A semisubmersible, while floating level, displaces 25,000 long tons. LCG is 2 feet forward of amidships. Bulk, weighing 300 long tons, is placed in P-tanks located 50 feet aft of amidships. What is the new LCG?
⢠Longitudinal center of gravity (LCG) and how it moves when weight is added forward or aft ⢠Trimming moment = weight à distance from reference point (amidships in this case) ⢠How to find new LCG using total moment á total displacement
⢠Start by writing down the original displacement and original LCG position relative to amidships. What is the original total longitudinal moment about amidships? ⢠Next, compute the moment of the added 300 long tons placed 50 feet aft of amidships. Will this be a positive or negative moment if forward is taken as positive? ⢠Add the moments together, then divide by the new total displacement to get the new LCG. Is the result closer to the original 2 feet forward, or has it moved significantly toward aft?
⢠Be sure to use consistent sign convention (e.g., forward positive, aft negative, or vice versa) and stick with it throughout. ⢠Update the total displacement after loading the 300 long tons before calculating the new LCG. ⢠Doubleâcheck the units: all weights in long tons and all distances in feet, and ensure the moment units are long tonâfeet.
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