What is the righting arm (GZ)?

The righting arm, often referred to as GZ, is defined as the horizontal distance between the center of gravity and the center of buoyancy when the vessel is heeled over. This distance is crucial in stability calculations, as it represents the lever arm that acts to return the vessel to an upright position after it has been inclined. The greater this distance, the more force there is to right the vessel, enhancing stability and reducing the risk of capsizing.

When a vessel heels, the center of buoyancy shifts, which creates this horizontal distance from the center of gravity. The righting arm is essential for assessing how effectively a vessel can recover from heel, making it a central concept in naval architecture and stability assessments.

The other options do not accurately represent the concept of the righting arm. The force acting on the center of gravity does not define GZ and is related to the overall forces impacting the vessel rather than the specific stability mechanics. The vertical distance from the center of buoyancy to the keel describes the metacenter and the vessel’s geometry but not the righting arm itself. The total length of the vessel from bow to stern is a measurement of size but has no direct correlation with the forces affecting its stability in relation to GZ.