A skeg (or skegg or skag) is a sternward extension of the keel of boats and ships which have a rudder mounted on the centre line.[1] The term also applies to the lowest point on an outboard motor or the outdrive of an inboard/outboard.[A][B] In more recent years, the name has been used for a fin on a surfboard which improves directional stability and to a movable fin on a kayak which adjusts the boat's centre of lateral resistance (it moves the center of resistance relative to the center of effort).[2] The term is also often used for the fin on water skis in the U.S. It has been used for the vertical fin on seaplane hulls and floats. The wear-bar on the bottom of snowmobile ski may also be called a skeg.
The word originates in the Scandinavian word for beard; in Old Norse, skegg. In Icelandic the word remains skegg, in modern NorwegianBokmål and Nynorsk, it appears as skjegg, in Swedish, it is skägg and in Danish, skæg. The Norwegian pronunciation of the letter combination skj is as in the Englishsh. 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.
In boats and shipsedit
A skeg-mounted rudder
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, 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 to be relatively small until screw propellers were introduced, when it had to reach below the screw and became a proportionately larger feature protecting both screw and rudder from damage.
On wooden vessels, the skeg may be protected from worm damage by the addition of a bug shoe, or a "a length of hardened material, such as ironbark, placed on the sternward keel extension (skeg) to protect from shipworm damage."[3]
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.
In surfing, windsurfing, and kitesurfing, skegs, usually known as "fins", are attached toward the tail of the board to improve directional stability and control through foot-steering. Fins allow the rider to control the board's direction by varying their side-to-side weight distribution.
Fixed fins were introduced to surfboards by surfing pioneer Tom Blake in 1935.[4] Around 1936, Woody Brown independently added a fixed fin to his second surfboard design, which further popularized the feature. The stability and control it allowed revolutionized the sport.[5]
Small single aluminum fins first evolved into larger wooden versions, then ones made from fiberglass and carbon fiber. In time, hydrodynamic improvements took place, pioneered by George Downing 2015-09-28 at the Wayback Machine who also created the first removable skeg, which was a teak wood skeg in a teak wood box which was supposed to be held in place by the swelling of the wood in water. In modern surfing board design, the conventional set-up is to have three fins, with single fins being a minority. While most windsurfing boards are single-fin, wave boards now feature some twin-fin, tri-fin and quad-fin designs. Directional kitesurfing boards are usually three-fin, with five-fin designs being used for improved upwind performance.
Kayaksedit
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 exposure of the skeg to the water, and also its effect on the position of the boat's centre of lateral resistance (CLR), is freely adjustable by the crew. The adjustment varies the degree to which the wind affects the boat - that is, the amount of lateral movement the wind can cause by impacting the upper parts of the boat and the crew.[2][6][7] In more conventional calculations, this would be the centre of effort of the sail area (CE). 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 CLR, it is possible to better control the boat's attitude towards the wind and waves. Irregular flowing movement of the water complicates the issue, however.[2] explains the subtleties of the kayak skeg. They may be made of wood, fiberglass or aluminum. Some are deployed using internal cables, but others use external ropes and bungee cord. Typically, these are retractable, and they are not a rudder.[6][7][8][9] If properly configured (e.g., use of street sign aluminum in a narrow box that extends through the hull) they will not flex, and will greatly decrease and counter pitch, roll and yaw, like a centerboard on a sailboat, when the craft is moving. In that sense, the skeg acts as a liftingfoil.
Aircraftedit
Skegs have been used to improve the directional stability of seaplanes. They have been installed on floats[10] and hulls[11]
The skis on a snowmobile have a metal wear-bar on the bottom of them. Many sledders call these "skegs". These skegs help the skis to steer on hard surfaces. These often have carbide embedded in them to reduce wear when driven on non-snow surfaces.
^"A small fin fitted aft of the keel to protect the rudder and propeller, and improve steering and tracking." MacKenzie, Mike (2005–2012). "Skeg". Seatalk, the Dictionary of English Nautical Language. Retrieved February 14, 2014.
