R-class speed and machinery tradeoffs

The R class has an attractive single-funnel arrangement and some pleasing shaping, but the specifications expose the cost of the machinery choices. The Revenge class is only about seven meters shorter and 0.6 meters narrower than the Queen Elizabeth class, with the same quoted draft, yet its speed falls from 24 to 21 knots. Its 18 Babcock and Wilcox boilers produce 40,000 shaft horsepower, compared with 75,000 from the Queen Elizabeth class's 24 water-tube boilers. The episode argues that 18 small-tube boilers could have delivered Queen Elizabeth-level power, which makes the reduction difficult to justify. The quoted range does favour the R class in one respect: 7,000 nautical miles at 10 knots against 5,000 nautical miles at 12 knots. Even so, the limited dimensional and machinery savings chiefly lowered the advertised price rather than producing a comparable design advantage.