What occurs to the GZ curve when GM is increased?

• A. The curve becomes flatter
• B. The curve steepens, indicating improved stability
• C. The curve shifts to the left
• D. The curve remains unchanged

Answer: (B)

When the metacentric height (GM) increases, the GZ (righting lever) curve steepens, which indicates an improvement in the vessel's stability. The GZ curve represents the righting arm (GZ) as a function of the angle of heel. A higher GM results in a greater righting arm for a given angle of heel, which translates to increased stability.

This steepening of the curve demonstrates that the vessel will have a more substantial righting moment at any given angle of heel, meaning that it can recover more effectively from heeling or listing. A larger value of GM signifies that the center of buoyancy rises more in relation to the center of gravity as the vessel heels, thus enhancing the vessel's stability. Consequently, it will return to an upright position more readily, making the vessel safer and improving its performance in various sea conditions.

The other options do not accurately represent the relationship between increased GM and the GZ curve. For example, the curve becoming flatter would suggest a decrease in righting ability, which contradicts the purpose of increasing GM. Shifting the curve to the left would imply a reduction in stability at smaller angles of heel, and unchanged suggests there is no variation in stability despite an increase in