floors, beams orframes with stringers, girders or keelsons), the smallest stiff-eners (longitudinals or frames) are to be continuous, andthe connection between the elements is to be made by cor-ner joints according to the principles defined in [6.1.2].

Fig 11 to Fig 13 give various examples of stiffeners.

Connections between stiffeners are to ensure good struc-tural continuity. In particular, the connection between deckbeam and frame is to be ensured by means of a flangedbracket. However, some types of connections withoutbracket may be accepted, provided that loads are lightenough. In this case, stiffeners are to be considered as sup-ported at their ends.

6.1.5 Pillars

Connections between metal pillars subject to tensile loadsand the laminate structure are to be designed to avoid tear-ing between laminate and pillars.

Connections between metal pillars subject to compressiveloads and the laminate structure are to be carried out bymean of intermediate metal plates. The welding of the pillarto the metal plate is to be carried out before fitting of theplate on board ship.

Fig 13 gives the principle for connection between the struc-ture and pillars subject to compressive loads.

6.1.6 Engine seating

The engine seating is to be fitted on special girders suitablypositioned between floors, which locally ensure sufficientstrength in relation to pressure and weight loads.

Fig 15 gives an example of possible seating.

Pt B, Ch 4, Sec 1


Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

50

75

100

125

150

d > 30 Δ t

Δ t

d > 3 t a

t a

Local

loads

Local loads

��

Hull

Deck

Hull

Deck

Hull

Deck

Fender

Pt B, Ch 4, Sec 1


Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Hull

DeckFender

Hull

Bulkhead

Hull

Bulkhead

��

��

��

��

��

��

��

��

��

Pt B, Ch 4, Sec 1


6.2 Engine exhaust

6.2.1 Engine exhaust discharge arrangements made oflaminates are to be of the water injection type with a nor-mal service temperature of approximately 70° C and a max-imum temperature not exceeding 120° C.

6.2.2 (1/1/2009)

The resins used for the lamination are to be type approvedand to have adequate resistance to heat and to chemicalagents as well as a high deflection temperature.

As a general rule, the exhaust ducts are to be internallycoated with two layers of mat of 600 g/m2 laminated withvinylester resin; a flame-retardant or self-extinguishing poly-ester resin, having a thickness of not less than 1,5 mm, witha low deflection at high temperature may be accepted.Details of these resins are to be enclosed with the listrequired in [3.1.1] and general characteristics are to bereported on the relevant drawings.

6.2.3 Additives or pigments which may impair themechanical properties of the resin are not to be used.

6.3 Tanks for liquids

6.3.1 General

Structural tanks are to be intended to contain fuel oil orlube oil. No integral tanks are to contain gasoline. Integraltanks may be of single-skin laminates and sandwich con-struction.

6.3.2 Single-skin laminates and sandwich tanks

For single-skin laminates and sandwich construction tanksthe following requirements are to be applied:

• the final ply of the laminate is to be covered with fibre-glass chopped strand mat of heavy weight (at least 600gr/m2). Alternatively, the internal thickness of the tanks isto be not less than 10 mm;

• the internal surface of the tanks is to have a heavy resincoat, which may incorporate a light fibre tissue, as abarrier to prevent any undue absorption by the lami-nate. This may be carried out with the use of specialresin (isophaltic type) resistant to hydrocarbons. Alterna-tively a suitable thickness of gelcoat is to be applied;

• stiffeners are not to penetrate the tank boundaries sothat, in the event of a fracture of the laminate or frame,the oil will not travel some distance along the continu-ous glass fibres due to a capillary action. Accordingly,the tank is to be isolated by means of diaphragms madeof laminates to form the final internal barrier layeragainst oil absorption;

• the outer surfaces of the tanks are to be coated with afire-retardant paint or resin.

In addition for sandwich construction tanks the follow-ing requirements are to be applied:

• the cores are to be end grain balsa or closed cell polyvi-nylchloride foam;

• each balsa block is to be individually set with the spacearound it filled with resin.

6.3.3 Single-skin laminates and sandwich tanks

Mechanical tests are to be carried out on samples of thelaminate “as is” and after immersion in the fuel oil at ambi-ent temperature for a week. After the immersion themechanical properties of the laminate are to be not lessthan 80% of the value of the sample “as is”. For scantlingcalculations the mechanical characteristics obtained by themechanical tests are to be assumed.

6.3.4 Tanks formed by plywood bulkhead

Where the tank is formed by plywood bulkhead, its surfaceis to completely protected against the ingress of liquid bymeans of a layer of laminate of at least 4 mm in thickness.

6.3.5 Pressure test


At the discretion of RINA, leak testing with an air pressureof 0,015 MPa may be accepted as an alternative, providedthat it is possible, using liquid solutions of proven effective-ness in the detection of air leaks, to carry out a visualinspection of all parts of the tanks with particular referenceto pipe connections.

6.3.6 Tanks protected with flexible inner fuel bladder (1/10/2009)

As an alternative to the requirements given in [6.3.2], theinternal surface of the structural tank can be protected witha flexible inner fuel bladder type approved; the outer sur-face of the structural tank is to be coated with a fire retard-ant paint or resin.

The flexible inner fuel bladder is to be fitted according tothe technical specifications of the manufacturer, to ensurethat the flexible fuel inner fuel bladder can withstand theworking conditions and also maintain adherence to the sup-porting structures.

Type approval for the flexible fuel inner bladder may beobtained providing the following requirements are com-plied with:

a) Dry heat resistance test according to the UNI EN ISO7840 Standard

b) Oil resistance test according to the UNI EN ISO 7840Standard

c) Abrasion test according to the UNI EN ISO 7840 Stand-ard

d) T-peel test according to the ASTM D 1876 Standard

e) Fuel permeability test according to [6.3.7] - Ref. MIL –DTL; tests are to be carried out on 3 specimens – (3tests)

During tests (a), (b) and (d), the load-elongation diagramis to be recorded.

The following minimum requirements are to be satisfiedfor the tests:

1) Dry heat resistance test: after heat aging, specimensare not to have a reduction in tensile strength of

Pt B, Ch 4, Sec 1


more than 20%, or a reduction in elongation ofmore than 50% of the tested value obtained

from the specimens not aged

2) Oil resistance test: after heat aging, specimens arenot to have a reduction in tensile strength of morethan 40%, or a reduction in elongation of more than40% of the tested value obtained from the speci-mens not aged

3) Abrasion test: after 1000 cycles, the test samples arenot to have any helical wire reinforcement exposedat the point of contact with the abrasive surface.

4) T-peel test: the test carried out according to theASTM D 1876 standard on specimens and with themodalities as required by this standard, is to give anaverage load of not less than 80 N.

5) Fuel permeability test: the permeability is to be lessthan 7,6 g/m2 per 24 hours. - The manufacturer is toprovide systems (i.e. foam baffling) to prevent slosh-ing effects and relevant damage inside the tank.

The junctures between the parts of the fuel bladder, the con-nections between the fuel bladder and the accessories forfilling, transfer and suction of fuel oil piping and the con-nection with the air pipes are to be manufactured accordingto methods approved by RINA.

In addition, for type approval, the manufacturer is to adopta quality control system recognized by RINA.

The requirements for the renewal of the certificate are to beagreed with RINA, and concern the abovementioned tests(a) to (e) : in determining which tests are to be carried outfor the renewal, special consideration will be given to thequality control system adopted by the manufacturer and itsdemonstrated efficiency during the last period of approvalof the certificate’s validity.

The certificate will be issued by RINA after examination ofthe test reports with a validity of 5 years.

6.3.7 Fuel permeability test for tanks protected with flexible inner fuel bladder (1/10/2009)

a) Specimen requirements

For fuel tanks employing vulcanized inner fuel bladders,the uncured inner fuel bladder is to be applied to a 25,5x 25,5 cm piece of corrugated fibreboard coated on oneside with a suitable water soluble breakaway agent. Theexposed surface of the inner fuel bladder is to be coatedwith prime cement and barrier resin (if required) thatconform to the manufacturer’s specifications. Theassembly is then to be wrapped in fuel cellophane andcovered with a suitable waterproof bag. The assembly isto be vulcanized by the method used in regular produc-tion. After vulcanization, the waterproofing and cello-phane are to be removed. The inner fuel bladder is thento be removed from the fiberboard. The free moisture is

then to be wiped from the assembly, and the assembly isto be conditioned for 24 hours at a temperature of 25°C

and a relative humidity of 50 to 65 percent.

For fuel tanks using non-vulcanized, continuous innerfuel bladders, the inner fuel bladder is to be applied byproduction method to a 25,5 x 25,5 cm piece of corru-gated fibreboard coated on one side with a suitablerelease agent. The exposed surface of the inner fuelbladder is to be coated with a barrier material that con-forms to the manufacturer’s specifications. The assemblyis then to be cured or otherwise processed by a methodused in regular production. The inner fuel bladder isthen to be removed from the fibreboard. The assembly isto be conditioned for 24 hours at a temperature of 25°Cand a relative humidity of 50 to 65 percent.

After conditioning, two discs 6.4 cm in diameter are tobe cut from the panel prepared above according to thisitem a). One hundred ml of ASTM D471 Ref Fuel B testfluid is to be placed in a cup conforming to Figure 16. Asuitable nylon solution is to be applied to the face of thecup flange covering the area inside the bolt circle.When the nylon solution is almost dry, the test disc is tobe applied to the cup with the barrier, if any, facing out-ward. The assembly is to be completed by attaching thebolting ring shown in the figure, and tightening the boltsin accordance with Tab 3.

b) Test procedure

The cup as prepared above is to be placed in a suitablerack and maintained at a temperature of 25 °C and a rel-ative humidity of 50 to 65 percent for a 1-hour equili-bration period. The cup is to be weighted to the nearest0.005 gram and placed in the rack with the face of thecup facing upward. The cup is to be maintained at atemperature of 25 °C ±5°C, and a relative humidity of50 to 65 percent for a 24 hour period. The cup is then tobe weighted to check for integrity of the seal. The cup isthen to be inverted (test disc down) in a rack that per-mits free access of air to the disc. The cup is to beweighted at the end of the third, fifth and eighth dayafter inverting. Defective films or leaks resulting fromfaulty assembly will usually be found when weightingon the third day. The diffusion rating calculation is to bemade on the fifth of the eight day period and expressedas gram per square meter per 24 hours.

Table 3 (1/10/2009)

Inner fuel bladder type: Bolt torque, in Nm:

Gum stocks 0,56 to 1,13

Coated fabrics 1,69 to 2,26

Unsupported plastic films 2,26 to 2,82

Pt B, Ch 4, Sec 1


Figure 16 : Cup for permeability test (1/10/2009)

0,78 0,78

;

Pt B, Ch 4, Sec 2


SECTION 2 MATERIALS

1 General

1.1

1.1.1 In addition to those in this Section, provisionsregarding the characteristics and test and quality controlprocedures for the manufacture of composite materials arealso specified in Part D, Chap 6.

1.1.2 The basic laminate considered in this Chapter iscomposed of an unsaturated resin, in general polyester, andof glass fibre reinforcements in the form of mat alternatedwith woven roving. The construction may consist of a sin-gle-skin laminate, a sandwich laminate, or a combination ofboth.The reinforcement contained in the laminate is not less than30% by weight; it is laid-up by hand, by mechanical pre-impregnation, or by spraying.

Laminates having a different composition or special systemsof lay-up will be considered by RINA on a case-by-casebasis upon submission of technical documentation illustrat-ing details of the procedure.

All of the materials making up the laminates are to haveproperties suitable for marine use in the opinion of theManufacturer. The products used in the production of thelaminates, whether single-skin or sandwich (resins, rein-forcements, stiffeners, cores, etc.), are to be type approvedby RINA; any structural parts in plywood are to be madewith material type approved by RINA. At the discretion ofthe latter, material type approved by other recognised Soci-eties may be accepted.

2 Definitions and terminology

2.1

2.1.1

Mat : Reinforcements made up of regu-larly distributed filaments on theflat with no particular orientationand held together by a bond so asto form a mat that can be rolledup. The filaments may be cut to apre-determined length or continu-ous.

Roving : Made up of parallel filaments.

Woven Roving : Made from the weaving of roving.Due to their construction theyhave continuous filaments.Woven rovings of different typesexist and can be differentiated by:the type of roving used in warpand weft, the name of the distri-

bution per unit of length, respec-tively in warp and weft.

Mat-woven roving : Combined reinforcement madeup of a layer of mat with cut fila-ments superimposed on a layer ofwoven roving by stitching orbonding.

Hybrid : Reinforcement having fibres oftwo or more different types; a typ-ical example is that of glass fibrewith aramid type fibre.

Unidirectional : Reinforcement made up of fibresthat follow only one directionwithout interweaving.

Biaxial : Reinforcement made up of fibresthat follow two directions (0°-90°), without interweaving.

Quadriaxial : Reinforcement made up of paral-lel fibres in the direction of fillingand warp (0°, 90°) and in twooblique directions (+ 45°).

3 Materials of laminates

3.1 Resins

3.1.1 Resins used are to be type approved by RINA formarine use.

Resins may be for laminating, i.e. form the matrix of lami-nates, or for surface coating (gel coat); the latter are to becompatible with the former, having mainly the purpose ofprotecting the laminate from external agents.

Polyester-orthophthalic type gel coat resins are not permit-ted. In the case of a hull constructed with a sandwich lami-nate on a male mould, the water resistance of the externalsurface will be the subject of special consideration.

Resins are to have the capacity for "wetting" the fibres of thelaminate and for bonding them in such a way that the lami-nate has suitable mechanical properties and, in the case ofglass fibre, not less than those indicated in 3.6.

The resins used are in general of the polyester, polyestervi-nylester or epoxide type; in any case, the resin is to have anultimate elongation of not less than 3,0% if on the surfaceand 2,5% if in the laminate.

Compliant resins used in different structural applicationsare, as a general rule, always to be adopted in conjunctionwith over bonding lamination. The acceptance of structuralfillets of compliant resins alone, without over bonding lami-nation, will be subject to special consideration after analy-sis of test results submitted by the Manufacturer

Pt B, Ch 4, Sec 2


demonstrating equivalent strength to over bonding lami-nates.

Resins are to be used within the limits and following theinstructions supplied by the Manufacturer.

3.1.2 Resins additivesResin additives (catalysts, accelerators, fillers, wax additivesand colour pigments) are to be compatible with the resinsand suitable for their curing process. Catalysts which initi-ate the curing process of the resin and the acceleratorswhich govern the gelling and setting times are to be suchthat the resin sets completely in the environmental condi-tions in which manufacture is carried out. The Manufac-turer's recommendations for the level of catalyst andaccelerator to be mixed into the resins are to be followed.

The inert fillers are not to significantly alter the properties ofthe resin, with particular regard to the viscosity, and are tobe carefully distributed in the resin itself in such a way thatthe laminates have the minimum mechanical propertiesstated in these requirements.

Such fillers are not to exceed 13% (including 3% of anythixotropic filler) by weight of the resins.

The colour pigments are not to affect the polymerisationprocess of the resin, are to be added to the resin as a col-oured paste and are not to exceed the maximum amount (ingeneral 5%) recommended by the Manufacturer. The thixo-tropic fillers of the resins for surface coating are not toexceed 3% by weight of the resin itself.

Details of the resins additives are to be enclosed in the listrequired in Sec 1, [3.1.1].

3.1.3 Flame-retardant additivesWhere the laminate is required to have fire-retarding orflame-retardant characteristics, details of the proposedarrangements are to be submitted for examination.

Where additives are adopted for this purpose, they are to beused in accordance with the Manufacturer's instructions.

The results of tests performed by independent laboratoriesverifying the required characteristics are to be submitted.

Where fire-retarding or flame-retardant characteristics arerequired by the flag Administration, such properties are tobe approved by the relevant Administration, or by RINAwhen authorised by the former.

Details of flame-retardant additives are to be enclosed inthe list required in Sec 1, [ 3.1.1].

3.2 Reinforcements

3.2.1 GeneralAll fibre reinforcements are to be type approved by RINA.The reinforcements used and their characteristics are to beenclosed with the list required in Sec 1, [3.1.1].

The reinforcements taken into consideration in theserequirements are mainly of fibres of three types: glass fibre,aramid type fibre and carbon type fibre.

The use of hybrid reinforcements obtained by coupling theabove-mentioned fibres is also foreseen.

Structures can be obtained using reinforcements of one ormore of the above-mentioned materials.

In the latter case the laminates may be made in alternatelayers, i.e. made up of layers of one material or using hybridreinforcements.

In any event, the manufacturing process is to be approvedin advance by RINA, and to this end a technical report is tobe sent illustrating the processes to be followed and thematerials (resins, reinforcements, etc.) used.

Reinforcements made of materials other than the precedingmay be taken into consideration on a case-by-case basis byRINA, which will stipulate the conditions for their accept-ance.

The materials are to be free from imperfections, discolora-tion, foreign bodies, moisture and other defects and storedand handled in accordance with the Manufacturer's recom-mendations.

3.2.2 Glass fibreThe glass generally used for the manufacture of reinforce-ments is that called type "E", having an alkali content of notmore than 1%, expressed in Na2O.

Reinforcements manufactured in "S" type glass may also beused.

Such reinforcements are to be used for the lamination inhull resin matrices, with the procedure foreseen by theManufacturer, such that the laminates have the samemechanical properties required in the structural calcula-tions and for "E" type glass, these not being less than thoseindicated in item [4].

Reinforcements in glass fibre are generally foreseen in theform of: continuous filament or chopped strand mat, roving,unidirectional woven roving and in combined products i.e.made up of both mat and roving.

3.2.3 Aramid type fibresReinforcements in aramid type fibres are generally used inthe form of roving or cloth of different weights (g/m2).

Such reinforcements can be used in the manufacture ofhulls either alone or alternated with layers of mat or rovingof "E" type glass.

Hybrid reinforcements, in which the aramid type fibres arelaid at the same time, in the same layer as "E" type glassfibres or carbon type fibres, may also be used.

3.2.4 Carbon-graphite fibresCarbon-graphite type fibres means those which are atpresent called "carbon" type, used in the form of productssuitable to be incorporated as reinforcements by themselvesor together with other materials like glass fibres or aramidtype fibres, in resin matrices for the construction of struc-tural laminates.

3.3 Core materials for sandwich laminates

3.3.1 Core materials are to be type approved by RINA;these materials are to be used in accordance with the Man-ufacturer's instructions and the method used in the sand-wich construction is to be forwarded for informationpurposes enclosed with the list required in Sec 1, [3.1.1].

The materials considered in these requirements are rigidexpanded foam plastics and balsa wood.

Pt B, Ch 4, Sec 2


Particular care is to be given to the handling of these materi-als which is to be in accordance to the Mnufacturer's rec-ommendations.

The use of other materials will be taken into considerationon a case-by-case basis by RINA, which will decide theconditions for acceptance on the basis of a criterion ofequivalence.

Polystyrene can only be used as buoyancy material.

3.3.2 "Rigid expanded foam plastics" means expandedpolyurethane (PUR) and polyvinyl chloride (PVC).These materials, just as other materials used for cores, are tobe of the closed-cell type, to be resistant to environmentalagents (salt water, fuel oils, lube oils) and to have a lowabsorption of water.

Furthermore, they are to maintain a good level of resistanceup to the temperature of 60°C and, if worked in nonrigidsheets made up of small blocks, the open weave backingand the adhesive are to be compatible and soluble in theresin of the laminate.

3.3.3 Balsa wood is to be chemically treated againstattacks by parasites and mould and oven dried immediatelyafter cutting.Its humidity is to be no greater than 12%; if worked in non-rigid sheets made up of small blocks, the open weave back-ing and the adhesive are to be compatible and soluble inthe resin of the laminate.The balsa wood is to be laid-up with its grain at right-anglesto the fibres in the surface laminates.

3.3.4 The ultimate tensile strength of the core materials isto be not less than the values indicated in Table 1. Suchcharacteristic is to be ascertained by tests; in any case, corematerials for laminates having an ultimate tensile strength<0,4 N/mm2 are not acceptable.

3.3.5 For the constructions of sandwich structures with thedry vacuum bagging techniques, core bonding paste is to beused; the characteristics are to be enclosed in the list as perSec 1, par 3.1.1. The construction procedures of such sand-wich structures will be subject to special consideration.

Table 1

3.4 Adhesive and sealant material

3.4.1 These materials are to be accepted by RINA beforeuse. Details are to be submitted enclosed with the listrequired in Sec 1 par 3.1.1.

3.5 Plywood

3.5.1 Plywood for structural applications is to be marineplywood type approved by RINA.

Where it is used for the core of reinforcements or sandwichstructures, the surfaces are to be suitably treated to enablethe absorption of the resin and the adhesion of the laminate.

3.6 Timber

3.6.1 The use of timber is subject to special considerationby RINA. In general, the Designer will be required to indi-cate on the drawings submitted the assumed characteristicssuch as strength and density.

3.7 Repair compounds

3.7.1 Materials used for repairs are to be accepted byRINA before use.

For acceptance purposes, the Manufacturer is to submit fullproduct details and user instructions, listing the types ofrepair for which the system is to be used.

Depending on the proposed uses, RINA may require sometests.

3.8 Type approval of materials

3.8.1 Recognition by RINA of the suitability for use (typeapproval) of materials for hull construction may berequested by the Manufacturer. The type approval of res-ins, fibre products of single-skin laminates and core materi-als of sandwich laminates is carried out according to therequirements set out in the relevant RINA Rules.

Table 2 lists the typical mechanical properties of fibrescommonly used for reinforcements.

4 Mechanical properties of laminates

4.1 General

4.1.1 The minimum mechanical properties in N/mm2 oflaminates made with reinforcements of "E" type glass fibremay be obtained from the formulae given in Table 3 as afunction of GC of the laminate as defined in Section 1.

These values are based on the most frequently used lami-nates made up of reinforcements of mat and roving type.

In the above-mentioned Table, the values indicated arethose corresponding to GC = 30, the minimum valueallowed of the content of glass reinforcement.

