The process is the opposite of what seems to explain the phrase in quotes. You need to calculate the water plane, fot the same displacement, the ship has at various heeling. For each float you calculate the center of buoyancy and, done that, deduct the value of KN. With it you get a series of values of KN for the same displacement, at several heeling.
The process for 3 or 4 other displacements is repeated (for the same set of heeling used above) and then you connect with a spline points corresponding to the same heel.
