Anchor
Last update: Friday 21st of November 2008
For other uses, see Anchor (disambiguation). An anchor is an object, often made out of metal, that is used to attach a ship to the bottom of a body of water at a specific point. There are two primary classes of anchors—temporary and permanent. A permanent anchor is often called a mooring, and is rarely moved; it is quite possible the vessel cannot hoist it aboard but must hire a service to move or maintain it. Vessels carry one or more temporary anchors which may be of different designs and weights. A sea anchor is a related device used when the water depth makes using a mooring or temporary anchor impractical. The vessel is attached to the anchor by the rode which is made with chain, cable or line or a combination of these. The hole in the hull through which the anchor rode passes is called "hawsepipe" because thick mooring lines are called "hawsers". An anchor works by resisting the movement force of the vessel which is attached to it. There are two primary ways to do this—via sheer mass, and by "hooking" into the seabed. While permanent moorings can use large masses resting on this seabed this is not practical for temporary anchors which need to be stowed onboard so almost all temporary anchors are of the type which have metal flukes which hook on to rocks in the bottom or bury themselves in soft bottoms. Wind and current generate steadier forces on the hull but the waves and motion of the vessel add the peak loads which the anchor and rode need to withstand. Reports from boats that have faced whole gale to cyclone winds at anchor, say that it is not the winds that break anchor gear and upset anchors, but the accompanying wave action which causes boats to pitch, surge, heave and yaw. Surge is the worst of these motions as the boat rides over the waves alternately stretching and relaxing the anchor warp like a horizontal yo-yo. Surging of the boat sometimes as much as doubles the loads felt from wind drag alone. The surge factor can be proportioned to the boat displacement and length. Surge is the motion forward and backward in the direction of boat travel, along the longitudinal axis. An interesting element of anchor jargon is the term aweigh, which describes the anchor when it is hanging on the rope, not resting on the bottom; this is linked to the term to weigh anchor, meaning to lift the anchor from the sea bed, allowing the ship or boat to move. An anchor is described as aweigh when it has been broken out of the bottom and is being hauled up to be stowed. Aweigh should not be confused with under way, which describes a vessel which is not moored to a dock or anchored, whether or not it is moving through the water. Thus, a vessel can be under way (or underway) with no way on (i.e., not moving).
Anchor
An anchor is an object, often made out of metal, that is used to attach a ship to the bottom of a body of water at a specific point. There are two primary classes of anchors ...
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Anchor - Wikipedia, the free encyclopedia
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