On boats and ships, the keel is either of two parts: a structural element that sometimes resembles a fin and protrudes below a boat along the central line, or a hydrodynamic element. These parts overlap. As the laying down of the keel is the initial step in the construction of a ship, in British and American shipbuilding traditions the construction is dated from this event. Only the ship's launching is considered more significant in its creation.

The word can also be used as a synecdoche to refer to a complete boat, such as a keelboat.

1 – mainsail Edit this on Wikidata 2 – staysail Edit this on Wikidata 3 – Spinnaker Edit this on Wikidata
4 – hull Edit this on Wikidata 5 – keel Edit this on Wikidata 6 – rudder Edit this on Wikidata 7 – skeg Edit this on Wikidata
8 – spar Edit this on Wikidata 9 – Spreader Edit this on Wikidata 10 – Shroud Edit this on Wikidata
11 – sheet Edit this on Wikidata 12 – boom Edit this on Wikidata 13 - spar Edit this on Wikidata
14 – Spinnaker pole Edit this on Wikidata 15 – Backstay Edit this on Wikidata
16 – Forestay Edit this on Wikidata 17 – boom vang Edit this on Wikidata
Sailing yacht with a fin keel
US Navy 091114-N-5549O-135 Robert Bowker welds the initials of Susan Ford Bales into the keel of the aircraft carrier Gerald R. Ford (CVN 78) during a keel laying and authentication ceremony
The initials of Susan Ford Bales being welded into the keel of the aircraft carrier USS Gerald R. Ford (CVN 78) during a keel laying and authentication ceremony at Northrop Grumman Shipbuilding in Newport News.


The adjustable centerboard keel traces its roots to the medieval Chinese Song dynasty. Many Song Chinese junk ships had a ballasted and bilge keel that consisted of wooden beams bound together with iron hoops. Maritime technology and the technological know-how allowed Song dynasty ships to be used in naval warfare between the Southern Song Dynasty, the Jin dynasty, and the Mongols.[1][2][3]

Structural keels

A structural keel is the bottom-most structural member around which the hull of a ship is built. The keel runs along the centerline of the ship, from the bow to the stern. The keel is often the first part of a ship's hull to be constructed, and laying the keel, or placing the keel in the cradle in which the ship will be built may mark the start time of its construction. Large, modern ships are now often built in a series of pre-fabricated, complete hull sections rather than being built around a single keel, so shipbuilding process commences with cutting the first sheet of steel.

The most common type of keel is the "flat plate keel", and this is fitted in the majority of ocean-going ships and other vessels. A form of keel found on smaller vessels is the "bar keel", which may be fitted in trawlers, tugs, and smaller ferries. Where grounding is possible, this type of keel is suitable with its massive scantlings, but there is always a problem of the increased draft with no additional cargo capacity. If a double bottom is fitted, the keel is almost inevitably of the flat plate type, bar keels often being associated with open floors, where the plate keel may also be fitted.

Duct keels are provided in the bottom of some vessels. These run from the forward engine room bulkhead to the collision bulkhead and are utilized to carry the double bottom piping. The piping is then accessible when cargo is loaded.

Hydrodynamic keels

Werking zwaard
A hydrodynamic keel creates lift that minimizes sideways motion, underway.
Capsizing effect of keel
Lateral resistance effect of a sailing keel
Segeln Gewichtsstabilitaet
Righting effect of a keel, where A is the center of buoyancy and G is the centre of gravity (hypothetical example).

Non-sailing keels

The keel surface on the bottom of the hull gives the ship greater directional control and stability. In non-sailing hulls, the keel helps the hull to move forward, rather than slipping to the side. In traditional boat building, this is provided by the structural keel, which projects from the bottom of the hull along most or all of its length. In modern construction, the bar keel or flat-plate keel performs the same function. There are many types of fixed keels, including full keels, long keels, fin keels, winged keels, bulb keels, and bilge keels among other designs. Deep-draft ships will typically have a flat bottom and employ only bilge keels, both to aid directional control and to damp rolling motions

Sailboat keels

In sailboats, keels use the forward motion of the boat to generate lift to counteract the leeward force of the wind. The rudimentary purpose of the keel is to convert the sideways motion of the wind when it is abeam into forward motion. A secondary purpose of the keel is to provide ballast. Keels are different from centreboards and other types of foils in that keels are made of heavy materials to provide ballast to stabilize the boat. Keels may be fixed, or non-movable, or they may retract to allow sailing in shallower waters. Retracting keels may pivot (a swing keel) or slide upwards to retract, and are usually retracted with a winch due to the weight of the ballast. Since the keel provides far more stability when lowered than when retracted (due to the greater moment arm involved), the amount of sail carried is generally reduced when sailing with the keel retracted.

