Daggerboard
From Academic Kids
A daggerboard is a type of centreboard used by various sailing craft. Daggerboards are symmetric foils that enable a craft to beat upwind, i.e. to make progress upwind without sliding to leeward excessively. The shape of the daggerboard converts the forward motion into a windward lift, countering the leeward push of the sail.
While other types of centreboard may pivot to retract, a daggerboard slides in a casing. Daggerboards are often longer and thinner than centerboards, 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. Unlike centreboards, daggerboards are not usually ballasted, but are locked in place by a clip.
If a daggerboard is located off center, then it is called a leeboard or a bilgeboard. See also keel.
The Mirror Dinghy, for example, uses a plywood daggerboard.
