Longitudinal framing

Longitudinal framing (also called the Isherwood system after British naval architect Sir Joseph Isherwood, who patented it in 1906) is a method of ship construction in which large, widely spaced transverse frames are used in conjunction with light, closely spaced longitudinal members.

Naval engineer J. Scott Russell, for instance, had built several longitudinally framed ships, including the SS Great Eastern.

The first commercial vessel constructed with the Isherwood system, the oil-tank steamer Paul Paix, of some 6,600 tons deadweight in 1908, was scrutinized by other shipbuilders and owners.

The success of it and the first general cargo liner to be constructed on the "Isherwood" system, the Gascony in early 1909, encouraged builders in a number of countries to use longitudinal framing as well.

They are in two parts called floors and side frames and, while necessary, subtract from cargo space inside the ship.