While in ocean transit, the COASTAL DRILLER experiences a single amplitude roll of 5 degrees. What is the minimum roll period that does not exceed the design limits of the legs?
• Relationship between roll period and GM (metacentric height) • How shorter vs longer roll periods affect acceleration and structural loads at a fixed roll angle • Basic proportionality of angular acceleration with respect to roll period for a given amplitude
• For a fixed roll angle of 5°, what happens to the rate of motion and acceleration if the period is very short compared to if it is longer? • If the legs have a maximum allowable dynamic load, would that be exceeded more easily by a quick, snappy roll or by a slow, gentle roll? • Among the choices, which period would give the least severe dynamic loading on the legs for the same 5° amplitude?
• Be clear that roll period is the time for a complete roll cycle, not the angle itself. • Remember that, for a given angle, shorter periods mean higher accelerations and forces; longer periods mean lower accelerations. • Before picking an option, compare which choice would keep dynamic loads on the legs within design limits by making the motion less violent.
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