Prada led halfway through the race, but AmericaOne found its speed and won.

The sail was changed and AmericaOne beat Prada of Italy by 1 minute, 33 seconds Thursday in the best-of-9 series, which continues Friday with the third race.

"It tore right on the deck" as it was being hoisted, AmericaOne crew member Curtis Blewett said. "Once it was on its way up, we kind of assessed it and felt it would hold."

It did, at least long enough for the crew to switch to its backup light-air gennaker, which is used on downwind runs in light breezes, before replacing that with a heavier sail when the wind picked up.

For the second straight day, the team that made the dramatic mistake was the winner. Prada won the first race by 24 seconds after having to make a penalty turn for bumping the American boat in maneuvering before the start.

The series winner faces defending champion New Zealand in another best-of-9 round for the America's Cup, the top prize in the sailing world.

The Italians made two mistakes: getting caught in the spectator fleet early and choosing to split with AmericaOne when the sail ripped after the third leg of the six-leg race.

"We assess our mistakes as a team and just make a plan for the next day," Prada helmsman Francesco de Angelis said.

That's what Dyer Jones, president of the America's Cup Challenge Association running the current series, plans to do with the spectator fleet.

Because of shifty winds, the race committee had to reset the course after the race began so that the legs would be directly downwind or upwind as much as possible.

"This put a number of yachts that were on the right-hand side of the course into the middle of the course," Jones said. Boats assigned to position the spectator fleet helped move it as the race developed.

"On days like today, everybody's job is made that much tougher," Jones said.

"It was definitely a strange race" because of the wind shifts, AmericaOne strategist Gavin Brady said. "It's good to survive these races. Sometimes it can go either way."

In a sport that relies on advanced technology and experienced sailing sense, AmericaOne rallied Thursday when its bad luck brought good fortune.

Cayard's boat trailed by 18 seconds after the third leg.

As it was turning around the buoy at the end of the upwind leg, it set a gennaker, but the sail ripped horizontally.

Had AmericaOne tried to turn, the tattered sail would have torn to shreds. So it kept sailing into the spectator fleet, where it got a push from better wind in the area.

Billy Bates, the sewerman who works in the dark inside the hull pulling in used sails and feeding out new ones, then gave his crewmates a new gennaker. This one stayed together.

By the end of the fourth leg on the 18½-mile Hauraki Gulf course, AmericaOne had opened a lead of 1:27, a gain of 1:45 on the leg.

Cayard, taking nothing for granted, stayed in control of his crew.

"Looking for (wind) pressure," he shouted as he turned the wheel at the back of the sleek, 80-foot boat. "Just chill out, everybody. Take a deep breath."

His crew could breathe even easier after the fifth leg, when AmericaOne built its lead to 1:35. Cayard was relaxed as the boat approached the finish line, sitting on the port side of the hull and steering with just one hand as his crew members showed little reaction.

Cayard, representing the St. Francis Yacht Club of San Francisco, is trying to win back the Cup the Americans held from the start of the competition in 1851 until Australia II won in Newport, R.I. in 1983. United States boats won the next three competitions until New Zealand's Black Magic scored a 5-0 sweep off San Diego in 1995.

Thursday's race began 65 minutes after the scheduled 1:15 p.m. starting time as officials waited for the wind to pick up. Two days earlier, the first race was delayed 24 hours because the wind was too strong and the sea too rough.

Wind at the start of the second race came from the southeast at 7 knots. The breeze kept shifting to the east and north throughout the race and stayed at 10 knots or less.