The minimum mechanical properties of the glass laminatesfound in testing, as a function of GC, are to be no less thanthe values obtained from the formulae of the above-men-tioned Table.

Laminates with reinforcements of fibres other than glass,described in 3.2, are to have mechanical properties that arein general greater than or at least equal to those given inTable 3, the reinforcement content being equal. RINAreserves the right to take into consideration possible lami-nates having certain properties lower than those given in

Material Density (kg/m3)Minimum shear

strength (N/mm2)

Balsa end-grain104 1,6

144 2,5

PVC, crosslinked80 0,9

100 1,4

PVC, linear 80-96 1,2

Polyurethane 90 0,5

Pt B, Ch 4, Sec 2


Table 3, and will establish the procedures and criteria forapproval on a case-by-case basis.

The scantlings indicated in this Chapter are based on thevalues of the mechanical properties of a laminate madewith reinforcements in "E" type glass, with a reinforcementcontent equal to 0,30.

Whenever the mechanical properties of the reinforcementare greater than those mentioned above, the scantlings may

be modified in accordance with the provisions of 4.2.1below.

The mechanical properties and the percentage of reinforce-ment are to be ascertained, for each yacht built, from testson samples taken preferably from the hull or, alternatively,having the same composition and prepared during the lam-ination of the hull (for the tests to be carried out, see Pt D,Ch 6, Sec.3).

Table 2

Table 3

The values of the mechanical properties are to be no lessthan those used for the scantling of the structures.

Where certain values are in fact found to be lower thanthose used for the scantlings, but no lower than 85% of the

latter, RINA reserves the right to accept the laminate subjectto any conditions for acceptance it may stipulate.

Specific gravityTensile modulus of elastic-

ity N/mm2

Shear modulus of elasticity N/mm2 Poisson’s ratio

E Glass 2,56 69000 28000 0,22

S Glass 2,49 69000 (1) 0,20

R Glass 2,58 (1) (1) (1)

Aramid 1,45 124000 2800 0,34

LM Carbon 1,8 230000 (1) (1)

IM Carbon 1,8 270000 (1) (1)

HM Carbon 1,8 300000 (1) (1)

VHM Carbon 2,15 725000 (1) (1)

(1) Values supplied by the Manufacturer and agreed upon with RINA prior to use

1 2

Rm = ultimate tensile strength = 1278 G2c - 510 Gc + 123 85

E = tensile modulus of elasticity = (37 Gc - 4,75) . 103 6350

Rmc = ultimate compressive strength = 150 Gc + 72 117

Ec = compressive modulus of elasticity = (40 Gc - 6) . 103 6000

Rmf = ultimate flexural strength = (502 G2c + 107) 152

Et = flexural modulus of elasticity = (33,4 G2c + 2,2) . 103 5200

Rmt = ultimate shear strength = 80 Gc + 38 62

G = shear modulus of elasticity = (1,7 Gc + 2,24) . 103 2750

Rmti = ultimate interlaminar shear strength = 22,5 - 17,5 Gc 17

Pt B, Ch 4, Sec 2


4.1.2 Mechanical properties of carbon fibre laminates

For carbon fibre laminates the following mechanical prop-erties indicated in Table 4 may be assumed.

Table 4

The above properties are reserved for hand laminated,woven roving and crossplied 0/90 reinforcement high-strengh carbon fibre.

For unidirectional reinforcement the following mechanicalproperties are to be considered.

Table 5

The glass content GC may be assured according to the fol-lowing.

Table 6

Mechanical Properties N/mm2

E = tensile module of elasticity (0° or 90° direction)

75000 GC - 6730

Rm = ultimate tensile strength (0° or 90° direction) 740 GC - 65

Rmc = ultimate compressive strength (0° or 90° direction) 460 GC - 40

Rmf = ultimate flexural strength

Rmtc = ultimate interlaminar shear strength 35 Mpa

Rmf 2 5Rm,

1 RmRmc------------+

⎝ ⎠⎛ ⎞----------------------------=

Mechanical Properties Parallel to the fibres Perpendic to the fibres

E = tensile module of elasticity 151500 GC - 15750 8025 GC2 - 3150 GC + 3300

Rm = ultimate tensile strength 1500 GC - 150 38 GC2 - 15 GC + 15

Rmc = ultimate compressive strength 820 GC - 82 1126 GC2 - 45 GC + 45

Rmf = ultimate flexural strength

Rmti = ultimate interlaminar shear strength 230 GC2 - 180 GC + 60 230 GC

2 - 180 GC + 60

2 5Rm,

1Rm

Rmc------------+⎝ ⎠

⎛ ⎞---------------------------- 2 5Rm,

1Rm

Rmc------------+⎝ ⎠

⎛ ⎞----------------------------

Type of ply reinforcement Open mould Vacuum bag

Simple Surface Complex surface

Chopped strand mat sprayed up 0,22 0,17 0,28

Chopped strand mat hand lay-up 0,22 0,17 0,28

Woven roving 0,40 0,28 0,50

Roving-mat combination [0,46 - 0,18 x Q ] - 0,08 [0,35 - 0,11 x Q ] - 0,08 [0,56 - 0,22 x Q ] - 0,08

Multidirectional fabric 0,41 0,30 0,50

Unidirectional fabric 0,46 0,32 0,57

Pt B, Ch 4, Sec 2


The total thickness in mm of the laminate may be calculatedwith the following formula:

where Q is in kg/m2.

In order to determine the total content GC of the laminate ofn ply the following formula may be applied:

where:

q : is the mass in kg/m2 of the single ply;

Gc : is the glass content of the single ply.

4.2 Coefficients relative to the mechanical properties of laminates

4.2.1 The values of the coefficients Ko and Kof relative tothe mechanical properties of the laminates that appear in

the formulae of the structural scantlings of the hull in thisChapter are given by:

where Rm and Rmf are the values, in N/mm2, of the ultimatetensile and flexural strengths of the laminate. Such valuesmay be calculated with the formulae in Table 3 for glassfibre reinforcements or obtained from mechanical tests onsamples of the laminate for other types of laminate.

Therefore, in the case of laminates with glass fibre havingGC = 30 (minimum allowed), it is to be assumed that:

The values Ko and Kof are to be taken as not less than 0,5and 0,7, respectively, except in specific cases considered byRINA on the basis of the results of tests carried out.

For laminates of sandwich type structures the coefficient isgiven by the formula:

where Rm is the ultimate tensile strength, in N/mm2, of thesurface laminate.

Q Total mass of matTotal mass of glass in laminate Mat Woven Roving+( )---------------------------------------------------------------------------------------------------------------------------------------------=

t Q2 160,---------------- 1 8,

Gc---------

⎝ ⎠⎛ ⎞ 0 6,–

⎝ ⎠⎛ ⎞=

GCq1 q2 q3 ....qn+ + +

q1gc1---------- q2

gc2---------- q3

gc3---------- .... qn

gcn----------+ + +

--------------------------------------------------------------------=

Ko 85 Rm⁄=

Kof152Rmf

----------⎝ ⎠⎛ ⎞

0 5,

=

Ko 1=

Kof 1=̂

Kof′ 85

Rm

------⎝ ⎠⎛ ⎞

0 5,

=

Pt B, Ch 4, Sec 3


SECTION 3 CONSTRUCTION AND QUALITY CONTROL

1 Shipyards or workshops

1.1 General

1.1.1 All construction is to be built using materials andworking processes approved or accepted by RINA.

The Builder is to obtain the approval or acceptance of thematerial used; furthermore it is the Builder’s responsibilityto ensure that all the materials are used in accordance withthe Manufacturer's instructions and recommendations.

Shipyards or workshops for hull construction are to be suita-bly equipped to provide the required working environmentaccording to these requirements, which are to be compliedwith for the recognition of the shipyard or workshop as suit-able for the construction of hulls in reinforced plastic. Thissuitability is to be ascertained by a RINA Surveyor, theresponsibility for the fulfilment of the requirements speci-fied below as well as all other measures for the proper car-rying out of construction being left to the shipyard orworkshop.

When it emerges from the tests carried out that the shipyardor workshop complies with the following provisions, usestype approved materials, and has a system of productionand quality control that satisfies the RINA Rules, so as toensure a consistent level of quality, the shipyard or work-shop may obtain from RINA a special recognition of suita-bility for the construction of reinforced plastic hulls.

The risks of contamination of the materials are to bereduced as far as possible; separate zones are to be pro-vided for storage and for manufacturing processes. Alterna-tive arrangements of the same standard may be adopted.

Compliance with the requirements of this Section does notexempt those in charge of the shipyard or workshop fromthe obligation of fulfilling all the hygiene requirements forwork stipulated by the relevant authorities.

1.2 Moulding shops

1.2.1 Where hand lay-up or spray lay-up processes areused for the manufacture of laminates, a temperature ofbetween 16° and 32°C is to be maintained in the mouldingshop during the lay-up and polymerisation periods. Smallvariations in temperature may be allowed, at the discretionof the RINA Surveyor, always with due consideration beinggiven to the resin Manufacturer's recommendations. Wheremoulding processes other than those mentioned above areused, the temperatures of the moulding shop are to beestablished accordingly.

The relative humidity of the moulding shop is to be kept aslow as possible, preferably below 70%, and in any caselower than the limit recommended by the resin Manufac-

turer. Significant changes in humidity, such as would lead tocondensation on moulds and materials, are to be avoided.

Instruments to measure the humidity and temperature are tobe placed in sufficient number and in suitable positions. Ifnecessary, due to environmental conditions, an instrumentcapable of providing a continuous readout and record ofthe measured values may be required.

Ventilation systems are not to cause an excessive evapora-tion of the resin monomer and draughts are to be avoided.

The work areas are to be suitably illuminated. Precautionsare to be taken to avoid effects on the polymerisation of theresin due to direct sunlight or artificial light.

1.3 Storage areas for materials

1.3.1 Resins are to be stored in dry, well-ventilated condi-tions at the temperature recommended by the resin Manu-facturer. If the resins are stored in tanks, it is to be possibleto stir them at a frequency for a length of time indicated bythe resin Manufacturer. When the resins are stored outsidethe moulding shop, they are to be brought into the shop indue time to reach the working temperature required beforebeing used.

Catalysts and accelerators are to be stored separately inclean, dry and well-ventilated conditions in accordancewith the Manufacturer's recommendations.

Fillers and additives are to be stored in closed containersthat are impervious to dust and humidity.

Reinforcements, e.g. glass fibre, are to be stored in dust-freeand dry conditions, in accordance with the Manufacturer'srecommendations. When they are stored outside the cut-ting area, the reinforcements are to be brought into the lat-ter in due time so as to reach the temperature of themoulding shop before being used.

Pre-impregnated reinforcements are to be stored in an areaset aside for the purpose. The quality control documenta-tion is to keep a record of the storage and depletion of thestock of such reinforcements.

Materials for the cores of sandwich type structures are to bestored in dry areas and protected against damage; they areto be stored in their protective covering until they are used.

1.4 Identification and handling of materials

1.4.1 In the phases of reception and handling the materialsare not to suffer contamination or degradation and are tobear adequate identification marks at all times, includingthose relative to RINA type approval. Storage is to be soarranged that the materials are used, whenever possible, inchronological order of receipt. Materials are not to be usedafter the Manufacturer's date of expiry, except when the lat-ter has given the hull builder prior written consent.

Pt B, Ch 4, Sec 3


2 Hull construction processes

2.1 General

2.1.1 The general requirements for the construction ofhand lay-up or spray lay-up laminates are set out below;processes of other types (e.g. by resin transfer, vacuum orpressurised moulding with mat and continuous filaments)are to be individually recognised as suitable by RINA.

2.2 Moulds

2.2.1 Moulds for production of laminates are to be con-structed with a suitable material which does not affect theresin polymerisation and are to be adequately stiffened inorder to maintain their shape and precision in form. Theyare also not to prevent the finished laminate from beingreleased, thus avoiding cracks and deformations. During construction, provision is to be made to ensure sat-isfactory access such as to permit the proper carrying out ofthe laminating.

Moulds are to be thoroughly cleaned, dried and brought tothe moulding shop temperature before being treated withthe mould release agents, which are not to have an inhibit-ing effect on the gel coat resin.

2.3 Laminating

2.3.1 The gel coat is to be applied by brush, roller orspraying device so as to form a uniform layer with a thick-ness of between 0,4 and 0,6 mm. Furthermore, it is not tobe left exposed for longer than is recommended by theManufacturer before the application of the first layer of rein-forcement. A lightweight reinforcement, generally not exceeding amass per area of 300 g/m2, is to be applied to the gel coatitself by means of rolling so as to obtain a content of rein-forcement not exceeding approximately 0,3.

In the case of hand lay-up processing, the laminates are tobe obtained with the layers of reinforcement laid in thesequence indicated in the approved drawings and eachlayer is to be thoroughly "wet" in the resin matrix and com-pacted to give the required weight content.

The amount of resin laid "wet on wet" is to be limited toavoid excessive heat generation.

Laminating is to be carried out in such a sequence that theinterval between the application of layers is within the lim-its recommended by the resin Manufacturer.

Similarly, the time between the forming and bonding ofstructural members is to be kept within these limits; wherethis is not practicable, the surface of the laminate is to betreated with abrasive agents in order to obtain an adequatebond.

When laminating is interrupted so that the exposed resingels, the first layer of reinforcement subsequently laid is tobe of mat type.

Reinforcements are to be arranged so as to maintain conti-nuity of strength throughout the laminate. Joints betweenthe sections of reinforcement are to be overlapped and stag-gered throughout the thickness of the laminate.

In the case of simultaneous spray lay-up of resin and cutfibres, the following requirements are also to be compliedwith:

• before the use of the simultaneous lay-up system, theManufacturer is to satisfy himself of the efficiency of theequipment and the competence of the operator;

• the use of this technique is limited to those parts of thestructure to which sufficiently good access may beobtained so as to ensure satisfactory laminating;

• before use, the spray lay-up equipment is to be cali-brated in such a way as to provide the required fibrecontent by weight; the spray gun is also to be calibrated,according to the Manufacturer's instruction manual,such as to obtain the required catalyst content, the gen-eral spray conditions and the appropriate length of cutfibres. Such length is generally to be not less than 35mm for structural laminates, unless the mechanicalproperties are confirmed by tests; in any event, thelength of glass fibres is to be not less than 25 mm;

• the calibration of the lay-up system is to be checkedperiodically during the operation;

• the uniformity of lamination and fibre content is to besystematically checked during production.

The manufacturing process for sandwich type laminates istaken into consideration by RINA in relation to the materi-als, processes and equipment proposed by the Manufac-turer, with particular regard to the core material and to itslay-up as well as to details of connections between prefabri-cated parts of the sandwich laminates themselves. The corematerials are to be compatible with the resins of the surfacelaminates and suitable to obtain strong adhesion to the lat-ter (Manufacturer’s instructions to be followed).

Attention is drawn, in particular, to the importance of ensur-ing the correct carrying out of joints between panels.

Where rigid core materials are used, then dry vacuum bag-ging techniques are to be adopted. Particular care is to begiven to the core bonding materials and to the holes pro-vided to ensure efficient removal of air under the core.Bonding paste is to be visible at these holes after vacuumbagging.

2.4 Hardening and release of laminates

2.4.1 On completion of the laminating, the laminate is tobe left in the mould for a period of time to allow the resin toharden before being removed. This period may vary,depending on the type of resin and the complexity of thelaminate, but is to be at least 24 hours, unless a differentperiod is recommended by the resin Manufacturer.

The hull, deck and large assemblies are to be adequatelybraced and supported for removal from the moulds as wellas during the fitting-out period of the yacht.

After the release and before the application of any specialpost-hardening treatment, which is to be examined byRINA, the structures are to be stabilised in the mouldingenvironment for the period of time recommended by theresin Manufacturer. In the absence of recommendations,the period is to be at least 24 hours.

Pt B, Ch 4, Sec 3


2.5 Defects in the laminates

2.5.1 The manufacturing processes of laminates are to besuch as to avoid defects, such as in particular: surfacecracks, surface or internal blistering due to the presence ofair bubbles, cracks in the resin for surface coating, internalareas with non-impregnated fibres, surface corrugation, andsurface areas without resin or with glass fibre reinforce-ments exposed to the external environment.

Any defects are to be eliminated by means of appropriaterepair methods to the satisfaction of the RINA Surveyor.

Dimensions and tolerances are to conform to the approvedconstruction documentation.

2.5.2 The responsibility for maintaining the required toler-ances rests with the builder.

Monitoring and random checking by the Surveyor does notabsolve the builder from this responsibility.

2.6 Checks and tests

2.6.1 Checks and tests are to be arranged during the lami-nation process by the hull builder, in accordance with therelevant quality system, and by the RINA Surveyor.

The hull builder is to maintain a constant check on the lam-inate.

Any defects found are to be eliminated immediately.

In general the following checks and tests are to be carriedout:

a) check of the mould before the application of the releaseagent and of the gel coat;

b) check of the thickness of the gel coat and the uniformityof its application;

c) check of the resin and the amount of catalyst, accelera-tor, hardener and various additives;

d) check of the uniformity of the impregnation of reinfor-cements, their lay-up and superimposition;

e) check and recording of the percentage of the reinforce-ment in the laminate;

f) checks of any post-hardening treatments;

g) general check of the laminate before release from themould;

h) check and recording of the laminate hardness beforerelease from the mould;

i) check of the thickness of the laminate which, in general,is not to differ by more than 15% from the thicknessindicated in approved structural plans;

j) mechanical tests on laminates taken from the hull orprepared during the lamination of the hull (in accor-dance with Pt D, Ch 6, Sec 3).

The thicknesses of the laminates are, in general, to be meas-ured at not less than ten points, evenly distributed acrossthe surface.

The above-mentioned checks and tests are to be carried outas a rule in the presence of a RINA Surveyor; where theshipyard has a system of production organisation and qual-ity control certified by RINA, the checks may be carried outdirectly by the shipyard without the presence of a RINA Sur-veyor.

2.6.2 Where ultrasonic thickness gauges are used, the rele-vant tools are to be calibrated against an identical laminate(of measured thickness).

2.6.3 As a general rule, a method of validating the com-plete laminate thickness is to be agreed on between thebuilder and the Surveyor.

Pt B, Ch 4, Sec 4



1 General

1.1

1.1.1 The structural scantlings prescribed in Chapter 4 arealso intended as appropriate for the purposes of the longitu-dinal hull strength of a yacht having length L not exceeding40 m for monohull yachts or 35 m for catamarans andopenings on the strength deck of limited size.

For yachts of greater length and/or openings of size greaterthan the breadth B of the hull and extending for a consider-able part of the length of the yacht, a test of the longitudinalstrength is required.

1.2


As a guide, the criteria used by RINA for tests of longitudi-nal hull beam strength are shown below.

2 Bending stresses

2.1

2.1.1 In addition to satisfying the minimum requirementsstipulated in the individual Chapters of these Rules, thescantlings of members contributing to the longitudinalstrength of monohull yachts and catamarans are to achievea section modulus of the midship section at the bottom andthe deck such as to guarantee stresses not exceeding theallowable values.

Therefore:

where:

Wf, Wp : section modulus at the bottom and the deck,respectively, of the transverse section in m3

MT : design total vertical bending moment defined inChap. 1, Sec. 5.



σl : the lesser of the values of ultimate tensile andultimate compressive strength, in N/mm2, of thebottom and deck laminate.

2.2

2.2.1 In order to limit the flexibility of the hull structure,the moment of inertia J of the midship section, in m4, is gen-erally to be not less than the value given by the followingformulae:

J = 200 . MT . 10-6 for planing vessels

J = 230 . MT . 10-6 displacement yachts.

2.3

2.3.1 Reference is to be made to Table 1 for plating andTable 2 for longitudinals for calculation of the midship sec-tion modulus.

Table 1

Where there is a sandwich member, the two skins of thelaminate are to be taken into account for the purposes ofthe longitudinal strength only with their own characteristics.The cores may be taken into account only if they offer lon-gitudinal continuity and appreciable strength against axialtension-compression.

For each transverse section within the midship region, thesection modulus, in m3, is given by:

where:

P :

A :

F :

tp, tm, tf, Ep, Em, Ef,: values defined in Table 1

tps, tms, tfs, Eps, Ems, Efs, Ips, Ims, Ifs, tpa, tma, tfa, Epa, Ema, Efa,Hpa,Hma, Hfa, np, nm, nf: values defiined in Table 2

Im, C’ : length, in m, defined in Figure 1.

σ f fσ l≤

σp fσ l≤

σ fMT

1000 Wf

----------------------- N mm2⁄=

σpMT

1000 Wp

------------------------ N mm2⁄=

Deck Side shell Bottom

Mean thickness, in mm tp tm tf

Young’s modulus, in N/mm2 Ep Em Ef

Wp1Ep

----- C' P C'6----- A 1 F P–

F 0 5 A⋅,+---------------------------+⎝ ⎠

⎛ ⎞⋅ ⋅+⋅ 10 3–⋅ ⋅=

Wf1Ef

---- C' P C'6----- A 1 F P–

F 0 5 A⋅,+---------------------------+

⎝ ⎠⎛ ⎞⋅ ⋅+⋅ 10 3–⋅ ⋅=

tp B Ep np Ips tps Eps tpa Hpa Epa⋅ ⋅+⋅ ⋅( )⋅+⋅ ⋅

2 tm Im Em nm tms Ims Ems tma Hma Ema⋅ ⋅+⋅ ⋅( )⋅+⋅ ⋅[ ]

tfB2--- Ef nf Ifs tfs Efs tfa Hfa Efa⋅ ⋅+⋅ ⋅( )⋅+⋅ ⋅

Pt B, Ch 4, Sec 4


Table 2

Figure 1

3 Shear stresses

3.1

3.1.1 The shear stresses in every position along the lengthL are not to exceed the allowable values; in particular:

where:Tt : total shear stress in kN defined in Chap. 1, [5.4]

f : defined in [2]τ : shear stress of the laminate, in N/mm2

Αt : actual shear area of the transverse section, inm2, to be calculated considering the net area ofside plating and of any longitudinal bulkheadsexcluding openings.

Deck Side shell Bottom

Flange

Mean thickness, in mm tps tma tfs

Young’s modulus, in N/mm2 Eps Ema Efs

Breadth in mm Ips Ims Ifs

Web

Equivalent thickness in Section I, in mm tpa tma tfa

Young’s modulus, in N/mm2 Epa Ema Efa

Height in mm Hpa Hma Hfa

Number of longitudinals np nm nf

Tt

At

----- 10 3– f τ⋅≤⋅

Pt B, Ch 4, Sec 5


SECTION 5 EXTERNAL PLATING

1 General

1.1

1.1.1 Bottom and side plating may be made using bothsingle-skin laminate and sandwich structure.

When the two solutions are adopted for the hull, a suitabletaper is to be made between the two types.

Bottom plating is the plating up to the chine or to the upperturn of the bilge.

When the side thickness differs from the bottom thicknessby more than 3 mm, a transition zone is to be foreseen.

.


2.1

2.1.1

S : larger dimension of the plating panel, in m

s : spacing of the ordinary longitudinal or trans-verse stiffener, in m

p : scantling pressure, in kN/m2, given in Chap. 1,Sec. 5

Kof, Ko : factors defined in Sec. 2 of this Chapter.

3 Keel

3.1

3.1.1 The keel is to extend the whole length of the yachtand have a breadth bCH, in mm, not less than the valueobtained by the following formula:

The thickness of the keel is to be not less than the value tCH,in mm, obtained by the following formula:

t being the greater of the values t1 and t2, in mm, calculatedas specified in 5 assuming the spacing s of the correspond-ing stiffeners.

Appraising s, dead rise edge > 12° is considered as a stiff-ener.

The thickness tCH is to be gradually tapered transversally, tothe thickness of the bottom and in the case of hulls having aU-shaped keel, the thickness of the keel is to extend, trans-versally, as indicated in Figure 2 b) in Section 1, taperingwith the bottom plating.

In yachts with sail and ballast keel, the thickness of the keelfor the whole length of the ballast keel is to be increased by

30%; this increase is to extend longitudinally to fore and aftof the ballast for a suitable length.

When the hull is laminated in halves, the keel joint is to becarried out as shown in Figure 5 in Section 1 or in a similarway.

4 Rudder horn

4.1

4.1.1 When the rudder is of the semi-spade type, such asType I B shown in Chapter 1, Section 2, Figure 2, the rele-vant rudder horn is to have dimensions and thickness suchthat the moment of inertia J, in cm4, and the section modu-lus Z, in cm3, of the generic horizontal section of the sameskeg, with respect to its longitudinal axis are not less thanthe values given by the following formulae:

where:

A : the rudder area, in m2, acting on the horn;

h : the vertical distance, in mm, from the skeg sec-tion to the lower edge of the pintle (rudderheel);

V : maximum design speed of the yacht, in knots.

5 Bottom plating

5.1

5.1.1 The thickness of bottom plating is to be not less thanthe greater of the values t1 and t2, in mm, calculated withthe following formulae:

where:

k1 : 0,26, when assuming p=p1

: 0,15, when assuming p=p2

ka : coefficient as a function of the ratio S/s given inTable 1.


The minimum bottom shell thickness is to extend to thechine line or 150mm above the statical load waterline,whichever is the greater.

bCH 30L=

tCH 1 4t,=

J A h2 V2⋅ ⋅36

------------------------10 3–=

Z A h V2⋅ ⋅55

----------------------=

t1 k1 ka s kof p0 5,⋅ ⋅ ⋅ ⋅=

t2 16 s ko f D0 5,⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 5


If the plating has a pronounced curve, as for example in thecase of the hulls of sailing yachts, the thickness calculatedwith the formulae above may be reduced multiplying by (1 -f/s), f being the distance, in m, between the connectingbeam and the two extremities of the plating concerned andthe surface of the plating itself. This reduction may not beassumed less than 0,70.

In sailing yachts with or without auxiliary engine in way ofthe ballast keel, when the width of the latter is greater thanthat of the keel, the thickness of the bottom is to beincreased to the value taken for the keel.

Table 1

6 Sheerstrake plating and side plating

6.1 Sheerstrake

6.1.1 A sheerstrake plate of height h, in mm, not less than0,025 L and thickness tc, in mm, not less than the value inthe following formula is to be fitted:

where t is the greater of the thicknesses t1 and t2, calculatedas stated in 6.2 below.

6.2 Side plating


where k1 and ka are as defined in 5.1.


7.1


The edges of openings are to be suitably sealed in order toprevent the absorption of water.

7.2

7.2.1 Openings in the curved zone of the bilge strakes maybe accepted where the former are elliptical or fitted withequivalent arrangements to minimise the stress concentra-tion effects.

7.3


8 Local stiffeners

8.1

8.1.1 The thickness of plating determined with the forego-ing formulae is to be increased locally, generally by at least50%, in way of the propulsion engine bedplates, stem (thethickness is not required to be greater than that of the keelin this case), propeller shaft struts, rudder horn or trunk, sta-bilisers, anchor recesses, etc.

8.2


8.3

8.3.1 The thickness of plating is to be locally increased inway of inner or outer permanent ballast arrangements asindicated in 3.1.1.

8.4

8.4.1 The thickness of the transom is to be not less thanthat of the side plating for the portion above the waterline,or less than that of the bottom for the portion below thewaterline.

Where water-jets or propulsion systems are fitted directly tothe transom, the scantlings of the latter will be the subject ofspecial consideration.

In such case a sandwich structure with marine plywoodcore of adequate thickness is recommended.

9 Cross-deck bottom plating

9.1

9.1.1 The thickness is to be taken, the stiffener spacing sbeing equal, no less than that of the side plating.

Where the gap between the bottom and the waterline is sosmall that local wave impact phenomena are anticipated,an increase in thickness and/or additional internal stiffenersmay be required.

S/s Ka

1 17,5

1,2 19,6

1,4 20,9

1,6 21,6

1,8 22,1

2,0 22,3

>2 22,4

tc 1 30t,=

t1 k1 ka s kof p0 5,⋅ ⋅ ⋅ ⋅=

t2 12 s ko f D0 5,⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 6



1 General

1.1 Scope



1.2.1 A centre girder is to be fitted. In the case of a keelwith a dead rise > 12°, the centre girder may be omitted butin such case the fitting of a longitudinal stringer is required.

Where the breadth of the floors exceeds 6 m, sufficient sidegirders are to be fitted so that the distance between themand the centre girder or the side does not exceed 3 m.





1.3.2 A centre girder is to be fitted. In the case of a keelwith a dead rise > 12°, the centre girder may be omitted butin such case the fitting of a longitudinal stringer is required.

Where the breadth of the floors exceeds 6 m, sufficient sidegirders are to be fitted so that the distance between themand the centre girder or the side does not exceed 3 m.



1.3.5 Floors are to be fitted in way of reinforced frames atthe sides and reinforced deck beams.

Any intermediate floors are to be adequately connected tothe ends.


2.1

2.1.1


p : scantling pressure, in kN/m2, given in Chap. 1,Sec.5;

Ko : coefficient defined in Sec. 2 of this Chapter.



3.1.1 The section modulus of longitudinal stringers is to benot less than the value Z, in cm2, calculated with the fol-lowing formula:

where:


: 1 assuming p=p2


3.2 Floors


where:

k1 : 2,4 assuming p = p1

1,2 assuming p = p2



In the case of a U-shaped keel or one with a dead rise edge≤12° but > 8°, the span S is always to be calculated consid-ering the distance between girders or sides; the modulus ZM

may, however, be reduced by 40%.


Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

ZM k1 b S2 Ko p⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 6


3.3 Girders

3.3.1 Centre girder


where:

k1 : defined in 3.2

b’PC : half the distance, in m, between the two sidegirders if supporting or equal to B/2 in theabsence of supporting side girders



where:

k1 : defined in 3.1

b’PC : half the distance, in m, between the two sidegirders if present or equal to B/2 in the absenceof side girders


3.3.2 Side girders


where:

k1 : defined in 3.2

b’PL : half the distance, in m, between the two adja-cent girders or between the side and the girderconcerned



where:

k1 : defined in 3.1


S : distance between the floors, in m.


4.1 Ordinary floors


where:

k1 : defined in 3.1


4.2 Centre girder


where:

k1 : defined in 3.2



4.3 Side girders


where:

k1 : defined in 3.2




5.1


ZPC k1 bPC S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPC k1 bPC′ S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL′ S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL′ S2 Ko p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPC k1 bPC S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL S2 Ko p⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 7



1 General

1.1

1.1.1 This Section stipulates the criteria for the structuralscantlings of a double bottom, which may be of either lon-gitudinal or transverse type.

The longitudinal type structure is made up of ordinary rein-forcements placed longitudinally, supported by floors.


1.1.2 The fitting of a double bottom extending from thecollision bulkhead to the forward bulkhead of the machin-ery space, or as near thereto as practicable, is requested foryachts of L > 50 m.

1.1.3 The dimensions of the double bottom, and in partic-ular the height, are to be such as to allow access for inspec-tion and maintenance.

In floors and in side girders, manholes are to be provided inorder to guarantee that all parts of the double bottom canbe inspected at least visually.



1.1.4 Openings are to be provided in floors and girders inorder to ensure down-flow of air and liquids in every part ofthe double bottom.

Holes for the passage of air are to be arranged as close aspossible to the top and those for the passage of liquids asclose as possible to the bottom.

The edges of the holes are to be suitably sealed in order toprevent the absorption of liquid into the laminate.



2 Minimum height

2.1

2.1.1 The height of the double bottom is to be sufficient toallow access to all areas and, in way of the centre girder, isto be not less than the value hdF, in mm, obtained from thefollowing formula:

The height of the double bottom is in any event to be notless than 700 mm. For yachts less than 50 m in length, RINAmay accept reduced height.


3.1

3.1.1 The thickness of the inner bottom plating is to be notless than the value t1, in mm, calculated with the followingformula:

where:

s : spacing of the ordinary stiffeners, in m

kof : coefficients for the properties of the materialdefined in Sec 2.

For yachts of length L <50 m the thickness is to be main-tained throughout the length of the hull.


Where the inner bottom forms the top of a tank intended forliquid cargoes, the thickness of the top is also to complywith the provisions of Sec 10.

4 Centre girder

4.1

4.1.1 A centre girder is to be fitted, as far as this is practi-cable, throughout the length of the hull.

The thickness of the core of a sandwich type centre girder isto be not less than the following value tpc, in mm:

where kof is defined in Sec 2.

Where a single-skin laminate is used for the centre girder,the thickness is to be not less than twice that defined above.

hdf 28B 32 T 10+( )+=

t1 1 3 0 04L, 5s 1+ +( )kof for gle skin laminate–sin,=

t1 0 04L, 5s 1+ +( )kof for sandwich laminate=

tpc 0 125L, 3 5,+( )kof=

Pt B, Ch 4, Sec 7


5 Side girders

5.1





Watertight girders are to have thickness not less than thatrequired in Sec 10 for tank bulkheads

5.2





6 Floors

6.1

6.1.1 The thickness of the core of sandwich type floors tm,in mm, is to be not less than the following value:

where kof is defined in Sec 2.

Where a single-skin laminate is used for floors, the thick-ness is to be not less than twice that calculated above.

Watertight floors are also to have thickness not less thanthat required in Sec 10 for tank bulkheads.

6.2

6.2.1 When the height of a floor exceeds 900 mm, verticalstiffeners are to be arranged. In any event, solid floors or equivalent structures are to bearranged in longitudinally framed double bottoms in the fol-lowing locations.• under buklheads and pillars• outside the machinery space at an interval no greater

than 2 m• in the machinery space under the bedplates of main

engines• in way of variations in height of the double bottom.

Solid floors are to be arranged in transversely framed dou-ble bottoms in the following locations:• under bulkheads and pillars• in the machinery space at every frame • in way of variations in height of the double bottom• outside the machinery space at 2 m intervals.


7.1

7.1.1 The section modulus of bottom stiffeners is to be noless than that required for single bottom longitudinals stipu-lated in Sec 6. The section modulus of inner bottom stiffeners is to be noless than 85% of the section modulus of bottom longitudi-nals.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the section modulus of longitudinals isto be no less than that required for tank stiffeners as statedin Sec 10.

tm 0 125L, 1 5,+( )kof=

Pt B, Ch 4, Sec 8



1 General

1.1

1.1.1 Where tanks intended for liquid cargoes arearranged above the double bottom, the section modulus oflongitudinals is to be no less than that required for tank stiff-eners as stated in Sec. 10.





2.1

2.1.1


p : scantling pressure, in kN/m2, defined in Part B,Chap. 1, Sec. 5 ;

Ko : factor defined in Sec. 2 of this Chapter.


3.1


where:


: 1,1 assuming p=p2



3.2



: 1 assuming p=p2


4 Reinforced beams


4.1.1 The section modulus of the reinforced frames is to benot less than the value calculated with the following for-mula:

where:k1 : 1 assuming p=p1

: 0,7 assuming p=p2



s : spacing, in m, between the reinforced frames orhalf the distance between the reinforced framesand the transverse bulkhead adjacent to theframe concerned;



4.2.1 The section modulus of the reinforced stringers is tobe not less than the value calculated with the following for-mula:

where:k1 : defined in 4.1KCR : 2,5 for reinforced stringers which support ordi-

nary vertical stiffeners (frames); : 1,1 for reinforced stringers which do not sup-

port ordinary vertical stiffeners;

Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

Z k1 KCR s S2 Ko p⋅ ⋅ ⋅ ⋅ ⋅=

Z k1 KCR′ s S2 Ko p⋅ ⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 8


s : spacing, in m, between the reinforced stringersor 0,5 D in the absence of other reinforcedstringers or decks;


Pt B, Ch 4, Sec 9


SECTION 9 DECKS

1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof decks, plating and reinforcing or supporting structures.

The reinforcing and supporting structures of decks consist ofordinary reinforcements, beams or longitudinal stringers,laid transversally or longitudinally, supported by lines ofshoring made up of systems of girders and/or reinforcedbeams, which in turn are supported by pillars or by trans-verse or longitudinal bulkheads.




2.1

2.1.1 (1/1/2009)



h : scantling height, in m, the value of which isgiven in Pt B, Ch 1, Sec 5;

Ko, Kof : factor defined in Sec 2 of this Chapter;L1 : scantling length, in m, to be assumed not less

than 15 m.

3 Deck plating

3.1 Weather deck


On yachts of L > 30 m a stringer plate is to be fitted withwidth b, in m, not less than 0,025 L and thickness t, in mm,not less than the value given by the formula:

where ka is defined in 5.1 in Sec. 5.

3.2 Lower decks

3.2.1 The thickness of decks below the weather deckintended for accommodation spaces is to be not less thanthe value calculated with the formula:

where ka is defined in 5.1 in Sec. 5.




4.1.1 The section modulus of the ordinary stiffeners ofboth longitudinal and transverse (beams) type is to be notless than the value Z, in cm3, calculated with the followingequation:

where:C1 : 1 for weather deck longitudinals

: 0,63 for lower deck longitudinals: 0,56 for beams.



where:



4.3 Pillars

4.3.1 Pillars are, in general, to be made of steel or alumin-ium alloy tubes, and connected at both ends to plates sup-ported by efficient brackets which allow connection to thehull structure by means of bolts. Details to be sent forapproval.The section area of pillars is to be not less than the value A,in cm2, given by the formula:

t 0 15, ka s kof L10 5,⋅ ⋅ ⋅ ⋅=

t 0 2, ka s kof L10 5,⋅ ⋅ ⋅ ⋅=

t 0 13, ka s kof L10 5,⋅ ⋅ ⋅ ⋅=

Z 14 s S2 h kof C1⋅ ⋅ ⋅ ⋅ ⋅=

Z 15 b S2 h ko⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 9


where:Q : load resting on the pillar, in kN, calculated with

the following formula:

where:A : area of the part of the deck resting

on the pillar, in m2

h : scantling height, defined in 2.1.1

λ : the ratio between the pillar length and the mini-mum radius of gyration of the pillar cross-sec-tion

C : 1 for steel pillars

: 1,6 for aluminium alloy pillars.

4.3.2 Pillars are to be fitted on main structural members.Wherever possible, deck pillars are to be fitted in the samevertical line as pillars above and below, and effectivearrangements are to be made to distribute the load at theheads and heels of all pillars.

4.3.3 The attachment of pillars to sandwich structures is, ingeneral, to be through an area of single-skin laminate.Where this is not practicable and the attachment of the pil-lar must be by means of bolting through a sandwich struc-ture then a wood, or other suitable solid insert is to be fittedin the core in way.

A Q C⋅12 5, 0 045λ,–---------------------------------------=

Q 6 87, A h⋅ ⋅=

Pt B, Ch 4, Sec 10



1 General

1.1

1.1.1 The number and position of watertight bulkheadsare, in general, to be in accordance with the provisions ofChap 1, Sec 1.

The scantlings indicated in this Section refer to bulkheadsmade of reinforced plastic both in single-skin and in sand-wich type laminates.

Whenever bulkheads, other than tank bulkheads, are madeof wood, it is to be type approved marine plywood and thescantlings are to be not less than those indicated in Chapter5 of Part B.

Pipes or cables running through watertight bulkhead are tobe fitted with suitable watertight glands.

2 Symbols

2.1

2.1.1



hs, hB : as defined in Part B, Ch 1, Sec 5

ko, kof : as defined in Sec 2.

3 Plating

3.1


The coefficient k1 and the scantling height h have the valuesindicated in Tab 1.

Table 1 (1/1/2009)

4 Stiffeners



The values of the coefficient c and of the scantling height hare those indicated in Tab 2.


4.2.1 The horizontal webs of bulkheads with ordinary ver-tical stiffeners and reinforced stiffeners in the bulkheadswith ordinary horizontal stiffeners are to have a sectionmodulus not less than the value Z, in cm3, calculated withthe following formula:

where:

C1 : 10,7 for subdivision bulkheads

: 18 for tank bulkheads


h : scantling height indicated in Tab 2.

Table 2 (1/1/2009)

5 Tanks for liquids

5.1

5.1.1 See Sec 1, [6.5].

tS k1 s ko f h0 5,⋅ ⋅ ⋅=

Bulkhead k1 h (m)




Bulkhead h (m) c




Z 13 5, s S2 h c ko⋅ ⋅ ⋅ ⋅ ⋅=

Z C1 b S2 h ko⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 11



1 General

1.1


Where the distance from the hypothetical freeboard deck tothe full load waterline exceeds the freeboard that can hypo-thetically be assigned to the yacht, the reference deck forthe determination of the superstructure tier may be the deckbelow the one specified above, see Ch 1, Sec 1, [4.3.2].



2.1


s : spacing between the stiffeners, in mh : conventional scantling height, in m, the value of

which is to be taken not less than the value indi-cated in Table 1.

Kof : factor defined in Sec 2.

Table 1

In any event, the thickness t is to be not less than the valuesshown in Table 2 of Sec. 1 of this Chapter.

3 Stiffeners

3.1

3.1.1 The stiffeners of the boundary bulkheads are to havea section modulus not less than the value Z, in cm3, calcu-lated with the following formula:

where:h : conventional scantling height, in m, defined in

2 .1Ko : factor defined in Sec 2s : spacing of the stiffeners, in mS : span of the stiffeners, equal to the distance, in

m, between the members supporting the stiff-ener concerned.


4.1 Plating

4.1.1 The superstructure deck plating is to be not less thanthe value t, in mm, calculated with the following formula:

where:s : spacing of the stiffeners, in mKof : factor defined in Sec 2h : conventional scantling height, in m, defined in

2.1.

4.2 Stiffeners

4.2.1 The section modulus Z, in cm3, of both the longitudi-nal and transverse ordinary deck stiffeners is to be not lessthan the value calculated with the following formula:

where:S : conventional span of the stiffener, equal to the

distance, in m, between the supporting mem-bers

s, h, Ko : as defined in 3.1.Reinforced beams (beams, stringers) and ordinary pillars areto have scantlings as stated in Sec. 9.


1st tier front 1,5

2nd tier front 1,0


t 3 7, s KOf h0 5,⋅ ⋅ ⋅=

Z 5 5, s S2 h Ko⋅ ⋅ ⋅ ⋅=

t 3 7, s KOf h0 5,⋅ ⋅ ⋅=

Z 5 5, s S2 h Ko⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 12


SECTION 12 SCANTLINGS OF STRUCTURES WITH SANDWICH

CONSTRUCTION

1 Premise

1.1

1.1.1 The sandwich type laminate taken into considerationin this Section is made up of two thin laminates in rein-forced plastic bonded to a core material with a low densityand low values for the mechanical properties.

The core material is, in general, made up of balsa wood,plastic foam of different densities or other materials (honey-comb) which deform easily under pressure or traction butwhich offer good resistance to shear stresses.

The thicknesses of the two skins are negligible compared tothe thicknesses of the core.

The thickness of the core is to be not less than 6 times theminimum thickness of the skins.

The thicknesses of the two skins are to be approximatelyequal; the thickness of the external skin is to be no greaterthan 1,33 times the net thickness of the internal skin.

The moduli of elasticity of the core material are negligiblecompared to those of the skin material.

Normal forces and flexing moments act only on the externalfaces, while shear forces are supported by the core .

The scantlings indicated in the following Articles of thisSection are considered valid assuming the above-men-tioned hypotheses.

The scantlings of sandwich structures obtained differentlyand/or with core materials or with skins not correspondingto the above-mentioned properties will be considered caseby case based on the principle of equivalence, on submis-sion of full technical documentation of the materials usedand on any tests carried out.

2 General

2.1 Laminating

2.1.1 Where the core material is deposited above a prefab-ricated skin, as far as practicable the former is to be appliedafter the polymerisation of the skin laminate has passed theexothermic stage.

2.1.2 Where the core is applied on a pre-laminated sur-face, even adhesion is to be ensured.

2.1.3 When resins other than epoxide resins are used, thelayer of reinforcement in contact with the core material is tobe of mat.

