SAN DIEGO - When America's Cup challenger oneAustralia snapped in two and sank 500 feet into the Pacific, some observers speculated that designers had gone too far in their use of lightweight plastics and composites. The first sinking of an America's Cup boat in 144 years happened March 5, in a qualifying race with Team New Zealand in about 21.3 knots of wind.
At the bottom of a wave, ``we heard a loud crack, almost like a cannon going off,'' said Skipper John Bertrand.
``The boat appeared to start to fold like a sheet of cardboard through the center, and [we heard] this sickening sound as the boat was breaking apart,'' he said.
``The loads are extremely high in the constant push on these yachts,'' Bertrand said. ``It is unclear to me exactly how the boat broke up and why.''
The Australian team began building hull AUS-35 July 11 atJ. McConaghy Industries Pty. Ltd. at Mona Vale on the northern beaches of Sydney, Australia. Hulls of America's Cup boats have inner and outer skins of carbon fiber and low-temperature-cure epoxy prepreg and honeycomb cores of Nomex aramid or aluminum.
SP Systems Ltd. on England's Isle of Wight supplied SE84 epoxy prepreg for the hull using T400 carbon fiber from Toray Industries Inc. of Tokyo. Plascore Inc. of Zeeland, Mich., supplied Nomex honeycomb for the hull and deck and ICI Fiberite of Tempe, Ariz., supplied the carbon fiber for the 110-foot mast. The boat initially raced Feb. 16.
Several designers and America's Cup sailors were quick to defend the use of the extremely lightweight composite materials.
``These boats are absolutely to the limit,'' said John Marshall, director of Pact '95 and former design team head for Stars & Stripes '87, winner of 1987's Cup.
``They're leading-edge stuff. This is a sport in transition from boats made out of metal to boats made out of composite plastics,'' he said in a Boston Globe interview.
``If you're pushing hard at technology and you fail, you're fun to pick on. But that is the challenge, to get as far out as you can,'' he said. ``If you're not going to take some chances, there's just no possibility of winning.''
``All boats have soft spots,'' said Heiner Melder, director of technology for America3. ``These are racing vehicles, and ... the ideal racing vehicle is one that falls to pieces right after it fin-ishes. But sometimes it happens before,'' he said.
Designers produced 99 computerized models before building AUS-35. The models allowed structural engineers to remove more than 440 pounds of carbon fiber from the keel structure alone, a weight savings of 30 percent, said corporate affairs director John Fitzgerald.
Designers John Reichel and Jim Pugh of Fluid Thinking Pty. Ltd. of Melbourne, Australia, and Iain Murray in Sydney were involved also in the early-1994 AUS-31 hull with which oneAustralia won the Oct. 28-Nov. 5 warm-ups. Bertrand termed the difference between the two hulls ``very small.''
As for recovery, the U.S. Navy agreed to help, ``but we're not going to tie ourselves in knots worrying about what's on the bottom,'' said Peter Morris, oneAustralia chief executive officer. ``Our concern is what's on the racecourse.''
MMI Insurance Ltd. of Sydney covered the $3 million loss.
Bertrand led a 1983 team that took the Cup from the U.S.