Sea anchor

A sea anchor (also known as a drift anchor, drift sock, para-anchor or boat brake) is a device used to stabilize a boat in heavy weather. Rather than tethering the boat to the seabed, the sea anchor increases the drag through the water and thus acts as a brake. When attached to the stern of a vessel, a sea anchor can prevent the vessel from turning broadside to the waves and being overwhelmed by them.

Often similar in design to the sea anchor is the usually smaller drogue, which is attached to the stern and intended to slow the boat for better control.

Anything that can act as a source of drag in the water can act as a sea anchor; a common improvised sea anchor is a long line (a docking warp or anchor rode) paid out into the water; while this does not provide much drag, it can act as a drogue and aid in running downwind. 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. A sail, weighed down with an anchor chain or other heavy object, will also work as an improvised sea anchor.

Early sea anchors were often improvised from spare parts aboard ship. An 1877 book used by the United States Naval Academy describes methods of making sea anchors. These took the form of a wooden or metal framework forming a simple kite-like shape of sail canvas, backed with a net or closely spaced ropes to provide strength. A small anchor attached to one corner kept the sea anchor from twisting. If the framework was wooden, the wood's buoyancy kept the sea anchor just under the surface, while an iron framework used a buoy to keep it at the proper depth.

Modern commercial sea anchors are usually made of cloth, shaped like a parachute or cone, and rigged so that the wider end leads and the narrower end trails. When deployed, this type of sea anchor floats just under the surface, and the water moving past the sea anchor keeps it filled. Some varieties are cylindrical, with an adjustable opening in the rear that allows the amount of braking to be adjusted when deployed.

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.

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Wikipedia