Length between perpendiculars (LBP)

Length between perpendiculars, LBP (or LPP), is the horizontal distance from the forward perpendicular to the after perpendicular, measured along the design waterline. The FP is at the stem-waterline intersection and the AP is conventionally at the after side of the rudder post or, where there is none, at the rudder stock axis. LBP is the length classification rules and the load-line convention use for scantlings, freeboard, and most form coefficients, because it excludes the bow and stern overhangs that LOA includes and is therefore a stable measure of the working hull. Block, prismatic, and waterplane coefficients are commonly defined on LBP or LWL; the choice must be stated, since the two differ on raked-stem hulls.