The SS AMERICAN MARINER arrived in port with drafts of: FWD 28'-04", AFT 30'-08". Cargo was loaded and discharged as indicated in table ST-0092 below. Use sheet 2 in the white pages of the Stability Data Reference Book to determine the final drafts.
Load 180 tons---155 feet fwd of amidships Discharge 160 tons---38 feet fwd of amidships Load 140 tons---75 feet aft of amidships Discharge 170 tons---205 feet aft of amidships
• Use moment to change trim (MCT) from sheet 2 of the Stability Data Reference Book for SS AMERICAN MARINER. • Remember sign convention: weights forward of amidships give bow-down moments, aft of amidships give stern-down moments. • Convert total longitudinal moments into change in trim, then split trim between forward and aft drafts using the LCF (Longitudinal Center of Flotation) method shown in the book.
• First, compute the net weight change and the algebraic sum of trimming moments about amidships for all four cargo moves. What direction (bow down or stern down) is the net trim? • Using the MCT from the reference sheet, determine the change in trim in feet and inches. Then think: if the ship trims by the stern, what happens to the forward draft versus the aft draft? • From the initial drafts and your calculated trim, which option shows the correct mean draft change (due to net weight) and the correct forward/aft difference (due to trim)?
• Verify you are using the correct MCT and LCF values specifically for the draft range that includes the ship’s mean draft. • Check the algebraic signs of each moment: loaded weight vs. discharged weight, and whether it is forward or aft of amidships. • Confirm that the change in mean draft (from net weight only) is the same at both ends, and only the trim component makes the forward and aft drafts different.
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