A gennaker 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 may ...

that was developed around 1990. 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 chosen cour ...

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 ...

, it is a cross between a

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

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 n ...

. It is not symmetric like a true spinnaker but is asymmetric like a genoa, but the gennaker 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 ...

like a jib or genoa. The gennaker is rigged like a spinnaker but 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 the ...

is fastened to the hull or to 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 that counteracts the forces from the forestays. The word ''bowsprit'' is thought to originate from the Middle L ...

. It has greater

camber Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...

than a genoa (but significantly less camber than a spinnaker). This is 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 m ...

. An early form of gennaker was the "gollywhomper", used briefly in the 1870s. The gennaker is a specialty sail primarily 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 goa ...

boats to bridge the performance gap between a genoa and a spinnaker. It is sometimes the only downwind sail on board because it is easier to use and less expensive than a spinnaker. Due to its geometry, the sail is less prone to collapsing than a spinnaker. A gennaker is optimal for a

beam reach Beam Reach is a redevelopment area in London, England and part of the London Riverside section of the Thames Gateway. It is an industrial area adjacent to the new neighbourhood of Beam Park. Geography It is located in the southern part of the L ...

, while an

asymmetrical spinnaker An asymmetrical spinnaker is a sail used when sailing downwind. Also known as an "asym", "aspin", or "A-sail" it can be described as a cross between a genoa jib and a spinnaker. It is asymmetric like a genoa, but, the asymmetrical spinnaker is not ...

is optimal for a

broad reach A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface. The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind ...

run Run(s) or RUN may refer to: Places * Run (island), one of the Banda Islands in Indonesia * Run (stream), a stream in the Dutch province of North Brabant People * Run (rapper), Joseph Simmons, now known as "Reverend Run", from the hip-hop group ...

References

{{Sail Types Sailing rigs and rigging