America's Cup Class yachts are built to a development rule with considerable leeway in the measurement system to allow for different hull shapes, keel and rudder configurations, and rigs. As in the past the big question will be whether designers, engineers, and sailmakers will be able to make any significant improvements over the boats that raced in 2000. That year, New Zealand won the Cup in five straight races from the Italians, who had eliminated 10 other challengers in the Louis Vuitton Challenger Elimination Series before coming up against an invincible Kiwi team.
To date, most of the nine would-be challengers have launched new boats. The most obvious difference in this year's crop of challengers is that they appear to all be using some form of the "Davidson bow"—the sharply knuckled profile that appeared on both of the 2000 New Zealand boats and was the brainchild of Laurie Davidson. He has since become an American citizen and the chief designer for the One World Challenge syndicate based in Seattle, WA. This configuration makes more efficient use of the AC Rule where it measures the bow overhang, and results in boats with a longer waterline at the same rating as boats with more conventional bows. The boat could have more sail area with the same measured length, as sail area and length are traded off under the rule.
The Davidson bow on the first boat built for the Swiss challenge seems from a distance to be almost identical to the New Zealand bows of 2000. Helmsman Russell Coutts and much of the afterguard of Switzerland's Alinghi Challenge made up the nucleus of the Kiwi crew who won the Cup from the San Diego Yacht Club in 1995 and successfully defended it off Auckland in 2000. This foundation of New Zealanders has been with the Swiss team for two years now.
As well as building two new boats, the Swiss also own Be Happy, the boat that sported fore and aft rudders during the 2000 series and showed flashes of speed, but was subject to breakdowns and was difficult to get into the groove. She has been given a conventional underbody and has a pronounced knuckle at the forward measurement point.
The boats representing Oracle Challenge from San Francisco, designed by the Bruce Farr office in Annapolis, MD, are sporting the new bow, but the knuckle is not as extreme as on the 2000 New Zealand boats. And of course Davidson himself has put his bow on the Seattle challenge's boats, which are now working out in Auckland.
|"Computers, test tanks, and the ocean have all confirmed that narrow is fast when it comes to IACC hull design."|
By 2000 most designers were onto the "narrow is fast" theory and the boats that did battle in the frequently rough N.Z. waters were all at least as narrow as the 1995 Kiwi pair. In fact some of them were so narrow that the jib sheeting angle—even with the sheet track right on the deck edge—was was too fine when the wind rose or if the boat had to crack off for several minutes due to one of the big wind shifts prevalent on the Hauraki Gulf. The jib-sheeting angle is the angle between the center line of the boat and a line drawn from the jib tack to the sheeting point. These angles were getting down near the six degree range, which is very fine even by America's Cup Class standards.
This year, although designers want the boats to be narrow on the waterline and above the water in the forward sections, most seem to have opted for just a hair more beam amidships where the jib sheet tracks are. With this increased beam it will be possible to sheet jibs at between six and eight degrees.
The AC rule dictates that there can be only two moveable appendages under water. These can be in the form of a rudder or rudders, and a trim tab on the keel. The normal configuration is a trim tab and an aft rudder. If the boat is to have rudders both fore and aft, it cannot have a trim tab on the keel. It appears that no design group has yet tried to control their boat with a rudder forward, a tab on the keel, and no aft rudder.
Although there can be small advantages to the forward appendage under some conditions it is not easy to control a boat with this steering system. Designers and crews are faced with the choice of minor benefit with the likelihood of creating maneuvering problems. During their 5-0 win over Italy's Prada challenge in 2000 the home team demonstrated an ability to maneuver their 80-foot sloop as though it were a two man dinghy. Team Prada's helmsman Francesco de Angelis said after the fourth race that he had no idea an America's Cup boat could be sailed like that. The ability to stop the boat dead, then accelerate to full speed quickly, to turn it in its own length and to make it back up when convenient, played a major role in New Zealand's superb starting strategy. Any advantage gained by a forward rudder would have to be considerable for a team to give up this kind of maneuverability. Time might better be spent learning how to handle the boats like the Kiwis did in 2000, and even trying to improve on that.
Another feature developed by New Zealand in 2000 was the three-spreader mast with diamond shrouds. This spar system created less windage than other America's Cup masts and versions of it are now appearing on most of the 2002-03 crop of boats.
The superiority of the New Zealand boats in both 1995 and 2000 was so marked that they have served as benchmarks for the subsequent challenges. This time the man who was either responsible for or who played a major roll in the Kiwi breakthroughs of the past has jumped ship and is leading Craig McCaw's Seattle effort. Time will tell if Laurie Davidson left behind enough design talent to keep New Zealand ahead of the rest of the world.
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