Class 4 (4th Engineer) SC&S 📅 Jan 2025

Exam Question

(a) Describe the provisions of additional structural strength to withstand pounding. (6)

(b) A ship is turning at 17 knots turns with a radius of 450 m when the rudder is put hard over. The centre of gravity is 7 m above the keel, the transverse metacentre 7.45 m above the keel and the centre of buoyancy 4 m above the keel. If the centripetal force is assumed to act at the centre of buoyancy, calculate the angle of heel when turning. The rudder force may be ignored. (10)

Reference Answer

### (a) Provisions of Additional Structural Strength to Withstand Pounding (6 Marks)
Pounding, or slamming, is the phenomenon where the ship's bow or forward bottom emerges from the water in heavy seas and re-enters with a severe, high-impact hydrodynamic load. This generates immense local and global stresses. To withstand these forces, significant structural reinforcement is provided in the forward region of the ship, typically extending over the forward 25% of the ship's length from the collision bulkhead.
Key structural provisions include:
1. **Increased Bottom Shell Plating Thickness**: The shell plating in the flat-of-bottom area forward of the 0.25L point is significantly thicker than the plating amidships. Classification society rules mandate this increase to resist the high impact pressures and prevent local deformation and damage.

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