AD/A-006 827

A STUDY OF PLANING CATAMARAN HULL ANDTUNNEL INTERACTIONS

T. Jeff Sherman, et al

Michigan University

Prepared for:

Office of Naval ResearchNaval Ship Systems Command

February 1975

DISTIUTED BY:-

N. L TMUT IU I-O

L Ln MII OF

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REPORT DOCUMkENTATION PACE RUA0^DIN ar',,UCT(ONS/1. nPORT HU'0EH. GOVT ACCESSION NO, I. fLCIPIBfit'" CATAt'00 Nw'-41f.Mt

011073-1-r- ,9h/ "az eW~74. TITLE (and Subtitle) S.-"rVAIE 01 REPORT 6 P,,Roo dbvan.o

A STUDY OF PLANING CATAMARAN FinalHULL AND TUNNEL INTERACTIONS 1 Apr 72 - 30 Aug. 74S. PER7OftMIAG 0110. REPORT NLdI.AOR

7. AUTrO.• Shm . CoNT•SCT)jT OR GRANT NUMiEmR~T. Jeff Sherman N0004-67-A-0181-0050"Peter A. FisherRichard B. Couch

S, PIERORMING ORGANIZATION NA14I AND AOORESS ""O. POCRAM, .[LEMCNT PROJECT. TASKt The University of Michigan AREA 6 WORK UNIT NUMea[tsNaval Architecture & Marine Eng. Dept.550 E. Univ. St, Room 126 NR 062-473Ann Arbor, Michigan 48104

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Office of Naval Research February 1975,800 N. Quincy St. 13. NUMSEROF PAGESArlington, VA 22217 37

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12. SUPPLEMENTA,74Y NOTES

12. KEY WOROS (Continue on ,°v,-.,aide i• • p€cea°ary and identify by block nutnbr)

high speed, low displacement, catamaran, hull separationhull interaction, resistance, tunnel height, model testprismatic planing boats, computer prediction

I20. AaSTnACT (Continue on roverse, side of necessary~ and Identity by block numnbec)A high speed, low displacement set of catamaran hulls hasbeen model tested with various hull separations and tunnelheights. Symmetric, axisymmetric and unsvmmetric hull formshavym been tested and cohipared in terms of resistance todetermiiie the interaction effects of the sponsons. A com-puter program for the prediction of power for prismaticplaning boats has been modified to include catamarans.DD , il 1473 EoTo lerdvsl yTo WDD , 3N, 3 NATIONAL TECHNICAL

INFORMATION SERVICE iccuoTy cL A,$IIc ATIO% OF TrWs PAGE rNo-re Soet Entee.-,US O alme4 d CmegmM

Spri.glI4d. VA. 221t1

IIII COLLEGE OF ENGINEERING

Department of Naval Architecture and Marine Engineering

Ship Hydrodynamics Laboratory

IA STUDY OF PLNING CATAMARAN

I HULL AND TUNNEL INTERACTIONS

IFinal Report

byT. Jeff Sherman

Peter Fisher

Project Director

IR. B. Couch'I

DRDA Project No. 011073under contract with:

Naval Ship Systems CommandI Contract No. N00014-67-A-0181-0050S

I Department of the NavyOffice of Naval Research

Arlington, Virginia 22217

February 1975 i7? II

I ,

Abstract

Little doubt exists that the catamaran hull form offers

a considerable operational advantage over the conventional

monohedron hull form under certain specified constraints.

There has been a renawed interest in the application of the

j catamaran for high speed ,limited displacemenK. service.However, in many instances, model tests have indicated con-

• Iflicting results in the evaluation of resistance data.

Three pairs of synmmetric, assymmetric, and unsymmetric

1 hulls have been tested at the Ship Hydrodynamics Laboratory

of The University of Michigan to determine the effects of

hull separation, hull form and tunnel height. Data has been

presented comparatively in each case and expanded to a full

scale corresponding to a displacement of I00,OOO pounds.I ,

II,!'U

-* $

U.|•

( NOMENCLATURE*SAp Projected planing-bottom area, excluding

area of external spray strip, sq. ft.

IB Beam on breadth over chines, excludingexternal spray strip, ft.

B PA : Mean breadth over chines: Ap/LP, ft.

I BPT Breadth over chines at transom, excludingoxternal spray strip, ft.

Bpx Maximum breadth over chines, excludingexternal spray strip, ft.

