Centreboard

In shipbuilding and seafaring is meant by a sword parallel to the direction perpendicular pushed on storm sails through the hull plate of steel, wood or fiberglass to reduce the drift or the implementation of the drift into propulsion. A catamaran can be equipped with swords, such as the Tornado.

Besides the main type, the central swords, one differentiates (two side boards inside the hull ) between the side swords ( laterally outboard mounted at Ewern and other coastal sailing vessels corresponding surfaces ) and Kimmschwertern; Kielschwerter to the merits of the sword, and made ​​up for the ballast keel together.

The depth of the sword can usually be adjusted continuously. This makes maneuvering in shallow water and allows for higher speeds by a pulling up the sword in downwind and vorwindnahen Raumschotskursen, as less water resistance is reduced. An adjustable blade is surrounded by a sword box.

A sword as part of the lateral plane has the function to reduce lateral drift. This is done firstly by the existing surface, on the other hand (especially at higher speeds ) by the dynamic lift of the adjacent laminar flow. It has - except for the ballast sword - for lack of weight no significant static protection against capsizing, such as a fin keel. The sword absorbs through the side water resistance to lateral movement and stabilizes the dinghy. A dinghy with fully Caught-up sword lost much one of stability.

Mechanisms

Most common is the folding sword, which is fastened at its head end in a direction transverse to the direction of axis. The head itself shows in the same direction, that is, the sword folds rearward facing from. With a grounding can therefore be folded back, which prevents may involve greater damage to the boat the sword. The height adjustment of the sword is done with light swords by two opposing lines ( sword case and vang ). Disadvantage of this design is the larger space required for the daggerboard - When ballast swords a rope to catch up, which can be translated to the power savings through a block and tackle ( pulley ) is sufficient.; some ballast swords are operated by crank drives or hydraulic.

Another embodiment provides non-rotatably mounted clamping sword or plug - sword represents the height adjustment happens by pushing up or down, while the sword stuck through his special form itself firmly in sword box. Disadvantage of this design is the increased stress of the sword at the edges and the opposite the folding sword not as precise and durable adjustable position. In addition, a fully caught up sword must usually be completely removed from the centreboard case and stowed on deck.

• Marine equipment