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Encyclopedia > Genoa (sail)

A genoa (pronounced like the city, or as jenny) is a type of large headsail used on bermuda rigged craft, commonly the single-masted sloop and twin-masted boats such as yawl and ketch. Its large surface area increases the speed of the craft in moderate winds; in high wind conditions a smaller jib is usually substituted, and downwind wind a spinnaker may be used. Genoa (Genova [] in Italian - Zena [] in Genoese) is a city and a seaport in northern Italy, the capital of the Province of Genoa and of the region of Liguria. ... A headsail is any sail set forward of the foremost mast of a sailing vessel. ... In sailing, a bermuda rig is: A rig of mainsail or course that consists of a triangular sail set aft of the mast, with its head raised to the top of the mast, its luff running down the mast and normally attached to it for all its length, its tack... A sloop-rigged J-24 sailboat A sloop (From Dutch sloep) in sailing, is a vessel with a fore-and-aft rig. ... Yawl sailing vessel. ... Square Topsl Gaff Ketch Hawaiian Chieftain on San Francisco Bay A ketch is a sailing craft with two masts: A main mast, and a mizzen mast abaft the main mast. ... It has been suggested that gennaker be merged into this article or section. ...

Contents

Definition

A jib, left, compared to a roughly 150% genoa, right. The foretriangle is outlined in red.

The term genoa is often used somewhat interchangeably with jib, but technically there is a clear delineation. A jib is no larger than the foretriangle, which is the triangular area formed by the mast, deck or bowsprit, and forestay. A genoa is larger, with the leech going past the mast and overlapping the mainsail. To maximize sail area the foot of the sail is generally parallel and very close to the deck when close hauled. Genoas are categorized by the percentage of overlap. This is calculated by looking at the distance along a perpendicular line from the luff of the genoa to the clew, called the LP (for "luff perpendicular"). A 150% genoa would have an LP 50% larger than the foretriangle length. Sail racing classes often specify a limit to genoa size. On International Offshore Rule boats, different classes of genoa have 150%, 130%, and 98% overlap, and so on. Under Performance Handicap Racing Fleet rules most boats are allowed 155% genoas without a penalty. Image File history File links Jib_vs_genoa. ... Image File history File links Jib_vs_genoa. ... mizzen mast, mainmast and foremast Grand Turk The mast of a sailing ship is a tall vertical pole which supports the sails. ... A deck is a permanent covering over a compartment or a hull[1] of a ship. ... Bowsprit of the Falls of Clyde, showing the dolphin striker, the use of chain for the bobstays, and three furled jibs. ... On a sailing vessel, a forestay is a piece of standing rigging which keeps a mast from falling backwards. ... diagram showing the names of the parts of a sail The lower edge of a triangular sail is called the foot of the sail, while the upper point is known as the head. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ...


Handling issues

Maximizing the sail area causes more difficult handling. It is harder to tack a genoa than a jib, since the overlapping area can become tangled with the shrouds and/or mast unless carefully tended during the tack. Genoas are very popular in some racing classes, since they count only the foretriangle area when calculating foresail size; a genoa allows a significant increase in actual sail area within the calculated sail area. In boats where sail restrictions are not applicable, genoas of 200% overlap can be found, although those over 150% are not often seen, since the additional area is shadowed by the mainsail when close hauled and generates diminishing returns in terms of power per actual sail area. Tack is a term, that depending on its application has several different meanings. ...


The gennaker

The Gennaker is a fairly new type of sail, and as the name suggests it is a hybrid between a genoa and an asymmetrical spinnaker. A brand name of North Sails, the gennaker is a cruising sail based on the Code 0 spinnakers used on racing boats. Gennakers and similar code 0 variants offered by other makers are even larger than genoas (200% overlaps are not uncommon) and they have a much greater camber for generating larger amounts of lift when reaching. Flat cut gennakers can be effective for angles as low as 60 - 70 degrees. Spinnakers perform much better when running because the main sail blocks the wind of gennaker above 135 -150 degrees. A gennaker is a downwind sail that can be described as a cross between a genoa and a spinnaker. ... It has been suggested that gennaker be merged into this article or section. ... This article is about brands in marketing. ... The camber in aerospace engineering is the asymmetry between the top and the bottom curves of an airfoil. ... Points of sail is the term used to describe a sailing boats course in relation to the wind direction. ...


History

In Dr Manfred Curry's influential book Yacht Racing[1], he describes his systematic experiments on yacht rigs in wind tunnels and on boats during the 1920s and 1930s. He stated that a larger jib overlap enhanced the venturi effect between the jib and the mainsail, especially when used with a fully battened mainsail, enhancing the low-pressure area behind the mainsail, so increasing the power available from the mainsail. He showed the analogy of jibs with aircraft slats. Later aerodynamic studies showed Curry's claims to be incorrect. There is no acceleration of airflow in the slot between the jib and mainsail. In fact, the circulation of air around the jib is opposed by the circulation around the mainsail, resulting in a net decrease in flow velocity in the slot.[2] Jibs and aircraft slats change the usable angle of attack, but this is not due to the Venturi effect. Manfred Curry (1899-1953) was born in Germany and is (self-proclaimed) discoverer of geomagnetic lines that are named after him. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Slats are small aerodynamic surfaces on the leading edge of an airplane wing which, when deployed, allow the wing to operate at a higher angle of attack. ...


Curry had difficulty promoting his concept at first. He stated[3]:


"It seemed impossible to convince yachtsmen of the value of the overlapping jib for beating to windward through the publication of articles until I beat the six metre boats on the Mediterranean by using the first overlapping jib at [a regatta at] Genoa (Italy) and until the Swedish boat "Maybe" beat the American six metres using these large jibs". Genoa (Genova [] in Italian - Zena [] in Genoese) is a city and a seaport in northern Italy, the capital of the Province of Genoa and of the region of Liguria. ...


Thus whether or not Curry invented these jibs, he developed their use on dinghies and yachts, and their name commemorates the first major regatta where they were used sucessfully - in his hands. In modern usage this sail would no doubt have been named the Curry jib.


However Curry did not evaluate the optimum distribution of sail area where all the sail area is measured. Modern research has shown that where jib overlap is not 'free' sail area, it is generally more efficient to use a larger mainsail or taller jib (or both) and reduce the jib overlap correspondingly.


References

  1. ^ Yacht Racing The Aerodynamics of Sails and Racing Tactics. Curry, M. First published in English 1928, Fifth edition 1948.
  2. ^ A Review of Modern Sail Theory, Proceedings of the Eleventh AIAA Symposium on the Aero/Hydronautics of Sailing September 12, 1981, p. 15
  3. ^ Curry p. 67

External links

  • North Sails G-series cruising gennakers

  Results from FactBites:
 
Genoa (sail) - Wikipedia, the free encyclopedia (432 words)
A genoa (pronounced like the city, or as jenny) is a type of large jib-sail used on bermuda rigged craft, commonly the single-masted sloop and twin-masted yawl, less frequently on a ketch.
Genoas are categorized by the percentage of overlap.
The gennaker is a fairly new type of sail, and is a hybrid between a genoa and an asymmetrical spinnaker.
  More results at FactBites »

 
 

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