A daggerboard is a type of keel used by sailing craft. It is housed in a receptacle, or sheath, on board the ship and is dropped into the water when necessary. These keels garner their name from their shape, which has one long, flat edge along the back and a slightly curved edge along the front. This curved edge will face into oncoming water when the board is dropped.
Daggerboards are used when a ship is beating into the wind, which means that it is attempting to travel in the same direction that the wind is coming from. Proper sail techniques and ship positioning can take advantage of wind, even if it is coming almost head-on. A daggerboard provides lift to the boat when dropped into the water, preventing it from bogging down. They are simple to operate, typically coming equipped with a release that allows them to be quickly dropped when needed, and a winch to retract them.
Another type of lift-producing board, the centerboard, is often confused with the daggerboard. While both types are located under the center of a ship, a centerboard is able to pivot underwater, whereas a daggerboard is not. Also, a centerboard cannot be retracted, allowing only a ship equipped with a daggerboard able to access shallow water.
Currently, the preference in boat-building — and specifically in catamarans — is to use a centerboard model. This is because the cost of adding dual daggerboards to a catamaran is far more expensive than a centerboard. The board must also be retracted at the correct time in order to safely sail the boat. If the boards are not hauled in when the boat is in shallow water or is beached, serious damage could result. For this reason, daggerboard-equipped vessels tend to be preferred by purists and sport sailors, rather than the general public or charter vessels.
It is essential that daggerboards and their housings, which are usually made of wood, be crafted properly. The housings, which are commonly known as trunks, must be solidly constructed in order to hold the keel when not in use, and also to prevent the board from rattling around or shifting position. If the shape of the board is deformed due to excessive wear and tear while in the trunk, it will not perform properly. This can limit or even cripple the performance of a ship.