Center of flotation (F)

The center of flotation F is the centroid of the waterplane area, the point about which the ship trims and heels for small changes of draft or load. Adding or removing a small weight directly over F changes mean draft without altering trim; placed away from F, the weight produces a trimming moment about F. Its longitudinal position LCF sets the moment arm in trim calculations and enters the moment to change trim one centimeter. F generally lies aft of midships in fine-sterned forms and shifts with draft because the waterplane shape changes. It is read from the curves of form against draft.