船舶专业英语(课文+翻译)

Chapter1ShipDesign（船舶设计）Lesson2ShipsCategorized（船舶分类）2.1Introduction（介绍）Theformsashipcantakeareinnumerable.一艘船能采用的外形是不可胜数的Avesselmightappeartobeasleekseagoinghotelcarryingpassengersalongtosomeexoticdestination;afloatingfortressbristlingwithmissilelaunchers;。oranelongatedboxtransportingtanksofcrudeoilandtoppedwithcomplexpipeconnections.一艘船可以看做是将乘客一直运送到外国目的地的优美的远航宾馆。竖立有导弹发射架的水面堡垒及甲板上铺盖有复杂管系的加长罐装原油运输轮Noneofthesedescriptionsofexternalappearance,however,doesjusticetotheshipsystemasawholeandintegratedunit所有这些外部特点的描述都不能说明船舶系统是一个总的集合体—self-sufficient,seaworthy,andadequatelystableinitsfunctionasasecurehabitatforcrewandcargo.——船员和货物的安全性功能：自给自足，适航，足够稳定。Thisistheconceptthatthenavalarchitectkeepsinmindwhendesigningtheshipandthatprovidesthebasisforsubsequentdiscussions,notonlyinthischapterbutthroughouttheentirebook.这是一个造船工程师设计船舶使必须记住的、能为以后讨论提供根据的观念，不仅涉及本章也贯穿全书。Inordertodiscussnavalarchitecture,itishelpfultoplaceshipsincertaincategories.Forpurposesofthistext,shipsareclassifiedaccordingtotheirmeansofphysicalsupportandtheirdesignedpurposes.将船舶分成一些特定的种类来讨论造船工程是有好处的。本文的目的就是根据船舶物理支撑方式和设计目的来将它们分类。2.2ShipsTypedAccordingtoMeansofPhysicalSupport（根据物理支撑方式来分类）Themodeofphysicalsupportbywhichvesselscanbecategorizedassumesthatthevesselisoperatingunderdesignedconditions-Shipsaredesignedtooperateabove,on,orbelowthesurfaceofthesea,sotheair-seainterfacewillbeusedasthereferencedatum.船舶按物理支撑的分类方式假设，船舶是在设计工况的条件下航行。船舶预定在海面上，海面中或海面以下航行，因此使用空气与水的接触面作为基准面。Becausethenatureofthephysicalenvironmentisquitedifferentforthethreeregionsjustmentioned,thephysicalcharacteristicsofshipsdesignedtooperateinthoseregionscanbediverse.由于上面提到的三个区域中物理环境的本质相差很大，所以那些区域中的船的物理特性也不同。AerostaticSupport（空气静力支撑）Therearetwocategoriesofvesselsthataresupportedabovethesurfaceoftheseaonaself-inducedcushionofair.Theserelativelylightweightvehiclesarecapableofhighspeeds,sinceairresistanceisconsiderablylessthanwaterresistance,andtheabsenceofcontactwithsmallwavescombinedwithflexiblesealsreducestheeffectsofwaveimpactathighspeed.有两种靠自身诱导的气垫浮于海面上的船。这些重量相对轻的船能够高速航行，这是因为空气阻力比水阻力小得多，而且船舶高速航行时，弹性密封圈没有与小波浪接触，因而降低了了波浪冲击的影响。Suchvesselsdependonliftfanstocreateacushionoflow-pressureairinanunderbodychamber.这种船依靠升力风扇在船体水下部分产生了低压气垫。Thiscushionofairmustbesufficienttosupporttheweightofthevehicleabovethewatersurface.这种空气气垫必须足够支撑水面上方船的重量。Thefirsttypeofvesselha.sflexible“skirts”thatentirelysurroundtheaircushionandenabletheshiptorisecompletelyabovetheseasurface.第一种船有完全围绕在气垫周围并且能够使船完全漂浮在水面以上的弹性围裙。Thisiscalledanaircushionvehicle(ACV),andinalimitedsenseitisamphibious.它被称为气垫船（ACV），某种有限的程度上适用于两栖。Theothertypeofair-cushioncrafthasrigidsidewallsorthinhullsthatextendbelowthesurfaceofthewatertoreducetheamountofairflowrequiredtomaintainthecushionpressure.另一种气垫船带有刚性侧壁，且有延伸到水下能够减小空气流量的瘦船体，该气流用来维持气垫压力。Thistypeiscalledacaptured-air-bubblevehicle(CAB).这种类型船称为束缚气泡减阻船Itrequireslesslift-fanpowerthananACV,ismoredirectionallystableandcanbepropelledbywaterjetsorsupercavitatingpropellers.