Deck General · Metacentric Height (GM)
If a vessel's rolling period is observed to have lengthened significantly since departure, a prudent officer should suspect:
- AAn increase in GM caused by consuming low ballast
- BA reduction in GM possibly caused by consuming fuel from double-bottom tanks or free surface in slack tanks✓ Correct
- CThe vessel has trimmed by the stern
- DThe metacenter has moved upward during the voyage
Explanation
Longer rolling period indicates reduced GM. During a voyage, consuming fuel and water from low tanks removes mass from below G, causing G to rise and GM to decrease. Slack tanks from partially consumed double-bottom tanks also add free surface effect, further reducing effective GM.
Authority: Stability & Trim (USCG deck topic)
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