A semisubmersible, 200 feet in length between draft marks with the LCF 10 feet aft of amidships, records the following drafts: Port Forward 64'-09"; Port Aft 68'-09"; Starboard Forward 59'-09"; and Starboard Aft 63'-09". What is the trim?
• Mean forward draft vs. mean aft draft and how to compute each from port and starboard readings • How to express trim (by the head or by the stern) and in what units • Effect (or non-effect) of LCF (Longitudinal Center of Flotation) location on simply reading the observed trim
• First, find the average forward draft from the two forward readings, and the average aft draft from the two aft readings. Which end is deeper? By how many feet? • Think about whether the LCF position changes the observed trim based on draft marks, or whether it mainly affects how added weight will change trim. • Compare the difference between forward and aft mean drafts to the multiple-choice options—do any match exactly in both magnitude and direction (head vs. stern)?
• Be sure you are averaging port and starboard at each end before comparing forward vs. aft. • Confirm which end is deeper: if the aft mean draft is greater, the vessel is "by the stern"; if the forward mean draft is greater, the vessel is "by the head." • Double-check unit consistency: ensure your difference in feet (ignoring inches after converting properly) matches one of the offered choices.
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