相对于ACV来说，它需要较低的升力风扇动力,航向稳定性更好，并且能使用喷水推进器和超空泡螺旋桨。Itisnotamphibious,however,andhasnotyetachievedthepopularityoftheACVs,whichincludepassengerferries,cross-channelautomobileferries,polar-explorationcraft,landingcraft,andriverinewarfarevessels.但是，它不是两栖用途的，也还没有ACVs那么广的适用范围，适用范围包括游客渡轮，横越海峡车客渡轮，极地考察船，登陆舰及内河舰艇。HydrodynamicSupport（水动力支撑）Therearealsotwotypesofvesselsthatdependondynamicsupportgeneratedbyrelativelyrapidforwardmotionofspeciallydesignedhydrodynamicshapeseitheronorbeneaththesurfaceofthewater.也有两种类型船，它们依赖通过船的相对高速前进运动来产生动力支持，这种船型的水上和水下部分的形状都经过特殊设计。Aprincipleofphysicsstatesthatanymovingobjectthatcanproduceanunsymmetricalflowpatterngeneratesaliftforceperpendiculartothedirectionofmotion.一个物理定理这样陈述：任何运动的物体都能造成不均匀的流态，产生一个垂直于运动方向的升力。Justasanairplanewith(airfoil)producesliftwhenmovingthroughtheair,ahydrofoillocatedbeneaththesurfaceandattachedbymeansofasurfacepiercingstrut,candynamicallysupportavessel’shullabovethewater.正如装有空气翼的飞机在空气中移动时气翼上能产生一个升力一样，位于水面以下且其上固定有穿透水面的柱体的水翼，能够动态支撑水面以上的船体。PlaninghullsarehullformscharacterisedbyrelativelyflatbottomsandshallowV-sections(especiallyforwardofamidships)thatproducepartialtonearlyfulldynamicsupportforlightdisplacementvesselsandsmallcraftathigherspeeds.滑行船体的特征是底部相对较平，横剖面呈浅V形（尤其是船的前半部分）。这种形状特点能够使船产生偏近满动力支持，适用于使小排水量船和高速小艇。Planingcraftaregenerallyrestrictedinsizeanddisplacementbecauseoftherequiredpower-to-weightratioandthestructuralstressesassociatedwithtravelingathighspeedinwaves.一般说来，滑行船体的尺寸和排水量有限制。这是因为需要满足动力和重量的比率要求，以及在波浪中高速航行时的结构应力要求。Mostplaningcraftarealsorestrictedtooperationsinreasonablycalmwater,althoughsome“deepV”hullformsarecapableofoperationinroughwater.虽然有一些‚深V型剖面船能够在恶劣的海况中航行，但大多数滑行船体也都限制在相当平静的水面上航行。Lesson3PrincipalDimensions（主尺度）3.1PrincipalDimensions（主尺度）Beforestudyingindetailthevarioustechnicalbranchesofnavalarchitectureitisimportanttodefinevarioustermswhichwillbemadeuseofinlaterchapters.Thepurposeofthischapteristoexplainthesetermsandtofamiliarisethereaderwiththem.在系统的学习船舶工程不同的技术分支之前，应该定义一些术语以便于后面章节使用，这很重要。本章旨在于解释这些术语，并且让读者熟悉它们。Inthefirstplacethedimensionsbywhichthesizeofashipismeasuredwillbeconsidered;theyarereferredtoas‘principaldimensions’.Theship,likeanysolidbody,requiresthreedimensionstodefineitssize,andthesearealength,abreadthandadepth.首先，考虑用来测量船舶尺寸的尺度；它们即是“主尺度”像任何其他固体一样，船舶需要三个尺度来定义其尺寸，它们是长度，宽度和高度。Eachofthesewillbeconsideredinturn.我们将依次来讨论它们。Length（船长）Therearevariouswaysofdefiningthelengthofaship,butfirstthelengthbetweenperpendicularswillbeconsidered.有多种定义船舶长度的方法，但是首先应该考虑艏艉两柱间长。Thelengthbetweenperpendicularsisthedistancemeasuredparalleltothebaseatthelevelofthesummerloadwaterlinefromtheafterperpendiculartotheforwardperpendicular.柱间长指的是平行于基底夏季载重水线，从艉柱到艏柱间的距离。Theafterperpendicularistakenastheaftersideoftherudderpostwherethereissuchapost,andtheforwardperpendicularistheverticallinedrawnthroughtheintersectionofthestemwiththesummerloadwaterlineInshipswherethereisnorudderposttheafterperpendicularistakenasthelinepassingthroughthecentrelineoftherudderpintles.