2.1.4 Prior to proceeding with glueing of the core, the lat-ter is to be suitably cleaned and treated in accordance withthe Manufacturer's instructions.

2.1.5 Where the edges of a sandwich panel are to be con-nected to a single-skin laminate, the taper of the panel isnot to exceed 30°. In zones where high density or plywood insert plates arearranged, the taper is not to exceed 45°.

2.2 Vacuum bagging

2.2.1 Where the vacuum bagging system is used, details ofthe procedure are to be submitted for examination. The number, scantlings and distribution of venting holes inthe panels are to be in accordance with the Manufacturer'sinstructions.

The degree of vacuum in the bagging system both at thebeginning of the process and during the polymerisationphase is not to exceed the level recommended by the Man-ufacturer, so as to avoid phenomena of core evaporationand/or excessive monomer loss.

2.3 Constructional details

2.3.1 In general the two skins, external and internal, are tobe identical in lamination and in resistance and elasticityproperties.In way of the keel, in particular in sailing yachts with a bal-last keel, in the zone where there are the hull appendages,such as propeller shaft struts and rudder horns, in way of theconnection to the upper deck and in general where connec-tions with bolts are foreseen, as a rule, single-skin laminateis to be used.

The use of a sandwich laminate in these zones will be care-fully considered by RINA bearing in mind the properties ofthe core and the precautions taken to avoid infiltration ofwater in the holes drilled for the passage of studs and bolts.

The use of sandwich laminates is also ill-advised in way ofstructural tanks for liquids where fuel oils are concerned.

Such use may be accepted by increasing the thickness ofthe skin in contact with the liquid, as indicated in Section10.

3 Symbols

3.1

3.1.1 (1/1/2009)

S : conventional span of the strip of sandwich lami-nate equal to the minimum distance, in m,

Pt B, Ch 4, Sec 12


between the structural members supporting thesandwich (bulkheads, reinforced frames);

p : scantling pressure, in kN/m2, as defined in PartB, Chap. 1, Sec. 5;

h : scantling height, in m, given in Part B, Chap. 1,Sec. 5;

Rto : ultimate tensile strength, in kN/m2, of the exter-nal skin;

Rti : ultimate tensile strength, in kN/m2, of the inter-nal skin;

Rco : ultimate compressive strength, in kN/m2, of theexternal skin;

Rci : ultimate compressive strength, in kN/m2, of theinternal skin;

τ : ultimate shear strength, in kN/m2, of the corematerial of the sandwich;

h : net height, in mm, of the core of the sandwich.

4 Minimum thickness of the skins

4.1

4.1.1 The thickness of the skin laminate is to be sufficientto obtain the section modulus prescribed in the followingArticles; furthermore, it is to have a value, in mm, not lessthan that given by the following formulae:

a) Bottom

b) Side and weather deck

where:

to : thickness of the external laminate of the sand-wich

ti : thickness of the internal laminate of the sand-wich.

Thicknesses less than the minimums calculated with theabove formulae, though not less than those in Table 2, maybe accepted provided they are sufficient in terms of buck-ling strength.

In the case of a sandwich structure with a core in balsawood or polyurethane foam and other similar products, thecritical stress σCR, in N/mm2, given by the following for-mula, is to be not less than 1,1 σC:

where:

EF : compressive modulus of elasticity of the lami-nate of the skin considered, in, in N/mm2;

EA : compressive modulus of elasticity of the corematerial of the skin considered, in N/mm2;

GA : shear modulus of elasticity of the core material,in N/mm2;

σC : actual compressive strength of the skin consid-ered, in N/mm2

ν : Poisson coefficient of the laminate of the skinconsidered.

5 Bottom

5.1

5.1.1 The section moduli ZSo and ZSi, in cm3, correspond-ing to the external and internal skins, respectively, of a stripof sandwich of the bottom 1 cm wide are to be not less thanthe values given by the following formulae:


: 0,4 assuming p=p2

The moment of inertia of a strip of sandwich 1 cm wide is tobe not less than the value IS, in cm4, given by the followingformula:

where:R : the greater of the ultimate compressive strengths

of the two skins, in N/mm2;ES : the mean of the four values of the compressive

and shear moduli of elasticity of the two skins,in N/mm2;

Z : ZSo or ZSi , in cm3, whichever is the greater.

The net height of the core ha, in mm, is to be not less thanthe value given by the formula:



6 Side

6.1

6.1.1 The section moduli ZSo and ZSi, in cm3, correspond-ing to the external and internal skins, respectively, of a stripof sandwich of the side 1 cm wide are to be not less thanthe values given by the following formulae:


: 0,4 assuming p=p2

to 0 50, 2 2, 0 25L,+( )⋅=

ti 0 40, 2 2, 0 25L,+( )⋅=

to 0 45, 2 2, 0 25L,+( )⋅=

ti 0 35, 2 2, 0 25L,+( )⋅=

σCR 0 4,EF EA GA⋅ ⋅( )

1 ν2–-------------------------------

1 3⁄

⋅=

ZSo k1 p S2 1Rco

-------⋅ ⋅ ⋅=

ZSi k1 p S2 1Rti

------⋅ ⋅ ⋅=

IS 40 S Z RES

----⋅ ⋅ ⋅=

hak1 p S⋅ ⋅

τ--------------------=

ZSo k1 p S2 1Rco

-------⋅ ⋅ ⋅=

ZSi k1 p S2 1Rti

------⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 12


The moment of inertia of a strip of sandwich of the side 1cm wide is to be not less than the value IS, in cm4, given bythe following formula:

where R and ES are as defined in Art. 5:




7 Decks

7.1

7.1.1 The section moduli ZSo and ZSi, in cm3, correspond-ing to the external and internal skins, respectively, of a stripof sandwich of the deck 1 cm wide are to be not less thanthe values given by the following formulae:

However, the modulus ZSo may be assumed not greater thanthat required for the side in 6.1, having the same S.

The moment of inertia of a strip of sandwich 1 cm wide is tobe not less than the value IS, in cm4, given by the followingformula:

where R and ES are as defined in Art.5.

The net height of the core ha, in mm, is to be not less thanthe value given by the following formula:

8 Watertight bulkheads and boundary bulkheads of the superstructure

8.1

8.1.1 The scantlings shown in this Article apply both tosubdivision bulkheads and to tank bulkheads.

They may also be applied to boundary bulkheads of thesuperstructure assuming for h the relevant value indicatedin Chap. 4, Sec. 11.

The section modulus ZS, in cm3, and the moment of inertiaIS, in cm4, of a strip of sandwich 1 cm wide are to be notless than the values given by the following formulae:

where:

R : the greater of the ultimate compressive shearstrengths of the two skins, in N/mm2;

ES : the mean of the values of the compressive mod-uli of elasticity of the two skins, in N/mm2;


IS 40 S Z RES

----⋅ ⋅ ⋅=

hak1 p S⋅ ⋅

τ--------------------=

ZSo 15 h S2 1Rco

-------⋅ ⋅ ⋅=

ZSi 15 h S2 1Rti

------⋅ ⋅ ⋅=

IS 40 S Z RES

----⋅ ⋅ ⋅=

ha7 h S⋅ ⋅

τ------------------=

ZS 15 h S2 1R---⋅ ⋅ ⋅=

IS 40 S Z RES

----⋅ ⋅ ⋅=

ha7 h S⋅ ⋅

τ------------------=

Pt B, Ch 4, Sec 13


SECTION 13 STRUCTURAL ADHESIVES

1 General

1.1

1.1.1 (1/1/2011)

Structural adhesives are to be used according to the Manu-facturer's specifications. The details of the structural adhe-sives are to be enclosed in the list required in Ch 1, Sec 1,[3.1.1].

The above-mentioned information is to include the materialdata sheet containing all the details of the structural adhe-sive.

The process for the application of the adhesive is to be sub-mitted and is to include:

• the maximum bondline thickness;

• surface preparation and cleanliness of the surface to bebonded;

• handling, mixing, application and curing requirementsof the structural adhesive;

• non-destructive test methods and acceptability criteriafor any defects found;

• remedial work in order to rectify excessive unevennessof the faying surface or local undulations;

• details relevant to the level of training required for per-sonnel involved in the application of structural adhe-sives.

Data listed in the material data sheet are to be specified inthe construction plan submitted for approval.

1.1.2 For hulls for which structural adhesives are used, aspecial class notation will be assigned as indicated in PartA.

1.2

1.2.1 (1/1/2011)

The structural adhesives are to have the following proper-ties:

a) the adhesive is to be compatible with the laminationresin;

b) it si recommended that the elastic modulus of the adhe-sive should be compatible with the elastic modulus ofthe GRP skin; this means that the ratio between the twoelastic moduli shall be such as to avoid stress concentra-tion in the skin substrate when a longitudinal shearforce is applied to the joint;

c) the mechanical properties of the adhesive are to be rap-idly achieved. That means no use of screws or bolts is

necessary to hold the substrate together while the adhe-sive cures;

d) a greater safety factor (ratio of failure strain to actualstrain) than the that of the adjacent structure is toachieved;

e) the minimum shear strength obtained from a lap-sheartest is to be not less than 7 N/mm2. All failures of testsamples are to be either cohesive or fibre tear;

f) the type approval of structural materials is issued byRINA subject to the satisfactory outcome of the follow-ing test carried out on the base of a testing schemeagreed with RINA:

• lap-shear static test to be performed according toASTM D3165 standard using FRP substrates; theshear strength is to be achieved on:

1) 5 samples at room temperature of 23° C ;

2) 5 samples at room temperature of 23° C afterexposure to 5 cycles of laboratory aging accordingto ASTM D1183 standard;

Requirements to be complied with: the average ofthe results obtained after conditioning according toASTM D1183 shall not be less than 85% of the aver-age of the results without conditioning;

• Peel-static test to be performed according to ASTMD3807 standard using FRP substrates; the strengthproperties are to be achieved on:

5 samples at room temperature of 23° C;

5 samples at room temperature of 23° C after expo-sure to 5 cycles of laboratory ageing according toASTM D1183 standard;

Requirements to be complied with the average ofthe results obtained after conditioning according toASTM D1183 is to be not less than 85% of the aver-age of the results without conditioning;

• lap-shear fatigue dynamic test to be performedaccording to ASTM D3163 standard using substratesthat can be metallic; the shear strength is to beachieved on:

5 samples at room temperature of 23 °C after expo-sure to 2 cycles of laboratory aging according toASTM D1183 standard.

Requirements to be complied with: the sample shallwithstand without breaks the fatigue tests carried outat 30 Hz, generally applying a load of 50% of thestatic shear strength for 1,000,000 cycles.

Pt B, Ch 4, Sec 13


2 Design criteria for bonded connec-tion

2.1

2.1.1 In general the shear stress at the inner surface of theplating is to be calculated by direct calculations according

to the requirements of Ch. 1, Sec 5. In general, the calcula-tion of the flange connection between the internal rein-forcement and the plating is to be carried out as indicatedin [2.1.2] of this paragraph.A typical stiffener/plating connection is shown in the fol-lowing figure:

Figure 1

The linear load due to the bending moment calculated atthe inner surface plating can be obtained from the followingformula:

where:

Qp : is the linear load in N/mm applied to the inner surfaceof the plating and due to the bending moment ;

P= 500 x p x s x S: is the total load in N applied to the panelof dimension (Sxs) and due to the design pressure as calcu-lated according to items [5.3] and [5.4] of Pt. 3, Ch. 1, Sec.5 ;

ExA=Ep x b x tp ;

where:

Ep: is the inplane elastic modulus of the plating in N/mm2;

b: is the width of the plate associated with the stiffener, inmm;

tp : is the thickness of the associated plate, in mm ;

Yp: is the distance from the centroid of the associated plateto the neutral axis, in mm ;

(ExI)sp :is the flexural rigidity of the composite element(stiffener and plating) combined around the neutral axis, inN/mm2;

The shear stress for the jointing adhesive for plating can becalculated with the following formula:

It is to be verified that τp is not greater than 20% of the nom-inal bond shear strength as indicated by the Manufacturer'sadhesive. For guidance, Tab 1 indicates some data regard-ing the nominal shear strength and the allowable designstress for certain structural adhesives.

Table 1

QpP E A×( )p× Yp×

E I×( )sp-------------------------------------------=

τpQpb

-------- N/mm2( )=

AdhesiveNominal bond shear strength

[N/mm2]Allowable design stress

[N/mm2]

Cold-cured epoxy 28 5,2

Polyester or vinylester resin or paste 14 3,5

Epoxy type paste 41 8,5


Part BHull

Chapter 5

WOOD HULLS

SECTION 1 MATERIALS

SECTION 2 FASTENINGS, WORKING AND PROTECTION OF TIMBER

SECTION 3 BUILDING METHODS FOR PLANKING

SECTION 4 STRUCTURAL SCANTLINGS OF SAILING YACHTS WITH OR WITHOUT AUXILIARY ENGINE

SECTION 5 STRUCTURAL SCANTLINGS OF MOTOR YACHTS

SECTION 6 WATERTIGHT BULKHEADS, LINING, MACHINERY SPACE

Pt B, Ch 5, Sec 1


SECTION 1 MATERIALS

1 Suitable timber species

1.1

1.1.1 The species of timber suitable for construction arelisted in Table 1 together with the following details:

• commercial and scientific denomination;• natural durability and ease of impregnation;• average physical-mechanical characteristics at 12%

moisture content.The durability classes are relative to the solid timber's resist-ance to moulds.

The suitability for use in the various hull structures is givenin Table 2.

The same species are suitable for the fabrication of marineplywood and lamellar structures in accordance with theprovisions of Article 2 below.

The use of timber species other than those stated in Table 1may be accepted provided that the characteristics of thespecies proposed are as similar as possible to those of oneof the species listed.

2 Timber quality

2.1 Planking

2.1.1 The timber is to be well-seasoned, free from sap-wood and any noxious organisms (moulds, insects, larvae,bacteria, etc.) which might impair its durability and struc-tural efficiency.

The moisture content at the time of use is to be not greaterthan 20% (according to the method UNI 8939 Planking -Check of batch moisture content).

Knots may be tolerated when they are intergrown, providedthat their diameter is less than 1/5 of the dimension parallelto such diameter, measured on the section of the knot. Thegrain is to be straight (the maximum admissible inclinationin relation to the longitudinal axis of the piece is equal to aratio of 1:10).Note 1: Timber with the above characteristics corresponds roughlyto Class 1 of UNI 8198 (Conifer planking - Classification on thebasis of mechanical resistance).

2.2 Marine plywood and lamellar structures

2.2.1 The suitable timber species and criteria for the use ofalternative species are listed in Table 1.

For marine plywood, the elevated temperatures reachedduring drying and pressing rule out the possibility of sur-vival of insects and larvae in the finished panels. Moreover,this factor contributes in enabling the marine plywood tohave a lower moisture content than that of solid timber of

the same species in the same ambient conditions, renderingit less prone to attacks of mould.

Therefore, assuming the same species of timber, the dura-bility of marine plywood is greater than that of solid timber.

In any case, the thickness of the individual layers constitut-ing the plywood or the lamellar structure is to be reduced indirect proportion to the durability of the species used; themaximum recommended thicknesses are listed in Table 1.

The minimum number of plywood layers used in the con-struction is 3 for thicknesses not greater than 6 mm and 5for greater thicknesses.

The marine plywood adopted for hull construction andstructural parts in general is to be type tested by RINA inaccordance with the relevant regulations.

2.3 Certification and checks of timber qual-ity

2.3.1 The quality of timber, plywood and lamellar struc-tures is to be certified as complying with the provisions of2.1 and 2.2 by the builder to the RINA Surveyor, who, inthe event of doubts or objections, will verify the circum-stances by performing appropriate checks.Such certification is to refer to the checks carried out duringbuilding survey in the yard, relative to the following cha-racteristics:

a) for solid timber: mass density and moisture content;b) for plywood and lamellar structures: glueing test.Such checks are not required for Quality Assurance mate-rial certified by RINA in pursuance of the relevant regula-tions.

2.4 Mechanical characteristics and struc-tural scantlings

2.4.1 The structural scantlings indicated in this Chapterapply to timber with the following density δ, in kg/m3, at amoisture content not exceeding 20%:• bent frames: δ = 720

• non-bent frames keel and stem: δ = 640• shell and deck planking, shelves and clamps, stringers

and beams: δ = 560.

The scantlings given in this Section are to be modified as afunction of the density of the timber employed and its mois-ture content, in accordance with the relationship:

S1 : corrected section (or linear dimension)S : Rule section (or linear dimension), obtained in

accordance with this Chapter

S1 S K⁄=

Kδe

δ---- U Ue–( ) 0 02,⋅+=

Pt B, Ch 5, Sec 1


δ : density of the timber species (or plywood) used;δe : standard density of the timber species of refer-

ence;U : standard moisture content percentage (20% for

solid timber, 15% for plywood or lamellarstructures);

Ue : maximum expected moisture content balancefor the part considered, in service conditions.

Reductions in scantlings exceeding those obtained usingthe formulae above may be accepted on the basis of themechanical base characteristics of the timber, plywood orlamellar structures actually employed.

Table 1 : Basic physical/mechanical characteristics of timbers for construction

Commercial name

Origin (1)

Botanical name (2)

Mass density (kg/m3)

Natural durability

(3)

Ease of imprega-

tion (3)

Mechanical characteristics (4)

Rf

(N/mm2)Ef

(N/mm2)Rc

(N/mm2)Rt

(N/mm2)

DOUSSIEIROKO

KHAYAMAKORE’MAHOGANYOKOUME’ ELMOAK

SAPELE

SIPO

TECKWHITE OAKCHESTNUTCEDAR(Western Red)DOUGLAS FIR

LARCH

AfricaAfrica

AfricaAfrica

AmericaAfricaEurope Europe

Africa

Africa

AsiaAmerica Europe

America

America

Europe

Afzelia sppChlorophoraexcelsaKhaya sppTieghemella sppSwietenia sppAucoumea KleineanaUlmus sppQuercus robur e Q. petraeaEntandrophragma cylindricumEntandrophragmautileTectona grandisQuercus sppCastanea sppThuja plicata

PseudotsugamenziesilLarix decidua

800650

520660550440650710

650

640

680730600380

500

550

AA/B

CABDDB

C

B/C

AB/CB

B/C

C/D

C/D

44

4443

2/34

3

3/4

4443

3/4

3/4

11485

7486795189

125

105

100

1001205951

85

89

1600010000

96009300

103007800

1020015600

12500

12000

106001500085007600

13400

12800

6252

445046274368

56

53

58653731

50

52

14,012,0

10,011,08,56,7

11,013,0

15,7

15,0

13,012,67,46,8

7,8

9,4

Abbreviations:Natural durability

A = very durableB = durable (maximum permissible thickness for the fabrication of marine plywood 5 mm)C = not very durable (maximum permissible thickness for the fabrication of marine plywood 2,5 mm)D = not durable (maximum permissible thickness for the fabrication of marine plywood 2 mm)

Ease of treatment for impregnation1 = permeable2 = not very resistant3 = resistant4 = very resistant

Note(1) Area of natural growth(2) Unified botanical name (spp = different species)(3) Level of natural durability and ease of treatment for impregnation according to Standard EN 350/2(4) Mechanical characteristics with 12% moisture content, source: Wood Handbook: wood as an engineering material - 1987,

USDA- Ultimate flexural strength Rf (strength concentrated amidships)- Bending modulus of elasticity Ef (strength concentrated amidships)- Ultimate compression strength Rc (parallel to the grain)- Ultimate shear strength Rt (parallel to the grain).

Pt B, Ch 5, Sec 1


Table 2 : Guide for selections of construction timbers

SPECIES OF TIMBERDoug-

lasCedar(red) Iroko Larch Makore

Mahor-gany

Elm eng-lish

White oak

Oak Sapeli TeakSTRUCTURAL ITEM

Keel, hog, stern-post, dead-woods

II II II II II II III I

Stern II II II II II III IBilge stringer III II II III IBeam shelves clamps water-ways

III II II II II III I

Floors II II II II II IFrames grown or web frames

II (2) II II (1) II (1) III I

Frames, bent frames II (1) II (1)Planking below water-line

III II II II II II III I

Planking above water-line

III II III II II III I

Deck planking II III II IBeams, bottom girders II II II (2) II (2) II (1) II (1) IBrackets vertical II II (1) II

Brackets horizontal II I IGunwale margin planks

II II II II

Note(1) The timber concerned may be employed either in the natural or in the laminated form.(2) The timber may be employed only in laminated form.Suitability of timber for use:I = very suitableII = fairly suitableIII = scarcely suitable

Pt B, Ch 5, Sec 2


SECTION 2 FASTENINGS, WORKING AND PROTECTION OF

TIMBER

1 Fastenings

1.1

1.1.1 Glues for timber fastenings are to be of resorcinic orphenolic type, i.e. durable and water-resistant in particular.

Ureaformaldehyde glues may only be used in well-venti-lated parts of the hull not subject to humidity.

Glues are to be used according to the Manufacturer'sinstructions on timber with moisture content not exceeding15-18% or, for urea-type glues, 12,5-15%.

The parts to be glued are to be carefully prepared andcleaned and, in particular, all traces of grease are to beremoved.

Where rivets, screws and bolts are not made of material rec-ognised as suitable for resisting corrosion from the marineenvironment, they are to be hot galvanised in accordancewith a recognised standard. In the absence of such stand-ard, after rivets, screws and bolts have been hot galvanisedand subsequently machine finished, the protective zinccoating on their surfaces is to remain intact.

Through bolts are to be clinched on washers, or tightenedby a nut, also on washers. Nuts and washers are to be ofthe same material as that of the bolts.

Where connecting bolts go through shell planking or keel,they are to have heads packed with cotton or other suitablematerial.

Where screw fastenings are used for planking, the threadingis to penetrate the support frame for a distance equal to theplanking thickness.

1.2

1.2.1 The use of suitable glues in place of mechanical con-nections will be the subject of special consideration byRINA.

In general, such replacement of fastening methods will beaccepted subject to the satisfactory outcome of tests, onrepresentative samples of the joints, conducted with proce-dures stipulated on the basis of the type of glue, the type ofconnection and any previous documented applications.

