naca tn 183 static stability of seaplane floats and hulls

7/27/2019 NACA TN 183 Static Stability of Seaplane Floats and Hulls

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NATIONALDJtSCFifHJM17TEEFORAEROiiAUTICs

NATIONALWISORY(lOMkJTTEEORAERONAUTICS.

NO.183

STATICSTABILITYF SEAPLAbiLOATSANDHULLS... By%. S.Diehl,Bureauof Aeronautics,.S.N.


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NATIONAII5VISORYCOMMITIHORAEROitAGTIC5.TECHNICALOTENO-183-

STATICSTABILITYF SEAPLANEFLOATSANDHULLS-*Bj7W. S.Diehl.

.Oneof theimportantactorsin seaplaneesignis the Sta --

bilityt rest on thewater.Ordinarilyhisis securedby .basinga newdesignon theproportionsollowedin someoldandsuccessfulesigq.Sufficientatahasbeencompiledrom.var- -ioussourcesto clearup thispointin eachof thecasesrequir- -ingstudy.Thesecasesarelateraland lon~itudinaltability---b of twinfloats,longitudinaltabilityf singlefloats,and lateralstabilityherefing tip floatsareused(aswitha sin-glemainfloator boathull). Thelongitudinaltabilityfboathullsis sogreatthatitmaybe neglected. .

Themethodfollowedinis to obtaina satisfactoryheightandstudythevalues

thecaseof singleandtwinfloats J-approximation.tohemetacentric .actuallysedin successfulesiOms-_

LATERALSTABILITY TWINFLOATS. .


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.

.-z-

thevolumeof displacement.et 6 be thespacingof tinefloa~son centerIinesjL thelength,and b thebeamof eachfloa~~.Then,assumingtheareaof thewaterplaneor eachflcattobe-Lb, themomentof inertiaof thetotalwaterplanereais

I ((s +b)3 - (s- b)3)= 12= +#6s2;+2b3)

Theweightof onecubicfootof seawateris 64lb.fore,thevolumedisplaceds

v = &* where ~ is thegrossweightof theseaplaneinpounds.ingtheexpressionsor I and V:

Themetacentriceight GM is thengivenbyGM= BM-BG=64L (6sb-+2b3) - h

where h is thedistanceof thec-g.abovethec.b.

..-

Thexe-

Combin-


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-3-

. GM = +whereA isthegrossdisplacementnpounds.

ThevalueofKI hasbeendeterminedroma seriesof testsat theWashingtonavyYardExperimentalodelBasin,andfoundtobe remarkablyonstantitha valueof 19.5as shownby Table .1. Theapplicationf thisformulatofullscaleindesignwill be discussedater.

LONGITUDINALTABILITY- SINGLEANDTWIHFLOATS.Followingher.ethodsedtodeterninehelateralrnetacen-tricheight,it tillbe assumedthatthewaterplane~ea.f each

floatisrectangularndofarea L X b, so thatY~emomentofinertiaof thetotalwaterplmeareais

1=%bL3where n is thenumberof floats.GM = 64nbL312A

.

Thisgives .--h


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-5-q

tobe sma21in comparisoniththemomentdueto inclination.tshou?.dherefozee alloxableoput

LI=CL2or A t COSCJ=.CWh sin6

ariddeterninehevalueof c correspo~dingo satisfac~y (and-.unsatisfactory)esigns.Thishasbeendonefortheseaplanes. .=listed.n TableIII,andit is foundthat C?variesfTOm~.~tO5.7. Onedesign,the YE-7 seaplane,avinga valueof C = 1.33,wasunsatisfactory.oublingthedisplacementf theWingtip --floatsothat C!= 2.67,q resultedin satisfactorytabi~..ity.Inviewof tieperfor~nceof thevariousseaplanesabulatedn.Table111,it is tobe concludedhatsatisfactoryateralsta-bilitywillbe obtainedThen C = 2.00.

APPLICATIONODESIGN.,.

Valuesof lateralad longitudir~le~centricheightsforVariOUS seaplaneshave been cal~la~ed by ~e~s of theapprOXi~te.formulajustderived.ThedataaregiveninTableIV. Upon .-


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-6-GM C 15 + .002~

GM beinginfeetandthegrossweightW inpoundsObviouslyhevaluesgivenby thesetwolinesareby no

meansfinal.Theyarebasedon a smallnumberof desiresand .refertoapproximatealueshm-ever,thatthevaluessorentpractice.Changesmaydatahavebeenaccumulated.