艉柱指的就是船舶舵柱的后侧，而艏柱是通过船艏与夏季载重水线的交点的竖直线。如果船上没有舵柱，那么艉柱就取通过舵销中心线的直线。Thelengthbetweenperpendiculars(L.B.P.)isusedforcalculationpurposesaswillbeseenlater,butitwillbeobviousfromFigure3.1thatthisdoesnotrepresentthegreatestlengthoftheship.两柱间长（L.B.P.）是用于后面的计算之用的，然而从图3.1中可以看出两柱间长不是船舶的最大长度。Formanypurposes,suchasthedockingofaship,itisnecessarytoknowwhatthegreatestlengthoftheshipis.明白船舶的最大长度是必要的，很多地方都能用到最大船长，比如船舶入坞。Thislengthisknownasthe‘lengthoverall’andisdefinedsimplyasthedistancefromtheextremepointattheafterendtoasimilarpointattheforwardend.这个长度称为“总长”，是以从船艉端点到船艏端点间的距离来定义的。ThiscanbeclearlyseenbyreferringagaintoFigure3.1.Inmostshipsthelengthoverallwiltexceedbyaconsiderableamountthelengthbetweenperpendiculars.大多数船的总长都比两柱间长超出很多。Theexcesswillincludetheoverhangofthestemandalsothatofthestemwherethestemisrakedforward.超出的长度包括船艉悬挂物和前倾型船艏悬挂物。Inmodemshipshavinglargebulbousbowsthelengthoverall(L.O.A.)mayhavetobemeasuredtotheextremepointofthebulb.现代大型球鼻艏船舶的总长（L.O.A.）应该以球鼻为端点测量。Athirdlengthwhichisoftenusedtparticularlywhendealingwithshipresistance,isthelengthonthewaterline(L.W.L.).第三种长度是水线长（L.W.L）常用于计算船舶阻力。Thisisthedistancemeasuredonthewaterlineatwhichtheshipisfloatingfromtheintersectionofthesternwiththewaterlinetotheintersectionofthestemwiththewaterline.水线长指的就是在船舶所漂浮的水线上从船艏与水线的交点到船艉与水线的交点间的距离Thislengthisnotafixedquantityforaparticularship,asitwilldependuponthewaterlineatwhichtheshipisfloatinganduponthetrimoftheship.一艘特定的船上的水线长不是一个固定值,它是取决于船舶所漂浮的水线的位置及船舶的纵倾程度Breadth（型宽）Themidpointofthelengthbetweenperpendicularsiscalled‘amidships’andtheshipisusuallybroadestatthispoint.两柱间长的中点称为“船舯”且船舶在该处的宽度是最大的。Thebreadthismeasuredatthispositionandthebreadthmostcommonlyusediscalledthe‘breadthmoulded’.我们所说的宽度就是在船舯位置测得的，该宽度一半称为“型宽”。Itmaybedefinedsimplyasthedistancefromtheinsideofplatingononesidetoasimilarpointontheothersidemeasuredatthebroadestpartoftheship.我们谨定义它为船舶最宽处一侧船壳板的内侧到另一侧船壳板内侧的距离。Asisthecaseinthelengthbetweenperpendiculars,thebreadthmouldeddoesnotrepresentthegreatestbreadthoftheship,sothattodefinethisgreatestbreadththebreadthextremeisrequired.就像两柱间长那种情况一样，型宽不是船舶最大宽度，以至于有必要定义船舶的最大宽度为计算宽度。Inmanyshipsthebreadthextremeisthebreadthmouldedplusthethicknessoftheshellplatingoneachsideoftheship.对于很多船，计算宽度等于型宽交上船舶两侧船体外板的厚度。Inthedaysofrivetedships,wherethestrakesofshellplatingwereoverlappedthebreadthextremewasequaltothebreadthmouldedplusfourthicknessesofshellplating,butinthecaseofmodemweldedshipstheextrabreadthconsistsoftwothicknessesofshellplatingonly.在铆接船的年代中，由于船舶外板列板相重叠，所以计算宽度就等于型宽加上四倍的船壳板厚度，然而现代焊接船仅加上两倍船壳板厚度。Thebreadthextrememaybemuchgreaterthanthisinsomeships,sinceitisthedistancefromtheextremeoverhangononesideoftheshiptoasimilarpointontheotherside.有些船的计算宽度可能比上述所说的还大，这是因为它指的就是船舶一舷侧突出物极限点至相对称的另一舷侧突出物极限点间的距离。Thisdistancewouldincludetheoverhangofdecks,afeaturewhichissometimesfoundinpassengershipsinordertoprovideadditionaldeckarea.这种距离可能包括甲板突出物宽度，我们能从客船中发现这种特性，这是为了扩大甲板面积。