Lines plan of winged keel model of 2 VINNEN II and KIEL V
Designer
Ben Lexcen
(1936 - 1988)
Datec 1982
Object numberANMS1543[307]
NamePlan
MediumInk on tracing film
DimensionsOverall: 2300 x 765
Copyright© Ben Lexcen
ClassificationsMaps, charts and plans
Credit LineAustralian National Maritime Museum Collection purchased with USA Bicentennial Gift funds
DescriptionOne of the proposal drawings from 1981 for the revolutionary ballast keel fitted to AUSTRALIA II, the Ben Lexcen designed 12m yacht which won the 1983 Americas Cup.
Marked Keel V (5), it is after the innovative move to invert the ballast keel, which lowers the centre of gravity and minimizes the ‘hull-keel interaction’ and the loss of side force due to the proximity of the water surface.HistoryAlan Bond began his quest for the America’s Cup the 1970’s using Ben Lexcen (then Bob Miller) as the chief designer. Their 1974 challenger SOUTHERN CROSS was not successful but they went on to design and build AUSTRALIA for the 1977 and 1980 races. During this period Ben Lexcen teamed up Johan Valentijn, a young but experienced Dutch naval architect, who had worked for ‘Sparkman & Stephens’ in the US. Lexcen and Valentijn spent seven months in 1976 testing 1/9th scale models of AUSTRALIA at the University of Delft test tank in the Netherlands. Both challenges by AUSTRALIA proved unsuccessful but were a considerable help in the future design and build of AUSTRALIA II which started late 1980 early 1981, and culminated in September 1983, when AUSTRALIA II won the Americas Cup for Australia. Lexcen wrote to Warren Jones, project director of the ‘Australia II’ group, in early February of 1981 asking for support to fund tank testing at the Netherlands Small Ship Basin (NSMB). The primary reason being the Dutch facility had the size and experience to test large models. Interestingly he mentions in the letter: "I have some novel ideas I would like to try in the keel area, which would be quite revolutionary, and if they work out would be quite a big breakthrough. But only with models of this size can we try these ideas." In order to tow the 1/3rd sized test model of the yacht, Lexcen redesigned and rebuilt the moving carriage, so the towing point would represent the centre of effort of the sails and provide more accurate results in the test tank. With so much at stake for the coming challenge, an element of secrecy developed which continued right up to the day of the race start. During late May 1981, Lexcen sent a Telex to Warren Jones saying he had made a significant breakthrough in the keel design (Keel III) and was about to take yacht design into the space age. He referred to the new keel design as ‘Darth Vader’ to maintain this secrecy. The design of AUSTRALIA II and the winged ballast keel, continued after Lexcen returned to Australia in 1981. When the full-scale lofting work of yacht and ballast keel arrived from The Netherlands later in 1981, they were laid out on the floor of the boatyard where Lexcen spent several days crawling over it, adjusting and fine tuning both the hull and ballast keel, prior to the start of the actual build.SignificanceBen Lexcen was keen to use the Netherlands Ship Model Basin (NSMB) in Wageningen as it had the right size to test the 1/3 scale model of AUSTRALIA II. This, and other similar design drawings, were part of the hull and ballast keel development program. The major design breakthrough designing the keel of AUSTRALIA II came with Version III in May 1981. This version is still part of the on-going design work but clearly shows the un-conventional inverted keel shape, the use of known NACA airfoil sections in the ballast keel and the winglets.Lexcen spent at least four months at the Dutch test tank facility in 1981 designing, testing and refining the hull and ballast keel. The Lexcen design of the America Cup challenger AUSTRALIA II resulted in the first major design change to 12m yachts since the Olin Stephens INTREPID in 1967. It has influenced all future 12m yacht designs since then.
