🔍 Key Concepts

• Relationship between roll period and metacentric height (GM) for a vessel in ocean transit • How to estimate maximum safe roll angle so that structural limits (like jack-up legs) are not exceeded • Typical range of roll angles for a relatively stiff vessel (short roll period) in a seaway

💭 Think About

• Given a roll period of 4 seconds, is the vessel relatively stiff (large GM) or tender (small GM)? How does that affect expected roll angles? • Think about what kind of roll angle would start to create high loads on the legs of a jack‑up rig in transit. Would the design limit likely be very small, moderate, or very large? • Compare the choices: which angles would be realistic as an operational limit for a stiff unit with sensitive structural members (legs)?

✅ Before You Answer

• Confirm that a shorter roll period generally corresponds to larger GM and smaller roll angles in a given sea state • Consider that jack‑up legs in transit are not meant to take large dynamic bending moments, so the allowed angle is usually conservative • Rule out any option that would clearly be too comfortable or too extreme for a structural design limit in ocean transit