Longitudinal framing

Longitudinal framing runs the primary stiffeners along the ship’s length, parallel to the keel, supported at intervals by transverse web frames and bulkheads. It outperforms transverse framing for resisting hull-girder bending because the longitudinals contribute directly to the deck and bottom section modulus and resist plate buckling under the in-plane compression that bending produces. Isherwood introduced the system in 1906; modern tankers and bulk carriers use it on deck and bottom, often with transverse framing kept in the side shell, a mixed arrangement. Frame (longitudinal) spacing is typically 0.7 to 0.9 m. The penalty is more intersections and end connections to detail and weld.