Bonjean curves

Bonjean curves plot, for each station along the hull, the immersed cross-sectional area and its moment about a baseline as functions of draft at that station. They let a naval architect read off section areas at any waterline, including a trimmed or wave-profile waterline, then integrate longitudinally to get displaced volume, LCB, and VCB for a non-level flotation. This is the standard route to launching calculations, longitudinal strength in waves (still-water and wave-profile buoyancy distribution), and flooding studies where the waterline is not parallel to the keel. Named after the French engineer Bonjean. They are drawn on the ship’s profile, one curve per station.