During an ice storm on board the DEEP DRILLER, the rig is uniformly covered with 414 tons of ice. At the beginning of the storm the rig was at 45 foot draft. After the storm the rig was at a 48 foot draft. Assume a KG of 127 feet for the new ice and an original KG of 58 feet. What is the new KG of the DEEP DRILLER?
• GG (new vertical center of gravity) calculation when weight is added at a known KG • Using draft change to estimate the vessel’s (or rig’s) original displacement and the displacement after icing • Weighted-average formula for combining original KG with added weight at a different KG
• How can you use the change in draft (from 45 ft to 48 ft) to estimate how much the displacement changed when 414 tons of ice was added? • Once you know the original displacement and the added weight, what formula combines the original KG and the new weight’s KG to find the new overall KG? • After finding the vertical shift GG, how do you apply it to the original KG to reach the new KG and compare it to the choices?
• Be sure to treat 414 tons of ice as added weight high above the waterline at KG = 127 ft • Confirm you are using total displacement (original + added) in the denominator when computing the new KG • Double-check unit consistency and that you are solving for KG(final) = KG(original) + GG(upward) before matching to the closest choice
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