A backstay, as commonly used in a nautical context, is a piece of standing rigging commonly found on a fore-and-aft-rigged sailboat. This line, usually constructed of multiple wound-wire strands, prevents the mast of the vessel from leaning too far forward. The forestay, on the other hand, prevents the mast from leaning too far backward. In conjunction, the backstay and forestay ensure that the mast will withstand the stress of various changes in wind speed without toppling.
Backstays are commonly found in two configurations, a permanent and a running backstay. Most recreational sailboats have a permanent backstay, one that is only adjusted for maintenance purposes. The permanent backstay runs from the very top of the mast to the center of the transom at the stern of the vessel.
Running backstays, conversely, are used mainly in competitive racing, and can be constantly adjusted to compensate for various changing wind directions and constant changes in heading, or course. Running backstays are usually mounted in pairs attached about two-thirds of the way up the mast, and run to the transom corners at the stern of the boat. Very often, running backstays will have multiple attachment points on the mast, resulting in better control of the sail and increased boom maneuverability under race conditions. Using adjusters, typically via hydraulically operated winches, tension on the running backstays can be increased or decreased as necessary to take advantage of wind direction and course corrections.
Sailboats change direction, or heading, in one of two ways, either by tacking or by jibing. Tacking means that the bow of the vessel is headed into and through the wind during a change of heading, with the wind direction switched from one side of the boat to the other. For this maneuver, a permanent backstay is adequate.
A running backstay, on the other hand, is better able to handle the stresses and convolutions of a jibe, which is a fairly stressful change of heading, where the stern of the boat is maneuvered through the wind. This often results in the sail boom, the horizontal spar anchoring the bottom of the mainsail, swinging rapidly from one side of the boat to the other in an effort to retain the wind. As well, jibing will entail a sudden and sometimes dangerous reversal of the boat’s heel, or lean. Jibing is often used in racing competition to round a marker buoy.
Often the backstay on a recreational sailboat will be used to mount radar apparatus and VHS radio antenna equipment, as well as “crew overboard” pennants. These accoutrements are known as backstay mounts. Most of these mounts, of course, are utilized with permanent backstays.