Keel laying
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The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a
hydrodynamic In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...
and counterbalancing purpose, as well. 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.


Etymology

The word "keel" comes from
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventu ...
,
Old Norse Old Norse, Old Nordic, or Old Scandinavian is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and th ...
, = "
ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep Sea lane, waterways, carrying goods or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally disti ...

ship
" or "keel". It has the distinction of being regarded by some scholars as the first word in the English language recorded in writing, having been recorded by
Gildas Gildas ( Breton: ''Gweltaz''; c. 500 – c. 570) — also known as Gildas the Wise or ''Gildas Sapiens'' — was a 6th-century Britons (historic), British monk best known for his scathing religious polemic ''De Excidio et Conquestu Britanniae'', ...
in his 6th century
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the ...

Latin
work ''
De Excidio et Conquestu Britanniae ''De Excidio et Conquestu Britanniae'' (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through ...
'', under the spelling ''cyulae'' (he was referring to the three ships that the
Saxons The Saxons ( la, Saxones, german: Sachsen, ang, Seaxan, osx, Sahson, nds, Sassen, nl, Saksen) were a group of early Germanic peoples, Germanic * * * * peoples whose name was given in the early Middle Ages to a large country (Old Saxony, la, ...

Saxons
first arrived in). is the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the ...

Latin
word for "keel" and is the origin of the term
careen Careening (also known as "heaving down") is the practice of grounding a sailing vessel at high tide (U.S.), low tide occurs roughly at moonrise and high tide with a high Moon, corresponding to the simple gravity model of two tidal bulges; at ...
(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 Careening Cove, is a bay on the northern side of Sydney Harbour Port Jackson, consisting of the waters of Sydney Harbour, Middle Harbour, North Harbour and the Lane Cove and Parramatta Parramatta () is a major commercial suburb and ...
, a suburb of Sydney, Australia, where careening was carried out in early colonial days.


Structural keels

A structural keel is the bottom-most structural member around which the hull (ship), hull of a
ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep Sea lane, waterways, carrying goods or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally disti ...

ship
is built. The keel runs along the centerline of the ship, from the Bow (ship), bow to the stern. The keel is often the first part of a ship's hull to be constructed, and keel laying, 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 the shipbuilding process commences with the cutting of 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.


Hydrodynamic keels

Hydrodynamic keels have the primary purpose of interacting with the water and are typical of certain sailboats. Fixed hydrodynamic keels have the structural strength to support the weight of the boat. with a fin keel Image:Capsizing effect of keel.svg, upLateral resistance effect of a sailing keel


Sailboat keels

In sailboats, keels serve two purposes: 1) as an underwater Foil (fluid mechanics), foil to minimize the lateral motion of the vessel under sail (leeway) and 2) as a counterweight to the lateral force of the wind on the sail(s) that causes rolling to the side (Heeling (sailing), heeling). As an underwater foil, a keel uses the forward motion of the boat to generate lift (force), lift to counteract the windward and leeward, leeward force of the wind. Related foils include Centreboard, centerboards and daggerboards, which do not have the secondary purpose of being a counterweight. As counterweight, a keel increasingly offsets the heeling Moment arm, moment with increasing angle of heel. Moveable sailboat keels may pivot (a swing keel), retract upwards (retracting keel), or swing sideways in the water canting keel, (canting keels) to move the ballasting effect to one side and allow the boat to sail in a more upright position.


See also

* Coin ceremony * Kelson * False keel * Daggerboard * Leeboard * Bilgeboard * Bruce foil * Keelhauling – an archaic maritime punishment


Notes


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 {{Authority control Nautical terminology Chinese inventions Naval architecture Sailing rigs and rigging Sailing vessel components Shipbuilding Sailboat components Song dynasty