Types of non-fixed keels include swing keels and canting keels. Canting keels can be found on racing yachts, such as those competing in the Volvo Ocean Race. They provide considerably more righting moment as the keel moves out to the windward-side of the boat while using less weight. The horizontal distance from the weight to the pivot is increased, which generates a larger righting moment.


The word "keel" comes from Old English cēol, Old Norse kjóll, = "ship" or "keel". It has the distinction of being regarded by some scholars as the very first word in the English language recorded in writing, having been recorded by Gildas in his 6th century Latin work De Excidio et Conquestu Britanniae, under the spelling cyulae (he was referring to the three ships that the Saxons first arrived in).[4][5]

Carina is the Latin word for "keel" and is the origin of the term careen (to clean a keel and the hull in general, often by rolling the ship on its side). An example of this use is Careening Cove, a suburb of Sydney, Australia, where careening was carried out in early colonial days.

See also


  1. ^ Teng, Jimmy (2014). Musket, Map and Money:: How Military Technology Shaped Geopolitics and Economics. Walter de Gruyter. p. 117. ISBN 978-8376560588.
  2. ^ Clancey, Gregory K.; Loy, Hui-chieh (2002). Historical Perspectives on East Asian Science, Technology and Medicine. World Scientific Publishing (published July 24, 2002). p. 498. ISBN 978-9971692599.
  3. ^ Deng, Gang (1999). Maritime Sector, Institutions, and Sea Power of Premodern China. Praeger. p. 9. ISBN 978-0313307126.
  4. ^ "Gildas, The Ruin of Britain &c. (1899). pp. 4–252. The Ruin of Britain".
  5. ^ G. W. Whittaker (1970). Collected Essays. Ayer Publishing. p. 44. ISBN 0-8369-1636-0.


  • Rousmaniere, John, The Annapolis Book of Seamanship, Simon & Schuster, 1999
  • Chapman Book of Piloting (various contributors), Hearst Corporation, 1999
  • Herreshoff, Halsey (consulting editor), The Sailor’s Handbook, Little Brown and Company
  • Seidman, David, The Complete Sailor, International Marine, 1995
  • Jobson, Gary, Sailing Fundamentals, Simon & Schuster, 1987

A centreboard or centerboard (US) is a retractable keel which pivots out of a slot in the hull of a sailboat, known as a centreboard trunk (UK) or centerboard case (US). The retractability allows the centreboard to be raised to operate in shallow waters, to move the centre of lateral resistance (offsetting changes to the sailplan that move the centre of effort aft), to reduce drag when the full area of the centreboard is not needed, or when removing the boat from the water, as when trailering. A centreboard which consists of just a pivoting metal plate is called a centerplate. A daggerboard is similar but slides vertically rather than pivoting.

The analog in a scow is a bilgeboard: these are fitted in pairs and used one at a time.

Lt. John Schank (c. 1740 – 6 February 1823) was an officer of the British Royal Navy and is credited with the invention of the centerboard. Schank, however, gave credit for the idea to British Brigadier General Earl Percy.

Draft (hull)

The draft or draught of a ship's hull is the vertical distance between the waterline and the bottom of the hull (keel), with the thickness of the hull included; in the case of not being included the draft outline would be obtained. Draft determines the minimum depth of water a ship or boat can safely navigate. The draft can also be used to determine the weight of the cargo on board by calculating the total displacement of water and then using Archimedes' principle. A table made by the shipyard shows the water displacement for each draft. The density of the water (salt or fresh) and the content of the ship's bunkers has to be taken into account. The closely related term "trim" is defined as the difference between the forward and aft drafts.

Estonian language

The Estonian language (eesti keel [ˈeːsti ˈkeːl] (listen)) is the official language of Estonia, spoken natively by about 1.1 million people: 922,000 people in Estonia and 160,000 outside Estonia. It is a Southern Finnic language and is the second most spoken language among all the Finnic languages.

Howard Keel

Harry Clifford Keel (April 13, 1919 – November 7, 2004), known professionally as Howard Keel, was an American actor and singer with a rich bass-baritone singing voice. He starred in a number of MGM musicals in the 1950s and in the CBS television series Dallas from 1981–1991.

Hull (watercraft)

A hull is the watertight body of a ship or boat. The hull may open at the top (such as a dinghy), or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline.

Keel-billed toucan

The keel-billed toucan (Ramphastos sulfuratus), also known as sulfur-breasted toucan or rainbow-billed toucan, is a colorful Latin American member of the toucan family. It is the national bird of Belize.

Keel (bird anatomy)

A keel or carina (plural carinae) in bird anatomy is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight. Keels do not exist on all birds; in particular, some flightless birds lack a keel structure.

Historically, the presence or absence of a pronounced keel structure was used as a broad classification of birds into two orders: Carinatae (from carina, "keel"), having a pronounced keel; and ratites (from ratis, "raft" — referring to the flatness of the sternum), having a subtle keel structure or lacking one entirely. However, this classification has fallen into disuse as evolutionary studies have shown that many flightless birds have evolved from flighted birds.

Keel laying

Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship.

Keel laying is one of the four specially celebrated events in the life of a ship; the others are launching, commissioning, and decommissioning.

In earlier times, the event recognized as the keel laying was the initial placement of the central timber making up the backbone of a vessel, called the keel. As steel ships replaced wooden ones, the central timber gave way to a central steel beam.

Modern ships are now largely built in a series of pre-fabricated, complete hull sections rather than being built around a single keel. The event recognized as the keel laying is the first joining of modular components, or the lowering of the first module into place in the building dock. It is now often called "keel authentication", and is the ceremonial beginning of the ship's life, although some modules may have been started months before that stage of construction.


A keelboat is a riverine cargo-capable working boat, or a small- to mid-sized recreational sailing yacht. The boats in the first category have shallow structural keels, and are nearly flat-bottomed and often used leeboards if forced in open water, while modern recreational keelboats have prominent fixed fin keels, and considerable draft. The two terms may draw from cognate words with different final meaning.

Labellum (botany)

In botany, the labellum (or lip) is the part of the flower of an orchid or Canna, or other less-known genera that serves to attract insects, which pollinate the flower, and acts as a landing platform for them.

Labellum (plural: labella) is the Latin diminutive of labium, meaning lip.

The labellum is a modified petal and can be distinguished from the other petals and from the sepals by its large size and its often irregular shape. It is not unusual for the other two petals of an orchid flower to look like the sepals, so that the labellum stands out as distinct.In orchids, the labellum is the modified median petal that sits opposite from the fertile anther and usually highly modified from the other perianth segments. It is often united with the column and can be hinged or movable, facilitating pollination. Often, the orchid labellum is divided into three or more lobes. Some have modified fleshy lumps on the upper surface generally referred to as the callus (plural: calli), with some being divided into multiple ridges or a central keel. When the callus is flat and broad, it is sometimes called a plate, which can have fringed margins. The callus can be highly modified with striking colors that may aid in pollinator deceit and mimicry.The labellum in orchids is often large and complex enough that terminology describing relative positions for structures on it becomes useful: the hypochile is the basal portion nearer the connection with the rest of the flower, the mesochile is the middle portion, and the epichile is the distal portion.

List of Star Trek characters (G–M)

This article lists characters of Star Trek that received attention from third-party sources in their various canonical incarnations. This includes fictional major characters and fictional minor characters created for Star Trek, fictional characters not originally created for Star Trek, and real-life persons appearing in a fictional manner, such as holodeck recreations.

Metacentric height

The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships.

Molding (decorative)

Moulding (also spelled molding in the United States though usually not within the industry), also known as coving (United Kingdom, Australia), is a strip of material with various profiles used to cover transitions between surfaces or for decoration. It is traditionally made from solid milled wood or plaster, but may be of plastic or reformed wood. In classical architecture and sculpture, the molding is often carved in marble or other stones.