^"Skeg, or Skegg. A projecting stump formerly left on the keel, abaft the stern-post. The after-end of the keel. The composition piece supporting the heel of an equipoise rudder." A naval encyclopædia: comprising a dictionary of nautical words and phrases; biographical notices, and records of naval officers; special articles of naval art and science. PHILADELPHIA: LR HAMERSLY & CO. 1881. Retrieved February 14, 2014. at Internet Archive
^ abcWatson, Tom (February 12, 2014). . paddling.net. Archived from the original on February 23, 2014. Retrieved February 12, 2014.
^"AFSC Historical Corner: Scoter, the Agency's Bristol Bay Boat". NOAA. Retrieved 6 April 2018.
^Motil, Guy (2007). Surfboards. Globe Pequot. p. 30. ISBN978-0-7627-4621-7. Retrieved April 8, 2013.
^Marcus, Ben (2005). Surfing USA!: An Illustrated History Of The Coolest Sport Of All Time. MVP Books. p. 46. ISBN1610606868. Retrieved April 10, 2013.
^ ab"Fixing up your boat: Installing a retractable skeg". Chesapeake Lightcraft. Retrieved February 15, 2014.
^ ab. Atlantic Kayak Tours. 2013. Archived from the original on February 23, 2014. Retrieved February 15, 2014.
^"Rudders vs Skegs". Sea Kayaker Magazine. May 28, 2008. Retrieved February 15, 2014.
^gnarlydog (16 February 2009). "Retrofitting your ruddered kayak with a skegg". gnarlydognews. Retrieved February 15, 2014.
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For other uses see Skag disambiguation A skeg or skegg or skag is a sternward extension of the keel of boats and ships which have a rudder mounted on the centre line 1 The term also applies to the lowest point on an outboard motor or the outdrive of an inboard outboard A B In more recent years the name has been used for a fin on a surfboard which improves directional stability and to a movable fin on a kayak which adjusts the boat s centre of lateral resistance it moves the center of resistance relative to the center of effort 2 The term is also often used for the fin on water skis in the U S It has been used for the vertical fin on seaplane hulls and floats The wear bar on the bottom of snowmobile ski may also be called a skeg Contents 1 Etymology 2 In boats and ships 3 Surfing 4 Kayaks 5 Aircraft 6 Snowmobiles 7 See also 8 Notes 9 References 10 Further readingEtymology editThe word originates in the Scandinavian word for beard in Old Norse skegg In Icelandic the word remains skegg in modern Norwegian Bokmal and Nynorsk it appears as skjegg in Swedish it is skagg and in Danish skaeg The Norwegian pronunciation of the letter combination skj 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 In boats and ships edit nbsp A skeg mounted rudderWhere 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 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 to be relatively small until screw propellers were introduced when it had to reach below the screw and became a proportionately larger feature protecting both screw and rudder from damage On wooden vessels the skeg may be protected from worm damage by the addition of a bug shoe or a a length of hardened material such as ironbark placed on the sternward keel extension skeg to protect from shipworm damage 3 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 Surfing editMain article Surfboard fin In surfing windsurfing and kitesurfing skegs usually known as fins are attached toward the tail of the board to improve directional stability and control through foot steering Fins allow the rider to control the board s direction by varying their side to side weight distribution Fixed fins were introduced to surfboards by surfing pioneer Tom Blake in 1935 4 Around 1936 Woody Brown independently added a fixed fin to his second surfboard design which further popularized the feature The stability and control it allowed revolutionized the sport 5 Small single aluminum fins first evolved into larger wooden versions then ones made from fiberglass and carbon fiber In time hydrodynamic improvements took place pioneered by George Downing Archived 2015 09 28 at the Wayback Machine who also created the first removable skeg which was a teak wood skeg in a teak wood box which was supposed to be held in place by the swelling of the wood in water In modern surfing board design the conventional set up is to have three fins with single fins being a minority While most windsurfing boards are