Lead Keel IV
Designer
Ben Lexcen
(1936 - 1988)
Date1936-1988
Object numberANMS1543[366]
NamePlan
MediumPencil on film
DimensionsOverall: 765 x 390
Copyright© Ben Lexcen
ClassificationsMaps, charts and plans
Credit LineAustralian National Maritime Museum Collection purchased with USA Bicentennial Gift funds
DescriptionAUSTRALIA II, ballast keel drawing. Made by Ben Lexcen in 1981, with handwritten notes and calculations, for the revolutionary inverted winged ballast keel on the 12mR Australian challenge yacht AUSTRALIA II.
HistoryAustralia’s quest for the coveted ‘Americas Cup’ began in 1962 with the Alan Payne designed GRETEL. This was followed in 1966 with the Warwick J. Hood yacht DAME PATTIE and by GRETEL II in 1970. Alan Bond took up the challenge hopes in 1973/74, when he hired Ben Lexcen (then Bob Miller) to design ‘SOUTHERN CROSS’ (KA-4). Based on a lifelong experience designing, building and racing, fast sailing yachts, Ben Lexcen, was the obvious choice for Alan Bond. A successful small boat designer and international Olympic sailor, Ben Lexcen (previously Bob Miller) had designed many successful ocean racing yachts including: ‘PLUM CRAZY’, ‘MERCEDES III’, ‘APOLLO’, ‘APOLLO II’ ‘GINKGO’, ‘BALLYHOO’ and ‘CEIL II’. The 1974 Australian challenge was not successful, but he went on to design and build AUSTRALIA (KA-5) for the 1977 and 1980 races. For the design of AUSTRALIA (KA-5) in 1977, Ben Lexcen teamed up Johan Valentijn, an experienced Dutch naval architect, who had worked for ‘Sparkman & Stephens’ in the US. Ben Lexcen and Johan Valentijn worked together on a number of yacht designs, including the 45-foot IOR yacht ‘GUIA V’ in 1976, for Italian ocean racing yachtsman, Giorgio Falck. Interestingly, Ben Lexcen and Johan Valentijn spent seven months in 1976 testing 1/9th scale models of AUSTRALIA (KA-5) at the University of Delft test tank in the Netherlands. This period of on-site design and tank testing scaled models in the water, proved helpful for future design work on AUSTRALIA II (KA-6). With experience in tank testing 12mR racing yachts, using the Netherlands Ship Model Basin in Wageningen was an obvious choice for Ben Lexcen as he wanted to test larger 1/3rd scale models. After four months designing and testing in Holland during early 1981, the final design of the hull and ballast keel was ready. Interestingly, the design of the rival 1983 American defending yacht LIBERTY, was designed by Johan Valentijn.
The lead ballast keel on a sailing yacht provides stability, and works as a counterweight to resist the pressure of the wind on the sails. It also prevents the yacht from being blown sideways. The shape of the keel is made to be like an aerofoil (wing) in order to create lift and reduce drag to a minimum. Lead is used as it is has high density and also resistant to corrosion. Ben Lexcen designed the ballast keel of AUSTRALIA II to provide low drag and very high lift, while at the same time placing the weight very low down.
Ben Lexcen’s AUSTRALIA II, was a revolutionary design far beyond just the inverted, winged keel. It was much lighter in weight, had the shortest waterline length ever measured on a 12mR yacht. It also used radical ‘vertical sail’ designs, all Kevlar running rigging and a lightweight carbon-fibre boom. The America’s Cup trophy was held by the New York Yacht Club, successfully defending twenty-four challenges for 132 years. This all changed in 1983, when the Australian yacht AUSTRALIA II (KA-6), designed by Ben Lexcen, captained by John Bertrand, and representing The Royal Perth Yacht Club of Australia, beat the American yacht LIBERTY.
SignificanceThe design work is an interesting insight into the design ideas and techniques used by Ben Lexcen in 1981 in developing the hull and ballast keel for the 12mR yacht AUSTRALIA II. The drawing indicates his use of the traditional method of drawing, measuring and mathematically calculating the volumes, areas, weights and centres. This work is now, almost universally carried out using computer aided drawing programs (CAD). 
