A jack-up with a calculated moment to change list one inch (MCL1") of 1,350 foot-kips intends to transfer drill water from a tank with a TCG of 82 feet to a tank with a TCG of 18 feet. How much weight should be transferred to change the draft on the port side from 11.0 to 11.5 feet?
• Moment to Change List One Inch (MCL 1") – what it represents and how it relates a heeling moment to inches of list or draft change at the side • How a transverse shift of weight creates a moment: Weight × change in TCG (transverse center of gravity) • The relationship between total moment required (from desired draft/list change) and the moment produced by the transferred weight
• First, determine the total moment required to change the draft at the port side by 0.5 ft using the given MCL 1" value. How do you convert 0.5 ft of draft change at the side into inches, and then into a total moment? • Next, express the heeling moment created by transferring an unknown weight between two tanks with different TCGs. What is the effective transverse distance the weight moves? • Finally, set the moment required (from MCL 1") equal to the moment created by the weight transfer and solve for the unknown weight. Which answer choice is closest to that value?
• Convert 0.5 ft of draft change at the port side into inches of list at the side and multiply by MCL 1" (1,350 ft-kips per inch) to find the required moment. • Correctly compute the TCG shift distance as the difference between 82 ft and 18 ft; use that as the lever arm in your moment equation. • Make sure your final weight has units of kips, and that your calculated value matches one of the choices without needing large rounding errors.
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