Itwouldbemeasuredoverfenders,whicharesometimesfittedtoshipssuchascrosschannelvesselswhichhavetooperateinandoutofportundertheirownpowerandhavefendersprovidedtoprotectthesidesoftheshipswhencomingalongsidequays.我们将这些突出物称为护舷材，护舷材只用在某些船上，例如海峡渡轮，它们依靠自身的动力来进出港口，并且停靠港口时护舷能够保护船体舷侧免受损害。Depth（型深）Thethirdprincipaldimensionsisdepth,whichvariesalongthelengthoftheshipbutisusuallymeasuredatamidships.第三个主尺度是深度，它沿船长方向会发生变化但通常以船舯处的值为标准。Thisdepthisknownasthe‘depthmoulded’andismeasuredfromtheundersideoftheplatingofthedeckatsideamidshipstothebaseline.这种深度称为“型深”。指的就是船舯舷侧甲板板下部至基线间的距离。ItIssometimesquotedasa‘depthmouldedtoupperdeck’or‘depthmouldedtoseconddeck’,etc.有时引用为“顶部甲板型深”或“次甲板型深”等等。Wherenodeckisspecifieditcanbetakenthedepthismeasuredtotheuppermostcontinuousdeck.如果没有指出是哪处的甲板，那么深度就以连续甲板的最高处为基准。Insomemodemshipsthereisaroundedgunwale.一些现代船舶有修圆的舷边。Insuchcasesthedepthmouldedismeasuredfromtheintersectionofthedecklinecontinuedwiththebreadthmouldedline.这种情况下，型深就取自甲板线与型宽线的交点。3.2OtherFeatures（其他特征参数）Thethreeprincipaldimensionsgiveageneralideaofthesizeofashipbutthereareseveraletherfeatureswhichhavetobeconsideredandwhichcouldbedifferentintwoshipshavingthesamelength,breadthanddepth.这三个主尺度能够总体的描述船舶的尺寸，然而，也得考虑其他的几个特征参数且同样长、宽、高的两艘船的这些特征参数可能是不同的。Themoreimportantofthesewillnowbedefined.现在来定义这些重要的特征参数。Sheer（舷弧）Sheeristheheightofthedeckatsideabovealinedrawnparalleltothebaseandtangenttothedecklineatamidships.舷弧是甲板边板离平行于基线且相切于船舯甲板线的直线的突出高度Thesheercanvaryalongthelengthoftheshipandisusuallygreatestattheends.舷弧沿船长方向会发生变化，而且首尾端最明显Inmodernshipsthedecklineatsideoftenhasavarietyofshapes:itmaybeflatwithzerosheeroversomedistanceoneithersideofamidshipsandthenriseasastraightlinetowardstheends;antheotherhandtheremaybenosheeratallonthedeck,whichwillthenbeparalleltothebaseovertheentirelength.现代船舶甲板边线的形状多种多样：一方面，船舯两侧的某些长度方向可能是平的，没有舷弧，但接着以向上的斜直线的形式向首尾两端延伸；另一方面，甲板上面可能完全没有舷弧，整个船长方向上甲板都平行于基底。InoldershipsthedeckatsidelinewasparabolicinprofileandthesheerwasquotedasitsvalueontheforwardandalterperpendicularsasshowninFigure3.1.Socalled‘standard’sheerwasgivenbytheformulae：老式船舶纵剖面上的甲板边线呈抛物线状，舷弧取自首尾两柱方向上的值，如图3.1所示。所谓的舷弧“标准值”用公式给出：首舷弧（in）=0.2Lft+20尾舷弧（in）=0.1Lft+10这些公式用英制单位表示为：首舷弧（cm）=1.666Lm+50.8尾舷弧（cm）=0.833Lm+25.4Itwillbeseenthatthesheerforwardistwiceasmuchasthesheeraftinthesestandardformulae.通过上面的标准公式可以看出，首舷弧值是尾舷弧值的两倍。Itwasoftenthecase,however,thatconsiderablevariationwasmadefromthesestandardvalues.然而，这些标准值也会发生相当大的变化，这种情况时常发生。Sometimesthesheerforwardwasincreasedwhilethesheerafterwasreduced.有时首舷弧会变大而尾舷弧会减小。Occasionallythelowestpointoftheupperdeckwassomedistanceaftofamidshipsandsometimesdeparturesweremadefromtheparabolicsheerprofile.顶部甲板的最低点离船舯尾部偶尔有一段距离，有时抛物线状的纵剖线会发生分离。舷弧值。Thevalueofsheerandparticularlythesheerforwardwastoincreasetheheightofthedeckabovewater(the‘heightofplatform’asitwascalled)尤其是首舷弧增加了甲板离水面的高度（称为“平台高度”）andthishelpedtopreventwaterbeingshippedwhenthevesselwasmovingthroughroughsea.Thereasonfortheabolitionofsheerinsomemodemshipsisthattheirdepthsaresogreatthatadditionalheightofthedeckabovewaterattheforeendisunnecessaryfromaseakeepingpointofview.