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Australia II

Australia II
Australia II pan.JPG
Yacht club  Royal Perth Yacht Club
Nation  Australia
Class 12-metre
Sail no KA–6
Designer(s) Ben Lexcen
Builder Steve Ward
Launched 1982
Owner(s) Alan Bond
Australian Government c.1985
Racing career
Skippers John Bertrand
Notable victories 1983 Louis Vuitton Cup
1983 America's Cup
America's Cup 1983
Specifications
Displacement 21.8 tons
Length 19.21 metres (63.0 ft) (LOA)
13.10 metres (43.0 ft) (LWL)
Beam 3.64 metres (11.9 ft)
Draft 2.72 metres (8 ft 11 in)
Sail area 175 square metres (1,880 sq ft)

Australia II (KA 6) is an Australian 12-metre-class America's Cup challenge racing yacht that was launched in 1982 and won the 1983 America's Cup for the Royal Perth Yacht Club. Skippered by John Bertrand, she was the first successful Cup challenger, ending a 132-year tenure (with 26 successful defences) by the New York Yacht Club.

Australia II was designed by Ben Lexcen, built by Steve Ward, owned by Alan Bond and helmed by John Bertrand. Lexcen's Australia II design featured a reduced waterline length and a short chord winged keel which gave the boat a significant advantage in manoeuvrability and heeling moment (lower ballast center of gravity) but it was a significant disadvantage in choppy seas. The boat was also very quick in stays. The winged keel was a major design advance, and its legality was questioned by the New York Yacht Club. During the summer of 1983, as selection trials took place for the Cup defence that autumn, the New York Yacht Club challenged the legality of the keel design. The controversy was decided in Australia II's favour.

Australia II sported a number of other innovative features that contributed to her success, including radical vertical sail designs, all kevlar running rigging and a lightweight carbon fibre boom.

In 2009, Dutch naval architect Peter van Oossanen claimed that the winged keel was actually designed by him and his group of Dutch designers, and not Ben Lexcen. If true, this would have been reason to disqualify Australia II, since the rules state that the yacht is to be designed by citizens of the nation it represents. The controversy arose due to Cup Rules allowing designers to use model basins for testing that are not located in the challenging country. Model testing was performed in the Netherlands and Peter van Oossanen and another Dutch engineer, Joop Sloof, performed measurements and analyses related to evaluation of winged keel designs. The suggestion that the vessel was not designed by Australians has been refuted by both John Bertrand and project manager John Longley. Furthermore, it is well established that Lexcen had been experimenting with wing adaptations to the undersurface appendages of boats before, including his 1958 skiffs Taipan and Venom, although in the latter application they were not determined to be effective and not further adopted. In 1983 Lexcen commented on the controversy: "I have in mind to admit it all to the New York Yacht Club that I really owe the secret of the design to a Greek guy who helped me out and was invaluable. He's been dead for 2000 years. Bloody Archimedes..."


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