Beam

Beam is the maximum width of a vessel, measured across the hull at its widest point, usually near amidships. It is a primary dimension in boat design and documentation, alongside length and draught. In seamanship, a bearing “on the beam” also means roughly 90 degrees to the vessel’s fore-and-aft line, either to port or starboard.

Beam affects stability, interior volume, deck layout, berth choice and handling. A wider Hull can resist Roll better and carry more form stability, but may create more drag or slamming in steep seas. When planning marinas, canals, locks or transport, beam is checked with Draft and overall length to confirm clearance and safe manoeuvring room.

For route and weather decisions, beam helps interpret comfort and risk: broad multihulls, narrow monohulls and powerboats respond differently to cross seas, swell and gusts. PredictWind Weather Routing, wave forecasts and polars support decisions about headings and departure windows that suit your vessel’s beam and motion characteristics.