这有助于防止船舶在汹涌的海况中航行时甲板上浪。某些现代船舶废除舷弧的原因是它们的型深如此之大，以至于首部额外的甲板高度就耐波性观点而言是不必要的。Deletionofsheeralsotendstomaketheshipeasiertoconstruct,butontheotherhanditcouldbesaidthattheappearanceoftheshipsuffersinconsequence.舷弧的取消也使得船舶的建造容易得多，但是就另一方面而言结果是船的外表变得难看了。DraughtandTrim（吃水和纵倾）Thedraughtatwhichashipfloatsissimplythedistancefromthebottomoftheshiptothewaterline.船舶漂浮时的吃水指的就是船底离吃水线的距离。Ifthewaterlineisparalleltothekeeltheshipissaidtobefloatingonanevenkeel,butifthewaterlineisnotparallelthentheshipissaidtobetrimmed.如果水线平行于龙骨，那么就说船舶平浮；但是若不平行，那么就说船舶发生了纵倾。Ifthedraughtattheafterendisgreaterthanthatattheforeendtheshipistrimmedbythestemandiftheconverseisthecaseitistrimmedbytheboworbythehead.如果船尾吃水比船艏大，那么就发生了艉倾；若船艏吃水比船尾大，那么就发生了艏倾。Thedraughtcanbemeasuredintwoways,eitherasamouldeddraughtwhichisthedistancefromthebaselinetothewaterline,orasanextremedraughtwhichisthedistancefromthebottomoftheshiptothewaterline.吃水可以分为两种：型吃水，即基线离水线的距离；计算吃水，即船底与水线间的距离。Inthemodemweldedmerchantshipthesetwodraughtsdifferonlybyonethicknessofplating，butincertaintypesofshipswhere,say,abarkeelisfittedtheextremedraughtwouldbemeasuredtotheundersideofthekeelandmayexceedthemouldeddraughtby15~23cm(6~9in).对于现代焊接形式的商船，这两种吃水仅是相差一块壳板厚度的区别，但是对于有些装有棒龙骨的船，计算吃水的测量至龙骨下表面，因此计算吃水可能比型吃水大15-23cm(6-9in)。Itisimportanttoknowthedraughtofaship,orhowmuchwatertheshipis‘drawing’,andsothatthedraughtmaybereadilyobtained,draughtmarksarecutinthestemandthestem.了解船舶的吃水或者说船舶“吃”水量，这很重要，因此一艘船的吃水能够直接获取，船艏和船艉都刻有吃水标志。Thesearefiguresgivingthedistancefromthebottomoftheship.吃水标志也就是一些离船底有一定距离的一些数字。Inimperialunitsthefiguresare6inhighwithaspaceof6inbetweenthetopofonefigureandthebottomofthenextone.这是数字用英制单位表示，6in高，而且上下相邻的两个数字的间距也是6in。Whenthewaterlevelisuptothebottomofaparticularfigurethedraughtinfeethasthevalueofthatfigure.当水位到达船底的某一个数字时，吃水就是那个数字的英尺值了。Ifmetricunitsareusedthenthefigureswouldprobablybe10cmhighwitha10cmspacing.若用十进制单位表示，那么这些数字就可能是10cm高，间隔10cm。Inmanylargevesselsthestructurebendsinthelongitudinalverticalplaneeveninstillwatertwiththeresultthatthebaselineorthekeeldoesnotremainastraightline.就许多大型船舶而言，即使是在平静的海况下，它们的纵向垂直面都发生了弯曲，结果是基线或龙骨都不能保持为一条直线。Themeandraughtatwhichthevesselisfloatingisnotthensimplyobtainedbytakinghalfthesumoftheforwardandafterdraughts.这就意味着船舶漂浮时吃水不能仅仅用艏艉吃水和的一半来表示。Toascertainhowmuchthevesselishoggingorsaggingasetofdraughtmarksisplacedamidshipssothatifda，dxanddfarethedraughtsattheafterend,amidshipsandtheforwardendrespectivelythen为了确定船舶中拱或中垂程度，在船舯做了一套吃水标志，因此如果船尾、船舯和船艏吃水分别为da、dx和df那么中拱或中垂=-dx+（da+df）/2Whenuseismadeofamidshipdraughts,itisnecessarytomeasurethedraughtonbothsidesoftheshipandtakethemeanofthetworeadingsincasetheshipshouldbeheeledtoonesideortheother.使用船舯吃水时，测量船舶两侧吃水，使用两个数据是必要的，以防船舶向一侧或另一侧倾斜。