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InternationalPrincipalDimensions目錄/Contents01LengthBreadth0203Depth0405SheerCamber06DraughtandTrim07FreeboardTASK2InternationalPrincipalDimensionsTherearevariouswaysofdefiningthelengthofaship,butthelengthbetweenperpendicularsshouldbeconsideredfirst.Thelengthbetweenperpendiculars(LBP)isthedistancemeasuredparalleltothebaseatthelevelofthesummerloadwaterlinefromtheafterperpendiculartotheforwardperpendicular.LengthTASK2InternationalPrincipalDimensionsTheafterperpendicularistakenastheaftersideoftherudderpostwherethereissuchapost,andtheforwardperpendicularistheverticallinedrawnthroughtheintersectionofthestemwithsummerloadwaterline.LengthTASK2InternationalPrincipalDimensionsThelengthbetweenperpendicularsisusedforcalculationpurposesaswillbeseenlater,butfromFigure1-13wecanfinditdoesnotrepresentthegreatestlengthoftheship.Formanypurposes,suchasthedockingofaship,itisnecessarytoknowwhatthegreatestlengthoftheshipis.LengthTASK2InternationalPrincipalDimensionsTheLengthOverall(LOA):Thiskindoflengthcanbesimplydefinedasthedistancefromtherearmostpointofthesterntotheforemostpointofthebow.LengthTASK2InternationalPrincipalDimensionsLoadedWaterlineLength(LWL)：Athirdlength，whichisoftenused,particularlyfordealingwithshipresistance,isthelengthonthewaterline.LengthTASK2InternationalPrincipalDimensionsThisisthedistancemeasuredonthewaterline,whiletheshipisfloating,fromtheintersectionofthesternwiththewaterlinetotheintersectionofthestemwiththewaterline.LengthTASK2InternationalPrincipalDimensionsThemidpointofthelength

iscalled“amidship”andthebreadthoftheshipisusuallythebroadestatthispoint.Thebreadthmeasuredatthisposition,themostcommonlyusedfigure,whichiscalledthe“breadthmoulded”.BreadthTASK2InternationalPrincipalDimensionsItmaybedefinedsimplyasthedistancefromtheinsideofplatingononesidetoasimilarpointontheothersidemeasuredatthebroadestpartoftheship.

BreadthTASK2InternationalPrincipalDimensionsAsisthecaseinthelengthbetweenthetwoperpendiculars,thebreadthmouldeddoesnotrepresentthegreatestbreadthoftheship.Soitisnecessarytodefinethisgreatestbreadthcalledbreadthextreme.

BreadthTASK2InternationalPrincipalDimensions

Formanyships,thebreadthextrememeansbreadthmouldedplusthethicknessoftheshellplatedoneachsideoftheship.Thebreadthextrememaybemuchgreaterthanthisforsomeships,sinceitisthedistancefromtheextremeoverhangononesideoftheshiptoasimilarpointontheotherside.

BreadthTASK2InternationalPrincipalDimensionsThisdistanceincludestheoverhangofdecks,afeaturewhichissometimesfoundonpassengershipsinordertoprovideadditionaldeckarea.BreadthTASK2InternationalPrincipalDimensionsItwouldbemeasuredoverfenders,whicharesometimesfittedtosomeshipssuchascrosschannelvesselswhichhavetobeoperatedinandoutofportundertheirownpowerandhavefendersprovidedtoprotectthesidesoftheshipswhencomingalongsidequays.

BreadthTASK2InternationalPrincipalDimensionsThethirdprincipaldimensionisdepth,whichvariesalongthelengthoftheshipbutisusuallymeasuredatamidship.

DepthTASK2InternationalPrincipalDimensionsDepthFigure1-14Thisdepthisknownasthe“depthmoulded”

andismeasuredfromtheundersideoftheplatingofthedeckatsideamidshiptothebaseline.ItisshowninFigure(a).

TASK2InternationalPrincipalDimensionsItissometimesquotedas“depthmouldedtoupperdeck”or“depthmouldedtoseconddeck”,etc.Whilenodeckisspecifieditcanbetakenasmeasuredtotheuppermostcontinuousdeck.

DepthTASK2InternationalPrincipalDimensionsDepthFigure1-14Insomemodernships,thereisaroundedgunwaleasshowninFigure(b).Insuchcases,thedepthmouldedismeasuredfromtheintersectionofthedecklinecontinuedwiththebreadthmouldedline.TASK2InternationalPrincipalDimensionsThethreeprincipledimensionsrevealthegeneralsizeofashipbutthereareseveralotherfeatureswhichhavetobeconsideredandcouldbedifferentfortwoshipswiththesamelength,breadthanddepth.Nowthesemoreimportantfeatureswillbeintroduced.

