mainsail n : the lowermost sail on the mainmast

English

Noun

mainsail

1. The largest (or only) sail on a sailing boat

Translations

• Finnish: isopurje
• French: grand-voile

A mainsail is the most important sail raised from the main (or only) mast of a sailing vessel.

On a square rigged vessel, it is the lowest and largest sail on the main mast.

On a fore-and-aft rigged vessel, it is the lowest and largest and often the only sail rigged aft of the main mast, and is controlled along its foot by a spar known as the boom. A sail rigged in this position without a boom is generally called a trisail, and is used in extremely heavy weather.

The modern bermuda rig uses a triangular mainsail as the only sail aft of the mast, closely coordinated with a jib for sailing upwind. A large overlapping jib or genoa is often larger than the mainsail. In downwind conditions (with the wind behind the boat) a spinnaker replaces the jib.

Traditional fore-and-aft rigs used a gaff to control the top of the mainsail, sometimes setting a topsail above it.