Lead line plan for tank test model 7205
Designer
Ben Lexcen
(1936 - 1988)
Date1972
Object numberANMS1543[079]
NamePlan
MediumPencil on drafting film
Dimensions390 x 770
Copyright© Ben Lexcen
ClassificationsMaps, charts and plans
Credit LineAustralian National Maritime Museum Collection purchased with USA Bicentennial Gift funds
DescriptionA Ben Lexcen (formally Bob Miller) ballast keel lines-plan with hand-written weight calculations, for a proposed lead ballast keel on the 12mR America Cup challenge yacht SOUTHERN CROSS designed in 1972 and 1973 for the 1974 Americas Cup races.
HistoryDuring the initial stages of a new design project, the yacht designer will gather as much information as possible what the owner wants and what the yacht will be used for. In the case of a high profile International 12mR yacht, built to challenge for the coveted America’s Cup, as much information about other similar yachts will also be studied in detail. The design of the 12mR SOUTHERN CROSS in 1972 and 1973 was first of seven such yachts Ben Lexcen would design in his career.
A self-taught naval architect, yacht designer and accomplished yachtsman, Ben Lexcen was born Robert Clyde Miller, on March 19th. 1936 at Boggabri, a small town in New South Wales, Australia. He left school at fourteen, after only five years formal education, to become an apprentice machinist at the New South Wales locomotive works. In 1952, at the age of 16, Ben Lexcen (then Bob Miller) designed and built his first sailing boat ‘THE COMET’ with his friend William Bennett. He soon began to make a name for himself at local sailing competitions. In 1960 he entered his boat ‘TAIPAN’ in the 18-Footer World Championships, and later winning the World Championship in 1961 with his design, the 18-foot skiff ‘VENOM’. In 1962, together with his friend Craig Whitworth, he set up the ‘Miller & Whitworth’ sail making business in Sydney, while continuing to design sailing dinghies. An accomplished sailor, then Bob Miller represented Australia in the Soling class at the 1972 at the Olympic Games at Munich, West Germany.
Bob Miller (later Ben Lexcen) soon became known for his fast, lightweight, racing yachts which included, PLUM CRAZY, MERCEDES III, APOLLO, APOLLO II, GINKGO, BALLYHOO and CEIL III. These early yacht designs were not tank tested as the process is costly and time consuming. It requires a number of different hull models to be designed, built, and tested in a purpose-built water tank facility. The costs involved would have been too high, and considered unnecessary, for owners of yachts of around 45-feet long.
Alan Bond and Bob Miller (later Ben Lexcen) were together at Newport, Rhode Island in 1970 for the Newport to Bermuda race. Together with the Australin team, they were preparing Alan Bond’s racing yacht ‘APOLLO’, at ‘Bob Direcktor’s Shipyard, at Mamaroneck, Yew York. While visiting a boatyard together at City Island, New York, Alan Bond spotted a large sailing yacht alongside, which unusually, had all the deck winches and crew positioned below deck. Alan Bond wanted a closer look so wondered down the pontoon to study the boat and layout but one of the crew took offence and shouted for him to go away. This did not go well, and when asked what type of boat it was anyway, was told it was the America Cup yacht ‘VALIANT’. Still mystified, Bob Miller explained what the America Cup was and about the yachts involved. To which Alan Bond told Bob Miller. ‘You design me one of those 12-metre boats, and we’ll come back here and win their bloody America’s Cup.’
In 1973, during the design and development of the 12mR yacht SOUTHERN CROSS (K-4) for Alan Bond and the Australian America Cup challenge team, several hull designs were proposed, and scale models of the hull hulls built and tested. Model 7205 is one of them.
The America’s cup challenge yacht SOUTHERN CROSS represented Australia, in its design, build, management and above all, in the crews sailing skills and ability. The defending American design team had a large budget, as well as the best materials and resources to draw on, so carried out extensive design work and tank testing. Several scaled models of SOUTHERN CROSS hull and ballast keel were built, varying from 1.41 metre to 1.51 metre in length overall. When tank testing, an allowance is made for the actual weight, so they can be tested in the water to check the designed hydrostatics, pounds per inch of emission, hull resistance, wave making, overall displacement and so forth. These tests take place in large, purpose-built water tanks, which allows the vessel to be towed though the water and information gathered to fully optimise the hull shape.
With a final overall length of 20.45 metres (67.09 feet) and beam of 3.71 metre (12.17 feet), SOUTHERN CROSS (KA-4) was built of aluminium at Terry Hills, Sydney by ‘Halvorsen Morson and Gowland’ of Mona Vale and launched in 1974. Following sea trials and crew training alongside the previous challenge yacht GRETEL II, SOUTHERN CROSS was shipped to the USA for the American elimination trials. The American 12mR yachts; ‘INTREPID’, MARINER’, VALIANT’ and COURAGEOUS were all trying to be the defending yacht for the cup challenge. Skippered by talented Australian Jim Hardy, SOUTHERN CROSS did her best but ultimately lost to COURAGEOUS. SOUTHERN CROSS was not successful in winning the America Cup in 1974 but in 1983 Alan bond returned to Newport with the Ben Lexcen designed AUSTRALIA II. Captained by John Bertrand, the yacht beat the American yacht LIBERTY and Australia finally won the America’s Cup.SignificanceThe lines-plan for a proposed lead ballast keel made by Ben Lexcen during early development work on Alan Bond’s first 12mR yacht ‘SOUTHERN CROSS in 1972/73. The work shows the ballast keel proposal with the hydrostatic calculation. It was used on the scale model of the hull to tank test the design. It represents the start of Alan Bond and Ben Lexcen’s quest for the coveted Americas Cup, when advanced designed, purpose built 12-metre yachts, raced against each other. 
