Daggerboard

A daggerboard is a retractable centreboard used by various sailing craft. While other types of centreboard may pivot to retract, a daggerboard slides in a casing. The shape of the daggerboard converts the forward motion into a windward lift, countering the leeward push of the sail. The theoretical centre of lateral resistance is on the trailing edge of the daggerboard.

Characteristics

Daggerboards are often long and thin, thus providing a better lift-to-drag ratio. Daggerboards are usually found in small craft such as day sailers, where their size is easily handled by a single person. Daggerboards are not usually ballasted, but are locked in place by a clip. They are raised vertically unlike a centreboard which can be set at different angles to the hull of the boat.

When a daggerboard is extended through the keel, it improves a ship's stability. Daggerboards can be raised when the a ship enters a shallow harbor, allowing the boat (for example) to load and unload cargo in locations that would not otherwise be accessible to larger ships.