In boats and ships, keel can refer to either of two parts: a structural element, or a hydrodynamic element. These parts overlap.
Contents |
Structural keels
A structural keel is a large beam around which the hull of a ship is built. A hull is the body of a Ship or Boat. It is a central concept in floating vessels as it provides the Buoyancy that keeps the vessel from sinking A ship /ʃɪp/ is a large vessel that floats on water Ships are generally distinguished from Boats based on size The keel runs in the middle of the ship, from the bow to the stern, and serves as the foundation or spine of the structure, providing the major source of structural strength of the hull. The bow (pronounced &mdashrhymes with how) is a nautical term that refers to the forward part of the hull of a Ship or Boat, The stern is the rear or aft part of a Ship or Boat, technically defined as the area built up over the Sternpost, extending upwards from the Counter A foundation is a Structure that transfers loads to the earth 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.
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 ship and other vessels. A form of keel found on smaller vessels is the bar keel. The bar keel may be fitted in trawlers, tugs,etc. . and this is also found in 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
Non-sailing keels
The keel surface on the bottom of the hull gives the ship greater directional control and stability. Ship stability is an area of Naval Architecture and ship design that deals with how a ship behaves at sea both in still water and in waves In non sailing hulls, the keel helps the hull to move forward, rather than slipping to the side. In some cases less is more The purpose of this article is to give an overview 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 perform the same function.
Sailboat Keels
In sailboats, keels use the forward motion of the boat to generate lift to counter the lateral force from the sails. A yacht is a recreational boat It designates two rather different classes of Watercraft, sailing and power yachts In some cases less is more The purpose of this article is to give an overview In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow A sail is any type of surface intended to generate Thrust by being placed in a Wind &mdashin essence a vertically-oriented Wing. Sailboats have much larger keels than non sailing hulls. Keels are different from centerboards and other types of foils in that keels are made of heavy materials to provide ballast to stabilize the boat. centreboard is a retractable Keel which pivots out of a slot in the hull of a Sailboat, known as a centerboard trunk (US or case Ballast is used in Sailboats to provide moment to resist the lateral forces on the Sail. 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 ballast. A winch is a mechanical device that is used to pull in (wind up or let out (wind out or otherwise adjust the " Tension " of a Rope or Wire rope 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. In Physics, the moment of force (often just moment, though there are other quantities of that name such as Moment of inertia) is a Pseudovector
There are several types of fixed keels including: full keels, fin keels, winged keels, bulb keels, and twin keels or bilge keels among other designs. A winged keel is a sailboat Keel, usually of high aspect ratio, that uses a nearly horizontal foil, the " Wing " at the bottom to provide A bulb keel is a Keel, usually made with a high aspect ratio foil, that contains a ballast -filled bulb at the bottom usually teardrop shaped Twin keels or bilge keels are two Keels that emerge at an angle from the hull of a Sailboat, at or near the Bilges The angle allows the boat Bilge Keel is a strake, or small keel or blister running along much of the length of the hull.
Types of non-fixed keels include swing keels and canting keels. A canting keel is a form of Sailing ballast, suspended from a rigid canting strut beneath the boat which can be swung to Windward of a boat under sail 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 distance from the weight to the pivot is increased, which generates a larger righting moment.
Etymology
The word "keel" comes from Anglo-Saxon cēol, Old Norse kjóll, = "ship" or "keel". Old Norse is the North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during the Viking Age A ship /ʃɪp/ is a large vessel that floats on water Ships are generally distinguished from Boats based on size 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 Britanniae, under the spelling cyulae (he was referring to the three ships that the Saxons first arrived in). Saint Gildas (c 494 or 516 – c 570 was one of the best-documented figures of the Christian church in the British Isles during the sixth century The 6th century is the period from 501 to 600 in accordance with the Julian calendar in the Christian / Common Era. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. The Saxons or Saxon people were a Confederation of Old Germanic tribes. [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). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Careening a sailing vessel means to beach it at high Tide in order usually to expose one side or another of the ship's hull for maintenance An example of this use is Careening Cove, a suburb of Sydney, Australia, where careening was carried out in early colonial days. Sydney (ˈsɪdniː is the most populous city in Australia, with a Metropolitan area population of approximately 4
References
- ^ Gildas, The Ruin of Britain &c. (1899). pp. 4-252. The Ruin of Britain..
- ^ G. W. Whittaker (1970). Collected Essays. Ayer Publishing, 44. ISBN 0836916360.
See also
- Leeboard
- Bilgeboard
- Daggerboard
- Bruce foil
- Centerboard
- Kelson
- False keel
- Keelhauling - a type of sailor's punishment
- Bulbous bow - the bulb that protrudes under the water line in large modern ships
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic