Skeg
From Wikipedia, the free encyclopedia
A skeg (or skag) is a sternward extension of the keel of boats and ships which have a rudder mounted on the centre line. In more recent years, the name has been used for a fin on a surfboard which improves directional stability and to a moveable fin on a kayak which adjusts the boat's centre of lateral resistance.
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[edit] Origins
The word originates in the Scandinavian word for beard; in Old Norse, skegg. In modern Norwegian Bokmål and Nynorsk, it appears as skjegg, in Swedish, it is skägg and in Danish, skæg. The Norwegian pronunciation of the letter combination sk is as in the English sh. The word is related to the English shaggy. It also appears in the English place name Skegness - 'beard point', from the way in which a series of tombolos forms, towards the nearby Gibraltar Point. Here, the English pronunciation reflects a probable Danish origin, which pronounces the sk letter combination as an English speaker would expect. However, 'Skegness' is pronounced with an un-Danish hard 'g'.
[edit] In boats and ships
Where a vessel's rudder is mounted on the centre-line, it is usual to hang it on gudgeons and pintles, the latter being upright pins and the former, rings to fit round them. Together, they form a hinge. This naturally leaves a small gap between the sternpost and the rudder, into which stray items like kelp and rope can catch, causing drag and threatening the security of the vessel's steering. In ships such as Mary Rose and HMS Victory, the skeg is a very small feature; a tapered extension of the keel below the leading edge of the rudder. This somewhat beard-like sternward extension of the keel is the basic skeg. Subsequently, the lowest pintle was commonly mounted below the rudder on a metal extension of the keel. This helped further stabilize and protect the rudder and the name, skeg was transferred to it. It used still to be relatively small until screw propellers were introduced, when it had to reach below the screw and became a proportionately larger fitting protecting both screw and rudder from damage.
In more modern installations, with more than one screw, a fitting supports each propeller shaft just ahead of its screw. This is usually called a shaft bracket but the part of it which extends below the shaft bearing to protect the lower part of the propeller is also a skeg. Similarly, the protective projection of the drive casing, below the rotational axis of the propeller of an outboard motor is another form of the skeg.
Where a yacht is designed with a fin keel, it will normally, also have a skeg-mounted rudder. This link shows the profile of such a boat. This type of skeg is pictured at the bottom of the same linked page.
[edit] Surfing
In the vocabulary of surfers, a skeg is a stabilizing strut or fin located at the rear of the surfboard. A surf board skeg improves the board's fundamental directional stability and enables directional control by banking: varying the surfer's side to side weight distribution.
The skeg was introduced in 1936 by Woody "Spider" Brown", later inventor of the modern catamaran, when he built America's first modern surfboard (i.e., capable of being surfed standing up) using principles learned during his decade of aeronautical experience.[1] Despite this, it is usually attributed to Tom Blake. Blake claimed to have removed a skeg from a water ski then screwed it onto the bottom of his solid wood board (not capable of being surfed standing up). Brown, whose later invention of the catamaran was subsequently patented by Hobie Alter, similarly refused to contest this claim.
Small single aluminum skegs first evolved into single larger wooden, then fiberglass/wood versions. In time hydodynamic streamlining took place, pioneered by George Downey who also created the first removable skeg, a teak wood skeg in a teak wood box which was supposed to hold in place due to the swelling of woods in water. Today (2007) one, two... sometimes as many as five smaller skegs are employed.
[edit] Kayaks
A skeg is employed in the type of kayak used on more open water such as the sea. Its purpose and use are rather different from those of the surfing skeg. In the kayak, the amount of the exposure of the skeg to the water; therefore of its effect on the position of the boat's centre of lateral resistance (c.l.r.) is freely variable by the crew. This varies its relationship with the effect of the wind on the upper parts of the combined boat and crew. In more conventional calculations, this would be the centre of effort of the sail area (c.e.). In still water, where the wind is pushing the boat sideways, a contrary force (lateral resistance) develops, resisting that movement. If the central points of the application of those two forces coincide, the boat moves steadily sideways. Otherwise, it rotates in the horizontal plane, until they are in line. By varying the c.l.r., it is possible to control the boat's attitude towards the wind. Irregular flowing movement of the water complicates the issue. This link explains its subtleties in respect of the kayak skeg.
[edit] Yorkshire dialect
In Hull, a city on the eastern coast of Yorkshire, UK, 'skeg' is often used to mean 'look' - usually as a noun, but sometimes as a verb. Hence, "Gis a skeg," meaning, "Could I please look?"; and (as a verb) "Skeg out the state a that daft silly git," meaning "Have you noticed the eccentric nature of that person over there?"
[edit] Slang
Skeg is an abbreviation for Skegness
[edit] References
- ^ Davison, Phil (2008.05.03) Record-breaking aviator who became a legendary surfer The Financial Times (obituary)
[edit] External links
- This site shows the fins on a surf kayak, a boat combining some of the features of a kayak with some of a surf board.
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