A harbour-defence ship could omit masts because it operated within reach of help. If its engines failed, another ship in company could tow it or a nearby base could send assistance. A Royal Navy warship expected to circle the globe could not depend on the same rescue arrangements. Auxiliary sail therefore remained useful on long voyages even when it compromised turret arcs. The acceptable risk of engine failure depended on where the ship would serve.
Notable Point · 21:13-21:49
Why coastal turret ships could abandon sail sooner
Engine-only turret ships were more acceptable for harbour defence because a nearby base or another ship could provide help after a breakdown.