At what speed was the Revenge hull most efficient?

Was the Revenge-class hull hydrodynamically designed to be most efficient at about 20 knots?

Not exactly; it could operate in the low twenties, but its strongest practical efficiency was probably nearer 12 to 18 knots.

A hull's attainable high-speed range differs from the speed around which economical cruising is optimized. Revenge and Queen Elizabeth hull forms were not radically different, and more power could push either faster. The Revenge class had a useful high-speed range in the low twenties, while its strongest practical efficiency was probably nearer 12 to 18 knots. Endurance and fuel economy are governed more often by cruising conditions than by a ship's headline maximum speed.