In any event, RINA reserves the right to require a minimumnumber of mechanical connections.

2 Timber working

2.1

2.1.1 Timber working is to be appropriate to the speciesand hardness of the timber, as well as to the type of hullconstruction, e.g. grown or web frames, lamellar structures,board or plywood planking.Lamellar structure is generally employed for bent structuralparts, with lamellas as continuous as possible or with scarfjoints and normally glued before bending.

The lamellas are generally to be made using the same spe-cies of timber.

The lamellas are to be arranged with their fibres parallel tothe length of the element to be constructed.

3 Protection

3.1

3.1.1 Inaccessible surfaces of internal hull structures areto be treated with a suitable wood preservative according tothe Manufacturer's instructions and compatible with theglues, varnishes and paints employed. The timber of theinternal bottom of the hull is to be smeared with oil or var-nish; any synthetic resins used as coating are to be appliedto dry timber with the utmost care.All cut edges of plywood are to be sealed with glue, paint orother suitable products such as to prevent the penetration ofmoisture along the end-grain.

Pt B, Ch 5, Sec 3


SECTION 3 BUILDING METHODS FOR PLANKING

1 Shell planking

1.1 Simple skin

1.1.1 Planks are to be arranged such that strake butts are atleast 1,20 metres apart from those of adjacent strakes and atleast three continuous strakes separate two butts arrangedon the same frame.

The butts of garboards are to be arranged clear of those inthe keel, and the butts of the sheerstrake are to be arrangedclear of those of the waterway.

Butts may be strapped or scarfed, and wooden straps are tohave thickness equal to that of the planking, width so as tooverlap adjacent strakes by at least 12 mm and length asnecessary for the connection while leaving a space forwater drainage between the strap edge and the frame.

Scarfs are to have length not less than 5 times the plankingthickness, to be centred on the frames and to be connectedby means of glueing and pivoting.

1.2 Double diagonal skin

1.2.1 This consists of an inner skin of thickness notexceeding 0,4 of the total thickness and an outer skinarranged longitudinally.

1.3 Double longitudinal skin

1.3.1 This consists of an inner and outer skin, arrangedsuch that the seams of the outer skin fall on the middle ofthe planks of the inner skin.The inner skin is to have thickness not exceeding 0,4 of thetotal thickness and to be connected to the frames by meansof screws or nails and to the outer skin by means of screwsor through bolts. The outer skin is, in turn, to be connectedto the frames by means of through bolts. When framesother than laminated frames are employed, the use ofscrews is permitted. A suitable elastic compound layer is tobe arranged between the two skins.

1.4 Laminated planking in several cold-glued layers

1.4.1 The construction of cold moulded laminated plank-ing is to be effected in loco at a constant temperature.

It is therefore of the utmost importance that the Manufac-turer should be equipped with adequate facilities for thistype of construction.

The planks forming the laminate are to be of width andthickness adequate for the shape of the hull; the width isgenerally not to exceed 125 mm.

The number of layers is to be such as to obtain the requiredthickness.

1.5 Plywood planking

1.5.1 Plywood planking consists of panels as large as prac-ticable in relation to the shape of the hull. The butts are tobe suitably staggered from each other and from machineryfoundations.

The connection of seams is to be achieved by means of glueand bolts; the connection of butts is to be effected by meansof scarfs or straps. Scarfs are to have length not less than 8times the thickness and, where effected in loco, to bebacked by straps, at least 10 times as wide as the thickness,glued and fastened.

The strap connection is to be effected using straps of thesame plywood.

1.6 Double skin with inner plywood and outer longitudinal strakes

1.6.1 This consists of two layers: one internal of plywood,arranged as described in 1.5, the other external, formed byplanks in longitudinal strakes arranged as described in 1.3.The plywood thickness is to be not less than 0,4 of the totalthickness.

1.7 Fastenings and caulking

1.7.1 Butt-straps on shell planking (see Figure 1) are to beconnected by means of through bolts of the scantlings givenin Table 1 for the connection of planking to frames, and areto be proportionate in number to the width a of panels, asfollows:

- a < 100 mm

3 bolts at each end of plank

- 100 ≤ a < 100 mm

4 bolts at each end of plank

- 200 ≤ a < 250 mm

3 bolts at each end of plank.

The number and scantlings of bolts to be used for connec-tion of planking to frames are given in Table 1.

The following types of connection are to be adopted:

- Type I framing: all through fastenings;

- Type II framing with grown or laminated frames:through bolts in way of bilge stringers or side longitudi-nals, wood screws for other connections;

- Type II framing with metal frames: all connectionsformed by through bolts with nuts;

- Type III framing: connections as above depending onwhether bent, grown, laminated or steel frames are con-cerned.

All fastenings for strengthened frames in way of masts are tobe through fastenings.

Pt B, Ch 5, Sec 3


When plywood planking is adopted, it is to be connected toframes by means of nails or screws spaced 75 mm apart andwith diameters as given in Table 2.

Planks of shell planking, if not glued, are to have caulkedseams and butts.

1.8 Sheathing of planking

1.8.1 When use is made of reinforced plastic or syntheticresin sheathing, the hull is to be prepared by carefully level-ling every joint and filling every bolt hole with suitablecompounds after adequate sinking of the bolts. The protec-tive sheathing is to cover keel, false keel and deadwood asfar as practicable, prior to the fitting of external ballast inthe keel, where envisaged.

When sheathing is applied, the moisture content of the tim-ber is to be as low as possible.

2 Deck planking

2.1 Planking

2.1.1 The butts of planks of two contiguous strakes are tobe spaced at least 1,20 m apart; two plank butts on thesame beam are to be separated by at least three strakes ofcontinuous planking.

Butts are to be set onto a beam and may be simple orscarfed.

2.2 Plywood

2.2.1 Plywood panels are to be as long as possible. Thebutts are to be arranged clear of those of adjacent panelsand are to be strapped or otherwise set onto a strong beam.Longitudinal joints are to be set onto longitudinal structuresof sufficient width for the connection. All joints are to besealed watertight.

2.3 Plywood sheathed with laid deck

2.3.1 The butts of plywood panels are to be in accordancewith the specifications given in 2.2.1, while the distributionof plank butts is to comply with the provisions of 2.1.1.

2.4 Longitudinal planking

2.4.1 When longitudinal planking is adopted, each plankis to be fastened to beams by means of a wood screw or lat-eral nail. In addition, each plank may be connected to that-adjacent by means of a glued, sunk-in strip.

Plywood planking is to be glued and riveted to beams, orotherwise fastened by means of screws with pitch not lessthan 75 mm and diameter in accordance with that shown inTable 1.

2.5 Caulking

2.5.1 Wood planking is to be caulked or made watertightby the application of a suitable elastic compound.

Wooden dowels used to cover bolt holes are to be glued.

Table 1 : Connections of shell and deck planking - scantlings of fastenings

Thickness of plank-

ing mm

SHELL PLANKING DECK PLANKING NUMBER OF FASTENINGS PER PLANK

Grown frame: laminated, or steel frames

Bent frames

Wood screws

diameter mm

Bolts with nuts

diameter mm

Width a of plank mm

diameter diameter

a < 100100 ≤ a<150

150 ≤ a<180

180 ≤ a<250

205 ≤ a<225

bolts with nuts mm

wood screws

mm

copper nailsmm

copper nailsmm

182022242628303234363840424446485052

4,54,566777888899

1012121414

5555

5,55,55,56,56,577888

8,58,51010

4,55

6,56,56,56,56,57,57,57,57,59,59,59,51111

12,512,5

2,53

3,53,53,54,54,55

5,55,55,566-----

4,555

5,55,55,55,56,56,56,5777888

8,58,5

4,54,5666668888899

10101212

222211111111111111

222222222222222222

333322222222222222

333333333222222222

333333333333333333

Pt B, Ch 5, Sec 3


Table 2 : Connections of shell and deck planking in plywood

Thickness of plywood

OVERLAP OF SEAMS

Width of butt-straps mm

DIAMETER OF FASTENINGS

shell and deck planking, on keel, stringers, shelves, or carlings

mm

Wood screws mm

Copper nails mm

68

10

252832

single fastening

150175200

single fastening

4,555

3,53,54,5

121416

353545

225250280

5,55,55,5

4,555

182022

455050 double fastenings

350350350 double fastenings

6,56,56,5

55,56

2426

6060

380380

77

6,56,5

Pt B, Ch 5, Sec 3


Figure 1 : Butt-straps on shell planking

1 - Frame

2 - Shell planking

3 - Butt - strap

Pt B, Ch 5, Sec 3


Figure 2 : Usual types of scarf-joints

1 - Plan scarf

2 - Hooked scarf

3 - Tabled scarf

4 - Tabled hooked scarf

5 - Double wedges

Pt B, Ch 5, Sec 4


SECTION 4 STRUCTURAL SCANTLINGS OF SAILING YACHTS

WITH OR WITHOUT AUXILIARY ENGINE

1 General

1.1

1.1.1 The scantlings in this Section apply to hulls of lengthL not exceeding 30 metres with round bottom of shape sim-ilar to that shown in Figures 1 and 2, and fitted with fixedballast or drop keel.

Yachts of length L exceeding 30 metres or hull shapes otherthan the above will be considered in each case on the basisof equivalence criteria.

2 Keel

2.1

2.1.1 The scantlings of wooden keels are given in Table 1.

The keel thickness is to be maintained throughout thelength, while the width may be gradually tapered at theends so as to be faired to the stem and the sternpost.

The breadth of the rabbet on the keel for the first platingstrake is to be at least twice the thickness and not less than25 mm.

The wooden keel is to be made of a minimum number ofpieces; scarf joints may be permitted with scarf 6 times aslong as the thickness and tip 1/4 to 1/7 of the thickness ofthe hooked or tabled type, if bolted, or of the plain type, ifglued. It is recommended that scarfs should not bearranged near mast steps or ends of engine foundation gird-ers.

Where the keel is cut for the passage of a drop keel, thewidth is to be increased.

Where the mast is stepped on the keel, it is to be arrangedaft of the forward end of the ballast keel. Where this is notpracticable, effective longitudinal stiffeners are to be

arranged extending well forward and aft of the mast stepand effectively connected to the keel.

Bolted scarfs are to be made watertight by means of soft-wood stopwaters.

3 Stempost and sternpost

3.1

3.1.1 The stempost is to be adequately scarfed to the keeland increased in width at the heel as necessary so as to fitthe keel fairing.

Stempost scantlings are given in Table 1.

The sternframe is shown in Figure 3 and sternpost scantlingsare given in Table 1.

The lower portion of the sternpost is to be tenoned or other-wise attached to the keel. The connection is completed bya stern deadwood and a large bracket fastening togetherfalse keel, keel and post by means of through bolts.

The counter stern is to be effectively connected to the stern-post; where practicable, such connection is to be effectedby scarfs with through bolts.

The cross-sectional area of the counter stern at the connec-tion with the sternpost is to be not less than that of the latter;such area may be reduced at the upper end by 25%.

4 Frames

4.1 Types of frames

4.1.1 Bent frames

Bent frames consist of steam warped listels. Their widthand thickness are to be uniform over the whole length; theframes are to be in one piece from keel to gunwale and,where practicable, from gunwale to gunwale, running con-tinuous above the keel.

Table 1 : Keel, Stempost, Sternpost

LengthL m

Keel Stempost Sternpost

Widthmm

Depthmm

at heel at head Depthmm

Depthmm

Width mm

Depthmm

Widthmm

Depthmm

24 26 28 30

435455470480

240255270290

240255270290

240255270290

190200215230

190200215230

190200215230

190200215230

Pt B, Ch 5, Sec 4


4.1.2 Grown framesGrown frames consist of naturally curved timbers con-nected by means of scarfs, or butted and strapped. Theirwidth is to be uniform, while their depth is to be graduallytapered from heel to head.

The length of scarfs is to be not less than 6 times the width,and they are to be glued.

4.1.3 Laminated framesLaminated frames consist of glued wooden layers. Theglueing may take place before forming where the latter isslight; otherwise it is to be carried out in loco or be prefabri-cated by means of suitable strong moulds.

4.1.4 Metal framesSteel frames consist of angles properly curved and bevelledsuch that the flange to planking is closely fayed to the sameplanking.

4.2 Framing systems and scantlings

4.2.1 The admissible framing systems and the frame scant-lings are indicated in Tables 2 and 3:

Type I : all equal frames, of the bent type;

Type II : all equal frames, of grown, laminated or steelangle type;

Type III : frames of scantlings as required for Type II, butalternated with one, two or three bent frames.

These types are hereafter referred to, respectively, as TypeIII1, Type III2, Type III3.

When a frame spacing other than that specified in the Tableis adopted, the section modulus of the frame is to be modi-fied proportionally. For wooden rectangular sections, abeing the width and b the height of the Rule section for thespacing s, a1 and b2 the actual values for the assumed spac-ing s1, it follows that:

The width of frames is to be not less than that necessary forthe fastening; their depth is in any case to be assumed asnot less than 2/3 of the width, except where increasedwidth is required for local strengthening in way of masts.

The Table scantlings, duly modified where necessary for thespecific gravity of the timber and for the frame spacing, areto be maintained for 0,6 of the hull length amidships; out-side such zone, the following reductions may be applied:

• for bent or laminated frames: 10% in width,

• for grown frames: 20% in width throughout the lengthof the frame, and 20% in depth of the head,

• metal frames: 10% in thickness.

Frames may have a reduction in strength of 25% wherecold laminated planking is adopted in loco, in accordancewith the provisions of 8.

Frames are to be properly shaped so as to fit the plankingperfectly.

Where no floors are arranged, the frames are to be wedgedinto and fastened at the heels of the centreline structuralmember of the hull.

When internal ballast supported by the frames is arranged,the latter are to be increased in scantlings.

Frames adjacent to masts are to be strengthened on eachside as follows, or equivalent arrangements are to be pro-vided.

• Type I framing

Three grown frames are to be fitted, with scantlings asrequired for Type II framing, but with constant depthequal to that indicated in Table 3.2 for the heel. Suchframes are to be arranged instead of alternate bentframes. Otherwise, six consecutive bent frames with across-section increased by 60% in respect of that shownin the above-mentioned Table may be fitted.

• Type II framing

Three grown frames are to be fitted, with a cross-sectionincreased by 50% in respect of that required for the heelin the above-mentioned Table and constant depth.Such frames are to be alternated with ordinary grownframes. If alternate frames are adopted, they are to bestiffened by reverse frames of scantlings as prescribedfor the reverse frames of plate floors.

• Type III framing

Three grown frames with a cross-section increased by50% in respect of that required for the heel in theabove-mentioned Table, and constant depth, are to bearranged at Rule spacing, with one or two intermediatebent frames. If steel frames are adopted, three are to bestiffened by reverse frames with scantlings as requiredfor the frames of plate floors, and arranged with one ortwo intermediate bent frames.

Where, in way of the mast, a sufficiently strong bulkhead isprovided, such increased frames may be reduced in numberto two.

5 Floors

5.1 General

5.1.1 Floors may be made of wood or metal (steel or alu-minium alloy).

• Wooden floors, as a rule, may only be employed inassociation with grown frames and are to be flanked bythem.

• Metal floors are employed in association with eitherbent, grown or laminated frames, and are arranged onthe internal profile of the frames.

• Angle floors may be employed with either bent, grownor laminated frames, and may be arranged as shown inTable 1. When they are arranged with a flange inside,an angle lug is to be fitted in way of the throat, for theconnection to the wooden keel (see the above Table).

• Plate floors may be employed in association with eithergrown or angle frames (see the above-mentioned Table).The internal edge is to be provided with a reverse angleor a flange; in the latter case, the thickness is to beincreased by 10%.

a1 b12 a b2 s1

s----⋅=

Pt B, Ch 5, Sec 4


5.2 Arrangement of floors

5.2.1 Where Type I framing with bent frames is adopted(see Tables 2 and 3), floors are to be fitted inside 0,6 Lamidships as follows:

• on every second frame if the hull depth does not exceed2,75 metres and on every frame in hulls of greaterdepth;

• on every second frame inside 0,6 L amidships, and out-side such area over an extent corresponding to the len-gth on the waterline;

• on every third frame elsewhere.

Where Type III framing is adopted, a floor is to be fitted inway of every grown, laminated or angle frame. Where oneor two intermediate bent frames are arranged, and the

depth D exceeds 2,40 metres, floors are to be fitted on bentframes located inside 0,6 L amidships.

Where three intermediate bent frames are arranged, a flooris to be fitted on the central frame.

5.3 Scantlings and fastenings

5.3.1 The scantlings of floors are given in Tables 4 and 5.At the hull ends, the length of arms need not exceed onethird of the frame span.

Wooden floors are to be made of suitably grained or lami-nated timber, and their height at the ends is to be not lessthan half the height of the throat.

Where the ballast keel bolts cross wooden floors, the widthof the latter at the throat is to be locally increased, if neces-sary, so as to be not less than three and a half times thediameter of the bolt.

Table 2 : Frames (1/1/2009)

Table 3 : Frames

Depth D1

mm (1)

TYPE IBent frames only

TYPE IIGrown frames, or laminated frames, or steel frames only

spacing mm

Grown frames Laminated frames Steel frames

spa-cingmm

widthmm

depthmm

widthmm

depthmm width

mmdepthmm

Section modulus

cm3

Scantlingsmm (2)

at heel at head

3,00 3,20 3,40 3,60 3,80 4,00 4,20

215225235245255265

-

576267727782-

404346495255-

305322340355375390408

616875818794100

748391100112124140

5358688092100117

8193103117122131143

525966748494102

3,14,46

7,910,212,514,5

50x50x560x30x665x50x775x50x680x60x790x60x790x60x8

(1) For hulls fitted with external ballast in the keel, 0,75 D1 may be assumed in place of D1 where the ballast/light displacementratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

(2) The scantlings of bars are given for guidance purposes.Solution I is only applicable where D1 does not exceed 3,60 metres.The frame spacing is intended as that measured amidships of the frames widths.

DepthD1

mm (1)

TYPE IIIMain frames (grown or laminated) alternated with bent frames

Spacing between main frames and intermediate frames Bent frames

1 bent framemm

2 bent framesmm

3 bent framesmm

lengthmm

depthmm

3,00 3,20 3,40 3,60 3,80 4,00 4,20

515560590620650680

-

620650690725765800

-

695730770800840870

-

434548505356-

333539434751-

(1) For hulls fitted with external ballast in the keel, 0,75 D1 may be assumed in place of D1 where the ballast/light displacementratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

Solution I is only applicable where D1 does not exceed 3,60 metres.The frame spacing is intended as that measured amidships of the frames widths.

Pt B, Ch 5, Sec 4


Table 4 : Frames

Table 5 : Frames

Lugs for the connection of angle or plate floors to thewooden keel, if penetrated by the ballast keel bolts, are tohave a flange width at least three times the diameter of thebolt and thickness equal to that of the plate floor plus 2,5mm.

At the end of the hull, when frames are continuous throughthe centre structure, floors need not be fitted; wheneverpracticable, however, the frames are to be attached to thecentre structure by means of three through-bolts.

Floors are to be connected to frames by at least three boltsfor arms with length l < 250 mm and at least 6 bolts forgreater l; for diameters of bolts, see Table 10.

6 Beam shelves, beam clamps in way of masts, bilge stringers

6.1 Beam shelves

6.1.1 The cross-sectional area of beam shelves through 0,6L amidships is to be not less than that indicated in Table 6.Outside such zone, the cross-section may be graduallydecreased to reach, at the end, a value equal to 75% of thatshown.

The cross-section to be considered is to be inclusive of thedappings for fixing of beams.

Where beam shelves are made of two or more pieces, theconnection is to be effected by means of glued scarfs ade-quately arranged so as to be staggered in respect of thesheerstrake, waterway and bracket joints.

Scarfs are generally arranged vertically.

When the weather deck is not continuous owing to thepresence of raised decks, the shelf is to extend to the hullend or, alternatively, stiffeners are to be fitted to preventexcessive discontinuity due to the interruption of the deck.The scantlings of frames may be required to be increased.

Where angle frames are employed, reverse lugs are to be fit-ted in order to allow connection to the beam shelf. WhenType III framing is adopted, the shelf is to rest on the bentframes with interposition of suitable chocks.

The shelves are to be connected to each frame by a throughbolt for heights < 180 mm and by two through bolts forgreater heights. If metal frames are adopted, bolting of theshelf is to be effected on a reverse lug. For bolt scantlings,see Table 10.

DepthD1

mm (1)

FLOORS ON BENT FRAMES Plate floors on grown or steel floors

Length of armsmm

forged steel angle floors (2)

at throatmm

at the endsmm

sectionmodulus

cm3

scantlings mm

for 2/3 Lamidships

mm

outside 2/3 L amidships

mm

3,00 3,20 3,40 3,60 3,80 4,00 4,20

430465495530

---

29x1531x1633x1735x17

---

24x625x627x628x6

---

1,41,41,51,5---

40x40x440x40x440x40x440x40x4

---

300x5320x5330x5340x6345x6350x6360x6

200x4220x4230x4240x4245x4250x4260x4

(1) For hulls fitted with external ballast in the keel, 0,75 D1 may be assumed in place of D1, where the ballast/light displacementratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

(2) The scantlings of angle floors are given for guidance purposes.

DepthD1

mm (1)

FLOORS ON GROWN OR LAMINATED FRAMES

Length of arms forged floors wooden floors steel angle floors (2)

for 3/5 L amidships

mm

outside 3/5 L amid-ships mm

at throat mm

at the endsmm

widthmm

depthmm

section modulus

cm3

scantlingsmm

3,00 3,20 3,40 3,60 3,80 4,00 4,20

580610650680720750780

430460500530560590620

56x2260x2464x2669x2873x3077x3180x31

50x1252x1354x1456x1658x1761x1863x20

51566064707580

135148160170180190200

2,403,605,706,906,909,0010,0

45x45x550x50x655x55x860x60x860x60x865x65x970x70x9

(1) For hulls fitted with external ballast in the keel, 0,75 D1, may be assumed in place of 0,25 circa. where the ballast/light dis-placement ratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

(2) The scantlings of angle floors are given for guidance purposes.

