What is a "stability/GZ curve"?

A stability/GZ curve is a critical tool in naval architecture used to visualize how a vessel behaves as it tilts or heels to one side. The GZ, or righting arm, represents the distance between the vertical centerline of the vessel and the center of buoyancy when the vessel is heeled at a specific angle. As the angle of heel increases, the stability of the vessel will change, which directly affects its ability to return to an upright position. The curve graphically depicts this relationship, illustrating how the righting arm varies with different angles of heel.

Understanding the stability/GZ curve is essential for determining the safety and seaworthiness of a vessel. A larger righting arm indicates greater stability, while a decreasing righting arm as heel increases suggests a potential for capsizing. This curve is fundamental for assessing how a vessel will respond to external forces such as wind and waves, thus allowing mariners to make informed decisions regarding load management and operational practices.