BL : Base Line

b : Breadth over spray strips at longitudinal[ center of gravity, ft.CL * Center Line

I" CG : Center of gravityCT : Total resistance coefficient

CR : Residuary resistance coefficient

Ii h : Finite water depth, ft.rFN: Froude number based on length =V/\I-•

I FNL Froude number based on depth m V/1'4" *Fv Froude number based on volume V

a•i T Acceleration of gravity, ft/sec2

i LAV Average ,vetted length, ft.LCG Longitudinal center of gravity

L: Projected chine length, ft.

LID * Lift- dracg ratio

P: Effective horsepower

SRT Total model resistance, lb f

1 -2-I!

RTS : Total ship resistance, lbf

RR/& : Residuary resistance - displacement ratio

" TS/•: Total ship resistance - displacement ratio

Rise/V1 / 3 : CG rise coefficient

S I Wetted surface, sq. ft.

S/v2/ 3 : Wetted surface coefficient

VW I Velocity of wave propagation, ft/sec.

SK: V elocity in knots

VM : Velocity of the model, ft/sec.

V/4tI- z Speed-length ratio

: Angle of attack at after portion ofplaring bottom, degrees

:z Scale ratio, ship to model

x W : Wave length, ft.

9 Deadrise angle of planing bottom

P : Mass density of water

V : Kinematiu viscosity

V : Volumetric displacement, cubic ft.

Displacement, lbf

V/ApH : Mean draft-water depth rat!.

W : Same as

*Nomenclature used is ITTC Standard Symb'l and that rec-

ommended in SNAME T & R Bulletin 1-23.

-3-

Introduction and Background

A significant amount of interest has been shown in the

possible application of the catamaran hull as an alternative

to the standard monohedron hull form. Isolated model tests

have been conducted to evaluate individual designs with re-

spect to resistance performance. However, only a limited

amount of actual experimental work has been done to dater-mine the hydrodynamic effects of hull interference.

[ In the 1960's the U.S. Navy limited investigationsshowed that one specific catamaran design had greater ro-

sistance than the equivalent mono hull forms. However,

theoretical investigations and model tests have shown that

a correctly designid catamaran can actually, have less re-

sistance in addition to its other operational advantages.

The theoretical work of Eggers concerning wave interference

effects revealed the strong possibility of reducing signifi-

cantly the wave drag below that of the single hulls. This

was accomplished by phase relitionships in the wave pattern.

Work at the National Physical Laboratory [3] has indicated,

however, that the interference effects on viscous resistance,

could in fact, be the opposite, resultin•g in an increase in

resistance.

There are various methods available for predicting the

performance of planing catamarans. Stevens Institute has

don% a significant amount of planing boat work both on the

theoretical and experimental levels. Savitsky of the

--4--

Davidson Laboratory (8] has developed a computer program for

the prediction of liower for prismatic planing craft. This

has been modified for catamarans but does not include inter-

ference effects on drag, trim and flow characteristics on

t sponsons and the connecting tunnel.Planing catamaran studies made by the U.S. Navy have

indicated that the catamaran is inferior at low speeds, only

performing well at high speeds, i.e. F - 5.0. However, a

study of this work revealed that the tunnel of the model was

wetted with solid water. This in effect decreased theLp/Bpv ratio of 6.2/1 (for each of the sponsons) to 2/1, in-

creasing the wetted surface significantly.

To gain an understanding of why this leads to a hull form

of poor resistance characteristicb and what can be done to

correct this particular aspect of catamaran hull forms,

Figure 1 is provided. For illustrative purposes, a catamaran

hull form can be approximated by a summation of two monohedron

hull forms. This is true only as long as the tunnel of the

catamaran hull form, hull form B, has a high, dry tunnel and

thereby sponsons with a 6/1 L P/B ratio. However, hull formC, with a lou wetted tunnel, acts on a monohedron hull form

with an L p/Bp, ratio of 2/I with bottom discontinuity. This

obviously leads to a hull form of poor resistance character-

istics. However, as was discussed in the first paragraphs as

the hull picks up speed, approximate Fv > 3.5, the tunnel is

no longer wetted with solid water and the hull becomes a

catamaran.

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- -- " - . .. .. .. i l liI i

HULL FORM COMPARISON

A. MONOHEDP.ON OIULL FORM

I.