Pt B, Ch 5, Sec 4


6.2 Beam clamps in way of masts

6.2.1 In way of masts, a beam clamp is to be arranged, oflength approximately equal to the hull breadth in the sameposition.

Such clamp, with cross-section equal to approximately75% of that required for shelves, may be arranged so that itswider side is faying to the beams and leaning against theshelf or, alternatively, it may be arranged below the shelf.

6.3 Bilge stringers

6.3.1 In hulls with Type I or Type III framing, a bilgestringer is to be arranged, having cross-section for 0,6 Lamidships not less than that given in Table 6. Outside suchzone, the cross-section may be decreased to reach, at theends, a value equal to 75% of that required.

The greater dimension of the stringer is to be arrangedagainst the frames.

When the stringer is built of two or more pieces, these areto be connected by means of glued scarfs parallel to theplanking. Such scarfs are to be properly staggered in theport and starboard stringers and arranged clear of the jointsof other longitudinal elements.

Where angle frames are adopted, these are to be connectedto the stringer by means of a reverse lug.

When Type III framing is adopted, chocks are to be fitted forthe connection between stringer and intermediate bentframes.

In lieu of a bilge stringer, two side stringers having cross-section equal to 60% of that required for the bilge stringermay be fitted.

6.4 End breasthooks

6.4.1 The beam shelves and the stringers are to be con-nected to each other at the hull ends, and with the cen-treline structure, by means of suitable breasthooks orbrackets.

In hulls with exceptionally raked ends, such breasthooksare to be given adequate attention.

7 Beams

7.1 Scantlings of beams

7.1.1 The scantlings of beams are given in Table 7. Wherethe spacing adopted is other than that shown in the Table,the scantlings, following correction as necessary for theweight of the timber employed, are to be modified inaccordance with the following relationship:

where a and b are the width and height of the Rule cross-section, a1 and b2 are the width and height of the modifiedsection, s is the Rule spacing, and s1 the assumed spacing.

Laminated beams may be reduced in width by 15%.

Strong beams are to be fitted in way of openings whichcause more than two beams to be cut and in way of masts,when deemed necessary by RINA.

Table 6 : Beam shelves and bilge stringers

Table 7 : Beams

a1 b12 a b2 s1

s----⋅=

Length L(m)

Cross-sectional area of beam shelvescm2

Cross-sectional area of bilge stringerscm2

24 26 28 30

190220250280

140160175190

Length of beam

m

Spa-cingmm

ORDINARY BEAMS FOR 3/5 L AMIDSHIPS

ORDINARY BEAMS OUTSIDE 3/5 L AMIDSHIPS, HALF BEAMS

STRONG BEAMS

Width

mm

DepthWidthmm

DepthWidth.

mm

Depth

at mid-beammm

at beam endsmm

at mid-beammm

at beam endsmm

at mid-beammm

at beam endsmm

3,003,504,004,505,005,506,006,507,007,50

350390430480520560600640680720

45515762687278838695

72809099106114121129132146

505763697580869296

105

39474852575962646769

54616774808795103113125

43485357626569717476

617278859398107116128140

8191101111120128136144156168

617278859398107116128140

Pt B, Ch 5, Sec 4


Table 8 : Vertical knees of beams

7.2 End attachments of beams

7.2.1 Beams are to be dovetailed on the shelf. When ply-wood deck planking is employed, in place of the dovetail asimple dapping may be adopted, having depth not less than1/4 of the beam depth; in this case, the beam is to be fas-tened to the shelf by means of a screw or pin.

Vertical knees are to be fitted, to the extent required inTable 8, to strong beams and to suitably distributed ordi-nary beams. Each arm of the knees is to be connected tothe shelf and the frame by means of 4 bolts, which need notgo through the planking, with a diameter as shown in Table10.

Bulkheads of adequate scantlings, connected to the beamand frame, can be considered as substitutes for knees.

At the ends of the hull, the length of knee arms may be notmore than one third of the span of the beam or frame.

In the above-mentioned Table, the scantlings of forged plateknees are given; the depth at the throat is to be not less than1,6 h for naturally curved wooden knees and not less than.

1,4 h for laminated wooden knees, h being the depth atheel of a grown frame.

Horizontal knees are to be fitted in way of hatch-end beamsand beams adjacent to mast wedgings. These knees neednot be arranged when plywood deck planking is adopted.

7.3 Local strengthening

7.3.1 The beams and decks are to be locally strengthenedat the attachments of halliards, bollards and cleats, at sky-light ends, and in way of foundations of winches.

In way of mast weldings, four strong beams are to be fitted,with scantlings as prescribed in Table 7, but constant sec-tion equal to that indicated for amidships. The beams are tobe arranged, as far as practicable, in proximity of the webframes dealt with in 4.2.

All openings on deck are to be properly framed so as toconstitute an effective support for half beams.

7.4 Lower deck and associated beams

7.4.1 In hulls with depth, measured from the upper side ofthe wooden keel to the weather deck beam at side, > 3metres, a lower deck or cabin deck is to be arranged and fit-ted with beams having scantlings not less than 60% of thoseof the weather deck.When the depth, measured as specified above, exceeds 4,3metres, vertical knees are to be arranged no smaller inscantlings than prescribed in Table 8 as a function of thebeam span, and in number equal to half of those requiredfor the weather deck.

8 Planking

8.1 Shell planking

8.1.1 The basic thickness of shell planking is given in Table9.Such thickness is to be modified as follows.

If the frame spacing is other than that indicated in Table 2,the thickness is to be increased where there is greater spac-ing, or may be reduced where there is smaller spacing, by:- 6 mm for every 100 mm of difference if Type I framing

is adopted;- 4 mm for every 100 mm of difference if Type II or III fra-

ming is adopted.

After correction for spacing as indicated above, and for theweight of the timber, where necessary, the planking thick-ness may be reduced: by 10% if arranged in diagonal orlongitudinal double skin; by 10% if laminated and coldmoulded in loco, when the frames are reduced in scantlingsby 25% in respect of the value given in Table 2; the thick-ness may be decreased by 25% where the frames have notbeen reduced in respect of the requirements of the Table.

When plywood is employed, the thickness may be reducedin relation to the type of framing adopted; the maximumreduction permitted is 25%.

Sheathing of the hull is not required; where envisaged, e.g.in copper or reinforced plastics, it will be considered byRINA on a case-by-case basis (see Sec 6. para. 1.8).

Length of beams

m

Number (1) of knees on

each side

LENGTH OF ARMS FORGED KNEES STEEL ANGLE KNEESPLATE KNEES

thicknessmm

for 3/5 L amidships

mm

outside 3/5 L amidships

mm

at throatmm

at the ends mm

scantlings (2) mm

sectionmodulus

cm3

3,003,504,004,505,005,506,006,507,007,50

56789

1010111212

400440490530570610650700740780

320350390420450490520560590620

34x1741x2048x2353x2657x2862x3067x3272x3478x3581x37

30x737x742x846x949x1052x1154x1255x1457x1658x17

40x40x550x50x555x55x560x60x675x50x675x50x790x60x790x60x8100x65x7100x65x8

1,703,004,305,907,509,30

11,5014,0016,0019,00

4445556667

(1) The number of knees is given on the basis of the maximum breadth B of the hull, using the column for the length of beam.(2) The scantlings of angles are only given as indications.

Pt B, Ch 5, Sec 4


8.2 Deck planking

8.2.1 Deck planking may be:

• constituted by planks parallel to the gunwale limited bya stringer board at side and by a kingplank at the centre-line;

• plywood;

• plywood with associated planks as above.

The thickness of the deck is given in Table 9 and is subjectto the following modifications:

• if the beam spacing is other than that indicated in Table7, the thickness is to be modified by 3 mm for every 100mm of variation in spacing;

• if plywood is employed, the thickness may be reducedby 30%;

• if plywood is adopted in association with planking, thespecific mass of the plywood/planking assembly is to be

not less than 430 kg/m3, and the combined thicknessmay be reduced by 30%. In addition, the plywood thi-ckness is to be not less than 30% of the combined thick-ness, or less than 6,5 mm; when the planking thicknessis less than 19 mm, the seams are to be made watertightby the application of a suitable elastic compoundapproved by RINA.

A further reduction of 1,5 mm may be applied to the deckthickness when the deck is sheathed with nylon, reinforcedplastics or other approved coverings.

The fixed fittings on deck, in particular winches, wind-lasses, ballards and fairleads, are to be well secured on suit-able basements and isolated by means of coatings ofappropriate materials. Before applying such insulatingmaterials to the basements, the timber is to be protected bysuitable preservative solutions or paints.

Guardrail stanchions are to be fastened by at least two pins,one of which is to be a through pin.

Table 9 : Planking - basic thickness

Table 10 : Floor fastenings

LengthLm

Shell and deck planking mm

Deck planking in deckhouses and coachroofs

mm

Coamings of coachroofs mm

24 26 28 30

45,547,55052

26272829

36363636

Depth of yachtDm

Diameter of bolts

at throat in the arms

Grown, or laminated, or steel frames

mm

Bent framesmm

Grown, or laminated, or steel frames

mm

Bent framesmm

≤2,4 2,6 2,8 3

3,2 3,4 3,6 3,8 4

4,2

12121414161820202022

89

1012121414---

891012121414141616

8888999---

FASTENINGS OF LONGITUDINAL STRUCTURES

Length of yachtLm

Diameter of bolts

Centreline structures of yachts

mm

Scarfs and breasthook armsmm

Beamshelves and beam kneesmm

24 26 28 30

20202222

14141618

11111214

Pt B, Ch 5, Sec 4


8.3 Superstructures - Skylights

8.3.1 When coachroofs are adopted, the opening on deckis to be well framed and the coaming on the weather deckis to be not less in thickness than that required in Table 9.

The coachroof deck is to have sheathing as prescribed inTable 9, though such sheathing may be reduced in thick-ness in accordance with the specifications in 8.2 for theweather deck. If the beam spacing is other than that indi-cated in Table 5, the thickness is to be modified by 3 mmfor every 100 mm of difference in spacing.

When deckhouses are adopted, they are to have a coamingfastened to the beams and carlings by means of throughbolts.

The structure of deckhouses is to be similar to that requiredfor coachroofs. Depending on their size, deckhouses are tobe adequately stiffened to the satisfaction of RINA.

Deck openings for skylights are to be well framed and pro-vided with shutters of adequate thickness.

8.4 Masts and rigging

8.4.1 Each yacht is to be provided with masts, rigging andsails sufficient in number and in good condition. The scant-lings of masts and rigging are left to the experience of build-ers and shipowners. Care will be taken by the RINASurveyor, however, in verifying that the attachments of

shrouds and stays to the hull are such as to withstand atleast twice the load expected on such rigging.The mast step is to be of strong construction, and is to beextended so as not to be connected to the transverse andlongitudinal framing of the bottom of the hull. The wedgingon deck is to be provided with watertight means.

When the mast rests on deck, the underlying structure is tobe strengthened in way such as to avoid giving way. If themast rests on a coachroof, the hull is to be strengthened inway by means of a bulkhead or a stiffened frame.

For shrouds and stays in wire and not in rod, the breakingloads of wires in galvanised steel 160 UNI 4434, in spiralshape, 1x19 wires (col. 1), and in stainless steel AISI 31618/10 (ASTM-A 368-55) 1x19 wires, in spiral shape (col. 2)are included below for information purposes.

Table 11

Diameter(mm)

Metallic

cross-sec-tion

(mm2)

Breaking load kN

Col. 1 Col. 2

345678

1012

5,379,5514,221,529,238,259,786,0

7,7513,7321,1030,9041,6054,9465,73

122,63

7,3613,7320,6029,4340,2252,9783,39

117,72

Pt B, Ch 5, Sec 4


Figure 1 : Sailing yachts - Constructional profile

1 -

Wo

od

ke

el

2 -

Exte

rna

l b

alla

st

3 -

Ho

g

4 -

Ra

bb

et

5 -

Ste

mp

ost

6 -

Ste

rnp

ost

7 -

Kn

ee

8 -

Ru

dd

er

9 -

Pro

pe

ller

ap

ert

ure

10

- F

loo

rs

11

- M

ain

ma

st ste

p

12

- M

izze

n s

tep

13

- S

tern

co

un

ter

14

- U

pp

er

ste

rn

15

- F

ram

es

16

- S

trin

ge

rs

17

- S

he

lve

s

18

- B

ea

ms

Pt B, Ch 5, Sec 4


Figure 2 : Midship section

1 - Wood keel

10 - Shelf

11 - Beam clamp

12 - Half beams

13 - Deck planking

14 - Waterway

15 - Seam

16 - Stay seam

17 - Carling

18 - Coaming "Coachroof"

19 - Side planking "Coachroof"

20 - Beam "Coachroof"

21 - Shelf "Coachroof"

22 - Top "Coachroof"

2 - Ballast

3 - Frame

9 - Sheerstrake

4 - Floor

5 - Stringers

6 - Bottom simple planking

7 - Planking inner skin

8 - Planking outer skin

Pt B, Ch 5, Sec 4


Figure 3 : Sternframe

1

- W

oo

d k

ee

l

2

- E

xte

rna

l b

alla

st

10

- H

og

6

- H

ee

l p

iece

dl

7

- R

ud

de

r

8

- P

rop

elle

r a

pe

rtu

re

9

- S

tern

co

un

ter

3

- R

ab

be

t

4

- S

tern

po

st

5

- K

ne

e

Pt B, Ch 5, Sec 4


Figure 4 : Typical floors

ANGLE FLOOR

ANGLE FLOOR

WOOD FLOOR

PLATE FLOOR

L = length of arms

h = height of floor

Pt B, Ch 5, Sec 5


SECTION 5 STRUCTURAL SCANTLINGS OF MOTOR YACHTS

1 General

1.1

1.1.1 The scantlings in this Section apply to yachts oflength L ≤ 35 metres with a chine hull of the type shown inFigures 1 and 2 and speed not exceeding 40 knots.For yacht which differ substantially from the above asregards dimensions and/or speed, or yachts with roundkeels, the scantlings are determined by equivalence criteria.

2 Keel - stempost

2.1

2.1.1 The minimum breadth of the keel and the aggregatecross-sectional area of keel and hog frame are given inTable 1.Such scantlings are to be maintained up to the stem end,while they may be reduced by 30% at the stern end.

Where they are made from a number of pieces, the keel andhog frame are to be scarfed. The scarfs are to be 6 times thethickness and of hooked or tabled type, if bolted, or of plaintype, if glued; the length may be reduced to not less than 4times the thickness where the scarf is bolted and glued.

The keel scarfs are to be spaced not less than 1,5 metresapart from those of the hog frame.

Stempost scantlings are given in Table 1 and a typical stern-frame is shown in Figure 3.

3 Transom

3.1

3.1.1 In chine hulls, the sternpost is replaced by a transom.

The transom structure consists of a frame having profileparts with a cross-section not less than 120% of bottomframes, side frames or beams; moreover, the structure's ver-tical stiffeners, arranged in way of keel and bottom girders,are to have a cross-section with a height equal to that of theside frames and width increased by 50%.

The stiffeners above are generally to be spaced not morethan 600 mm apart.

The thickness of transom planking is to be equal to thatgiven in Table 2 (col. 2), with any modifications required inaccordance with those specified for shell planking.

4 Floors and frames

4.1 General

4.1.1 The ordinary framing of the hull is divided into threeparts:

- bottom frames, comprising those between the keel andthe chine stringers;

- side frames, comprising those between the chine string-ers and the waterways;

- beams.

The bottom frames, generally made of two pieces, one portand one starboard of the keel, are butted in way of the cen-treline and connected by means of a double plywood floor.

The side frames are in one piece connected to the bottomframes by means of double plywood brackets.

The beams are connected to the side frames by means ofdouble plywood brackets.

Table 1 : Keel and stempost

LengthL

m

KEEL STEMPOST

Minimum breadth

mm

Cross-section of keel or keel and hog (1)

cm2

Width at heel and at head

mm

Cross-section at heel

cm2

Cross-section at head

cm2

1 2 3 4 5 6 24 26 28 30

230245260280

413462516570

230245260280

413462516570

289324361399

(1) Where there is no hog frame, a reduction in keel area of 10% in respect of that prescribed may be permitted. A keel cross-sec-tion reduced such as to be not less than 0,85 of that given in col. 3 may be accepted provided that the difference is compen-sated by an increased cross-section of girders.

Pt B, Ch 5, Sec 5


4.2 Bottom and side frames

4.2.1 Frame scantlings are given in Tables 3, 4 and 5,where three different types of frames are considered:Type I : solid or laminated frames, of constant scantlings

throughout the length of the hull;Type II : solid or laminated frames, alternated with one

or two bent frames. Only the former are con-nected by means of floors and brackets; thescantlings are as prescribed for Type I frames;

Type III : solid or laminated frames, associated with bentlongitudinals; this type of framing is to be asso-ciated with double-skin cross planking or coldmoulded laminated multi-layer planking or,alternatively, with plywood planking.

4.3 Floors

4.3.1 The floors connecting bottom frames (see 4.1) are tohave thickness equal to half that required for the latter,extend at the yacht's centreline to a height not less thantwice that prescribed for the heel of such frames and over-

lap the frames by a distance not less than 2,5 times theirdepth so as to constitute an effective connection by meansof glue and clenched bolts. The space between the twofloors above the frames is to be fitted with a chock; alterna-tively, the frames may be shaped so as to have, at the cen-treline, a depth above the keel equal to that required for theheel of the frames. For floors, see Figure 4.

4.4 Frame and beam brackets

4.4.1 The connection of bottom frames to side frames andof the latter to beams is to be achieved be means of doublebrackets similar to those described for floors, but overlap-ping both frames and beams by a distance not less thantwice their respective depths (see Figures 5 and 6).

In lieu of the brackets above, the frame-beam connectionmay be effected by simply overlapping, preferably dovetail-ing the beam on the shelf (with glueing and pivoting), andprovided that transverse bulkheads are arranged, with spac-ing not exceeding approximately 2 metres, so as to consti-tute main transverse strengthening elements of the hull, andthat no superstructure is arranged on the weather deck.

Table 2 : Shell and deck planking

LenghtLm

SHELL PLANKING Weather deck planking

mm

Deck of superstructures (quarterdeck, deckhouses, coachroofs, trunks)

mmType I and II framing

mmType III framing

mm

1 2 3 4 5

24 26 28 30

323436

37,5

28,53032

33,5

323436

37,5

21212121

Pt B, Ch 5, Sec 5


Table 3 : Frames

Table 4 : Frames

5 Side girders and longitudinals

5.1

5.1.1 On bottom frames, at least two continuous girdersare to be fitted each side, with a cross-section not less than90 cm2.

Such girders, continuous over bottom frames, are to be con-nected to the bottom planking by means of chocks betweenframes, set on a bent longitudinal continuous through the

floors and connected to the planking. The chocks and thebent longitudinal may be omitted, but in such case the bot-tom planking thickness given in Table 2 is to be augmentedsuch as to achieve a cross-section throughout the bottomincreased by at least half that of the longitudinals.

A similar longitudinal, but with a cross-section reduced to0,65 of those described above and not fastened to theplanking, is to be fitted on side frames.

Such longitudinal may be omitted where Type III framing isadopted.

Table 5 : Frames

DepthDm

TYPE I FRAMING (EITHER GROWN, OR LAMINATED FRAMES ONLY)

Spac-ing of webmm

BETWEEN KEEL AND CHINE BETWEEN CHINE AND DECK

Grown frames Laminated frames Grown frames Laminated frames

widthmm

depthwidthmm

depthmm

widthmm

depthwidth.mm

depthmmat heel

mmat head

mmat heel

mmat head

mm

3,0 3,1 3,3 3,5 3,7 3,9

322340355375390408

353944505560

127140148162178200

116127135148162182

353944505560

93104113125135157

353944505560

103117122131143156

90108110115123130

353944505560

8594

103114125143

DepthD

mm

TYPE II FRAMING (EITHER GROWN OR LAMINATED FRAMES WITH BENT FRAMES IN BETWEEN)

Spacing between main frames and alternate frames Bent frames

one bent framemm

two bent framesmm

three bent framesmm

widthmm

depthmm

3,0 3,1 3,3 3,5 3,7 3,9

560590620

---

650690725

---

730770800

---

363840---

252730---

DepthDm

TYPE III FRAMING (GROWN OR LAMINATED FRAMES OR BENTWOOD LONGITUDINALS)

Spacing of web

mm

BETWEEN KEEL AND CHINE BETWEEN CHINE AND DECK

Grown frames Laminated frames Grown frames Laminated frames

widthmm

depthwidthmm

depthmm

widthmm

depthwidthmm

depthmmat heel

mmat head

mmat heel

mmat head

mm

3,0 3,1 3,3 3,5 3,7 3,9

640680710750780820

374146525862

148160176192208232

126136150163176197

374146525862

92103112124135156

374146525862

104112122135146160

94106110115122129

374146525862

8493

103113123142

Pt B, Ch 5, Sec 5


Table 6 : Frames

6 Beams

6.1

6.1.1 The arrangement of beams is generally to be carriedout as follows:

- for hulls with Type I framing: beams on every frame;

- for hulls with Type II or III framing: beams in way ofsolid or laminated frames, with bracket connection andintermediate beams, without brackets, let into the shelf.

Beams are to have width equal to that of the frames towhich they are connected and section modulus, in cm3, notless than:

At the ends of large openings, beams are to be fitted havinga section modulus, in cm3, not less than:

where:

Z1,Z2 : section modulus of beams without plankingcontribution, in cm3

a : width of beams, in cm

s : beam spacing, in cm

K1,K2 : coefficient given by Table 7 as a function of thebeam span.

Where laminated beams are arranged, the section moduliZ1 and Z2 may be reduced to 0,85 of those indicated above.

