Class 4 (4th Engineer) SC&S 📅 Jun 2023

Exam Question

(a) Sketch the curve of statical stability for a ship with positive initial GM and indicate the following clearly: maximum value of GM, angle of heel at which maximum GZ occurs, angle of vanishing stability, Range of positive stability, Initial GM. (10)

(b) What is dynamical stability and how can it be ascertained from the curve. (6)

Reference Answer

### (a) Curve of Statical Stability
A curve of statical stability is a graphical representation of a ship's transverse stability at various angles of heel. The righting lever (GZ), in metres, is plotted on the Y-axis against the angle of heel (θ), in degrees, on the X-axis. This curve is specific to a particular displacement and vertical centre of gravity (KG) of the ship.
For a ship with a positive initial GM, the curve starts at the origin, rises to a maximum value, and then decreases, eventually crossing the X-axis at the angle of vanishing stability.
The following points are indicated on the curve:

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