Naval Historywith Dr. Alex

Q&A · 2:07:56-2:09:49

Why many battleships converged near 27 knots

Twenty-seven knots often marked a workable balance between hull form, machinery weight, fuel, armor, and armament before the power cost of additional speed rose steeply.

BattleshipsNaval EngineeringPropulsionWarship Design
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Question

Why did several battleship classes converge on a speed of about 27 knots?

Short answer

It was a design sweet spot before the machinery, weight, and fuel cost of more speed increased sharply.

Notes

Speed does not increase in a simple proportion to installed horsepower. Around 27 knots, many battleship designs found a practical balance between machinery volume, hull form, displacement, protection, weapons, and endurance. Pushing faster could require a sharply larger share of the ship for power and propulsion. A German dreadnought that lost a planned diesel center shaft yet retained similar speed shows how removing machinery weight can partly offset lost power. Naval design joins speed, displacement, and propulsion in one coupled set of tradeoffs.