single fin wave boards now feature some twin fin tri fin and quad fin designs Directional kitesurfing boards are usually three fin with five fin designs being used for improved upwind performance Kayaks editA 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 exposure of the skeg to the water and also its effect on the position of the boat s centre of lateral resistance CLR is freely adjustable by the crew The adjustment varies the degree to which the wind affects the boat that is the amount of lateral movement the wind can cause by impacting the upper parts of the boat and the crew 2 6 7 In more conventional calculations this would be the centre of effort of the sail area CE 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 CLR it is possible to better control the boat s attitude towards the wind and waves Irregular flowing movement of the water complicates the issue however 2 This link explains the subtleties of the kayak skeg They may be made of wood fiberglass or aluminum Some are deployed using internal cables but others use external ropes and bungee cord Typically these are retractable and they are not a rudder 6 7 8 9 If properly configured e g use of street sign aluminum in a narrow box that extends through the hull they will not flex and will greatly decrease and counter pitch roll and yaw like a centerboard on a sailboat when the craft is moving In that sense the skeg acts as a lifting foil Aircraft editSkegs have been used to improve the directional stability of seaplanes They have been installed on floats 10 and hulls 11 Snowmobiles editThis section does not cite any sources Please help improve this section by adding citations to reliable sources Unsourced material may be challenged and removed April 2022 Learn how and when to remove this template message The skis on a snowmobile have a metal wear bar on the bottom of them Many sledders call these skegs These skegs help the skis to steer on hard surfaces These often have carbide embedded in them to reduce wear when driven on non snow surfaces See also editGlossary of nautical terms A L Glossary of nautical terms M Z Notes edit A small fin fitted aft of the keel to protect the rudder and propeller and improve steering and tracking MacKenzie Mike 2005 2012 Skeg Seatalk the Dictionary of English Nautical Language Retrieved February 14 2014 Skeg or Skegg A projecting stump formerly left on the keel abaft the stern post The after end of the keel The composition piece supporting the heel of an equipoise rudder A naval encyclopaedia comprising a dictionary of nautical words and phrases biographical notices and records of naval officers special articles of naval art and science PHILADELPHIA LR HAMERSLY amp CO 1881 Retrieved February 14 2014 at Internet ArchiveReferences edit Smyth W H Belcher E 1867 Skegg p 638 a href Template Cite book html title Template Cite book cite book a work ignored help a b c Watson Tom February 12 2014 Rudders amp Skegs Maneuvering Aids paddling net Archived from the original on February 23 2014 Retrieved February 12 2014 AFSC Historical Corner Scoter the Agency s Bristol Bay Boat NOAA Retrieved 6 April 2018 Motil Guy 2007 Surfboards Globe Pequot p 30 ISBN 978 0 7627 4621 7 Retrieved April 8 2013 Marcus Ben 2005 Surfing USA An Illustrated History Of The Coolest Sport Of All Time MVP Books p 46 ISBN 1610606868 Retrieved April 10 2013 a b Fixing up your boat Installing a retractable skeg Chesapeake Lightcraft Retrieved February 15 2014 a b How does a kayak skeg work Atlantic Kayak Tours 2013 Archived from the original on February 23 2014 Retrieved February 15 2014 Rudders vs Skegs Sea Kayaker Magazine May 28 2008 Retrieved February 15 2014 gnarlydog 16 February 2009 Retrofitting your ruddered kayak with a skegg gnarlydognews Retrieved February 15 2014 http www aircraft reports com aircraft structures navy training courses manual 1944 1945 Figure 38 Float construction https calhoun nps edu handle 10945 24676 p 6Further reading editRousmaniere John June 1998 The Illustrated Dictionary of Boating Terms 2000 Essential Terms for Sailors and Powerboaters Paperback W W Norton amp Company p 174 ISBN 0393339181 ISBN 978 0393339185 nbsp Look up skeg in Wiktionary the free dictionary Retrieved from https en wikipedia org w index php title Skeg amp oldid 1126157289 In boats and ships, wikipedia, wiki, book, books, library,
