Professional BoatBuilder Magazine Online

Winged Victory

wingedvictoryVan Oossanen & Associates

In the summer of 1983, in the months leading up to the 25th America’s Cup competition in Newport, Rhode Island, a storm of controversy gathered over the challenging Australian and defending New York Yacht Club syndicates.

At that time, the rules governing the Cup required that each yacht be designed by citizens of the country it represented. The principal designer of Australia II, the eventual winner, was indeed a “national”—Ben Lexcen. Much of the development work on that boat, however, was performed at the Netherlands Ship Model Basin (now known by the acronym MARIN), in Wageningen, by Peter van Oossanen. On seeing Australia II perform in the challenge trials in Rhode Island Sound, the New York Yacht Club sought to disqualify her on the basis of the rule cited above.

But to do so, the NYYC had to establish that Van Oossanen, not Lexcen, had designed the boat, or had made a significant contribution. Though he didn’t know how to run a computer, Lexcen maintained an office at MARIN; all insisted he was the team leader. In the end, the issue was dropped. Australia II competed, and won in a stirring seventh and final race.

Prior to my visit with Van Oossanen in Wageningen, I’d been warned that he was tired of talking about the famous wing keel, and that his more recent work was overlooked. When we sat down to an interview in his conference room, it turned out that Van Oossanen very much wanted to set the record straight. Despite his long-standing affection for Australia, where he grew up, he wished to clarify the roles he and Lexcen played; in short, to give credit where credit is due. Though many of the details of the 1983 parrying were reported in the book Upset, by Michael Levitt and Barbara Lloyd, and in a paper written by Van Oossanen published by the Society of Naval Architects and Marine Engineers (Jersey City, New Jersey) in 1985, Van Oossanen’s present take on those events is quite interesting.

After Alan Bond failed to win the 1977 Cup with Australia (Bond had also funded the 1974 challenge), Van Oossanen wrote a letter to Bond, enclosing an early copy of the paper he would later present to the Chesapeake Sailing Yacht Symposium, in Annapolis, Maryland. Here, we’ll let Van Oossanen pick up the story:

“Lo and behold, I got a letter back from Alan Bond quite quickly, asking whether I could come over and meet with him and Ben Lexcen. I happened to know Ben, a little, because when I lived in Sydney I was sailing Moths at the Balmoral Sailing Club. Ben was also a member of that club.

“I went to Perth and met up with Alan. He was particularly interested in organization and cost: what it would cost to enlist the services of the Netherlands Ship Model Basin. He asked me to work out of Sydney and meet up with Ben, which I did. We spent the whole weekend together. Ben came over to The Netherlands and two months later it was all canceled. Alan was in some financial difficulty. I kept on working at what was now called MARIN for the next two years. Did some studies and model testing. And then out of the blue, Ben visited me early in 1981. Ben said, ‘We’re on.’

“We spent the day together in Wageningen. Then I got a telex from Warren Jones [Bond’s project manager] asking me to meet him in Perth, Australia, which I did in March or April ’81. Contracts were signed and details discussed, such as confidentiality. We started work in April–May. We very quickly built a model of Australia. I had suggested a whole series of keel tests because I felt that the keel was lacking. While this was going on I visited the National Aerospace Laboratory in Amsterdam. I met with their chief aerodynamicist, Joop Slooff, who was also a bit of a yachting bloke. He would play a very important role in what was to follow.

“We identified four different keels with different taper ratios and aspect ratios: a swept-back configuration where the sweep on the leading edge is the same as the sweep on the trailing edge; a keel without any sweep at all; a keel with an upside-down configuration; and a keel with a leaning-forward sweep. One of the things I had learned as a researcher is that if you make small changes in any of your parameters, you’re going to get results that are very close together, and it’s hard to discern a trend. What you have to do is make big jumps in your parameter field and pick up on the big trends. We elected to do just that, and arranged with the Australians to test different keels in the tank. It was a major cost item.

“During our conversation Slooff said to me, ‘We have a computer program that at least for airplanes is capable of pinpointing the viscous drag, the induced drag, and the lift forces.’ Slooff also said to me, ‘If you give us a contract, we can develop the code a little bit to get some idea about the wave resistance.’ Because when you produce any sort of force just below the water surface, like a keel will do, you also have a wave-resistance component.

