Wikipedia
A mainsail is the most important sail raised from the main (or only) mast (sailing)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 (sail)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.Sail Types Category:Sailing vessels and riggingnl:grootzeil