YACHTELEMENTSOF DESIGN NORMAN L.BY SKENE, S.B. PHOTO BY EDWIN LEVICK 50-FootersAT CLOSE Mystic QUARTERSI and Iroquois II DODD, MEADNEW1945 YORK & COMPANY THECHAPTER HYDROPLANE XVI and light weight were rest,resistance.scoops,frictionalIn yetthe bauersdiagram,there resistant.. is and thei -.appreciableother waterRudders, hull pressure struts,projections, amount is skidshown of fln, wettedeach acting propeller adds surfaceupward to hubs,the withfrom watertotal its A FIFTYorandovei'that skimmingavailable, reinvented nothe boatyears surface couic!hullthe before a of basic dozenwere the float engines wateridea unsuccessfultimes. the of insteadpower of aEarly hullhigh requiredof attemptsbecause withpower going a bottom throughtoengines to drivebuild formed itwerelier awas hydroplane at soinvented toa heavyspeedskim anding"willthisto P mustcenter perpendicularrise.or leaping Onebe is thetoo of motion pointfarthe to aft, commonestthe about caused the bottom. bow which by willfaultsThe the the drop;pointweight ofboat a if Phydroplane balancestooofis thethe far center boat,forward, when is the aof "porpois- pressurelifted. thrustthe bow ofIf beganhighwave-makingpercentageIt lias enough about been of 1910. tooftheshown plane.the total hull in resistanceThe previousof normalidea isto chapters form. oldaboat's but It itshas motionhow practical been an isevershown caused applicationincreasing how by thethe speeditedresistanceplane and causesthatwhere depend speedsincreases the on whole l)ottomof the boatsso lengths.t)Oatrapidiy is of so theto formed atriseThis displacement high b does dily thatspeed notand forward forholdtypeto bea aretruesmallsupportedmotiondefInitelyof increase the athyclro- by high lim- the in surfacesdesignerAlldynamicAll major ideas andmustreaction forces of rounded stabilitythink are between entirelyof shapes asthem figured the dynamic as which water such. for normal inandmightOn character the causeforms bottomand aresuctions ofthenull thethe hydroplane and boat. boat,must void. alibe another.thenormalnorhe determined screwcan upward itUnfortunately, beand given theby thrust alift bysimple ofany the the mathematicalinspectionactual planeplanesFIG. location150is being the of rsìiltant theformula improperly of lines the of pointknownof many the related of hydroplane, today. elementarylift cannotone This to variousisandavoided.additionflow completely of around water forms Inthere other aleaving planing bodyofis anotherresistancewords in edges onthe the theand water. designercleanlypreviously surface important When and mustof mentioned thethe sharplyfactor. think resistancewater ofrather isimpacts,are analyzed,of foundthan a hull reactionsthink andallwhich the inof paradoxofmanywaterpressures the haspointcases, that strongand where thethe suctions. downward actualcenter the keel C.G. Evenof touches thesuctions of a resultant thetrue tlìewhole insteadplane water, upward boatmoving of thus lifts may pressure creating atat hethe an carried afterangle onthe thecuriousend. aheadto bot- the In componenteddyface.InThe addition, resistanceThe hydroplane displaced ofthere thebehind ishas perpendicularwater a thefrictionalhorizontal createsshafts, resistancestruts,wave-making resistancepressure rudders ononwhich her resistanceandthe actual other inclinedis the appendages.and wettedhorizontal planingthere sur- is cessfulsuspicionexaggeratewatertomThe of surface. normalthehydroplane. ofboat this upward An upward iscondition. aheadupward curvature pressure of curve Bottomthe point at AP thelines, of can afterstern contact therefore, beend if resolved the ofof thehulltheshould bottom bottom intois to avoid twobe withtends a com- suc- any the to ofsurfacelliRh Fig.the the water1 of 50 boat the represents iii bottom.planes, the direction therea simple must shown hydroplane 210be water by the displacedmoving arrow.along withNo matter consequentthe surface how ponenofponents, the boatt equal AB thus which to actingthe istotal horizontalas weightan added ofand resistance,the opposed boat. andtothe BP, forward a vertical motion corn- anglegiven1'Ioili decreases.value uR; of BP, At equalfirst .sight, to the it weight might appear6f the bt, that.. AB .. to decreasesmake, t' asadded the model.mathematical Many nav2 relationr---------------------o'rchitects between of awide motor experience kiven-------- boat on displacementand .a towed forboatincreasessistancealthoughtheresistance mosta at plane the decrease efficientbothClue very small sui thisto small, face angle.the as hydroplane.horizontal theadded thatby Byangle keeping thäilo amountmathematical componento This decreases, shötildthe of however, anglesurface treatmentbeand Othe ipproximatelyrequired small,the frictionalis notwave it would thecan for making resistance truthbelifting