Longitudinal metacenter (ML)

The longitudinal metacenter ML is the point where successive lines of buoyant action intersect the ship’s centerplane for small changes of trim, the trim analogue of the transverse metacenter. Its height above the center of buoyancy, BML, equals the longitudinal moment of inertia of the waterplane divided by displaced volume (BML = I_L / V), and because I_L is large, BML and the resulting GML run on the order of the ship’s length, far larger than the transverse BM. The large GML is why ships are stiff in trim. GML feeds the moment to change trim one centimeter, MCT1cm = (displacement * GML) / (100 * L).