Also called kites or chutes (as in "parachutes"), spinnakers also have become known as a pain in the neck to Paul Cayard's crew. The San Franciscans have had eight of their great lime-green billowing sails rip apart like mail-order suits over the last few months, while the opposition's have remained incredibly intact.

It didn't happen to AmericaOne in Tuesday's 34-second win that brought the team back to a 3-2 deficit in the best-of-nine Louis Vuitton Cup challenger finals, but it has happened often enough to raise some questions. Why has it happened so often? Why hasn't it happened to Prada?

"Their kites are really strong so they don't tear," AmericaOne skipper Paul Cayard noted earlier. "They have different material."

That material is a modified form of Spectra, originally created for Bill Koch's America3 defence campaign at San Diego in 1992, and dubbed Cuben-fibre.

"We have nylon kites," Cayard said. "The Italians have a Cuben-fibre cloth ... Spectra cloth. It's really solid and it's not gonna break. It's a weapon they have."

Spectra material is made in Phoenix, Ariz., on special order. For this America's Cup, Prada cornered the market.

"They basically bought the entire production run," said Robert (Hooky) Hook, AmericaOne's chief sail designer. "It's a cost-prohibitive product for the ordinary sailing world."

But it's also considerably stronger than conventional nylon for the same weight.

Guido Cavalazzi, Prada's sail designer, said, "It's five times the cost of nylon. It's laid by hand ... very, very complicated, very expensive. They use the basic material in different ways. We gave them our specifications. The material was made only for us."

Prada then used the finished material to build the sails. But the Italians don't use their Spectra spinnakers all the time.

"It's a wind to wave situation," Cavalazzi said. "Nylon is more forgiving when there's movement in the boat and you want the spinnaker to be more stretchy. On the first two runs Sunday we used Spectra, but we won the race using a nylon spinnaker."

Normally, Cavalazzi said, a Spectra chute would be used exclusively in flat water and any time the wind is over 17 knots, "because it doesn't break."

Prada has lost only one spinnaker -- Spectra or nylon -- and that was when the crew accidentally dropped one overboard in the first round robin.

The Italians also used Spectra gennakers in the earlier rounds, but haven't recently because of more disturbed seas due to a larger spectator fleet.

Spectra is not always an advantage. In Saturday's race, before AmericaOne dropped out because of a suspected mast problem, Cayard figured that when his boat ploughed into a wave and slowed suddenly, causing the spinnaker to burst across its midsection, it probably relieved pressure that would have pulled down his spar.

The next day when Cayard turned sharply onto the wind to luff the overtaking Prada, AmericaOne's chute tore out at the corners from the sudden pressure in the 25 knots of breeze.

But the blow-out allowed Cayard to wheel up higher into the wind and luff Prada, which lurched into a broach with its all-white spinnaker plastered into the rigging.

"One thing we found out is that his kite's not gonna break," Cayard said. "When they went head to wind, if the kite wasn't gonna break then, it's not gonna break. Thanks to American technology, they've got a good kite."

The wind has been only a partial factor in AmericaOne's spinnaker failures.

"Half of them broke because of getting stuck in the hatch or something and getting a little hole," Cayard said.

Hook said, "If you look at the eight spinnakers that broke, five have torn on the jumpers or while being hoisted. The other day one caught on a hatch cover. The one on Sunday blew up on a 135-degree reach; Saturday, from burying the bow in a wave."

Cavalazzi believes that AmericaOne's green spinnakers are weaker because of the dying process. "We had experience with very shiny pink material that was very brittle," he said.

Would AmericaOne be better off with plain white chutes? "Absolutely," Cavalazzi said.

Hook disagrees. That may have been true in the past, he said, "but with the dying processes we have now, what you find is that some of the brighter colours have better tearing strength."

Either way, AmericaOne is destined to live or "dye" with its verdant kites. Early on the second downwind leg Tuesday, a small vertical tear appeared in yet another one.

"Believe me, we were aware of that," Cayard said. "We just thought it was kind of in the middle there and as long as we didn't reach we didn't think it would explode. It's a different cloth to the one we've been using. It's a lot more resistant."