Sea anchor
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A sea anchor, used to stabilize a boat in heavy weather, anchors not to the sea floor but to the water itself, as a kind of brake. Sea anchors are known by a number of names, such as drift anchor, drift sock, para-anchor, and boat brakes. These all function the same way, by pulling large amounts of water along as the boat moves, and they are all used to counter the effects of high winds. Similar in design and use to the sea anchor is the relatively smaller drogue.
[edit] Design
Sea anchors are usually made of cloth, shaped like a parachute or cone, and rigged so that the open end points in the direction of the boat's movement. When deployed, this type of sea anchor floats just under the surface, and the water moving past the sea anchor keeps it filled. When attached to the bow of a vessel,the drag pulls the stern of the craft leeward, causing incoming waves to lift the boat front to back rather than side to side, lessening the risk of capsize. Some varieties are cylindrical, with an adjustable opening in the rear that allows the amount of braking to be adjusted when deployed[1]. When used in heavy seas, the sea anchor is attached to the hull with a long line, as much as 15 boat lengths, to act as a shock absorber. The size of the sea anchor determines how much water it can displace, and how much braking it can provide. It is also possible to use more than one sea anchor to increase the braking, and one type, the series drogue, consists of many small anchors spread out along a line to ease retrieval under heavy conditions[2].
Most larger sea anchors will provide a mechanism to collapse the anchor for retrieval. This is called a trip line, and attaches to the rear of the anchor, allowing it to be pulled in back first, shedding water rather than filling. This trip line can be rigged a number of ways, depending on the preference of the user[3].
Anything that can act as a source of drag can act as a sea anchor; a common improvised sea anchor is a long line (a docking warp or anchor rode) played out into the water. In The Sea-Wolf, author and sailor Jack London described using various torn spars and sails, tied to a line, as an improvised sea anchor[4]. A sail, weighed down with an anchor chain or other heavy object, will also work as an improvised sea anchor[5].
[edit] Use
Sea anchors can be used by vessels of any size, from kayaks[6] to commercial fishing vessels[7]. While the purpose of the anchor is to provide drag to slow the vessel, there are a number of ways this can be used.[8]:
- The first, and probably most well known use, of the sea anchor is to aid vessels in heaving to in heavy weather. A boat that is not kept bow- or stern-on to heavy seas can easily be rolled by the action of the waves. By attaching the sea anchor to a bridle running from bow to stern, the boat can be held at any angle relative to the wind. This is useful in sailboats in conditions too windy to use the sails to maintain a heading, and in motor vessels that are unable to make sufficient headway to maintain steerage.
- Sea anchors also reduce the speed at which a vessel will drift with the wind. Often sold as drift anchors or drift socks, sea anchors are used in fishing vessels to hold them relatively stationary relative to the water to allow a certain area to be fished, without having to use the motor.
- A sea anchor can provide directional control of a sailboat in the case of a steering failure. By towing a sea anchor from a bridle off the stern, the direction of the boat can be controlled on a running course.
- A sea anchor can be used to control the speed of a sailboat, in cases where delicate handling is required in high winds.
- A sea anchor can be used behind a towed vessel to maintain tension on the towing line, and prevent the radical side-to-side motion exhibited by some vessels under tow.
- Sea anchors may also be used as anchors to allow warping of a vessel in deep water.
[edit] References
- ^ Adjustable boat brake
- ^ Article on the series drogue
- ^ Trip lines
- ^ The Sea Wolf, e-text at Project Gutenberg
- ^ Sailing Multihulls in Heavy Weather
- ^ Kayak sea anchors
- ^ Commercial fishing sea anchors for vessels up to 2800 tons displacement
- ^ Four uses for drouges
