The COASTAL DRILLER, in field transit at a draft of 10 feet 0 inches with winds less than 70 knots, has a KGT of 39.0 feet and a KGL of 38.6 feet. The margin on the maximum allowable KG is __________.
β’ Difference between maximum allowable KG and actual KG (KGT vs KGL) for stability margins β’ How to calculate a margin when given two KG-related values in feet β’ Which of the given KG values represents the limit and which represents the current condition
β’ Ask yourself: does the margin represent how much higher the KG could go before reaching the limit, or something else? β’ Which of the given numbers (39.0 ft and 38.6 ft) is the maximum allowable KG and which is the current KG under the stated conditions? β’ Once you know which is which, what simple arithmetic operation gives you the margin between them?
β’ Be sure you can clearly state which value is KGT and which is KGL, and what each abbreviates in stability terminology. β’ Confirm that the margin is expressed in feet of KG (vertical center of gravity), not in percentage or any other unit. β’ Before picking an answer, quickly subtract the two KG-related numbers and compare that small difference to the answer choices to see which are even numerically plausible.
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