Class 4 (4th Engineer) SC&S 📅 Jul 2022

Exam Question

(a) Briefly explain with sketches on moment of static stability at small angle of heel, give the Factors responsible for making the ship tender or stif.(10)

(b) A ships displacement is 12400 t and CG position from keel is 9.8 m. A bulk cargo weighing 298t was removed from the lower bottom (KG = 1.85m). Calculate the final KG (6)

Reference Answer

### (a) Moment of Static Stability and Factors for Tender/Stiff Condition
#### 1. Moment of Static Stability
When a ship is heeled by an external force (e.g., wind, waves), its underwater volume changes shape, causing the center of buoyancy (B) to shift to a new position (B₁). The ship's weight (W) continues to act vertically downwards through the center of gravity (G), while the force of buoyancy (Δ or W) acts vertically upwards through the new center of buoyancy (B₁).
These two equal and opposite forces form a couple. The moment of this couple, which tends to restore the ship to its upright position, is known as the **Moment of Static Stability** or the **Righting Moment (RM)**.

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