USCG Stability Practice Test

The impact of Gm, which refers to the metacentric height, is crucial in understanding the statical stability of a vessel. Gm contributes to how a vessel behaves in response to heeling.

When a ship begins to tilt or heel, the point of buoyancy shifts, and the metacenter (M) serves as a pivot point for the ship's center of gravity (G). The height of Gm is integral in determining the magnitude of the righting lever arm (GZ). At small angles of inclination, the established righting arms tend to be predominantly influenced by Gm, making this parameter significant in this range.

However, as the angle of heel increases, other factors, such as the shape of the hull and the distribution of weight, become more influential. Therefore, while Gm has a significant role at small angles, its effectiveness diminishes as the vessel heels beyond these angles. This understanding highlights why the correct choice emphasizes Gm's influence primarily at smaller inclinations, where its effect is more pronounced in creating righting moments.