Keel

Source: Wikipedia, the free encyclopedia.
For other uses, see Keel (disambiguation).
drydock

The keel is the bottom-most longitudinal structural element on a watercraft. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. The laying of the keel is often the initial step in the construction of a ship. In the British and American shipbuilding traditions, this event marks the beginning date of a ship's construction.[1]

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 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).[2][3]

Sydney, Australia
, where careening was carried out in early colonial days.

History

Origins

Carvel-built
hull construction (right) lines planks up edge to edge

The use of a keel in sailing vessels goes back to antiquity. The wreck of an ancient Greek merchant ship known as the Kyrenia ship establishes the origin of the keel at least as far back as 315 BC.[4][page needed] The Uluburun shipwreck (c. 1325 BC) had a rudimentary keel, but it may have been more of a center plank than a keel.[5]

Construction styles

Further information: Boat building

Frame first

In

carvel-built hulls, construction began with the laying of the keel, followed by the stern and stem. Frames were set up afterward, set at key points along the keel. Later, the keelson was attached to the keel, either bolted or with treenails.[6]

Plank first

Look up planking in Wiktionary, the free dictionary.

Structural keels

A structural keel is the bottom-most structural member around which 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 the shipbuilding process commences with the cutting of the first sheet of steel.[7]

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.[citation needed]

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.[8]

Sailing yacht with a fin keel
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).

Sailboat keels

In

moment
with increasing angle of heel.

Moveable sailboat keels may pivot (a swing keel),[9] retract upwards (retracting keel),[10] or swing sideways in the water (canting keels) to move the ballasting effect to one side and allow the boat to sail in a more upright position.[11]

See also

Notes

  1. ISBN 9781854357311
    .
  2. ^ "Gildas, The Ruin of Britain &c. (1899). pp. 4–252. The Ruin of Britain".
  3. ISBN 0-8369-1636-0
    .
  4. ISBN 9781785707520
    .
  5. doi:10.1111/j.1095-9270.1998.tb00803.x
    .
  6. OCLC 862401040
    .|p=76}}
  7. ISBN 9783861951643
    .
  8. ISBN 978-0-924486-71-5
    .
  9. ISBN 9780071778770
    .
  10. ISBN 978-1-119-99918-8
    .
  11. ISBN 9783319132754
    .

Bibliography

Wikimedia Commons has media related to Keels.
  • 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
Retrieved from "https://en.wikipedia.org/w/index.php?title=Keel&oldid=1188246554"
This page is based on the copyrighted Wikipedia article: Keel. Articles is available under the CC BY-SA 3.0 license; additional terms may apply.Privacy Policy