KN curve

A KN curve is a single cross-curve of stability giving the righting arm measured from the keel, KN, as a function of displacement at one fixed heel angle, computed for an assumed center of gravity at the keel. Because KN is referenced to K and not to the actual G, it is a pure hull property independent of loading. The true righting arm at a real condition follows from GZ = KN minus KG * sin(theta), subtracting the correction for the actual vertical center of gravity. A family of KN curves at several heel angles forms the cross-curves of stability, the input to building the GZ curve for any loading.