A "plain" molding has right-angled upper and lower edges. A "sprung" molding has upper and lower edges that bevel towards its rear, allowing mounting between two non-parallel planes (such as a wall and a ceiling), with an open space behind.

Sagittal keel

The sagittal keel (torus) is a thickening of bone on part or all of the midline of the frontal bone, or parietal bones where they meet along the sagittal suture, or on both bones. Sagittal keels differ from sagittal crests, which are found in some earlier hominins (notably the genus Paranthropus) and in a range of other mammals. While a proper crest functions in anchoring the muscles of mastication to the cranium, the keel is lower and rounded in cross-section, and the jaw muscles do not attach to it.

Sagittal keels occur in several early human species, most noticeably in Homo erectus, occasionally in Homo heidelbergensis and in some Upper Paleolithic Homo Sapiens specimens. Most modern Homo sapiens groups have lost them, likely as part of the general trend toward thinning of the cranial bones to make room for larger brains during the Pleistocene. However, there is a very small portion of modern humans who have this, but its function and etiology are unknown. Patrick Stewart of Star Trek: The Next Generation and the martial artist Shi Yan Ming present good examples of modern humans (Homo sapiens sapiens) with this feature. Australian Aborigenes also possess it. The keel appears to be tied to general cranial robusticity, and is more common in adult men than in women, and absent in children.


A sailboat or sailing boat is a boat propelled partly or entirely by sails smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture.


Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word slug is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a small internal shell, particularly sea slugs and semislugs (this is in contrast to the common name snail, which applies to gastropods that have a coiled shell large enough that the animal can fully retract its soft parts into the shell).

Various taxonomic families of land slugs form part of several quite different evolutionary lineages, which also include snails. Thus, the various families of slugs are not closely related, despite a superficial similarity in the overall body form. The shell-less condition has arisen many times independently during the evolutionary past, and thus the category "slug" is a polyphyletic one.

Võro language

Võro (Võro: võro kiilʼ [ˈvɤro kʲiːlʲ], Estonian: võru keel) is a language belonging to the Finnic branch of the Uralic languages. Traditionally, it has been considered a dialect of the South Estonian dialect group of the Estonian language, but nowadays it has its own literary standard and is in search of official recognition as an autochthonous regional language of Estonia. Võro has roughly 75,000 speakers (Võros) mostly in southeastern Estonia, in the eight parishes of the historical Võru County: Karula, Harglõ, Urvastõ, Rõugõ, Kanepi, Põlva, Räpinä and Vahtsõliina. These parishes are currently centred (due to redistricting) in Võru and Põlva counties, with parts extending into Valga and Tartu counties. Speakers can also be found in the towns of Tallinn and Tartu and the rest of Estonia.


A yacht is a watercraft used for pleasure or sports. The term originates from the Dutch word jacht (which means "hunt"), and was originally referencing light fast sailing vessels that the Dutch Republic navy used to pursue pirates and other transgressors around and into the shallow waters of the Low Countries. The yacht was popularized by Charles II of England as a pleasure or recreation vessel following his restoration in 1660.

Today's yachts differ from other vessels by their leisure purpose. A yacht is any sail or power vessel used for pleasure, cruising or racing. A yacht does not have to have luxury accommodations to be a yacht, in fact many racing yachts are stripped out vessels with the minimum of accommodations. The term 'sailboat' is sometimes used in America to differentiate sail from powerboat. See also 'yachting'. There are currently about 6,500 yacht over 24m on the market.Charter yachts are a subset of yachts used for pleasure, cruising or racing, but run as a business for profit. Ownership can be private or corporate. The paid crews of these vessels call themselves 'yachties'.

Yacht lengths normally range from 7 metres (23 ft) up to dozens of meters (hundreds of feet). A luxury craft smaller than 12 metres (39 ft) is more commonly called a cabin cruiser or simply a cruiser. Yachts may be classified as "large" (over 24 m (79 ft), which have higher construction standards, "commercial", carrying no more than 12 passengers, "private", solely for the pleasure of the owner and guests, or by flag, the country under which it is registered. A superyacht (sometimes "mega yacht") generally refers to any yacht (sail or power) above 40 m (131 ft).

Parts of a sailing ship

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