Sails & rigs
Trysail
A small heavy-weather mainsail set when the normal main is too large or unsafe.
DutchTrysailour Dutch loft →
A trysail is a small, very strong storm mainsail used when the regular main is reefed as far as it can sensibly go, or when carrying it at all would be too hard on the boat. It usually has no boom attachment; the clew is sheeted to strong points aft so the sail can work without loading the boom.
The shape is flat and simple. In storm conditions the aim is not speed, but control: enough drive to keep the bow behaving and enough balance to reduce strain on the helm. Compared with a normal main, a trysail has far less area and much heavier cloth and reinforcement.
Many offshore boats use a separate mast track for it, so the trysail can be hoisted without removing the mainsail slides from the mast. That detail matters when the deck is no place for careful threading.