Trysail

A trysail (also known as a spencer[citation needed]) is a small triangular or gaff rigged sail hoisted in place of a larger mainsail when winds are very high.

It is hoisted abaft (i.e., directly behind) the mainmast (taking the place of the much larger mainsail) or, on a brig, abaft the foremast.

In the Royal Navy in the late nineteenth century, the term 'trysail' came to denote the main fore-and-aft sail on any mast.

This included the mainsail of the 'great brig' HMS Temeraire, the largest fore-and-aft sail ever used by a warship.

Naval trysails were usually gaff-rigged and 'loose-footed', with a spar along the head but no boom, and small auxiliary trysails continued in intermittent use into the 1920s for seakeeping and station-keeping.