Class 4 (4th Engineer) SC&S 📅 Dec 2024

Exam Question

(a) What is the significance of GM-GZ curve? (6)

(b) The pitch of a propeller is measured by means of a batten and cord. The horizontal ordinate is found to be 40 cm while the vertical ordinate 1.15 m at a distance of 2.6 m from the centre of the boss. Calculate the pitch of the propeller and the blade width at that point. (10)

Reference Answer

### (a) Significance of the GM-GZ Curve (Curve of Statical Stability)
A neat, fully labelled diagram of the GZ curve versus angle of heel is essential for full marks and should be drawn by the candidate.
The GM-GZ curve, also known as the Curve of Statical Stability, is the most comprehensive graphical representation of a vessel's transverse static stability. Its significance lies in its ability to define the stability characteristics of a vessel at all angles of heel, from zero until the point of capsize. While the initial metacentric height (GM) is an indicator of initial stability only (valid for small angles, typically < 7-10°), the GZ curve provides a complete picture.
The key information derived from the curve is as follows:

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