Beam (nautical)

The maximum beam (BMAX) is the distance between planes passing through the outer sides of the ship, beam of the hull (BH) only includes permanently fixed parts of the hull, and beam at waterline (BWL) is the maximum width where the hull intersects the surface of the water.

[1] Generally speaking, the wider the beam of a ship (or boat), the more initial stability it has, at the expense of secondary stability in the event of a capsize, where more energy is required to right the vessel from its inverted position.

Some examples: As catamarans have more than one hull, there is a different beam calculation for this kind of vessel.

The BOC for vessels is measured as follows: For a catamaran: the perpendicular distance from the centerline of one hull to the centerline of the other hull, measured at deck level.

For a trimaran: the perpendicular distance between the centerline of the main hull and the centerline of either ama, measured at deck level Other meanings of 'beam' in the nautical context are: