What happens to a vessel's stability if its center of gravity is raised?

When the center of gravity of a vessel is raised, the vessel's stability decreases. Stability in a floating vessel primarily relies on the relationship between the center of gravity (CG) and the center of buoyancy (CB). The center of buoyancy is the point where the buoyant force acts, and it acts vertically upwards through the center of the submerged volume of the hull.

When the CG is elevated, the metacentric height (GM) diminishes. Metacentric height is a critical factor in determining a vessel's stability—the greater the GM, the more stable the vessel is, as it will return to an upright position more readily after being tilted. By raising the CG, the distance from the center of buoyancy to the center of gravity reduces, leading to a lower metacentric height. As a result, the vessel becomes less stable, making it more prone to capsizing under lateral forces or tilting.

When considering the fundamental principles of stability, it’s important to understand the impact that the vertical position of CG has on the overall balance of the vessel. Thus, when the CG is raised, the loss of stability poses risks in rough seas and while maneuvering.