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1、LessonFourShipDesignThedesignofashipinvolvesaselectionofthefeaturesofform,size,proportions,andotherfactorswhichareopentochoice,incombinationwiththosefeatureswhichareimposedbycircumstancesbeyondthecontrolofthedesignnavalarchitect.Eachnewshipshoulddosomethingsbetterthananyothership.Thiss
2、uperioritymustbedevelopedintheevolutionofthedesign,intheuseofthemostsuitablematerials,totheapplicationofthebestworkmanship,andintheapplicationofthebasicfundamentalsofnavalarchitectureandmarineengineering.Assipshaveincreasedinsizeandcomplexity,plansforbuildingthemhavebecamemaredetaileda
3、ndmorevaried.TheintensiveresearchsincetheperiodjustpriortoWorldWar2hasbroughtaboutmanytechnicaladvancesinthedesignofships.Thesechangeshavebeenbroughtaboutprincipallybythedevelopmentofnewweldingtechniques,developmentsinmainpropulsionplants,advancesinelectronics,andchangesinmaterialsandm
4、ethodsofconstruction.Allshipshavemanyrequirementswhicharecommontoalltypes,whethertheyarenaval,merchant,orspecial-purposeships.Thefirstofsuchrequirementsisthattheshipmustbecapableoffloatingwhencarryingtheloadforwhichitwasdesigned.Ashipfloatsbecauseasitsinksintothewateritdisplacesanequal
5、weightofwater,andthepressureofthewaterproducesanupwardforce,whichiscalledthebuoyancyforceisequaltotheweightofthewaterdisplacedbytheshipandiscalledthedisplacement.Displacementisequaltotheunderwatervolumeoftheshipmultipliedbythedensityofthewaterinwhichitisgloating.Whenfloatinginstillwate
6、r,theweightoftheship,includingeverythingitcarries,isequaltothebuoyancyordisplacement.Theweightoftheshipitselfiscalledthelightweight.Thisweightincludestheweightofthehullstructure,fittings,equipment,propulsionmachinery,pipingandventilation,cargo-handlingequipmentandotheritemsrequiredfort
7、heefficientoperationoftheship.Theloadwhichtheshipcarriesinadditiontoitsownweightiscalledthedeadweight.Thisincludescargo,passengers,crewandeffects,stores,freshwater,feedwaterfortheboilersincaseofsteampropellingmachinery,andotherweightswhichmaybepartoftheshipsinternationalload.Thesumof
