General Naval Arch

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Naval Architecture INaval Architecture I

Dr.Ahmed M H ElhewyDr.Ahmed M H Elhewy

Naval Architecture and Marine Engineering DepartmentNaval Architecture and Marine Engineering Department

20082008



Time Table : 2 Lectures / week

-Tuesday: 10:10 -11:50

-Wednesday: 10:10 -11:50

Course total Marks (150)-Final Exam (90)

-Term work (60) = 30 Midterm

30 Term work

1



Course Contents

• Ship Types and Hull forms

• Transverse stability at small and large angles

• Longitudinal stability and trim• Stability when grounded

• Horsepower and hull resistance

• IMO regulations

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3

1 Ship Types



Classification of Ship by UsageClassification of Ship by Usage

• Merchant Ship

• Naval & Coast Guard Vessel

• Recreational Vessel

• Utility Tugs

• Research & Environmental Ship

• Ferries

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Classification of Ship by Support Type

• Aerostatic Support

- ACV (Air Cushion Vehicles)- SES (Captured Air Bubble)

• Hydrodynamic Support

- Hydrofoil

- HYSWAS (HYdrodynamic Small Waterplane Area Ship)

- Planning Hull

• Hydrostatic Support

- Conventional Ship

- Catamaran

- SWATH (Small Waterplane Area Twin Hull)

- Deep Displacement

• Submarine

- Submarine

- AUV/ROV4



- Supported by cushion of air generated by a fan.

- ACV (Air Cushion Vehicle)

hull material : rubber

propeller : placed on the deck

amphibious operation

- SES (Surface Effect Ship)side hull : rigid wall(steel or FRP)

bow : skirt

propulsion system : placed under the water

water jet propulsion

supercavitating propeller

not amphibious operation

Aerostatic Support

5



Air Cushion VehicleAir Cushion Vehicle6



SES Ferry

NYC SES

Fireboat

7



250’ SES Ferry

8



• Planning HullPlanning Hull

-- supported by the hydrodynamic pressure developed supported by the hydrodynamic pressure developed under the hull at high speed under the hull at high speed

-- V or flat type shapeV or flat type shape-- commonly used in pleasure boat, patrol boat,commonly used in pleasure boat, patrol boat,missile boat, racing boatmissile boat, racing boat

Hydrodynamic SupportHydrodynamic Support

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• Hydrofoil ShipHydrofoil Ship

-- supported by a hydrofoil, like wing on an aircraftsupported by a hydrofoil, like wing on an aircraft

-- fully submerged hydrofoil shipfully submerged hydrofoil ship

-- surface piercing hydrofoil shipsurface piercing hydrofoil ship

Hydrodynamic Support

Hydrofoil Ferry

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Hydrostatic Support

• Displacement ship

- conventional type of ship

- carries high payload

- low speed

• SWATH

- small water plane area twin hull (SWATH)- low wave-making resistance

- excellent roll stability

- large open deck

- disadvantage : deep draft and cost

• Catamaran/Trimaran- twin hull

- other characteristics are similar to the SWATH

• Submarine12



SWATH vessel13



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Archimedes Principle

Law: a body floating or submerged in a fluid

is buoyed up by a force equal to the weight of

the water it displaces

Depth to which ship sinks depends on density

of water (r = 1 ton/35ft3

seawater)

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Ship sinks until weight of water displaced by

the underwater volume is equal to the weight

of the ship

Forces of gravity: G = mshipg =Wship

Forces of buoyancy: B = rwater Vdisplaced

Wship

= water

Vdisplaced

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• A FLOATING BODY DISPLACES A VOLUME

OF WATER EQUAL IN WEIGHT TO THE

WEIGHT OF THE BODY.

DISPLACEMENT

00

G

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DISPLACEMENT

00

G



DISPLACEMENT

04

G

B



DISPLACEMENT

09

G

B



DISPLACEMENT

16

G

B



DISPLACEMENT

20

G

B



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Center of Gravity (G):Center of Gravity (G): all gravity forces as

one force acting downward through ship’sgeometric center

Center of Buoyancy (B):Center of Buoyancy (B): all buoyancy forcesas one force acting upward through

underwater geometric center



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Definition

11-- PerpendicularsPerpendiculars Imaginary lines perpendicular to the base line or plane (and the

water line)

On the ship there is a :

-- Forward PerpendicularForward Perpendicular (F(Fpppp or For Fpp))

This is the line crosses the intersection of the water line and the

front of the stem

--Aft PerpendicularAft Perpendicular (A(Apppp or Aor App))

This line usually aligns the centre line of the rudder stock. This

is the imaginary line around which the rudder rotates.



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24



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2. Waterlines2. Waterlines

The waterline of a ship lying in the water . There are different

waterlines (i.e load-lines) for different loading conditions, suchas:

-- Light waterlineLight waterline

The waterline of a ship carrying only her regular inventory.

-- Fully loaded waterlineFully loaded waterline

The waterline of maximum load draft in sea water.

-- Construction (Scantling) waterlineConstruction (Scantling) waterline (C(CWLWL))

The waterline used as the limit to which the various structuralcomponents are designed .



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33-- Plimsoll Mark (freeboard mark)Plimsoll Mark (freeboard mark)

The freeboard mark is a symbol indicating the maximal

immersion of the ship in the water, leaving a minimal freeboard for safety.

The mark consists of a circle

with a diameter of 300 mm,

through which a horizontallines is drawn with its upper

edge going through the centre

of the circle.



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This level indicates the minimal freeboard in salt water summer

conditions. Beside this circle the loadline mark consists of a number of

horizontal lines indicating the minimal freeboard required for other than

summer conditions.All freeboard lines are 25 mm wide and are connected by a vertical line.



