Question 4743 Deck General

The correct answer is D) natural roll period. Laying down drill pipe from the derrick of a semisubmersible reduces the weight on the top of the structure, which in turn decreases the vessel's natural roll period. The natural roll period is the time it takes for the vessel to complete one full roll cycle. Reducing the weight aloft decreases the vessel's moment of inertia, resulting in a shorter natural roll period. The other options are incorrect because: A) Waterplane area is not affected by the change in weight distribution. B) Metacentric height, which determines the vessel's stability, is also not directly affected by the weight change. C) Righting moment, the force that returns the vessel to an upright position, is not reduced by laying down the drill pipe.