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

Exam Question

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

(b) The pitch of a propeller is measured by means of 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 GM-GZ Curve
The **GM-GZ curve**, also known as the **Static Stability Curve** or **Righting Lever Curve**, is a fundamental tool in naval architecture and marine engineering for assessing a vessel's stability characteristics. It provides a comprehensive graphical representation of a ship's stability across its full range of heel angles, which is critical for ensuring safety and compliance with international regulations.
#### 1. Metacentric Height (GM)
GM represents the **Metacentric Height**, which is the vertical distance between the vessel's centre of gravity (G) and the transverse metacenter (M). Its significance is primarily in assessing a ship's *initial static stability* at small angles of heel (typically up to 10-15 degrees).

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