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The freeboard mark is placed

midships on each side of the ship.

The minimal operating freeboard

depends on:

-Ship’s position at sea

-The time of year (summer, winter,etc,.._



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44-- Deck LineDeck Line

In general this is the extended line from the upper side of the

freeboard deck at the ship’s side.

The deck line is placed above the Plimsoll mark so that the

freeboard can be easily monitored by the ship’s crew or other

interested parties

55-- Permanent marks on the shipPermanent marks on the ship’’s hulls hullIt is very important the draft marks can be accurately read

as easily as possible.



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1. Draft to portside fore :

53.8 dm



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2. Draft to portside fore:

5.17 meters



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3. Draft on the stern is given in

meters and feet: 9.36 m = 30’ 7”



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4. Draft to starboard aft: 9.35

meters



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5- Draft midships: 7.00 meters

6- Deck line

7. Plimsoll mark



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Dimensions

FP Forward Perpendicular

AP After Perpendicular

WL Waterline



36 WL WaterlineWL Waterline

CL CentrelineCL Centreline



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11- Length over all LOA

It is the overall length of the vessel, i.e the horizontal distance over the

extremities from stem to stern

22- Length between perpendicular LPP

It is the horizontal distance between the FP and AP

33-- Length waterline LLWLWL

Horizontal distance between the fore and aft when the ship is loaded atthe summer mark, less the shell.

44-- Breadth over allBreadth over all BBOAOA

The maximum breadth of the ship as measured from the

outer hull on the starboard to the outer hull on port side,including rubbing bars, permanent fenders.



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44-- Breadth or beamBreadth or beam BMLD

The greatest moulded breadth, measured from side to side at the

outside of the frames, but inside the shell

55- DepthDepth D

The vertical distance between the base line and the upper continuous

deck and is measured at the half L pp at the side of the ship

66- Draft ForwardDraft Forward (TFWD)

Vertical distance between the waterline and the underside of the

keel, as measured at the forward perpendicular

66- Draft at the sternDraft at the stern (TAF)

Vertical distance between the waterline and the underside of the

keel, as measured at the after perpendicular



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77- FreeboardFreeboard

The distance between the waterline and the top of the deck at the side ( at

the deck line). The term summer freeboard means the distance from the

top of the summer loadline and the upper edge of the deck line

88- Air draftAir draft

The vertical distance between the waterline and the highest point of the

ship. The air draft is measured from the summer mark.

SheerSheer

This is the upward rise of the ship’s deck from mid length towards the

bow and stern. The sheer gives the vessel extra buoyancy at the stem

and stern

CamberCamber

The transverse curvature of the weather deck. The curvature

helps to ensure sufficient drainage of any water on deck



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Base lineBase line

Top of the flat keelplace

Keel (K)Keel (K)Inter section of the base line and the center line plane

Beam: B Camber

Depth: D

Draft: T

Freeboard WL

K

CL



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FlareFlare

•• FlareFlare : outward curvature of ship’s hull surface above the waterline

• Tumble HomeTumble Home : opposite of flare

Tumble HomeTumble Home



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Positions of the shipPositions of the ship

ListList

Heeling to one side about the fore and aft axis

Heel to port side



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Trim (t)Trim (t)

The difference between the draft at the stern and the draft at the stem i.e

the trim fore (tF) + the trim aft (tA)

On an even keelOn an even keel, in proper trim

The draft of the stern equals the draft of the stem

Trim by head TF

more than TA



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Trim by stern TA more than TF



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Volumes and weightsVolumes and weights

Register ton (RT)To determine the size of a ship the RT is used. It is based on

volume where one register ton equals 100 cubic feet or 2.83

m3



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Gross Register TonnageGross Register Tonnage

The Gross Register Tonnage (GRT or GT) usually called Gross Tonnage,

is calculated using a formula that takes into account the ship’s volume in

cubic meters below the main deck and the enclosed spaces above themain deck

Net Register TonnageNet Register Tonnage

The Net Register Tonnage is also a non-dimensional number that

describes the volume of the cargo space. The NT is derived from the

GT by subtracting the volume of space occupied by:

- crew

- Navigation equipment

-The propulsion equipment- work stations

- Ballast



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Volume of DisplacementVolume of Displacement V mV m33

The displacement is the volume of the part of the ship below the

waterline including the shell plating, propeller and rudder

DisplacementDisplacement ΔΔ tonton

The displacement is the weight of the volume of water displaced by the

ship

Lightship weight (ton)Lightship weight (ton)

This is the weight of the ship including the regular inventory

but without any cargo, fuel or crew. The regular inventory

includes: anchors. Life-saving equipment, lubricating oil,

paint

D d i h ( )D d i h ( )



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Deadweight (ton)Deadweight (ton)

This is the weight of the a ship can take on until the maximal allowable

immersion is reached. This is a fixed value, unique to each ship.

Cargo Capacity (t)Cargo Capacity (t)

This is the total weight of cargo a ship is designed to carry at a

given time.



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Hull Form CoefficientsHull Form Coefficients

Line coefficients define the characteristics of the vessel’s shape at and

below the waterline. This makes it possible to get an impression of the

shape of the underwater body of a ship without extensive use of anydata.

11-- Block Coefficient, Coefficient of finenessBlock Coefficient, Coefficient of fineness CCBB

The block coefficient gives the ratio of the volume of the underwater

body (V) and the rectangular block bounded by LPP

, BMLD

and draft (T).

The vessel with a small block coefficient is reoffered to as fine.



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2- Waterline coefficient CW

The waterline coefficient gives the ratio of the area of the waterline (Aw)

and the rectangular plane bounded by LPP, BMLD.

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General Naval Arch