🔍 Key Concepts

• Tow limitations for mobile offshore drilling units (MODUs), including maximum allowable single-amplitude pitch during ocean tow • How increasing draft on a semi-submersible rig affects motion characteristics (pitch, heave, acceleration) in a seaway • Relationship between wave period and vessel natural period and why an 8‑second pitching period might be important

💭 Think About

• Compare a 7.5° single-amplitude pitch against typical safe tow criteria for MODUs—does this sound conservative or excessive for a long ocean tow? • Think about what happens to a semi-submersible’s waterplane area, metacentric height (GM), and motion response when you increase draft from a shallow, near-transit draft toward a deeper operating draft. • Ask yourself which options actively reduce pitching motions versus which options mainly change heading or simply rely on monitoring without changing the underlying cause.

✅ Before You Answer

• Verify whether 7.5° single-amplitude pitch is within commonly accepted limits for safe MODU towing; if it exceeds typical guidance, a corrective action is usually required. • Check which ballasting option (if any) moves the rig toward a more typical transit/operating tow draft used to reduce motions and improve stability margins. • Confirm whether simply altering course into the wind or just monitoring motions is considered sufficient when measured motions are already at or beyond recommended limits.