For the second straight day the Italian entry Prada just managed to beat a top-rated U.S. team in America's Cup challenger trials, and once again it needed outside help.

Prada and the New York Yacht Club's charcoal gray Young America dueled like twin scimitars on a sparkling sea for two hours, never straying more than a few boat lengths apart as they matched each other's moves, tack for tack.

Young America won the start and held the lead at every turn until the final downwind run to the finish, when a shackle controlling the spinnaker came loose, the shimmering sail flew out in front of the boat and Prada swept past to claim a 10-second victory in the second-closest race of the Cup so far.

When the silver Italian bullet crossed the line with Young America right behind, Prada support boats in the spectator fleet erupted with horn blasts and shouts. The win left Prada the only challenger still undefeated at 8-0 with two races to go in this first round of trials. Young America and rival U.S. entry AmericaOne are tied for second place with one loss apiece.

Prada is starting to look like a team of destiny with luck on its side. On Friday, skipper Francesco de Angelis was behind AmericaOne's Paul Cayard by a few boat lengths just 300 yards from the finish when Cayard's spinnaker split and Prada swept ahead to win by 17 seconds.

Today he pulled out another win on the strength of his foe's bad luck.

The nip-and-tuck matchups of these three top-rated teams at the end of the first challengers' round-robin have established the trio as the boats to beat in the budding Cup season.

Prada, with a $40 million budget underwritten by the Milan fashion house of the same name, came into the Cup the acknowledged team to beat. The Italians have been practicing for more than two years and were among the first to launch two new boats last spring. They seem to have limitless resources for sails, equipment and facilities.

By contrast, no U.S. team has had unlimited time or money to prepare. But the America's Cup often goes to the team that builds and develops during the racing season, and the two top U.S. entries were keen to see if they were at a reasonably even starting point with Prada. The sting of two straight losses was tempered by the close racing and the fact both American boats could have won the races but for bad luck.

Young America, from the venerable New York Yacht Club, is banking on a fast boat from the desk of Annapolis's Bruce Farr, considered the top big boat designer in the world. AmericaOne, the San Francisco team, has Cayard, the hottest big-boat sailor in the world at the wheel.

Cayard had his first turn against the favorites Friday and seemed pleased with the result as the lead changed hands several times and speed looked equal. "It's going to be great," he said of the upcoming three months of racing to winnow the challenger field of 11 down to two finalists, then one trials winner to race Team New Zealand for the Cup in February.

"You've got a few boats that will be fighting for two spots and I'm thankful it looks like we're going to be one of them. We're happy to be in a tight boat race with Prada." Likewise for Young America. In today's test, Baird, the former world match-race world champion, hit the start line at full speed, ahead and to windward of Prada, just as the gun fired to take an early lead.

An afternoon breeze had settled in at 12 knots after a long, windless morning, but it was a shifty and spotty breeze. As the skippers played the shifts the advantage changed hands; Prada forged in front at one point up the first leg but Young America took the lead back on the next wind shift and led by 35 seconds at the first turning mark, the biggest margin either boat would enjoy all day.

Prada roared back to 18 seconds behind on the downwind leg and threatened for the lead all the way back upwind. She turned the final mark just 13 seconds behind. The boats battled evenly downwind until the shackle opened on Young America's spinnaker and the sail flapped in the breeze, Prada powering through.

It marks the third time in this week-old Cup season that a shackle has failed in racing. Prada lost control of its spinnaker twice to shackle trouble in the race against Cayard, and Nippon bowman Toshiki Shibata wound up in the hospital with a broken jaw and lost teeth when a shackle on the spinnaker pole opened and the pole bashed him in the face.

While Young America battled away, Cayard had an easy day scoring a 1 minute 18 second win over the Hawaiian entry Abracadabra and a one-minute win over Stars & Stripes. On Sunday, the last of the big first-round matchups features AmericaOne and Young America for the right to claim the best U.S. record in the opening round of the long Cup season.

CAPTION: When a shackle controlling a spinaker came loose on Young America, Prada, above, surged ahead to improve to 8-0.