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

Exam Question

(a) Show by means of diagrams how the centre of gravity of the liquid in a partly filled tank moves during rolling. (6)

(b) A box barge is 15 m long, 6 m wide and floats in water of 1.016 t/m³ at a draught of 3 m. 150 tonne of cargo is now added. Calculate the load exerted by the water on the sides, ends and bottom. (10)

Reference Answer

### (a) Movement of the Centre of Gravity of Liquid in a Partly Filled Tank During Rolling
When a vessel with a partly filled tank undergoes rolling, the free surface of the liquid within the tank shifts, leading to a dynamic change in the liquid's centre of gravity (CG). This phenomenon is known as the "Free Surface Effect" (FSE) and has significant implications for a vessel's transverse stability.
* **Initial State (Vessel Upright)**:
* When the vessel is upright, the liquid in the tank is level, and its centre of gravity (cg) is at a specific point, typically at the geometric centre of the liquid's volume, on the vessel's centreline.

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