Table 7

7 Beam shelves and chine stringers

7.1

7.1.1 The cross-sectional area of beam shelves and chinestringers is to be not less than that given by Table 8 belowas a function of L and to have the ratio h/t < 3, where h isthe depth and t the thickness of the bar.The cross-section of shelves and stringers is to be consid-ered as inclusive of the dappings for beam and frame ends.

DepthDm

TYPE III FRAMING (GROWN OR LAMINATED FRAMES OR BENTWOOD LONGITUDINALS)

BENTWOOD LONGITUDINALS

spacingmm

between keel and chine between chine and deck

widthmm

depthmm

widthmm

depth mm

3,0 3,1 3,3 3,5 3,7 3,9

285300315330345360

454850535558

303336394245

454850535558

252730333639

Z1 K1 a s⋅ ⋅=

Z2 K2 a s⋅ ⋅=

Beam span(m)

Coefficients for calculation of beam section mod-ulus

K1 K2

At thecentreline

At the endsAt the

centrelineAt the end

≤22,53

3,54

4,55

5,56

6,57

7,5

14,318

22,224,728,330,632,435,136,938,739,640,5

6,438,5

10,712,513,914,916,317,118,119,520,523

2331

38,643,648,752,556,860

63,570

73,581

11,415,117,722,223,625,227,728,731,835

40,245,4

Pt B, Ch 5, Sec 5


Table 8

8 Shell planking

8.1 Thickness of shell planking

8.1.1 The basic thickness of shell planking is given in Table2.

If the frame spacing is other than that shown in Table 3, theplanking thickness is to be increased or may be reduced,accordingly, by 10% for every 100 mm of difference.

After correction for spacing, the planking thickness may bereduced:

- by 10% if a diagonal or longitudinal double-skin plank-ing is adopted;

- by 15% if composite planking constituted by inner ply-wood skin and one or two outer longitudinal diagonalstrakes is adopted;

- by 25% if laminated planking (i.e. at least three cold-moulded layers) or plywood is adopted.

Moreover, the plywood thickness is to be not less than 30%of the total thickness or less than 6 mm.

Yachts with speed > 25 knots are to have bottom frames(floors and longitudinals) stiffened in respect of the scant-lings in this Section and planking thickness increased as fol-lows (for deadrise = 25°) in respect of the values in Table 2:

- speed from 26 to 30 knots: 5%

- speed from 31 to 35 knots: 10%

- speed from 36 to 40 knots: 15%.

When the deadrise is between 25° and 30° and outer longi-tudinal strakes are fitted on the bottom planking, the above

increase in thickness may be reduced but is generally to beno less than half of the percentage values above.

9 Deck planking

9.1 Weather deck

9.1.1 Deck planking may be constituted by planks flankedby a stringer board at side and by a kingplank at the cen-treline. Such planking may be solely plywood or plywoodwith associated planking arranged as described above.The thickness of deck planking is given in Table 2. If thebeam spacing is other than that prescribed in 4.2, the plank-ing thickness is to be increased or may be reduced, accord-ingly, by 10% for every 100 mm of difference.

After correction for spacing, the planking thickness may bereduced by 30% if plywood or plywood associated withplanking is employed.

Moreover, the plywood thickness is to be not less than 30%of the total thickness or less than 6 mm.

9.2 Superstructure decks

9.2.1 The thickness of planking of superstructure decks isgiven in Table 2.Such thickness is subject to the reductions and increases forweather deck planking as provided for in 9.1.

9.3 Lower deck

9.3.1 In hulls with depth, measured between the upperkeel side and the weather deck beam, greater than or equalto 3,10 metres, a lower or cabin deck is to be arranged,with beams having a section modulus not less than 60% ofthat prescribed in Article 6 for weather deck beams andeffectively fastened to the sides by means of a shelf with across-sectional area not less than 2/3 of that required inTable 8.When the depth, as measured above, exceeds 4,30 metres,the fastening of beams to side is to be completed by meansof plywood brackets arranged at least at every second beamand having scantlings as prescribed in 4.4.

The scantlings of the deck planking are to be not less thanthose required in 9.2.

Length L of the hull(m)

Cross-sectional area of beam shelves (cm2)

Cross-sectional area of chine stringers (cm2)

242628303235

95110125140155177

112128140152164182

Pt B, Ch 5, Sec 5


Figure 1 : Motor yachts - Constructional profile

1 -

Kee

l

2 -

Hog

3 -

Gro

wn

fram

e

4 -

Chi

ne s

trin

ger

5 -

Ben

t fra

me

6 -

Ste

mpo

st

8 -

Ste

m

7 -

Apr

on

9 -

She

lf

10 -

Kne

e

11 -

Tra

nsom

stif

fene

rs

12 -

Tra

nsom

fram

e

13 -

Tra

nsom

fram

e

14 -

Chi

ne k

nees

15 -

Flo

ors

16 -

Bea

m k

nees

17 -

Bea

m

Pt B, Ch 5, Sec 5


Figure 2 : Midship section

1 -

Kee

l2

- H

og

3 -

Bot

tom

fram

e4

- S

ide

fram

e5

- D

oubl

e kn

ee6

- C

hine

7 -

Ben

t fra

me

8 -

Bea

m9

- D

oubl

e kn

ee

10-

Bot

tom

str

inge

rs11

- D

eadw

ood

12-

Sid

e st

ringe

rs13

- S

helf

14-

Car

ling

15-

Bot

tom

and

sid

e pl

anki

ng -

Inne

r sk

in

16-

Bot

tom

and

sid

e pl

anki

ng -

Out

er s

kin

17-

Dec

k pl

anki

ng -

Inne

r sk

in18

- D

eck

plan

king

- O

uter

ski

n19

- W

ater

way

Pt B, Ch 5, Sec 5


Figure 3 : Stem

1 -

Kee

l

2 -

Hog

3 -

Ste

m

4 -

Ste

mpo

st

5 -

Apr

on

Pt B, Ch 5, Sec 5


Figure 4 : Detail of floor

1 -

Kee

l

2- H

og

3 -

Bot

tom

fram

e

4 -

Bot

tom

str

inge

r

5 -

Ben

t fra

me

6 -

Pla

nkin

g -

Inne

r sk

in

7 -

Pla

nkin

g -

Out

er s

kin

8 -

Dou

ble

floor

Pt B, Ch 5, Sec 5


Figure 5 : Detail of floor

1 -

Bot

tom

fram

e

2 -

Sid

e fr

ame

3 -

Dou

ble

knee

s

4 -

Chi

ne s

trin

ger

5 -

Pla

nkin

g -

Inne

r sk

in

6 -

Pla

nkin

g -

Out

er s

kin

7 -

Chi

ne

Pt B, Ch 5, Sec 5


Figure 6 : Detail of gunwale connection

1 -

Sid

e fr

ame

2 -

Bea

m

3 -

Dou

ble

knee

s

4 -

She

lf

5 -

Hul

l pla

nkin

g -

Inne

r sk

in

6 -

Hul

l pla

nkin

g -

Out

er s

kin

7 -

Dec

k pl

anki

ng -

Inne

r sk

in

8 -

Dec

k pl

anki

ng -

Out

er s

kin

9 -

Wat

erw

ay

10 -

Rub

bing

pie

ce

Pt B, Ch 5, Sec 6


SECTION 6 WATERTIGHT BULKHEADS, LINING, MACHINERY

SPACE

1 Wooden bulkheads

1.1

1.1.1 Wooden watertight bulkheads normally consist ofplywood boards of adequate thickness in relation to the hullsize and the spacing and strength of stiffeners. Glues fortimber fastenings are to be of resorcinic or phenolic type,i.e. durable and water-resistant in particular.As regards the number of watertight bulkheads, attention isdrawn to the provisions of Chap 1, Sec 1.

The plywood, normally arranged in vertical panels, is to bescarfed or strapped in way of vertical stiffeners.

Connection to the hull is to be effected by means of agrown or laminated frame and made watertight by packingwhere necessary.

2 Steel bulkheads

2.1

2.1.1 Steel watertight bulkheads are to be of thickness asshown in Table 1 as a function of the spacing of stiffenersand the height of the bulkhead.The scantlings are given on the assumption that the loweststrake is horizontal and subsequent strakes vertical. Whenall strakes are horizontal, the thickness of the third andhigher strakes may be decreased by a maximum of 0,5 mmper strake so as to reach a reduction of 25%, in respect ofthe Table thickness, for the highest strake.

If the spacing is other than that shown in the Table, thethickness is to be modified by 0,5 mm for every 100 mm ofdifference in spacing. The spacing of vertical stiffeners isnot to exceed 600 mm for the collision bulkhead.

The scantlings of vertical stiffeners, in cm3, without endconnections are to be not less than:

where:

Z : section modulus of vertical stiffener with associ-ated strip of plating one spacing wide, in cm3

h : distance from midpoint of stiffener to top ofbulkhead, in m

s : spacing of vertical stiffeners, in m

S : aggregate span of vertical stiffeners.

The connection of the bulkhead to planking is to be effectedon grown or laminated frames, and provided with water-tight packing where necessary.

Bulkheads are to be caulked or made watertight by meansof suitable gaskets. On completion, any watertight bulk-heads and doors are to be tested using a strong jet of water.

3 Internal lining of hull and drainage

3.1

3.1.1 Where ceilings or internal linings are arranged, theyare to be fitted so as to be, as far as practicable, easilyremovable for maintenance and painting of the underlyingstructures. Linings are to allow sufficient ventilation of airspaces between them and planking.

Limber holes are to be provided in the bottom structuressuch as to allow the drainage of bilge liquids into suctionwells.

4 Machinery space structures

4.1

4.1.1 The scantlings of floors, web frames and foundationgirders are to be adequate for the weight, power and type ofmachinery; their suitability and that of associated connec-tions is to be satisfactory with particular regard to enginerunning and navigation tests when required by these Rule.Z 4 2, 4h+( )s S2⋅=

Pt B, Ch 5, Sec 6


Table 1 : Watertight steel bulkheads

Height of bulkheadmm

Spacing of vertical stiffenersmm

Thickness of lower strakemm

Thickness of other strakesmm

≤2,40 2,60 2,80 3,00 3,20 3,40 3,60 3,80 4,00 4,20 4,40 4,60 4,80 5,00

375390410425440460475490510525540560575590

455

5,55,55,56666

6,56,56,56,5

3,54,54,5555

5,55,55,55,56666


Part BHull

Chapter 6

STABILITY

SECTION 1 STABILITY

APPENDIX 1 INCLINING TEST AND LIGHTWEIGHT CHECK

APPENDIX 2 STABILITY INFORMATION BOOKLET

Pt B, Ch 6, Sec 1


SECTION 1 STABILITY

1 General

1.1

1.1.1 This Section outlines the minimum requirements forintact stability for both motor and sailing vessels.

This Section deals with the standards for intact stability.

1.1.2 An intact stability standard proposed for assessmentof a vessel type not covered by the standards defined in thisSection is to be submitted to RINA for approval at the earli-est opportunity.

1.1.3 If used, permanent ballast is to be located in accord-ance with a plan approved by RINA and in a manner thatprevents shifting of position. Permanent ballast is not to beremoved from the ship or relocated within the ship withoutthe approval of RINA. Permanent ballast particulars are tobe noted in the ship's stability booklet. Attention is to bepaid to local or global hull strength requirements from thefitting of additional ballast.

2 Intact Stability Standards

2.1 Motor vessels

2.1.1 Monohull Vessels

The curves of statical stability for seagoing conditions are tomeet the following criteria:

a) the area under the righting lever curve (GZ curve) is notto be less than 0,055 metre-radians up to 30º angle ofheel and not less than 0,09 metre-radians up to 40ºangle of heel, or the angle of downflooding, if this angleis less;

b) the area under the GZ curve between the angles of heelof 30º and 40º or between 30º and the angle of down-flooding if this is less than 40º, is not to be less than0.03 metre-radians;

c) the righting lever (GZ) is to be at least 0,20 metres at anangle of heel equal to or greater than 30º;

d) the maximum GZ is to be occur at an angle of heelpreferably exceeding 30º but not less than 25º;

e) after correction for free surface effects, the initial meta-centric height (GM) is not to be less than 0,15 metres;

f) in the event that the vessels intact stability standard failsto comply with the criteria defined in a) to e) RINA maybe consulted for the purpose of specifying alternativebut equivalent criteria.

g) crowding of passengers

The angle of heel on account of crowding of passengersto one side is not to exceed 10° and in any event thefreeboard deck is not to be immersed.

For ships less than 20 m in length, the angle of heel isnot to be greater than the angle corresponding to a free-board of 0,1 m before the deck’s immersion, or 12° ifless.

2.1.2 Multi-hullsThe curves of statical stability for seagoing conditions are tomeet the following criteria:

a) the area under the righting lever curve (GZ curve) is notto be less than 0,075 metre-radians up to an angle of20º when the maximum righting lever (GZ) occurs at20º and, not less than 0,055 metre-radians up to anangle of 30º when the maximum righting lever (GZ)occurs at 30º or above. When the maximum GZ occursat angles between 20º and 30º the corresponding areaunder the GZ curve, Areq is to be taken as follows:

Areq={0,055 + 0,002(30 - qmax) metre radians;

where qmax is the angle of heel in degrees where the GZcurve reaches its maximum.

b) the area under the GZ curve between the angles of heelof 30º and 40º or between 30º and the angle of down-flooding if this is less than 40º, is not to be less than0,03 metre-radians;

c) the righting lever (GZ) is to be at least 0,20 metres at anangle of heel where it reaches its maximum;

d) the maximum GZ is to occur at an angle of heel not lessthan 20º;

e) after correction for free surface effects, the initial meta-centric height (GM) is not to be less than 0,15 metres;

f) if the maximum righting lever (GZ) occurs at an angle ofless than 20º, approval of the stability is to be consid-ered by RINA as a special case.

2.1.3 For the purpose of assessing whether the stability cri-teria are met, GZ curves are to be produced for the loadingconditions applicable to the operation of the vessel.

2.1.4 Superstructures

a) The buoyancy of enclosed superstructures complyingwith regulation 3(10)(b) of the ICLL may be taken intoaccount when producing GZ curves.

b) Superstructures, the doors of which do not comply withthe requirements of regulation 12 of ICLL, are not to betaken into account.

2.1.5 High Speed Vessels

In addition to the criteria above, Designers and builders areto address the following hazards which are known to effect

Pt B, Ch 6, Sec 1


vessels operating in planing modes or those achieving rela-tively high speeds:

a) directional instability, often coupled to roll and pitchinstabilities;

b) bow diving of planing vessels due to dynamic loss oflongitudinal stability in calm seas;

c) reduction in transverse stability with increasing speed inmonohulls;

d) porpoising of planing monohulls being coupled withpitch and heave oscillations;

e) generation of capsizing moments due to immersion ofchines in planing monohulls (chine tripping).

2.2 Sailing vessels

2.2.1 Monohull

a) Curves of statical stability (GZ curves) for at least theLoaded Departure with 100% consumables and theLoaded Arrival with 10% consumables are to be pro-duced.

b) The GZ curves required by a) should have a positiverange of not less than 90º. For vessels of more than 45m,a range of less than 90º may be considered but may besubject to agreed operational criteria.

c) In addition to the requirements of b), the angle of steadyheel is to be greater than 15 degrees (see figure). Theangle of steady heel is obtained from the intersection ofa 'derived wind heeling lever' curve with the GZ curverequired by a).

In the figure:

'dwhl' = the 'derived wind heeling lever' at any angle qº

where:

Figure 1

Noting that:

WLO is the magnitude of the actual wind heeling leverat 0º which would cause the vessel to heel to the 'downflooding angle' θf or 60º whichever is the lesser.

GZf is the lever of the vessel's GZ at the down floodingangle (θf ) or 60º whichever is the lesser.

θf is the angle at which the 'derived wind heeling' curveintersects the GZ curve. (If θd is less than 15º the vesselwill be considered as having insufficient stability).θd the 'down-flooding angle' is the angle of heel causingimmersion of the lower edge of openings having anaggregate area, in square metres, greater than:

where Δ = vessels displacement in tonnes.

All regularly used openings for access and for ventila-tion are to be considered when determining the down-flooding angle. No opening regardless of size whichmay lead to progressive flooding is to be immersed at anangle of heel of less than 40º. Air pipes to tanks can,however, be disregarded.

If, as a result of immersion of openings in a superstructure, avessel cannot meet the required standard, those superstruc-ture openings may be ignored and the openings in theweather deck used instead to determine f). In such cases theGZ curve is to be derived without the benefit of the buoy-ancy of the superstructure.It might be noted that provided the vessel complies with therequirements of [2.1.1], [2.1.2] and [2.1.3] and is sailedwith an angle of heel which is no greater than the 'derivedangle of heel', it should be capable of withstanding a windgust equal to 1,4 times the actual wind velocity (i.e. twicethe actual wind pressure) without immersing the 'downflooding openings', or heeling to an angle greater than 60º.

2.2.2 Multi-hull

a) Curves of statical stability in both roll and pitch are tobe prepared for at least the Loaded Arrival with 10%consumables. The VCG is to be obtained by one of thethree methods listed below:

1) inclining of complete craft in air on load cells, theVCG being calculated from the moments generatedby the measured forces, or

2) separate determination of weights of hull and rig(comprising masts and all running and standing rig-ging), and subsequent calculation assuming that thehull VCG is 75% of the hull depth above the bottomof the canoe body, and that the VCG of the rig is athalf the length of the mast (or a weighted mean ofthe lengths of more than one mast), or

3) detailed calculation of the weight and CG positionof all components of the vessel, plus a 15% marginof the resulting VCG height above the underside ofcanoe body.

b) If naval architecture software is used to obtain a curve ofpitch restoring moments, then the trim angle must befound for a series of longitudinal centre of gravity (LCG)positions forward of that necessary for the design water-line. The curve can then be derived as follows:GZ in pitch = CG' x cos (trim angle)

dwhl =0 5, WLO× Cos θ1 3,×

WLOGZf

Cos θ1 3,f

--------------------=

)º( elgnA leeH09f51>0

GZ

Lever

(M)

WLO

dw

hl

GZ

f

evruC ZG

devireDleeHelgnA

d

Δ1500-------------

Pt B, Ch 6, Sec 1


where:

CG' = shift of LCG forward of that required for designtrim, measured parallel to base line

TFP = draught at forward perpendicular

TAP = draught at aft perpendicular

LBP = length between perpendiculars

Approximations to maximum roll or pitch moments arenot acceptable.

c) Data is to be provided to the user showing the maxi-mum advised mean apparent wind speed appropriate toeach combination of sails, such wind speeds being cal-culated as the lesser of the following:

or

where:

vw = maximum advised apparent wind speed (knots)

LMR = maximum restoring moment in roll (N-m)

LMp = limiting restoring moment in pitch (N-m), definedas the pitch restoring moment at the least angle of thefollowing:

1) angle of maximum pitch restoring moment, or

2) angle at which foredeck is immersed

3) 10º from design trim

A'S = area of sails set including mast and boom (squaremetres)

h = height of combined centre of effort of sails and sparsabove the waterline

fR = heel angle at maximum roll righting moment (inconjunction with LMR)

fP = limiting pitch angle used when calculating LMP (inconjunction with LMP)

AD = plan area of the hulls and deck (square metres)

b = distance from centroid of AD to the centreline of theleeward hull

This data is to be accompanied by the note:

In following winds, the tabulated safe wind speed foreach sail combination should be reduced by the boatspeed.

d) If the maximum safe wind speed under full fore-and-aftsail is less than 27 knots, it is to be demonstrated by cal-culation using annex D of ISO 12217-2 (2002) that,

when inverted and/or fully flooded, the volume of buoy-ancy, expressed in cubic metres (m3), in the hull, fittingsand equipment is greater than:

1.2 x (fully loaded mass in tonnes)

thus ensuring that it is sufficient to support the mass ofthe fully loaded vessel by a margin. Allowance fortrapped bubbles of air (apart from dedicated air tanksand watertight compartments) is not to be included.

e) The maximum safe wind speed with no sails set calcu-lated in accordance with c) above is to exceed 36 knots.

f) Trimarans used for unrestricted operations are to havesidehulls each having a total buoyant volume of at least150% of the displacement volume in the fully loadedcondition.

g) The stability information booklet is to include informa-tion and guidance on:

1) the stability hazards to which these craft are vulnera-ble, including the risk of capsize in roll and/or pitch;

2) the importance of complying with the maximumadvised apparent wind speed information supplied;

3) the need to reduce the tabulated safe wind speedsby the vessel speed in following winds;

4) the choice of sails to be set with respect to the pre-vailing wind strength, relative wind direction, andsea state;

5) the precautions to be taken when altering coursefrom a following to a beam wind.

h) In vessels required to demonstrate the ability to floatafter inversion (according to c) above), an emergencyescape hatch is to be fitted to each main inhabitedwatertight compartment such that it is above bothupright and inverted waterlines.

2.3 Element of Stability

2.3.1 Unless otherwise specified, the lightship weight, ver-tical centre of gravity (KG) and longitudinal centre of gravity(LCG) of a vessel are to be determined from the results of aninclining experiment.

2.3.2 An inclining experiment is to be conducted inaccordance with a detailed standard which is approved byRINA and, in the presence of a RINA Surveyor.

2.3.3 The inclining experiment and the lightweight checkare to be conducted in accordance with the provisions ofApp 1.

2.3.4 The report of the inclining experiment and the light-ship particulars derived are to be approved by RINA prior totheir use in stability calculations.

2.3.5 For sister vessels, in order to verify the stability docu-mentation the following procedure is to be applied:

a) the shipyard declares that a ship is dealt with as a proto-type.

