What is the righting arm (GZ)?

The righting arm, commonly referred to as GZ, is defined as the horizontal distance between the center of gravity (G) and the center of buoyancy (B) when a vessel is heeled over. This measurement is crucial for understanding a vessel's stability, as it represents the lever arm that acts to bring the vessel back to an upright position after being tilted by forces such as wind or waves.

When a vessel is heeled, the center of buoyancy shifts, affecting the relationship between the center of gravity and the center of buoyancy. The longer the righting arm (GZ), the greater the force that acts to restore the vessel to an upright position, enhancing its stability.

The other options discuss aspects of stability and buoyancy but do not accurately define the righting arm. The vertical distance from the keel to the waterline pertains to draft, while the distance from the center of buoyancy to the center of gravity when heeled refers more to the critical point of stability but not specifically to GZ. The angle of tilt, while related to stability, does not define the horizontal distance necessary for calculating the righting arm.