Back a Sail

To trim or hold a sail so the wind presses on the side opposite its normal driving side.

A backed headsail can push the bow away from the wind during a tack, help balance a vessel when hove to, or drive the vessel astern in a controlled manoeuvre. A sail may back unintentionally when the apparent wind crosses it.

The effect depends on which sail is backed, helm position, keel and hull form, wind strength and momentum. Sheets and booms can load or move abruptly, so crew should remain clear of their paths.