Thedifferencebetweentheforwardandafterdraughtsofashipiscalledthe‘trim’,sothattrimT=da-df,andaspreviouslystatedtheshipwillbesaidtobetrimmingbythesternorthebowaccordingasthedraughtaftorthedraughtforwardisinexcess.船舶首尾吃水的不同称为“纵倾”因而纵倾T=da-df，正如前面所说的那样，船舶艉吃水或艏吃水过多时，将发生艏倾或艉倾。Foragiventotalloadontheshipthedraughtwillhaveitsleastvaluewhentheshipisonanevenkeel.对于稳定航行的船，在已知的总载荷作用下，船舶吃水将有一个最小值。Thisisanimportantpointwhenashipisnavigatinginrestricteddepthofwaterorwhenenteringadrydock.这一点对于在限制水深的区域航行的船或船舶进入干船坞时很重要Usuallyashipshouldbedesignedtofloatonanevenkeelinthefullyloadedcondition,andifthisisnotattainableasmalltrimbythestemisaimedat.船舶的设计通常应满足在满载荷作用下船能够平浮的要求，如果船达不到这种状况，那么就设计成小角度艉倾。Trimbythebowisnotconsidereddesirableandshouldbeavoidedasitreducesthe’heightofplatform’forwardandincreasestheliabilitytotakewateronboardinroughseas.艏倾这种情况是不期望发生的，应该避免,这是因为艏倾会降低艏部“平台高度”，增加在恶劣海况中甲板上浪的可能性。Freeboard（干舷）Freeboardmaybedefinedasthedistancewhichtheshipprojectsabovethesurfaceofthewaterorthedistancemeasureddownwardsfromthedecktothewaterline.干舷被定义为船舶离水面的距离，或甲板与下部水线的间距。Thefreeboardtotheweatherdeck,forexample,willvaryalongthelengthoftheshipbecauseofthesheerofthedeckandwillalsobeaffectedbythetrim,ifany.Usuallythefreeboardwillbeaminimumatamidshipsandwillincreasetowardstheends.例如，由于受到甲板舷弧的影响，干舷与露天甲板的间距沿船长方向将会发生变化，而且一定条件下间距也受纵倾的影响。一般说来，船舯干舷值最小，向首尾两端逐渐增大。Freeboardhasanimportantinfluenceontheseaworthinessofaship.干舷对船舶的适航性有重要的影响。Thegreaterthefreeboardthegreateristheabovewatervolume,andthisvolumeprovidesreservebuoyancy,assistingtheshiptorisewhenitgoesthroughwaves.干舷值越大，船舶水上部分的体积也就越大，而且这部分体积用来提供储备浮力，促使船舶在波浪中航行时能够上浮。Theabovewatervolumecanalsohelptheshiptoremainafloatintheeventofdamage.水上部分的体积也能帮助船舶破损时保持漂浮状态。Itwillbeseenlaterthatfreeboardhasanimportantinfluenceontherangeofstability.干舷对船舶稳定性的变化有重要影响，这种情况后面将会介绍到MinimumfreeboardsarelaiddownforshipsunderInternationalLawintheformofLoadLineRegulations.国际法载重公约中设定了船舶干舷最小值。Lesson4BasicGeometricConcepts（基本几何概念）ThemainpartsofatypicalshiptogetherwiththetermsappliedtotheprincipalpartsareillustratedinFig.4.1.示例船舶的主要部分以及相关的名字都在图4.1中画出来了。Because,atfirst,theyareoflittleinterestorinfluence,superstructuresanddeckhousesareignoredandthehulloftheshipisconsideredasahollowbodycurvedinalldirections,surmountedbyawatertightdeck.首先，由于没有利害关系或影响，船舶上层建筑和甲板室都被忽略了，船体看成所有方向上都是曲线、上部用水密甲板覆盖的中空壳体。Mostshipshaveonlyoneplaneofsymmetry,calledthemiddlelineplanewhichbecomestheprincipalplaneofreference.大多数船舶只有一个对称面，称为中线面，这是主要谈论的面。Theshapeoftheshipcutbythisplaneisknownasthesheerplanorprofile.被该面截得的船型称为舷弧面或纵剖面。Thedesignwaterplaneisaplaneperpendiculartothemiddlelineplane,chosenasaplaneofreferenceatornearthehorizontal;itmayormaynotbeparalleltothekeel.设计水线面垂直于中线面，取作水平或接近水平的面；它可能不与龙骨平行。Planesperpendiculartoboththemiddlelineplaneandthedesignwaterplanearecalledtransverseplanesandatransversesectionoftheshipdoes,normally,exhibitsymmetryaboutthemiddleline.与中线面和设计水线面都垂直的面称为横剖面，船舶横剖面通常关于船体中线面对称。Planesatrightanglestothemiddlelineplane,andparalleltothedesignwaterplanearecalledwaterplanes,whethertheyareinthewaterornot,andtheyareusuallysymmetricalaboutthemiddleline.