produce shown 2'° and, re-the to whosep1p_designhydroplanes.boatsmodelbeen accuratelyhave embodyingperformance, been is The to misted determined.make safest any chacteistici aby proposed proceduremodel misinterpretation This of modeldesigna to known followeed;61er, can or and of imrovément.bein model developingsuccessfulused and astank weight a check resultsButboat, a hydro- haveeven onone on a angleplaneoncreateperimentsLittle successful islessthe contemplated.accurate leastrather on hydroplanes.smallpossible than information model greater resistance, hydroplanesIt if iscan any advisable which be departure obtained agrees as to to makefrom thewellfrom actual thewiththe model conventional angleangles resistance, tank of 'used ex-tile / asourmentsTogivespeed practical attemptknowledge, comparative oras theis done toactionresults divide not with resultsat areat speedthe ships all concerned, total only,practical of and a resistance andfull their andsizer!thenitcan models is only ofboat.definitelybe a assumed is,ifhydroplane Model carefullyin the misleading. tests presentthat interpreted.into canthe state andits resist-As ele- dofarof frictionalofsistance,theices the calculated of two. the requires resistance Anymodel frictional attempt an and accurateand boat theto resistance separate have wave-makingestimate the theofsame of the resistancethe ratio resistance, modelarea as of thefromofthe theby displacementsmodel the subtractingmodel total in con-into re- resistancestionalmodelstactUnder with resistance and average the vary in water. determining directlyis conditions, far The greater as error thethe the than displacementsproper insurface themaking errorcoefficients tension involvedsuch at correspondingof estimates waterto inlise assuming is for a on constant.thespeeds.smallfric-that modelthistiletowed boatmust ofin hadtilea be successful tankactuallyused at with speeds boat,made. caution acorresponding recordFIG. for ISt breakingcases tollave thechampion, occurredofficial speedscouldwhere notwhich the be ThiswhiteSurfacethisthin sizeglassyconstant spray. tension is exactlysheet. Ondetermines will the On the holdmodel, the same, theboat, tilesizesmall both this glassy of bow wavedropsfor bowwavethe willwhich model wave of break a water model willand up willadhere forinto together theformdrops toboat. andinthe or a notaticalthis tankModels available tankresults is owned caneight if theytobe feet, and theobtained, could operatedprivateten feet,he towedhydroplane naval orby twelve the inarchitect a United high feet design speedin and,States length will tank.until Government,continuewould theAlthough servicesgive to prac- besuchit-is ofa foundtotalamountboatThe weight,and inpropeller of themay wetted boat.is cause another thrust, surface a suction force too, and wilichbeing whichthe resistance acauses entirelyfairly the large of changes modelthe percentage model and the boat fromtrim, ofto that theactthe andthaninhit theand careful on perfect miss any experimental ruletruly tuning of scientific thumb up changesof affair design the wheremotor in based the success and bottom on onexactdependspropellerof knowledge.the actual more experiments oriboat small and 1.)'C1i1L It is usually unsafe to have the center o!gravity over b per cent ot tte 4.3.2.5. SingleInvertedThree'Iultiple-step Step.withpoint "V" two hydroplanes. hydroplanesor points "shingled" forward.aft. orhyciroplanes."Sea Sleds." i feetcenterwateran inch. of line theof This gravity lengtl.bottom hook, canshow however,the go a boat slightsomewhat abafthasdownward otherthe further fore disadvantages hook endaft ifofof the thEwaperhaps last and tertwo ais quarterÌire. notor three con-The of usuallythenotedIn after Fig. that shows third 151the6. bottom a isHydrofoils.of slight shownthe lineslengthamount a carrymodern are ofconcavitybacksttaíhTliñes. stepless so that hydroplane.thethis In buttocks amount section, fordependingIt the willat least"V" be I andducive is, therefore,to safety in a ahe sea avoided nor toFIGsafetyif possible. 152 when making high speed turns A MODERN STEPLESS 1-IVDROPLANEgeneral way, the steeper inadditionhas Thecontact been exact tothe with upward action subject the ofwaterpressures of the much waterissubjected oridiscussion. onthethe bottom, tobottoni a It downward is ofconcededa great a stepless suction.part today hydroplaneof the Itthat, is areaforin oneonconcave.the the "V.:)"V"side'or steepness angle, In the very othei theof flat the greaterat "V's" anglehigh thespeedunlessit ofis thetendency uiìnecessary "V." thisIn for a is tothe corrected use boat much to byheel or concavingninabouts even over any to invertedexcellentformsthisVarious reason in laps whichresults forms that of anthe theinof attempt many longitudinalsteplessplanking