🔍 Key Concepts

• Leverage and moment arms when the rotary table is offset from the vessel’s centerline • How distance aft of the transom and offset to starboard affect allowable hook load on a MODU (Mobile Offshore Drilling Unit) • Structural or stability limits that may be imposed when loads are carried off-center

💭 Think About

• How does moving the rotary farther aft change the bending moment on the hull structure compared with a more central position? • What effect does a sideways (starboard) offset of the rotary have on the maximum safe hook load and why would this tend to increase or decrease the limit? • Among the answer choices, which values seem more consistent with a reduced allowable load due to increased moment, and which seem more like ‘full rated capacity’ numbers?

✅ Before You Answer

• Verify how moment = load × horizontal distance from the support point applies to this problem • Consider whether placing the rotary 34 feet aft and 2 feet to starboard would increase or decrease the structural moment compared to a rotary placed near the centerline • Before choosing, ask: does this new placement likely require a significant derating, a moderate derating, or only a small reduction from the design hook load?