🔍 Key Concepts

• Relationship between roll period and stiffness/GM (metacentric height) of the unit • How design limits for leg stresses are linked to maximum safe roll angle in good weather • Why a longer roll period generally means a different allowable roll angle than a very short, “stiff” roll

💭 Think About

• Compare what a 9‑second roll period tells you about how quickly and violently the unit is rolling—would that normally allow a larger or smaller angle before leg stresses become critical? • Think about typical "good weather" operating limits for a MODU’s legs: are they usually just a few degrees, or can they be quite large before design limits are reached? • Look at the answer choices and ask yourself which value is most consistent with a moderate roll period and a conservative design limit for structural safety of the legs.

✅ Before You Answer

• Be sure you understand that roll period alone doesn’t give the angle; it’s used with design criteria/curves or tables provided for that specific unit (like COASTAL DRILLER). • Confirm that in good weather the unit would not be operating near extreme survival angles, so the limit should be conservative but realistic. • Before choosing, eliminate any angle that seems unrealistically small for normal good‑weather operations or too large to keep leg stresses within design limits.