Quasi-static heel

Quasi-static heel is the steady inclination reached when an applied transverse moment varies slowly enough that roll inertia and damping are negligible, so the ship sits where the righting moment equals the heeling moment. It is the equilibrium read directly off the GZ curve at the intersection with the heeling-arm curve, used for steady wind, a sustained turn, a tow-line pull, or off-center loading. It contrasts with the dynamic case, where a gust or wave imparts energy and the ship rolls past the static equilibrium, the situation the IMO weather criterion addresses by comparing areas under the GZ curve. Quasi-static analysis gives the heel angle but not the dynamic margin.