B. CAT-AMARA.N HULL FORM (HIGH TUNNEL)

I ___T (each side)

C. CATAMARAN HULL FORM (L.W TUN=•,EW

-. 6 * F 3.5

EL TI FIgureI Figure I

1 -6-

I

TADU I

?MODEL CIIARNCTRISTICS

I LOA 36"

Beam 6.0" (per Sporicn)Dopth 5.625"Displacement 8.C.6" (per Sponadn )

lba. 0 700 F

Volume .129 PT 3

LCG 9.0" Af t Of FP

Tunnel Hiiqhtlow 4.31 Off Basc Iino•high 5.3" Off Base Linn

Sponson Spacing 0"6"

12 "

I

I

I -7 -

Throe pairs of mdels were constructed at tho Ship

Hydrodjynariied Laboratory of The University of MichLgan.

A sketch of each im provided in figures 4, 5 and 6 for

the symmetrical, assymmetricaL end unsymmetrical hull

forms, respeotivoly.

The test matrix included the three variations of

hull spacing from zero, six, and twelve inches. The sin-

gle sponson was also towed to provide a smean of ca qpari-

son. Tunnel height was also varied by on" inch to deter-

mine thu effect of height on resistance. in all oases,

LCG location and displacement were kept constant. Test

conditions are listed in table 1.

An attempt was made to match test results to pre-

dicted values for resistance. The Prismatic planinV boat

prediction corputar proqrar. s developed by thn Naval

Ship Engineering Center# was modified to be used on tho

cat Amaran form.

Iq

II

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Instrurr.entation

A planinq bnot dynavo:eter" developed at The University

of Michiqan was usei to reasure the tovinq force along the

propeller shaft centerline. The system In set such that a

sorvo-mn•chanism automaticaliy follows tho m~odel trim so that

the towinig rod corresponds to the shaft lino as desired.

I The dynamometer emplovy a two arm sestem.

II! . .... .~... Ca4ef"t "

S--- . q ARIM

LC'IAER AWA-e~t ~ ..

IN MODEL

I ~Figura 2f1 The modfti is touved so that the lower arm is in the thrust

plane (so that pivots B and C are in the thrust plane).

I Th upper arm is servo driven to retain this relationshipithe feed back transducer to the servo is at the tow point C.

.1 | Then, any attempted displacament of the lower arm from thethrust plane results in an angular displaeiment about the

pivot tow point C, and the upper arm angle at pivot A is

servo drive such that pivot B returns to the thrust plane.

IIt -9-

Figure 2 illustrates a schem~atic diagramy of thePlaning boat dynamnometer.

Fiqure

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P. S. 4 V.PIVOT A READOUT(a)

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Results and Conclusions

Test results are presented as curves of total resis-

tance per pound of displacement versus speed-length ratio

for all conditions. Figure ' lists the results for all

three of the single sponson conditions. Models were

ballasted in order to acheive the "even keel" conditions

for comparison to the various catamaran configurations.

While the curves have indicated that these hull forms

have a close comparison, the symmetrical form had a bit

higher resistance especially at the lower speed-length

ratio, while the assymmetric sponson was low by comparison

to the other.

Correlation of resistance values for the symmetrical

configuration are listed in figure 8 which the assymme-

trical and unsymmetrical configurations are provided in

figures 9 and 10,respectively.

While some specific trends are observed for each

set of tests, the overall results appear somewhat incon-

clusive . In all cases, the single sponson is the best

overall performer. As might be expected, however, the

worst performer was the combination of sponsons with

z ro spacing. In general the greater the hull spacing,

the lower resistance was observed. It was also observed

that the tunnel had a distinct effect on the total resis-

tance at lower speeds. However at a speed-length ratio

-14-

)

I ,

of about 2.5 the effect was lessened, as the tunnel wetness

I- was reduced.

Hull form appeared within the scope of the model tests

t have a distinct effect on resistance results. TheF1 unsymmetrical hulls were in general the best performers with1 the symmentrical hulls only slightly inferior to the assy-

ii mmetrical sponsons.Tunnel height, measured from the base line as 4.3"and

5.3" showed almost no variation with results and theyefore

are not plotted. Since maximum variations were on the order

of 2%, (within the accuracy of the measurements) if it felt

3 that the variation in tunnel height was not sufficient tocompletely divorce its effects.

3 It is felt that the results do not lend themselvesto prediction methods and therefore were not incorporated

I within the computer program for prediction of prismaticplaning craft.

