A modern innovation in boat design. First invented by Julian Bethwaite in the late 1970s to use on his 18ft Skiffs, the asymmetric spinnaker greatly simplifies the traditional spinnaker design. It was inspired by the balloon genoas of J-Boats - racing yachts - and the America's Cup boat Intrepid. The sail is supported around the top of the mast, on the end of a bowsprit and by a spinnaker sheet controlled by the crew.

This invention was to be a massive advance in boat design. In 18ft skiffs the spinnaker can now be set in as little as five seconds, compared to thirty seconds with a traditional spinnaker. Gybing becomes far easier as with no spinnaker pole to move the asymmetric spinnaker can be gybed as easily as a jib, and the sail is far easier to handle with only one control (the sheet), compared to the complicated traditional system with its sheets, guys, reaching hooks etc. The large asymmetric spinnakers enable the boat to point higher than ever before, and allowes modern 18ft skiffs to sail faster than the wind!

Asymmetric spinnakers have revolutionised downwind sailing: Whereas with a traditional symmetrical spinnaker can be set dead downwind, the asymmetric can not be set below a broad reach. This creates a no-go zone downwind similar to the one encountered upwind, meaning boats must gybe downwind as they would tack upwind.

Asymmetric spinnakers are now standard on most new designs of dingy, for example in the 29er, 49er, RS200 and Cherub classes.

While the A-spin seems to be intended as a simplification, it has its own arcane set of practices that must be observed and may actually make things more complicated.

Instead of sailing dead downwind, the boat may sail on more of a broad reach at higher speeds and not necessarily on a steady course. As the boat heads up-wind a little, speed increases and the sheet is trimmed in and the kite operates more like a large Genoa jib. After Speed is built, the boat may bear away and head more directly downwind with more speed. Then there's the variable of how tight or loose to trim the tack and head of the sail. As the boat heads down and speed decreases, the crew shifts weight to try to heel the hull to windward in order to get the kite to rotate to windward to expose more surface area to the direct wind. J-105 Spinnaker:


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