The SS AMERICAN MARINER arrived in port with drafts of: FWD 28'-04", AFT 31'-10". Cargo was loaded and discharged as indicated in table ST-0007 below. Use sheet 2 in the white pages of The Stability Data Reference Book to determine the final drafts.
Load 200 tons---180 feet fwd of amidships Discharge 60 tons---25 feet fwd of amidships Discharge 80 tons---165 feet aft of amidships Discharge 40 tons---230 feet aft of amidships
• Use sheet 2 – Hydrostatic data: especially displacement at the original mean draft, MT1" (moment to trim 1 inch), and the position of LCF (Longitudinal Center of Flotation) relative to amidships • Convert each load/discharge into a trimming moment: (tons) × (distance in feet from amidships), keeping careful track of fwd vs aft signs • Relate total trimming moment to change in trim (inches), then distribute that trim between FWD and AFT drafts based on LCF and length between perpendiculars (LBP)
• What is the ship’s original mean draft, and which line on sheet 2 should you interpolate on to get MT1" and LCF for that draft? • After you calculate each individual trimming moment, is the net trimming moment trying to put the ship more down by the bow or down by the stern? How will that affect FWD and AFT drafts? • Once you know the change in mean draft (from net weight change) and the change in trim, how do you combine those to get the final individual drafts at the bow and stern?
• Be sure all distances are taken from amidships, using one consistent sign convention (e.g., fwd = negative, aft = positive, or vice versa) and apply it consistently • Verify that you used the correct displacement and MT1" corresponding to the initial mean draft, not the final draft • After finding the final drafts, confirm that the change in displacement matches the net weight loaded/discharged and that the direction of trim matches the sign of your total trimming moment
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