The SS AMERICAN MARINER arrived in port with drafts of: FWD 19'-06.6", AFT 20'-05.6". Cargo was loaded and discharged as indicated in table ST-0079 below. Use sheet 2 in the white pages of The Stability Data Reference book to determine the final drafts.
NMC has NOT supplied the weights to load or discharge for this question.
⢠Use Sheet 2 â Hydrostatic Data for SS AMERICAN MARINER: find the correct displacement, TPI (tons per inch immersion), LCF (longitudinal center of flotation), and MT1 (moment to change trim 1 inch) for the initial mean draft. ⢠Separate the problem into change of mean draft (total weight loaded) and change of trim (algebraic sum of trimming moments about midships or LCF). ⢠Remember the sign convention: weights forward of LCF tend to trim the ship by the head, and weights aft of LCF tend to trim by the stern.
⢠First, compute the total weight loaded and use the appropriate TPI at the starting mean draft to find the change in mean draft. How does that affect both forward and aft drafts equally? ⢠Next, calculate the trimming moment of each weight about the LCF (or about midships then correct to LCF using its position). What is the net trimming moment, and does it trim by the head or stern? ⢠After you find the total change in trim, use the foreâandâaft draft correction formula to split that trim between the forward and aft drafts. Which answer choice best matches those corrected drafts?.
⢠Be sure you are using the correct row on Sheet 2 that matches the initial mean draft (average of the given FWD and AFT drafts). ⢠Doubleâcheck your lever arms: convert the distances in the table (feet forward/aft of amidships) to moments about the LCF, not just amidships, using the LCFâs position from Sheet 2. ⢠Before picking an option, confirm that the direction of trim (more draft forward or aft) in your result matches the physical expectation from the locations of the loaded weights.
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