Beam (B)

The beam B is the maximum breadth of the hull, the principal transverse dimension, normally quoted as molded beam to the inside of the shell plating or as extreme beam over the plating and rubbing strakes. It governs transverse stability through the metacentric radius BM = I_T / V, and since I_T scales with the cube of beam, a wider hull gains transverse stability fast. Beam also sets the beam-to-draft ratio that drives form resistance and roll behavior, fixes the deck area and container rows, and is constrained by canal and lock limits (the Panamax 32.31 m beam, the Suezmax draft-beam envelope). It appears in nearly every rule scantling and stability formula as the symbol B.