The London Naval Treaty allowance used for Tribal leaders did not apply to the J, K and N classes. The figures given are about 1,720 tons standard for the Js and Ks and nearer 1,800 for the Ns, against a nominal 1,850 for the Tribals. The Tribals themselves did not always meet their nominal standard displacement. Putting both boiler rooms together saved length, helped manoeuvrability and let the uptakes use a single funnel. Flooding in a large machinery space was dangerous on its own, and a hit in that area could put both rooms out of action.
Notable Point · 13:30-15:32
The J, K and N classes' adjacent boiler rooms
A shorter machinery arrangement made a compact, single-funnel destroyer and exposed both boiler rooms to damage in the same area.