An asymmetrical spinnaker is a

sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails ma ...

used when

sailing Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, windsurfer, or kitesurfer), on ''ice'' (iceboat) or on ''land'' ( land yacht) over a chose ...

downwind Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference ...

. Also known as an "asym", "aspin", or "A-sail" it can be described as a cross between a

genoa Genoa ( ; it, Genova ; lij, Zêna ). is the capital of the Italian region of Liguria and the sixth-largest city in Italy. In 2015, 594,733 people lived within the city's administrative limits. As of the 2011 Italian census, the Province of ...

jib and a

spinnaker A spinnaker is a sail designed specifically for sailing off the wind on courses between a reach (wind at 90° to the course) to downwind (course in the same direction as the wind). Spinnakers are constructed of lightweight fabric, usually ny ...

. It is asymmetric like a genoa, but, the asymmetrical spinnaker is not attached to the

forestay On a sailing vessel, a forestay, sometimes just called a stay, is a piece of standing rigging which keeps a mast from falling backwards. It is attached either at the very top of the mast, or in fractional rigs between about 1/8 and 1/4 from the t ...

over the full length of its luff, being rigged like a spinnaker. The asymmetrical spinnaker has a larger camber than a genoa, making it optimal for generating lift at larger

angles of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is ...

, but the camber is significantly less than that of a spinnaker. The asymmetrical spinnaker is a specialty sail used on

racing In sport, racing is a competition of speed, in which competitors try to complete a given task in the shortest amount of time. Typically this involves traversing some distance, but it can be any other task involving speed to reach a specific go ...

boats, bridging the performance gap between a genoa, which develops maximum driving force when the

apparent wind Apparent wind is the wind experienced by a moving object. Definition of apparent wind The ''apparent wind'' is the wind experienced by an observer in motion and is the relative velocity of the wind in relation to the observer. The ''velocity ...

angle is between 35 and 60 degrees, and a spinnaker, which has maximum power when the apparent wind is between 100 and 140 degrees. Due to its geometry, the sail is less prone to collapsing than a spinnaker and does not require the use of

spinnaker pole A spinnaker pole is a spar used in sailboats (both dinghys and yachts) to help support and control a variety of headsails, particularly the spinnaker. However, it is also used with other sails, such as genoas and jibs, when sailing downwind ...

. The sail can benefit greatly and be much larger if the boat is equipped with a

bowsprit The bowsprit of a sailing vessel is a spar extending forward from the vessel's prow. The bowsprit is typically held down by a bobstay A bobstay is a part of the rigging of a sailing boat or ship. Its purpose is to counteract the upward tensio ...

. Some boats (e.g., the Melges 17), have retractable bowsprits for this sail. A form of asymmetrical spinnaker is also used on cruising boats as being easier to handle than a symmetrical spinnaker and known as a "cruising chute". Rigging is different from other spinnakers. Maximizing performance and effective sailing of asymmetrical spinnakers requires unique sail and boat trim. It is often paired with a

Spinnaker chute A spinnaker is a sail designed specifically for sailing off the wind on courses between a reach (wind at 90° to the course) to downwind (course in the same direction as the wind). Spinnakers are constructed of lightweight fabric, usually n ...

. Since the 1960s many faster sailing craft, starting with catamaran classes, had discovered that it is faster to sail downwind on a series of broad reaches with efficient airflow across the sail rather than directly downwind with the sails stalled. This technique had developed to the extent that in bar conversation at the end of one season

Andrew Buckland Andrew Frederick Buckland (born 4 February 1954 in Zimbabwe) is a South African award-winning playwright, performer, film director, mime, and academic. Biography Born and schooled in Zimbabwe. He is married to actress Janet Buckland. Their ...

observed that the 18 Foot Skiffs had sailed all season (1982/83) without pulling the spinnaker pole back from the forestay and that all the systems could be simplified by eliminating the pole and setting the spinnaker from a fixed (but often retractable) bowsprit. The concept quickly evolved to a sail with a loose luff much more like a conventional spinnaker than the old jib style asymmetric sails. Working with his sail maker, Andrew Buckland, Julian Bethwaite was the first to rig and sail a boat with one the next season, followed shortly by Buckland himself. The first modern both keelboat and offshore sailboats to incorporate a retractable bow sprit and an asymmetric spinnaker was the popular J/Boats

J/105 The International J/105 is a fixed keel one design racing sailboat. It was the first production boat featuring a retractable bowsprit, which allows for an unusually large asymmetrical spinnaker. It was introduced in 1991 by J/Boats and designed ...

designed in 1992. The concept has spread rapidly through the sailing world. The

tack TACK is a group of archaea acronym for Thaumarchaeota (now Nitrososphaerota), Aigarchaeota, Crenarchaeota (now Thermoproteota), and Korarchaeota, the first groups discovered. They are found in different environments ranging from acidophilic ...

of the sail may be attached at the bow like a

but is frequently mounted on a

, often a retracting one. If the spinnaker is mounted to a special bowsprit, it is often possible to fly the spinnaker and the jib at the same time; if not, then the spinnaker will be shadowed by the jib, and the jib should be furled when the spinnaker is in use. The asymmetric has two sheets, very much like a jib, but is not attached to the forestay along the length of the luff, but only at the corners. Unlike a symmetric spinnaker, the asymmetric does not require a spinnaker pole, since it is fixed to the bow or bowsprit. The asymmetric is very easy to gybe since it only requires releasing one sheet and pulling in the other one, passing the sail in front of the forestay. Asymmetrics are less suited to sailing directly downwind than spinnakers, and so instead the boat will often sail a zig-zag course downwind, gybing at the corners. An asymmetric spinnaker is particularly effective on fast planing dinghies as their speed generates an

on the bow allowing them to sail more directly

. It is also particularly useful in cruising yachts in the form of a ''cruising spinnaker'' or ''cruising chute'', where the ease of handling is important.

Notes

External links

* * {{Sail Types Sailing rigs and rigging da:Gennaker de:Gennaker fr:Gennaker it:Gennaker nl:Gennaker fi:Genaakkeri