Scarce high-performance freighters could carry cargoes that truly required speed. Ordinary convoy work could instead accept the Liberty ship's roughly 11-knot performance. Two oil-fired boilers, one triple-expansion engine, and a single screw supplied enough propulsion for that mission without competing for advanced machinery. The design was efficient because its speed matched the delivery system it actually served.
Chapter · 39:24-40:14
Liberty ship speed fits ordinary convoy delivery
An 11-knot freighter with modest machinery could meet the central requirement of moving ordinary cargo reliably through wartime convoys.