It is recommendedhat

for thesedesigns=It is thought,indicatedrea reliableguideto cur-be raieas founddesirablehenmorethelongitudinalndlateralmetacen-.

tricheights be ~~e equalandof thevaluegivenbyGM= 15 + .002w. Theproperlen@h or ~uacing~equiredtoatisfytheindicated.

valuemaYthenbe obtainedfrcmsubstitutionn theapprOXim~te _formulaeformetacentriceight.


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.

. -7-

ltodel

, Loening. CT

IIIIII11TS-1DT .Ss

q TABLEI.LATERALSTABILITYF TWINFLOATSFORSEAPLANES.

DETERMINATIONF KI IN TKEFORMULA

LengthLft.

2:332.0832.0832.0832.0832.0831.8322q 0451.75

Beambft.-:292.34s.348.348.348.348.241.296.245

Spacingon&,sft..875

1.0001q0001.Ooe1.0001;000q777-833.791

Dis-place-rlenAlb.4-676.075.084.353.632.722.733.942.61

Heta-centricheightGMft.2-1192.3282.9?3.174.015.061.9551.8902.030

Lbs2A

.1117

.1192

.1423

.1663

.1993.2660

.0983

.1067

.~028

19.013.5 .=20.9 -:19.120.1 .19.019.9 .17:719.8


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.

Model

q LoeninIICTII

II

n

H

TS-1DT

TAE.LE1.LONGITUDZNAHTABIJTYOl?SIIAPL&NELOATS.DeterminationF Q IN THEFOR.KULA

LengttLft.

2.332.312.0832.0832.0832.0832.0831.8322.945

GM . ~nbL3AMODELTESTDATA.

Beam1liumbe~ofb floatsinft.I ._J..,__

.2921 2t

i.348 2.348.348.241.296

2222

Dis-place-mentAlb.4-674.906.075.084.353.632.722.713.94

Meta-centricheightGMft.3.1642.6142.0532.903.473.i94.142.3602.423

nbL3A

1.581.2531.0341,~371.4431.7302.3101.0931.284

.

K2-.

-- - -2.00 -.1.99 --....2.34....1

:.-. s2.40. ...,. .-2q07 _.=;1,79 .:...2.16 :..--__,,1.89 ._,


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TABIJ3II.LATERALSTABILITYEAPLANESITHWINGTIPFLOATS.

.

Seaplane

N9HS-2 qHS-33-16F-5-LNCMI?iFVE-7VE-7Mod.40

GroBSweightw

lb.24006430643010900135002200024908850260026002467

Dis- .*place- a;o$ement c.b,eachwing htipfloatil.lb. ft.160 I 5.7

WingtipfloattoG1.f-h19.1

275 I 4.9 I26.4*O 4.51170 6.01175 6,0laoo ?.5160 4.01000 5.0190 6.0380 6.0265 4*3

26.430.433.241.515.6Z.513.513.514.75

Angletosub-mergewingtipfloato$977874*.5.1097710

tan9

.158

.123,123.140.123*079.176~158q 123.123.176

c?

1.421,875.033.883.925.7019433.231.332.672.08

Remarks-

.

.,

-.-+ .

lJnsatis-,fat- .tory


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Seaplam

bening~~TS-1

DTSsVTR6BoeingWATG

q N9* NcGB

TABEEIV.FULLSCALEMETACENTRICEIGHTOF SEAPLANES. 6

(CALCULATEDY FORMULA)Dis-place-mentAlb.2450100002025697546158615.395024554~(30..~8~24002200065000

Lerqth Beamofboat~ bft. f-t18.67I 2.3325.00 4.716.50 2.1824.53 3.5521*O I 2.9325.75 3.6120.0 [email protected] 2.2E!25.06 3.2521.251.2517.83 3.4844.8 I 10.064.g6 I14.6

Number;Spacingon&

Tn sft.2z

222,22211111

7.012*O

\ 70I IO*OI 9.0I\ 11.83II 11.0I1 7.5

I

Longitu-LateraldinalGM GMft ft.

26.027.420.331.624.829.921.316.025.623.317.386.0129.0

17.029.317.0 _24.320.9..29.429.816.4


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Fig.1,

naca tn 183 static stability of seaplane floats and hulls

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