Longitudinal center of flotation (LCF)

The longitudinal center of flotation LCF is the fore-and-aft position of the centroid of the waterplane, the axis about which the ship trims. A weight added or removed over LCF changes mean draft without trimming; placed elsewhere it generates a trimming moment equal to weight times the longitudinal distance from LCF. LCF therefore sets the lever in every trim calculation and in the moment to change trim one centimeter. It usually lies aft of midships in fine-sterned hulls and moves with draft as the waterplane changes shape. It is read from the curves of form and computed as the first moment of waterplane area over waterplane area.