Some North Carolina studies paired nine 14-inch guns with a proposed speed of 30 knots, opening a broader question about what extra speed buys. Moving from 21 to 28 knots can transform strategic mobility, while moving from 36 to 40 knots consumes disproportionate power and tonnage for a smaller operational gain. Aircraft also reduce the protective value of being only a few knots faster than an enemy capital ship. Greater machinery power density makes it easier to combine useful fleet speed with battleship protection. The Queen Elizabeth class illustrates the earlier constraint: the machinery installed did not deliver the speed needed for the fast-battleship role described here. A hypothetical 26-knot Queen Elizabeth in 1913 or 1914 would probably have earned that description, although 28 knots would have been needed to keep pace with the cruiser line.
Notable Point · 1:37:12-1:42:12
When extra battleship speed stops paying
As machinery power density improved, designers could combine useful fleet speed with battleship protection instead of sacrificing armor for a few diminishing knots.