Nelson and Rodney came in roughly 1,000 to 1,500 tons below the treaty ceiling, leaving a theoretical margin for a longer hull and stronger machinery. Boiler count and steam generation, rather than turbine footprint, were the main machinery differences among the O3, F2, and F3 concepts. A bank of roughly twelve higher-output boilers instead of Nelson's eight Admiralty three-drum boilers points toward F3-like performance. Period naval architects believed two shafts could carry the power, though sustained high-speed work would increase machinery wear. Dropping to 15-inch/50 guns could free further weight, while F3's longer arrangement also improved forward gun clearance and the ability to choose the engagement angle.
Notable Point · 46:22-52:21
A thousand tons could buy Nelson more speed
Nelson's margin below the 35,000-ton ceiling could fund a longer hull and more boiler power, but driving high output through two shafts would raise wear.