The DEEP DRILLER is loaded as shown in the Sample Load Form #1 (Transit). Although winds are less than 70 knots, excessive motion requires ballasting to survival draft. Assume that 4087 long tons of ballast are added at an average VCG of 8.32 feet, and upon arrival at 45 feet, port and starboard ballast tanks 1, 3, and 8 are slack. What will be the new margin on the maximum allowable KG?
• Effect of adding ballast on vessel KG and GM • How slack tanks affect virtual rise of G and maximum allowable KG • Reading and comparing current KG vs maximum allowable KG from a loading condition (Sample Load Form #1)
• First, think about how adding 4087 LT of ballast at a given VCG will change the overall KG of the unit compared to the original transit condition. • Consider what happens to the maximum allowable KG and the margin when tanks become slack and you must apply a free-surface correction. • Ask yourself: after you reach the 45-foot survival draft, is your new actual KG closer to or farther from the maximum allowable KG than it was in the original transit condition?
• Be sure you correctly recompute the new KG after adding ballast using a weighted-average approach. • Apply the free surface correction (FSC) for the specified slack tanks and adjust the effective KG accordingly. • Compare the effective KG at survival draft to the maximum allowable KG from the stability data to determine the remaining margin, and match that to the closest choice.
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