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A R ENo. 3K08
NATIONALDVISORYOMMITTEEORERONAUTICS
WARTIMEREPORTORIGINALLY ISSUEDNovember9^3sAdvance^eportK08DESIGNRITERIONSOR E EDIMENSIONSFHEF O R E B O D Y FAONG-BANGSLYINGOAT
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NATIONAL ADVISORYCOMMITTEEFOBAERONAUTICS
3 ADVANCEEPORT
0E S IGNRITERIONSORH EIMENS IONSFH E FOREBODYOFAONG-RANGEL Y I NGOAT
ByohnB.ParkinsonSUMMARY
A correlation is madeof thegrossload coefficientandtheforebodylength-beam ratiofor a limited numberofpresent-daymultienginelong-rangeflyingboatsforwhich thespraycharacteristics areknown.hespraycriterion and thederivedrelationshipspermita choice
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problems,ndincreasethehazard'sofoperationinroughwater. Thebestoveralldesignisonef orwhichthemaximumgrossweightandtheseaworthinessrequiredf ortheintendedservicehavebeenproperlyestimatedandoperatingexperiencewithsimilarflyingboatshasbeenconsidered.
Thebeneficialeffectofincreasingforebodylengthorforebodylengthbeamratioonspraycharacteristicsatlowspeedshasbeendemonstrated(references and2).Ageneralrelationshipbetweenbeamloadingandlength-beamratiof oralargenumberofactualseaplanesisgiveninreference3
Thispaperpresents.ingandtheforebodylengthofcontemporarymultienginewhichthespraycharacteristTheresultsofthecorrelati
orrelationofthebeamratioofalimlongrangeflyingbicsinserviceareonhavebeenofval
e a r n1oad-it ednumberoatsf orknown,ueinana
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operatedsucces s fullyatheavieroverloadsandundermoradverses eaconditionsthanwouldnormallybeconsideredpracticable. Suchoperationisoutsidethescopeofthepresentstudy.or-i- ?ntable thesymbolsusedaredefinedasfollovrs:
Lf/h forebodylengthbeamratioC^ grossloadcoefficient (A/wbwhereLf lengthofforebodyfromt > o wtostep,feetb maximumbeam,feet
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Forflyingboatswithsprayconsideredsatisfactoryf ornormaloperations.. . . . . . . .,0675Fortheflyingheatwithverylightspray,,0525Theconstant k apparentlyvariesmoreorles s linearlywiththeseverityofthespraycharacteristics
andis ,herefore, suitablecriterionf orinvestigat-ingtheeffectofchangesinthedimensionsofthefore-bodyonthesprayorf ordeterminingthedimensionsofaforebodyf orvariousdegreesofseaworthiness.
DerivedRelationshipsRelationshipbetween C ^ A and Lf/bc Equation 1 )
indicatesthat,oragivenvalueof k andhencef orcom-oarablespraycharacteristics. CA variesas (L^/b)3
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or-f
Effectof Lf and Lf/b forcomparablesizesofhull0Aspointedoutinreference2 ,theeffectofforaseriesofhullsismorenearlyisolatedifthesiofthehullsremaincomparable. Thisconditionisnearsatisfiedbymaintainingequalplanformareasandapprimatelyequalstructuralweightsofbottomorbyholdintheproduct Lfb constant. Let
Lfb= (3)
where c i s constantrepresentingthesizeofthefobody Ifequation(3)iscombinedwithequation(2),
k-WCL-f
(4)
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remainsthesameandcomparablespraycharacteristics aremaintainedif Lf" " b isheldconstantas Lf /D i svaried. Bytransposingtermsinequation(6)
3 /B
\b/
or
c -. w k /B/z
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oI I
normalserviceandisrecommendedfordeterminingthedimensionsoftheforebodyinpreliminarydesign,3, For givengrossweight,thespraycriterionvariesinverselyasthebeamandinverselyasthesquarej L oftheforebodylengthy Theforebodylengthhas rel-
ativelygreaterinfluencethanthebeamonthespraycharacteristics,4V Foragivengrossweightandproductoffore-bodylengthandbeam( sizeofforebody),thespraycriterion k variesinverselyastheforebodylengthandin-verselyasthesquareroot ftheforebodylengthbeamratio,. Largeincreasesinlengthbeanratioarerequiretoobtainadefiniteimprovementinspraycharacteristic5 . Foragivengrossweightandvalueofthespraycriterion k , theproductofforebodylengthandbeam( sizeofforebody)variesinverselyasthecuberootof
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NACA TA B L E I
PART IC ULAR SNDPRAYHARACTERISTICSPIXMTJLT IENO INB , LONO-RANOELYINOOATS NATIONALADVISORY
COMMITTEEO RERONAUTICSPlyingboat Numberofengines
Portbodylength-beamratio,LfAOroes-loadooefflolent,
A oSprayCharaoterlatloa
A 2 2.49 0.43
.5 0
Satisfactorybowspray.Negligibleapraythroughpropellerandstrik-ingwingortailsurfacea. Success-fullyoperatedunder widevarietyofadversewindan dseaconditions.Heavybowapray. Maintenanceandcorrosionproblemslnoreasedbu tacceptablefo roverloadunderaverageaeaconditions.
B 4 2.97 0.69 Excessivebowspray. Waterthroughpropellersdrenchesengines,wingandtallsurfaces. Erosionofduralpropellerswithanyadditionalover-loadprohibitive.
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HA.CA Fig
C D
3^ to
< > " C.1
1 * c o
,tVi-fj o
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ITITlE:Des lgnCrlterlonsforth eDimens ionsofth e orebodyof aLong -Ran g e lyingBoatA U T H O R ( S ) : Parkinson,JohnB .ORIGINATINGAGENCY:Lang l e yMemorialAeronauticalLaboratory,Lang i e yFie ld ,V a.P U B L I S H E D Y:NationalAdvisoryCommitteeor Aeronautics,Washington,D .C .
ATO-S0(N
AR( SaDA KN ov 43 DO COAUUnc la s s . V.S. LAMUAOI-Eng.AC39table ,graphABSTRACT: Essentialparticularsandknownspraycharacteristicsofsixflyingboatsforwhichoperatingexperienceisdefinitelyknownare summarized. Correlation ofthebeamloadingan dtheforebodyl ength-beamratioofth eflying boatsispresented. Spraycriterionandthederivedrelationshipspermitrelativeeffectsofforebodyl ength,beam,andl ength-beamratiotobetudiedanalytical ly. Itisconcludedthatth egross-loadcoefficientforcomparablepraycharacteristics
variesasth esquareoftheforebodyl ength-beamratio.
D I S T R I B U T I O N : Requestcopiesof thiseportonlyfromPublishing Agency D I V I S I O N :Water -Borne Aircraft(21)S E C T I O N : SprayControi(3 )AT IHEETNO.: R-21-3-1
S U B J E C THEADINGS:F ly ingboats Spraycharacteristics(41760);H uDes i gn(49698.8) Ai rDocumentaDhrfofon,frtolllfjoncoDoportmonlAi rMatariolComraand AIQECHNICALNDEX Wrioht-PafloraonAi rortsDayton,Ohio