I

-15-

II

Figure 7

SINGLE SPONSON COMPARISON

RT/ A

vs

SPEED-LENGTH RATIO

I °-N /!

S----- -Symmetrical Hull

'•. .. Unsymmetrical Hull

Assymmetrical Aull

S" I IUNIVERSkTY of MICHIGAN•/ISHIP HYROR•YNAMIC$ LABORATORY

DOEPAR TMENT o NVAL ARCHITECTUREAND MARINE ENGINEERING

ANN ARBOR, MICHIGAN

0 1 2 3 4 5 6

speed-length ratio

v41T-16-

S. . ..... --.. .. , , -' , ' i "-I " I I I •'II i

rigure B

SYMMETRICAL CATAMARAN

I- - - -.SPEED LENGTH RATIO

6" • • 12" svacin

01,acing .000

C .."4 / siragle sponson

single sponmon

"-. - 0" spacing

____,, 6" spacing

--- 12" spacing

UNIVERSITY Of MICHIGANI SHIP HYDRODYNAMICS LABORATORY

DEPARTMENT of NAVAL ARCHITECTUREI AND MARINE ENGINEERING1 ANN ARBOR, MICHIGANI /i/

I I a,- 9

0 1 2 3 4 5 6

speed- length ratio

IN

Ii rigure 9

ASSYMMETRICAL SPONSON

vs

jSPEED-LENGTH RATIO

6" 1a 12" a acing

sigl 3ponsonIIi

"---- Oi. l spacing

6 spacing

I ,12" spacing

1- / UNIVERSITY of MICHIGANI SHIP HYDRODYNAMICS LABORATORY

/ DEPARTMENT of NAVAL ARCHITECTUREE AND MARINE ENGINEERINGI ,./ ANN ARBOR, MICHIGAN

O _ L , A I I 1 _ I

0 1 2 3 4 5 6

~ I •speed-length ratioVA L

Fic•ace 10

UNSYM&TRICAL SPONSONS

vsSPEED-LENGTH RATIO

'-4

0" spacin

x -- ~-single sporimon

*--- 0" spacihig

12" spacing

/~UNIVERSITY Of MICHIGANSHIP HYDRODYNAMICS LABORATORY

DEPARTMENT of NAVAL ARCHITECTURE

AND MARINE ENGINEERINGANN ARBOR, MICHIGAN

I

0 1 2 3 4 5 6

speed-length ratio! v/,.':L

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SINOLE SPONUCM

j UNSMINITRICAL HULL FORM

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REFERENCES

1. E. P. Clement and D. L. Blount, "Resistance Tests of aSystematic Series of Planing Hull Forms," TransactionsSNAME, Vol. 71, 1963.

2. E. P. Clement, "Graphs for Predicting the Ideal High-Speed Resistance of Planing Catamarans," DTMB Report 1573,November 1961.

3. J. T. Everest, "Some Research on the Hydrodynamics ofCatamarans and Multi-hulled vessels in Calm Water,National Physical Laboratory, Ship Report No. 128,November 1968.

4. E. D. Fry and T. Graul, "Design and Application of ModernHigh-Speed Catamarans," Marine Technology, Volume 9, No. 3,July 1972.

5. R. Leopold, "A New Hull Form for High-Speed Volume-Limited,Displacement-Type Ships," Spring Meeting, SNAME, 1969.

Z. J. L. Moss, "Resistance Test Results for 1/12 Scale Modelsof Three Planing Catamarans," The University of Michigan,Ship Hydrodynamics Laboratory, Report 02644, July 1969.

7. T. M. Pemberton, "Resistance and Powering Data for aSeries of Amored Troop Carrier (ATC) Hull Forms Representedby Models 5155, 5155A-I, 5206, 5206-1, and 5207 (U'),"NSRDC Report No. 6-334-H-01, May 1969 (confidential).

8. D. Savitsky, "Hydrodynamic Design of Planing Hulls,"Marine Technology, Vol. No. 1, October 1964.

9. T. Tahaher, R. Tasaki, J. L. Moss, "Wave Making ResistanceInterference Effects on a Catamaran Model," The Universityof Michigan, March 1963.

10. Andras Toro, "Shallow-Water Performance of a Planing Boat,"The University of Michigan, 1969.

11. "Manned Model Planing Catamaran Tests," U. S. Navy Buship'sCode 449, Washington, D. C., 1961.

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