keel

WordNet

a projection or ridge that suggests a keel
one of the main longitudinal beams (or plates) of the hull of a vessel; can extend vertically into the water to provide lateral stability
the median ridge on the breastbone of birds that fly
river boat with a shallow draught and a keel but no sails; used to carry freight; moved by rowing or punting or towing
a metal plate projecting from the keel of a shallow vessel to give it greater lateral stability
a longitudinal beam connected to the keel of ship to strengthen it
Eurasian bulbous plant (同)Allium carinatum

PrepTutorEJDIC

(船などの)竜骨,キール
〈人〉‘に'船底をくぐらせる(規律違反者などを縛り,足におもりをつけ船底をくぐらせる刑罪) / 〈人〉‘を'厳しくしかる

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/26 06:28:22」(JST)

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Sailing yacht with a fin keel

"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."

In boats and ships, keel can refer to 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 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.

Structural keels

Keel laid for the USS United States in drydock

A structural keel is a beam around which the hull of a ship is built. The keel runs in the middle of the ship, from the bow to the stern, and serves as a basic foundation or spine of the structure, providing the major source of structural strength of the hull. The keel is generally 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, is often a momentous event in a ship's construction — so much so that the event is often marked with a ceremony, and the term lay the keel has entered the language as a phrase meaning the beginning of any significant undertaking. Modern ships are now largely built in a series of pre-fabricated, complete hull sections rather than being built around a single keel, so the start of the shipbuilding process is now considered to be when the first sheet of steel is cut.

The keel converts sideways force into a forward force.

The keel contributes substantially to the longitudinal strength and effectively local loading caused when docking the ship. 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.

If a ship suffers severe structural stress — classically during a shipwreck when running aground in a heavy sea — it is possible for the keel to break or be strained to the extent that it loses structural integrity. In this case the ship is commonly said to have "broken its back". Such a failure means that the entire structure of the ship and its machinery has been compromised and repairing such damage would require virtually re-building the ship from the ground up. A ship that has broken its back is almost certainly unsalvagable and subsequently written off by its insurers.

Hydrodynamic keels

Lateral resistance effect of a sailing keel

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.

Etymology

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).^[1]^[2]

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.

Notes

^ "Gildas, The Ruin of Britain &c. (1899). pp. 4-252. The Ruin of Britain.".
^ G. W. Whittaker (1970). Collected Essays. Ayer Publishing. p. 44. ISBN 0-8369-1636-0.

Bibliography

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

UpToDate Contents

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English Journal

Sampling methodology and site selection in the National Eye Health Survey (NEHS): an Australian population-based prevalence study.

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Names in programming are vital for understanding the meaning of code and big data. We define code2brain (C2B) interfaces as maps in compilers and brains between meaning and naming syntax, which help to understand executable code. While working toward an Evolvix syntax for general-purpose programming
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Patterns of postnatal ontogeny of the skull and lower jaw of snakes as revealed by micro-CT scan data and three-dimensional geometric morphometrics.

Palci A1,2, Lee MS1,2, Hutchinson MN1,2,3.
Journal of anatomy.J Anat.2016 Dec;229(6):723-754. doi: 10.1111/joa.12509. Epub 2016 Jun 22.
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Evolutionary and Functional Features of Copy Number Variation in the Cattle Genome.

Keel BN1, Lindholm-Perry AK1, Snelling WM1.
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Japanese Journal

Radiographic and ultrasonographic characteristics of ventral abdominal hernia in pigeons (<i>Columba livia</i>)

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係留船舶におけるビルジキールの動揺抑制効果に関する検討

土木学会論文集B2(海岸工学) 73(2), I_985-I_990, 2017
NAID 130006172019

船の操縦運動に及ぼすビルジキールの影響

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A new and ontogenetically younger specimen of Numataphocoena yamashitai from the upper part of the Horokaoshirarika Formation (lower Pliocene), Numata, Hokkaido, Japan