The SS AMERICAN MARINER has drafts of: FWD 28'-00", AFT 29'-00". Use the white pages of the Stability Data Reference Book to determine the drafts if you ballast the forepeak with 81.05 tons of seawater.
• Trim and mean draft: how adding weight at one end changes forward and aft drafts • Using the white pages hydrostatic/trim tables for SS AMERICAN MARINER to get TPI (tons per inch immersion) and moment-to-change-trim values • Distinguishing between change in mean draft and change in trim when weight is added at the bow
• First, decide: when you add 81.05 tons at the forepeak, will the ship trim more by the head or by the stern? How should that affect FWD and AFT drafts? • Think through two separate steps: (1) change in mean draft from the extra displacement, and then (2) change in trim from adding the weight at the bow. How do you combine these to get new FWD and AFT drafts? • From the trim calculation, which draft (FWD or AFT) will change more, and by roughly how many inches compared to the mean draft change?
• From the white pages, confirm the correct TPI (tons per inch immersion) near the original mean draft before you compute change in mean draft. • From the same reference, verify the correct moment to change trim 1 inch (MCT 1") at the original mean draft before you compute trim change. • After you estimate the direction and magnitude of trim, check which multiple-choice option matches both: (a) the expected increase in mean draft from 81.05 tons, and (b) the expected difference between FWD and AFT drafts due to trim.
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