OtherfeaturesTASK2InternationalPrincipalDimensionsSheeristheheightofthedeckateachsideabovealinedrawnparalleltothebaseandtangenttothedecklineatamidship.Thesheercanvaryalongthelengthoftheshipandisusuallythegreatestattheendsoftheship.SheerTASK2InternationalPrincipalDimensionsInmodernships,thedecklineateachsideoftenhasavarietyofshapes:itmaybeflatwithzerosheeroversomedistanceoneithersideofamidshipandthenriseasastraightlinetowardstheends.SheerTASK2InternationalPrincipalDimensionsOntheotherhand,theremaybenosheeratallonthedeck,whichwillbeparalleltothebaseovertheentirelength.Inolderships,thedeckatsidelinewasparabolicinprofileandthesheerwasquotedasitsvalueontheforwardandtheafterperpendiculars.

SheerTASK2InternationalPrincipalDimensionsItwillbeseenthatthesheerforwardistwiceasmuchasthesheeraftinthesestandardformulae.Sometimesthesheerforwardwasincreasedwhilethesheerafterwasreduced.SheerTASK2InternationalPrincipalDimensionsCamberFigure1-14

CamberorroundofbeamisdefinedastheriseofthedeckoftheshipingoingfromthesidetothecentreasshowninFigure1-14(a).TASK2InternationalPrincipalDimensionsThecambercurvesusedtobeparabolicbutnowadaysstraightlinecambercurvesareusedortheremaybenocamberatallondecks.CamberTASK2InternationalPrincipalDimensionsCamberisusefulontheweatherdeckofashipfromadrainagepointofview,butthismaynotbeveryimportantiftheshipisveryrarelyuprightandatrest.CamberTASK2InternationalPrincipalDimensionsIngeneral,iftheweatherdeckofashipiscambered,thelowerdecksparticularlyinpassengershipsmayhavenocamberatall,asthismakesforhorizontaldecksinaccommodationwhichisanadvantage.CamberTASK2InternationalPrincipalDimensionsCamberisusuallystatedasitsvalueonthemouldedbreadthoftheshipandstandardcamberwastakenasone-fiftiethofthebreadth.Thecamberonthedeckdiminishestowardstheendsoftheshipasthedeckbreadthsbecomenarrower.

CamberTASK2InternationalPrincipalDimensionsDraughtissimplythedistancefromthebottomoftheshiptothewaterlinewhileashipfloats.

Ifthewaterlineisparalleltothekeel，theshipissaidtobefloatingonanevenkeel.Ifthewaterlineisnotparallel,theshipissaidtobetrimmed.

DraughtandTrim

TASK2InternationalPrincipalDimensionsIfthedraughtattheafterendisgreaterthanthatattheforeend,theshipistrimmedbythestern.Iftheconverseisthecaseitistrimmedbytheboworbythehead.DraughtandTrim

TASK2InternationalPrincipalDimensionsThedraughtcanbemeasuredintwoways,eitherasamouldeddraughtwhichisthedistancefromthebaselinetothewaterline,orasanextremedraughtwhichisthedistancefromthebottomoftheshiptothewaterline.DraughtandTrim

TASK2InternationalPrincipalDimensionsItisimportanttoknowthedraughtofashiporhowmuchwatertheshipis“drawing”andthedraughtmaybereadilyobtained.Draughtmarksarecutinthestemandthestern.Thesearefiguresgivingthedistancefromthebottomoftheship.DraughtandTrim

TASK2InternationalPrincipalDimensionsWhenthewaterlevelisuptothebottomofaparticularfigurethedraughtinfeetwhichhasthevalue.DraughtandTrim

TASK2InternationalPrincipalDimensionsThedifferencebetweentheforwardandtheafterdraughtsofashipiscalledthe“trim”,whichissaidtobetrimmingbythesternorthebowaccordingasthedraughtafterorthedraughtforwardisinexcess.DraughtandTrim

TASK2InternationalPrincipalDimensionsForagiventotalloadontheshipthedraughtwillhaveitsleastvaluewhentheshipisonanevenkeel.Thisisanimportantpointwhenashipisnavigatinginrestricteddepthofwaterorwhenenteringadrydock.DraughtandTrim

TASK2InternationalPrincipalDimensionsFreeboardmaybedefinedasthedistancewhichtheshipprojectsabovethesurfaceofthewaterorthedistancemeasureddownwardsfrom