与中线面成一定交角且平行于设计水线面的平面称为水线面，无论在水中与否，它们都成立，而且它们通常关于中线面对称。Waterplanesarenotnecessarilyparalleltothekeel.Thus,thecurvedshapeofashipisbestconveyedtoourmindsbyitssectionscutbyorthogonalplanes.水线面不一定平行于龙骨。因此，通过被正交面截得的面，能够向我们最清楚地表达船舶的曲线形状。Lesson5ShipFormandFormCoefficients（船型系数）5.2RequirementsofShipForm（船型需求）Thehullformofashipmustbedesignedtofulfilcertainrequirements,andthefirsttobeconsideredistheprovisionofsufficientbuoyancytocarrythevariousloadssuchastheweightoftheshipitself,pluscargo,fuel,etc.船型设计是用来满足特定的需求，而且首先要考虑的是能够提供做够的浮力来支撑多样的载荷，例如船舶本身重量，加货物，燃料等。Inotherwordstheshipformmustprovideacertaindisplacementuptotheloadwaterline.Callingthisdisplacement△itfollowsthat换句话说，船舶必须提供一定的排水量，直至载重水线处。称这个排水量为△，表示如下△=gVρwereρisthedensityofthewaterinwhichtheshipisfloating,gistheaccelerationduetogravity,andVistheunderwatervolume.其中ρ是船舶所在水域的密度，g是重力加速度，V是水下部分的体积。Itmaybesaid,therefore,thatthedesignermustsodesigntheformthatsomeunderwatervolumeVisobtained.因此可以说设计师应该有目的地设计船型，以便能够获得一些水下部分体积V。Anotherimportantrequirementoftheunderwaterformisthatthecentroidofthevolumemustbeinaparticularpositionintheforeandaftdirection.水下部分的船型的另一个重要的要求就是，体积中心必须在首尾方向的特定位置处5.3Formcoefficients（船型系数）Iftheshipformconsistedsimplyofrectangularblockoflengthequaltothelengthbetweenperpendiculars,breadthequaltothebreadthmoulded,anddepthequaltothedraught,thentheunderwatervolumewouldbegivensimplyby如果船型仅由长、宽、深分别等于两柱间长、型宽、吃水的长方体组成，那么水下部分体积将仅由如下给出V=L×B×dItwill,however,beclearthattheactualvolumeislessthanthevolumeofthisblock,orinotherwordstheshipformcanbeimaginedtohavebeencutoutofthisblock.而，真实的体积很明显小于这个长方体体积，或者换句话说，船型假想为是从这个长方体中切出来的。Whatiscalledthe‘blockcoefficient’istheratiooftheactualvolumeoftheunderwaterformtothevolumeLBd.Inotherwords所谓的“方形系数”就是真实船型水下部分体积与LBd体积的比值。用另一种方式表示为BlockcoefficientCB=V/(L×B×d)方形系数CB=V/（L×B×d）Whentheshipdesignerhasdecidedwhatvolumeisrequiredhethenhasfourfactorstoconsider:thelength,breadthanddraughtoftheship,andalsotheblockcoefficient.当船舶设计师已经决定需要何种体积时，那么他就要考虑四个因素：船长，船宽，船舶吃水，和方形系数。Thereisaninfinitenumberofcombinationsofthesefactorswhichwillgivetherequiredresultandtheproblemistodecidewhatarethebestvaluesofthefourparameters.Inthemeantime,however,theblockcoefficientonlywillbeconsidered.这些因数有无数种组合，能够给出最理想的结果，并且问题就是如何决定这四个系数的最佳值。同时，但唯独将只考虑方形系数。Generallyitisgovernedbyresistanceconsiderations.这一般是由阻力因素决定的。Atthisstageitmaybesaidthatfastshipsrequirelowvaluesofblockcoefficientwhileinslowshipshighvaluesoftheblockcoefficientarepermissible.在此阶段，可以说高速船舶要求方形系数值低，而低速船只允许方形系数值高。Inslowspeedships,sayofthebulkcarriertype,ahighvalueofblockcoefficientmeansalargedisplacementongivenprincipaldimensions,whichmeansthatthereisalargeamountofdisplacementavailableforthecarriageofcargo.对于低速船，例如散货船，高的方形系数值意味着在主尺度一定的情况下排水量大，这就意味着有很大排水量来维持货物运输。Infastshipsitisessentialtokeepdownthevalueoftheblockcoefficient,sotheynormallyhavelowerblockcoefficientsthanslowships.对于高速船，降低方形系数值是必要的，因此相比于低速船它们有更低的方形系数值。