Longitudinal center of buoyancy (LCB)

The longitudinal center of buoyancy LCB is the fore-and-aft position of the centroid of the displaced volume, quoted as a distance from midships or from the after perpendicular, or as a percentage of length. It must lie on the same vertical as the LCG for the ship to float without trimming, so LCB drives the trim balance in design and loading. Its optimum position for low resistance shifts with Froude number: fuller, more forward LCB suits low-speed full forms, finer, more aft LCB suits higher-speed hulls, a relationship captured in standard-series resistance data. LCB is read from the curves of form against draft and computed from the Bonjean or section-area distribution.