An inclining experiment is to be carried out this firtsship (prototype) and, on the basis of the results, a full

trim angle 1–tanTFP TAP–

LBP

---------------------⎝ ⎠⎛ ⎞=

vw 1 5 LMR

A'Sh φcos R ADb+-------------------------------------------,=

vw 1 5 LMP

A'Sh φcos P ADb+-------------------------------------------,=

Pt B, Ch 6, Sec 1


stability booklet is to be prepared, taking into accountthe Rule stability requirements.The above documents are to be examined andapproved.

b) In the case of a declared sister ship (same hull, machin-ery, subdivision, general arrangement and furniture (asfar as reasonable), a lightweight survey is to be carriedout instead of an inclining test, provided that:

1) the ship is built by the same shipyard;

2) the same drawings are used;

3) when the sister ship is built the light ship displace-ment difference in comparison to the prototype isnot greater than + 2-3%;

4) a sister ship statement is communicated to RINA,thus formalising the request to waive the incliningexperiment for the sister ship.

Should a ship be declared a sister ship of a prototype, thefollowing documentation is to be sent for approval:

a) light-ship weight report (duly signed by the attendingRINA Surveyor and by the shipyard representative);

b) stability booklet as photocopy of the prototype, onlyupdatef for the general description (ship’s name, port ofregistry, flag, etc.).

2.4 Stability Documents

2.4.1 A vessel is to be provided with a stability informationbooklet for the Master, which is to be approved by RINA.

2.4.2 The stability information booklet is to be contain theinformation specified in App 2.

2.4.3 A vessel with previously approved stability informa-tion which undergoes a major refit or alterations is to besubjected to a complete reassessment of stability and pro-vided with newly approved stability information.

A major refit or major alteration is one which results in achange in the lightship weight of 2% and above and/or achange in the longitudinal centre of gravity of 1% andabove (measured from the aft perpendicular), and/or anincrease in the calculated vertical centre of gravity of 0,25%and above (measured from the keel).

2.4.4 Sailing vessels are to have, readily available, a copyof the Curves of Maximum Steady Heel Angle to PreventDownflooding in Squalls, or in the case of a multihull, thevalues of maximum advised mean apparent windspeed, forthe reference of the watchkeeper. This should be a directcopy taken from that contained in the approved stabilitybooklet.

2.4.5 The overall sail area and spar weights and dimen-sions are to be as documented in the vessel's stability infor-mation booklet. Any rigging modifications that increase theoverall sail area, or the weight/dimensions of the rig aloft,must be accompanied by an approved updating of the sta-bility information booklet.

Pt B, Ch 6, App 1


APPENDIX 1 INCLINING TEST AND LIGHTWEIGHT CHECK

1 General

1.1 Aim of the Appendix

1.1.1 Prior to the test, RINA's Surveyor is to be satisfied ofthe following:

a) the weather conditions are to be favourable;

b) the yacht is to be moored in a quiet, sheltered area freefrom extraneous forces, such as to allow unrestrictedheeling. The yacht is to be positioned in order to mini-mise the effects of possible wind, stream and tide;

c) the yacht is to be transversely upright and the trim is tobe taken not more than 1% of the length between per-pendiculars. If this condition is not satisfied, hydrostaticdata and sounding tables are to be available for theactual trim;

d) cranes, derrick, lifeboats and liferafts capable of induc-ing oscillations are to be secured;

e) main and auxiliary boilers, pipes and any other systemcontaining liquids are to be filled;

f) the bilge and the decks are to be thoroughly dried;

g) preferably, all tanks are to be empty and clean, or com-pletely full. The number of tanks containing liquids is tobe reduced to a minimum taking into account theabove-mentioned trim.

The shape of the tank is to be such that the free surfaceeffect can be accurately determined and remains almostconstant during the test. All cross connections are to beclosed;

h) the weights necessary for the inclination are to bealready on board, located in the correct place;

i) all work on board is to be suspended and crew or per-sonnel not directly involved in the inclining test are toleave the yacht;

j) the yacht is to be as complete as possible at the time ofthe test. The number of weights to be removed, addedor shifted is to be limited to a minimum. Temporarymaterial, tool boxes, staging, sand, debris, etc. on boardis to be reduced to an absolute minimum.

2 Inclining weights

2.1

2.1.1 The total weight used is preferably to be sufficient toprovide a minimum inclination of one degree and a maxi-mum of four degrees of heel to each side. RINA may, how-ever, accept a smaller inclination angle for large yachtsprovided that the requirement on pendulum deflection or

U-tube difference in height specified in [3] is compliedwith. Test weights are to be compact and of such a configu-ration that the VCG (vertical centre of gravity) of the weightscan be accurately determined. Each weight is to be markedwith an identification number and its weight. Re-certifica-tion of the test weights is to be carried out prior to theincline. A crane of sufficient capacity and reach, or someother means, is to be available during the inclining test toshift weights on the deck in an expeditious and safe man-ner. Water ballast and people are generally not acceptableas inclining weight.

2.1.2 Where the use of solid weights to produce the inclin-ing moment is demonstrated to be impracticable, the move-ment of ballast water may be permitted as an alternativemethod. This acceptance would be granted for a specifictest only, and approval of the test procedure by RINA isrequired. The following conditions are to be met:

a) inclining tanks are to be wall-sided and free of largestringers or other internal members that create air pock-ets;

b) tanks are to be directly opposite to maintain the yacht'strim;

c) specific gravity of ballast water is to be measured andrecorded;

d) pipelines to inclining tanks are to be full. If the yacht'spiping layout is unsuitable for internal transfer, portablepumps and pipes/hoses may be used;

e) blanks must be inserted in transverse manifolds to pre-vent the possibility of liquids being "leaked" duringtransfer. Continuous valve control must be maintainedduring the test;

f) all inclining tanks must be manually sounded beforeand after each shift;

g) vertical, longitudinal and transverse centres are to becalculated for each movement;

h) accurate sounding/ullage tables are to be provided. Theyacht's initial heel angle is to be established prior to theincline in order to produce accurate values for volumesand transverse and vertical centres of gravity for theinclining tanks at every angle of heel. The draught marksamidships (port and starboard) are to be used whenestablishing the initial heel angle;

i) verification of the quantity shifted may be achieved by aflowmeter or similar device;

j) the time to conduct the inclining is to be evaluated. Iftime requirements for transfer of liquids are consideredtoo long, water may be unacceptable because of thepossibility of wind shifts over long periods of time.

Pt B, Ch 6, App 1


3 Pendulums

3.1

3.1.1 The use of three pendulums is recommended but aminimum of two are to be used to allow identification ofbad readings at any one pendulum station. However, foryachts of a length equal to or less than 30 m, only one pen-dulum can be accepted. They are each to be located in anarea protected from the wind. The pendulums are to belong enough to give a measured deflection, to each side ofupright, of at least 10 cm. To ensure recordings from indi-vidual instruments are kept separate, it is suggested that thependulums be physically located as far apart as practical.

The use of an inclinometer or U-tube is to be considered ineach separate case. It is recommended that inclinometers orother measuring devices only be used in conjunction withat least one pendulum.

4 Means of communication

4.1

4.1.1 Efficient two-way communications are to be pro-vided between central control and the weight handlers andbetween central control and each pendulum station. Oneperson at a central control station is to have complete con-trol over all personnel involved in the test.

5 Documentation

5.1

5.1.1 The person in charge of the inclining test is to haveavailable a copy of the following plans at the time of thetest:

a) hydrostatic curves or hydrostatic data;

b) general arrangement plan of decks, holds, inner bot-toms;

c) capacity plan showing capacities and vertical and longi-tudinal centres of gravity of cargo spaces and tanks.When water ballast is used as inclining weights, thetransverse and vertical centres of gravity for the applica-ble tanks, for each angle of inclination, must be availa-ble;

d) tank sounding tables;

e) draught mark locations;

f) docking drawing with keel profile and draught markcorrections, if available.

6 Calculation of the displacement

6.1

6.1.1 The following operations are to be carried out for thecalculation of the displacement:

a) draught mark readings are to be taken at aft, midshipand forward, at starboard and port sides;

b) the mean draught (average of port and starboard read-ing) is to be calculated for each of the locations wheredraught readings are taken and plotted on the yacht'slines drawing or outboard profile to ensure that all read-ings are consistent and together define the correctwaterline. The resulting plot is to yield either a straightline or a waterline which is either hogged or sagged. Ifinconsistent readings are obtained, the freeboards/draughts are to be taken again;

c) the specific gravity of the sea water is to be determined.Samples are to be taken from a sufficient depth of thewater to ensure a true representation of the sea waterand not merely surface water, which could contain freshwater from run off of rain. A hydrometer is to be placedin a water sample and the specific gravity read andrecorded. For large yachts, it is recommended that sam-ples of the sea water be taken forward, midship and aft,and the readings averaged. For small yachts, one sampletaken from midship is sufficient. The temperature of thewater is to be taken and the measured specific gravitycorrected for deviation from the standard, if necessary;

d) A correction to water specific gravity is not necessary ifthe specific gravity is determined at the inclining experi-ment site. Correction is necessary if specific gravity ismeasured when the sample temperature differs from thetemperature at the time of the inclining test. Where thevalue of the average calculated specific gravity is differ-ent from that reported in the hydrostatic curves, ade-quate corrections are to be made to the displacementcurve;

e) all double bottoms, as well as all tanks and compart-ments which can contain liquids, are to be checked,paying particular attention to air pockets which mayaccumulate due to the yacht's trim and the position ofair pipes;

f) it is to be checked that the bilge is dry, and an evalua-tion of the liquids which cannot be pumped, remainingin the pipes, boilers, condenser, etc., is to be carriedout;

g) the entire yacht is to be surveyed in order to identify allitems which need to be added, removed or relocated tobring the yacht to the lightship condition. Each item is tobe clearly identified by weight and location of the cen-tre of gravity;

h) the possible solid permanent ballast is to be clearlyidentified and listed in the report.

Pt B, Ch 6, App 1


7 Inclining procedure

7.17.1.1 The standard test generally employs eight distinct weightmovements as shown in Fig 1.

Figure 1

The weights are to be transversally shifted, so as not to mod-ify the yacht's trim and vertical position of the centre ofgravity.

After each weiht shifting, the new position of the transversecenter of gravity of the weihts is to be accurately deter-mined.

After each weight movement, the distance the weight wasmoved (centre to centre) is to be measured and the heeling

moment calculated by multiplying the distance by theamount of weight moved. The tangent is calculated for eachpendulum by dividing the deflection by the length of thependulum. The resultant tangents are plotted on the graphas shown in Fig 2.

The pendulum deflection is to be read when the yacht hasreached a final position after each weight shifting.

During the reading, no movements of personnel areallowed.

For yachts with a length equal to or less than 30 m, six dis-tinct weight movements may be accepted.

Figure 2

8 Lightweight check

8.1

8.1.1 An inclining test for an individual yacht may be dis-pensed with by RINA on a case by case basis, provided thatbasic stability data are available from the inclining test of asister yacht and a satisfactory lightweight check is per-formed in order to prove that the sister yacht corresponds tothe prototype yacht.

Pt B, Ch 6, App 2


APPENDIX 2 STABILITY INFORMATION BOOKLET

1 Information to be included

1.1 General

1.1.1 A stability information booklet is a stability manual,to be approved by RINA, which is to contain sufficientinformation to enable the Master to operate the yacht incompliance with the applicable requirements contained inthe Rules.

1.2 List of information

1.2.1 The following information is to be included in thestability information booklet:

a) a general description of the yacht, including:• the yacht's name and RINA classification number• the yacht type and service notation• the class notations• the yard, the hull number and the year of delivery• the flag, the port of registry, the international call

sign• the moulded dimensions• the design draft• the displacement corresponding to the above-men-

tioned draughts;

b) clear instructions on the use of the booklet;

c) general arrangement and capacity plans indicating theassigned use of compartments and spaces (stores,accommodation, etc.);

d) a sketch indicating the position of the draught marksreferred to the yacht's perpendiculars;

e) hydrostatic curves or tables corresponding to the designtrim, and, if significant trim angles are foreseen duringthe normal operation of the yacht, curves or tables cor-responding to such range of trim. A clear reference rele-vant to the sea density, in t/m3, is to be included as wellas the draught measure (from keel or underkeel);

f) cross curves (or tables) of stability calculated on a freetrimming basis, for the ranges of displacement and trimanticipated in normal operating conditions, with indica-tion of the volumes which have been considered in thecomputation of these curves;

g) tank sounding tables or curves showing capacities, cen-tre of gravity, and free surface data for each tank;

h) lightship data from the inclining test, including lightshipdisplacement, centre of gravity co-ordinates, place anddate of the inclining test, as well as RINA approvaldetails specified in the inclining test report. It is recom-mended that a copy of the approved test report beenclosed with the stability information booklet. Wherethe above-mentioned information is derived from a sis-

ter yacht, the reference to this sister yacht is to be clearlyindicated, and a copy of the approved inclining testreport relevant to this sister yacht is to be included;

i) standard loading conditions and examples for develop-ing other acceptable loading conditions using the infor-mation contained in the booklet

j) intact stability results (total displacement and its centerof gravity co-ordinates, draughts at perpendiculars, GM,GM corrected for free surfaces effect, GZ values andcurve when applicable, reporting a comparisonbetween the actual and the required values) are to beavailable for each of the above-mentioned operatingconditions;

k) information on loading restrictions when applicable;

l) information about openings (location, tightness, meansof closure), pipes or other progressive flooding sources;

m) information concerning the use of any special cross-flooding fittings with descriptions of damage conditionswhich may require cross-flooding, when applicable;

n) any other necessary guidance for the safe operation ofthe yacht;

o) a table of contents and index for each booklet.

2 Loading conditions

2.1

2.1.1 The standard loading conditions to be included inthe stability information booklet are:

a) yacht in the fully loaded departure condition, with fullstores and fuel and the full number of guests;

b) lightship condition;

c) yacht in the fully loaded arrival condition, with only10% stores and fuel remaining and the full number ofguests.

Such loading cases are considered as a minimum require-ment and additional loading cases may be included asdeemed necessary or useful.

3 Stability curve calculation

3.1 General

3.1.1 Hydrostatic and stability curves are normally pre-pared on a designed trim basis. However, where the operat-ing trim or the form and arrangement of the yacht are suchthat change in trim has an appreciable effect on rightingarms, such change in trim is to be taken into account.

The calculations are to take into account the volume to theupper surface of the deck sheathing.

Pt B, Ch 6, App 2


3.2 Superstructures and deckhouses which may be taken into account

3.2.1 Enclosed superstructures complying with the Inter-national Load Line Convention (ILLC) may be taken intoaccount.

The second tier of similarly enclosed superstructures mayalso be taken into account. Deckhouses on the freeboarddeck may be taken into account, provided that they complywith the conditions for enclosed superstructures laid downin the ILCC.

Where deckhouses comply with the above conditions,except that no additional exit is provided to a deck above,such deckhouses are not to be taken into account; however,any deck openings inside such deckhouses are to be con-sidered as closed even where no means of closure are pro-vided.

Deckhouses, the doors of which do not comply with therequirements in the ILCC, are not to be taken into account;however, any deck openings inside the deckhouse areregarded as closed where their means of closure complywith the requirements of the ILCC. Deckhouses on decksabove the freeboard deck are not to be taken into account,but openings within them may be regarded as closed.Superstructures and deckhouses not regarded as enclosedmay, however, be taken into account in stability calcula-tions up to the angle at which their openings are flooded (atthis angle, the statical stability curve is to show one or moresteps, and in subsequent computations the flooded space isto be considered non-existent).

Trunks may be taken into account. Hatchways may also betaken into account having regard to the effectiveness oftheir closures.

3.3 Angle of flooding

3.3.1 In cases where the yacht would sink due to floodingthrough any openings, the stability curve is to be cut short atthe corresponding angle of flooding and the yacht is to beconsidered to have entirely lost its stability.

Small openings such as those for passing wires or chains,tackle and anchors, and also holes of scuppers, dischargeand sanitary pipes are not to be considered as open if theysubmerge at an angle of inclination more than 30°. If theysubmerge at an angle of 30° or less, these openings are tobe assumed open if RINA considers this to be a source ofsignificant progressive flooding; therefore, such openingsare to be considered on a case by case basis.

4 Effects of free surfaces of liquids in tanks

4.1 General

4.1.1 For all loading conditions, the initial metacentricheight and the righting lever curve are to be corrected forthe effect of free surfaces of liquids in tanks.

4.2 Consideration of free surface effects

4.2.1 Free surface effects are to be considered wheneverthe filling level in a tank is less than 98% of full condition.

Free surface effects need not be considered where a tank isnominally full, i.e. filling level is 98% or above. Free surfaceeffects for small tanks may be ignored under the conditionin [4.8].

4.3 Categories of tanks

4.3.1 Tanks which are taken into consideration whendetermining the free surface correction may be one of twocategories:

a) Tanks with fixed filling level (e.g. liquid cargo, waterballast). The free surface correction is to be defined forthe actual filling level to be used in each tank;

b) Tanks with variable filling level (e.g. consumable liquidssuch as fuel oil, diesel oil, and fresh water, and also liq-uid cargo and water ballast during liquid transfer opera-tions).

Except as permitted in [4.6], the free surface correction is tobe the maximum value attainable among the filling limitsenvisaged for each tank, consistent with any operatinginstructions.

4.4 Consumable liquids

4.4.1 In calculating the free surfaces effect in tanks con-taining consumable liquids, it is to be assumed that for eachtype of liquid at least one transverse pair or a single cen-treline tank has a free surface and the tank or combinationof tanks taken into account are to be those where the effectof free surface is the greatest.

4.5 Water ballast tanks

4.5.1 Where water ballast tanks, including anti-rollingtanks and anti-heeling tanks, are to be filled or dischargedduring the course of a voyage, the free surfaces effect is tobe calculated to take account of the most onerous transitorystage relating to such operations.

4.6 GMo and GZ curve corrections

4.6.1 The corrections to the initial metacentric height andto the righting lever curve are to be addressed separately.

In determining the correction to the initial metacentricheight, the transverse moments of inertia of the tanks are tobe calculated at 0 degrees angle of heel according to thecategories indicated in [4.3].

The righting lever curve may be corrected by any of the fol-lowing methods:

a) Correction based on the actual moment of fluid transferfor each angle of heel calculated; corrections may becalculated according to the categories indicated in[4.3];

b) Correction based on the moment of inertia, calculatedat 0 degrees angle of heel, modified at each angle of

Pt B, Ch 6, App 2


heel calculated; corrections may be calculated accord-ing to the categories indicated in [4.3].

c) Correction based on the summation of Mfs values for alltanks taken into consideration, as specified in [4.3].

Whichever method is selected for correcting the rightinglever curve, only that method is to be presented in theyacht's stability information booklet. However, where analternative method is described for use in manually calcu-lated loading conditions, an explanation of the differenceswhich may be found in the results, as well as an examplecorrection for each alternative, are to be included.

4.7 Free surface moment

4.7.1 The values for the free surface moment at any incli-nation in metre-tonnes for each tank may be derived fromthe formula:

where:

v : Tank total capacity, in m3

b : Tank maximum breadth, in m

ρ : Mass density of liquid in the tank, in t/m3

k : Dimensionless coefficient to be determined from Tab 5according to the ratio b/h. The intermediate values aredetermined by interpolation.

δ : Tank block coefficient, equal to:

l : Tank maximum length, in m

h : Tank maximum height, in m.

4.8 Small tanks

4.8.1 Small tanks which satisfy the following conditionusing the values of k corresponding to an angle of inclina-tion of 30° need not be included in the correction:

where:

Δmin : Minimum yacht displacement, in t, calculated at dmin

dmin : Minimum mean service draught, in m, of yacht with-out cargo, with 10% stores and minimum waterballast, if required.

4.9 Remainder of liquid

4.9.1 The usual remainder of liquids in the empty tanksneed not to be taken into account in calculating the correc-tions, providing the total of such residual liquids does notconstitute a significant free surface effect.

Table 1 : Value of coefficient k for calculating free surface corrections

MfS vbρkδ0·5=

δ vblh---------=

MfS

Δmin

---------- 0 01m,<

θ b/h

5° 10° 15° 20° 30° 40° 45° 50° 60° 70° 75° 80° 85° θ b/h

20 0,11 0,12 0,12 0,12 0,11 0,10 0,09 0,09 0,09 0,05 0,04 0,03 0,02 20

10 0,07 0,11 0,12 0,12 0,11 0,10 0,10 0,09 0,07 0,05 0,04 0,03 0,02 10

5,0 0,04 0,07 0,10 0,11 0,11 0,11 0,10 0,10 0,08 0,07 0,06 0,05 0,04 5,0

3,0 0,02 0,04 0,07 0,09 0,11 0,11 0,11 0,10 0,09 0,08 0,07 0,06 0,05 3,0

2,0 0,01 0,03 0,04 0,06 0,09 0,11 0,11 0,11 0,10 0,09 0,09 0,08 0,07 2,0

1,5 0,01 0,02 0,03 0,05 0,07 0,10 0,11 0,11 0,11 0,11 0,10 0,10 0,09 1,5

1,0 0,01 0,01 0,02 0,03 0,05 0,07 0,09 0,10 0,12 0,13 0,13 0,13 0,13 1,0

0,75 0,01 0,01 0,01 0,02 0,02 0,04 0,04 0,05 0,09 0,16 0,18 0,21 0,16 0,75

0,5 0,00 0,01 0,01 0,02 0,02 0,04 0,04 0,05 0,09 0,16 0,18 0,21 0,23 0,5

0,3 0,00 0,00 0,01 0,01 0,01 0,02 0,03 0,03 0,05 0,11 0,19 0,27 0,34 0,3

0,2 0,00 0,00 0,00 0,01 0,01 0,01 0,02 0,02 0,04 0,07 0,13 0,27 0,45 0,2

0,1 0,00 0,00 0,00 0,00 0,00 0,01 0,01 0,01 0,02 0,04 0,06 0,14 0,53 0,1

k θsin12

----------- 1 θtan( )2

2-------------------+

⎝ ⎠⎛ ⎞ b

h--- ,⋅ ⋅= where θcot b

h---≥

k θcos8

------------ 1 θtanb h⁄------------+

⎝ ⎠⎛ ⎞⋅ θcos

12 b h⁄( )2⋅----------------------------- 1 θcot( )2

2-------------------+

⎝ ⎠⎛ ⎞ ,⋅–= where θcot b

h---<