Your vessel's drafts are: FWD 14'-04", AFT 17'-08". The LCG of the forepeak is 200 feet forward of amidships. How many tons of ballast must be pumped into the forepeak in order to have a drag of 2 feet? (Use the reference material in Section 1, the blue pages, of the Stability Data Reference Book)
• Trim and draft change when adding weight forward • Using the ship’s moment to change trim (MCT 1 in.) or its equivalent from the Stability Data Reference Book • Relationship between LCG of added weight, distance from LCF/amidships, and trimming moment
• First, figure out what the present drag is from the given drafts, then determine what change in trim is needed to reach a 2-foot drag. • From the blue pages, identify the correct MCT value and how to convert between inches of trim and foot-tons (or ton-feet) of trimming moment. • Work out the trimming moment created by putting weight in the forepeak using its LCG: how far is that from amidships/LCF, and how many tons would give the trimming moment you just calculated?
• Be sure the initial and final drags are both clearly written in feet and inches and converted consistently to inches of trim. • Confirm you are using the correct MCT (for 1 inch of trim) for the vessel condition specified in the question and that you have the units right (ton-feet vs foot-tons). • Double-check the distance from the LCG of the forepeak to amidships (or LCF, if given in the tables) and use that distance in feet when computing the trimming moment.
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