The design begins with oil fuel, geared turbines, an auxiliary diesel, the best available shafts and steering, a double bottom, and limited anti-flooding measures. These choices determine speed, range, reliability, and basic survivability. Even efficient 1940 machinery uses most of the small hull's allowance before guns or torpedoes are fitted. Very little weight remains for the systems that turn the hull into a fighting ship.
Notable Point · 3:03-6:01
Machinery consumes the small destroyer's weight margin
A 1940 destroyer's speed, range, machinery, steering, and basic flooding protection use much of its displacement before weapons arrive.