Theinfluenceofblockcoefficientontheshapeofthehullformisthatinshipswithhighvaluesofthiscoefficientconsiderableparallelmiddleislikelytobefoundandtheslopesofthewaterlinesattheendsaresteep,whereaswithlowblockcoefficientsparallelmiddleisoftenquiteshortormaynotexistatallandtheslopesofthewaterlinesattheendswillbesmallalso.方形系数对船型的影响表现为，对于方形系数值高的船，会发现平行中体程度相当大而且船舶两端水线范围陡，而对于方形系数值低的船，平行中体通常很小或可能完全不存在，而且船舶两端水线范围也很陡。Anothercoefficientwhichisusefuliswhatisknownasthe‘prismaticcoefficient’.另外一个有用的系数就是所谓的“棱形系数”。TheshipformcouldbeimaginedtohavebeencutfromaprismoflengthequaltothelengthoftheshipandofconstantcrosssectionofareaequaltoTheimmersedmidshiparea.Thus船型可以想象为是从棱柱体中切割出来的，棱柱体长度等于船长且截面积等于船舯浸没部分的面积的。因此PrismaticcoefficientCp=V/(Midshiparea×L)棱形系数Cp=V/（舯面积×L）Thisparticularcoefficienthasitsuseindealingwithresistance.处理船舶阻力时能用到这个特殊的系数。Acoefficientwhichisusedtoexpressthefullnessofthemidshipsectionisthemidshipareacoefficient.Ifthemidshipsectionisimaginedtobeoutoutofartx:tangleofdimensionsbreadth×draughtthen一个用来表示船舯剖面丰满度的系数是中站面系数。若将船舯剖面想象为是从尺度等于船宽吃水的矩形中切割出来的，那么MidshipareacoefficientCm=Midshiparea/(B×d)中站面系数Cm=舯面积/（B×d）ThethreecoefficientssofardiscussedarerelatedtooneanothersinceCB=V/(L×B×d)=[V/(Midshiparea×L)]×[Midshiparea/(B×d)]CB=Cp×Cm目前为止讨论的这三种系数是相互关联的，因为CB=V/（L×B×d）=[V/（舯面积×L）]×[舯面积/（B×d）]CB=Cp×CmGenerallyspeaking,astheblockcoefficientbecomesfinerthemidshipareacoefficientbecomesfinei,asdoestheprismaticcoefficient.一般认为,方形系数越小，中站面系数也越小，棱形系数也一样。Thewaterplaneareaofaship,i.e.theareaenclosedbyanyparticularwaterline,canalsobeexpressedintermsofacoefficientandtheareaofthecircumsectingrectangle.HencewaterplaneareacoefficientCw=Waterplanearea/(L×B)船舶水线面面积，即被特殊水线包围的面积，也能够用一个系数和该面的外切矩形来表示。因此，水线面系数Cw=水线面面积/（L×B）Chapter2ShipRudiments（船舶基本原理）Lesson7EquilibriumandStability（平衡性和稳定性）7.1Introduction（引言）Inchapter2theconditionforstaticequilibriumwasdefinedintermsofthebalanceofforcesandmoments.第二章中的静力平衡状态是以力和力矩的平衡来定义的FromNewton’slawsofmotion,itisseenthatabodycanbeatrestormovingatconstantspeedonlyifthesumofallforcesandmomentsactingonthebodyisequaltozero.从牛顿运动定律中可以知道，若作用于物体上的合外力和和外力矩等于零，那么物体将处于静止或以恒定不变速度运动。Theconceptofstabilityissomewhatmorecomplex.稳定性的概念某种程度上更复杂些。Here,oneisconcernedwithwhetherornotabodywillreturntoaninitialstateofstaticequilibriumwhendisturbedbyanunbalancedforceormoment.其中一种情况与物体受到不平衡的力或力矩的干扰时是否能够回复到初始静力平衡状态有关。Whileinthebroadersenseequilibriumreferstoanoverallbalanceofforces,whichinvolvesnoaccelerationordeceleration,staticequilibriumisdefinedasfollows:Abodyatrestissaidtobeinstaticequilibrium.静力平衡如下定义：处于静止状态的物体就出于静力平衡。但广义上的平衡指的是合力的平衡，与加速和减速无关。Ifthisbodyisdisturbedbyanoutsideforceandreturnstoitsoriginalpositionwhentheforceisremoved,itissaidtobeinstableequilibrium.Anexampleofthisconditionisaroundballlyinginanupwardfacingbowl,asinFigure7.1(a).若此物体受外力作用而当外力移除时又回到初始位置，那么就说物体处于稳定平衡状态。一个这种状态的例子是，一个处于开口朝上的碗中的圆球，如图7.1（a）所示。Theballwillalwaysreturntoitsrestpositionwhendisturbedbyanoutsideforc