Đang chuẩn bị liên kết để tải về tài liệu:
Ship Hydrostatics and Stability 2010 Part 8

Tham khảo tài liệu 'ship hydrostatics and stability 2010 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Weight and trim calculations 171 7.5 Summary Stability and trim calculations require the knowledge of the displacement and of the position of the centre of gravity. To calculate these quantities it is necessary to organize the ship masses into weight groups. The sum of the weight groups that do not change during operation is called lightship displacement for merchant vessels it is the sum of hull outfit and machinery masses. The sum of the masses that are carried in operation according to the different loading cases is called deadweight it includes the crew and its equipment the cargo and passengers the fuel the lubricating oil the fresh water and the stores. To find the displacement of a given loading case it is necessary to add the masses of the lightship and the deadweight items carried on board in that case. To find the coordinates of the centre of gravity LCG and VCG KG it is necessary to sum up the moments of the above masses with respect to a transverse plane for the first a horizontal plane for the second. The calculations can be conveniently carried out in an electronic spreadsheet or by software such as MATLAB. Once the displacement A is known one can find the corresponding mean draught Tm by reading the hydrostatic curves. These curves also yield the values of the longitudinal centre of buoyancy LCB the longitudinal centre of flotation LCF and the moment to change trim by 1 m MCT. If the trim is small it can be found from T.-r. A LCG - LCB F A MCT For normal loading situations the trim is always small. Then the trimmed waterline WgLg intersects the waterlines of the ship on even keel W0Lq along a line passing through the centre of flotation F of WqLq. To obtain the forward draught Tf and the aft draught TA it is necessary to add to or subtract from the mean draught a part of the trim proportional to the distance of the respective perpendicular from the centre of flotation 2a Tm - trim m npp TGF Tp Tm trim I 1------- __ m X pp If the trim is large the .