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Keel laying of eighth anti-submarine warfare ship held June 1, 2025, 8:23 AM ET (The Hindu)

keel, in shipbuilding, the main structural member and backbone of a ship or boat, running longitudinally along the centre of the bottom of the hull from stem to stern. It may be made of timber, metal, or other strong, stiff material. Traditionally it constituted the principal member to which the ribs were attached on each side and to which the stem and sternpost were also attached. Another type of main keel—properly, the “full keel,” or “ballast keel”—is a vertical downward extension of the boat’s hull, narrowly V-shaped; it is usually ballasted or weighted for stability and lateral resistance.

The backbone keel may be supplemented by other keels (see Figure). A “centreboard”—also called a drop keel, or sliding keel—is a retractable keel midships that may be lowered to increase lateral resistance and prevent sideslip. A “skeg” is an aftward extension of the keel intended to keep the boat moving straight and to protect the propeller and rudder from underwater obstructions. A “fin keel” is a narrow plate (of wood, metal, or other material) fixed midships to the keel of a shallow boat (such as a racing yacht) and projecting downward to provide lateral resistance. It is intended both to steady the boat and to make it handy to steer. A “bilge keel” is one of a pair of longitudinal plates that, like fins, project from the sides of a ship or boat and run parallel to the centre keel. They are intended to check rolling. On large ships the outward projections of the bilge keels may be slight; on small yachts they may be comparatively deep.


Bilge

emperor of Mongolia
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Also known as: Bilgä, Mo-chi-lien, Mojilian, P’i-chia, Pijia
Quick Facts
Also spelled:
Bilgä
Wade-Giles romanization:
P’i-chia, orMo-chi-lien
Pinyin:
Pijia, orMojilian
Died:
734
Title / Office:
khan (716-734), Mongolia

Bilge (died 734) was the khagan, or great khan, of Mongolia from 716 until his death. His name literally translates as “Wise Emperor.”

Bilge assumed leadership of the T’u-chüeh, a tribe of Turks in control of southern Central Asia, when his brother instigated a palace coup against the old ruler. When the T’ang emperor Hsüan Tsung refused his offer of an alliance, Bilge decimated the Chinese army, forcing them to sue for peace in 721. Bilge is even better known, however, for advising his successors that the power of the T’u-chüeh came from their nomadic life and that to settle in agricultural communities on the Chinese border would weaken them.

This article was most recently revised and updated by Encyclopaedia Britannica.