“Slooff came to Wageningen with his results just as we were about to test the second model in the tank. He pinpointed the inverse taper/upside-down keel as being quite superior to the other three for the low-aspect-ratio configuration we were looking at. I was impressed, because the results were quite a bit better. He said to me, ‘The only problem we can see with this upside-down keel is the major tip vortex at the bottom, because the chord length is quite long there. It’s a worry. If we can find something to fix it, this keel will be a major improvement.’

“Then he mentioned the word winglets, and he cited a patent by NASA’s Richard Whitcomb, in 1978. Nearly the same configuration as on the Boeing 747, except Whitcomb’s concept utilizes two winglets, including a small winglet pointing downward at the very front of the wingtip.

“What a winglet does is this: At the tip of any lifting surface there is a major flow from the high-
pressure side to the low-pressure side, around the tip. Depending on how highly loaded the wing is, the vorticity in this roll-up mechanism can be either small or major. There’s a huge amount of energy in there, and if you can recover it, it makes the wing much more efficient. The winglet has a very special setting. Relative to the incoming flow, it produces a lift force in a plane normal [perpendicular] to the winglet that counteracts the tendency of the flow to want to go around the wing tip.

“If you test a keel with winglets in a wind tunnel and visualize the flow, you see a small vortex coming off the tip of the winglet—but none where the old tip was. It’s a very efficient way of getting rid of the tip vortex or decreasing it substantially.

“While all this was going on, Ben Lexcen wasn’t in The Netherlands; he was back in Australia. I sent a telex to Warren [Jones] and Ben saying we needed to test this. Ben came over a second time, and he and I started sketching what the winglets would have to look like on a keel. On a keel you obviously need two winglets, for port and starboard tacks, because the lift direction changes.

“We at MARIN made the drawings for the upside-down keel. Ben had nothing to do with it. He wasn’t even here when we tested it. The numbers were miraculously better. When we saw the numbers out of the tank there was no doubt to us that the improvement was substantial: about 25% less induced drag going upwind for the same side force. Huge!

“The next noteworthy occurrence came when Alan Bond, Warren Jones, and skipper John Bertrand came over in August ’81. That was a very difficult meeting because they only had an afternoon to spare. They flew in on a private jet. We picked them up. John Bertrand set the scene at the start of the meeting. He said, ‘Hey guys, you don’t think I’m a fool, do you? There’s no way we’re going to build a boat like that or anything that even resembles it! We’ll be the laughingstock of the whole yachting community.’

“Warren was a shrewd character. He had great respect for our ability. He said, ‘Well, hang on, John. Let Peter tell his story and we’ll discuss this afterwards.’

“I went through it and explained it to them. I had Warren and Alan utterly convinced. John has a degree from MIT, but I think he didn’t understand what I was presenting. He doesn’t want to take risks, especially when helming the boat.

“Anyway, Warren pulled me to one side as they were leaving, and said, ‘Peter, Alan has enough money. We’re going to build two boats—a radical boat and a normal boat. So we can cover all our avenues and possibilities.’

“And that’s exactly what happened. Australia II, with the wing keel, won out. The conventional boat was sold, and also campaigned in ’83 as Challenge 12. But I’m getting ahead of the story.

“After all these tests were done and Steve Ward, the builder in Fremantle, was preparing to build, we did a final set of predictions. They showed that in very light conditions, say 6 knots of wind, the wetted surface area of the boat was still more than we wanted—because the winglets were adding wetted surface. In very light conditions the keel performance is not a big part of the makeup of the boat. Because the upside-down configuration has a lot more ballast, I suggested cutting down the waterline length to the bare minimum, which was 44'3" [13.5m], reducing the displacement by 11⁄2 tons, and increasing sail area. I went back to my paper of 1979. I then had to explain all this to the group in Australia, and they all agreed. We did the final set of full-scale loftings, the final hull design, the final keel design. It was all done by us. I went to see Steve Ward in Perth to get him going. The boat was built in aluminum, of course. Ben made the construction drawings. Lloyd’s approved the design and construction drawings. The boat was built.

“Initially, John Bertrand failed to realize the boat needed to be pointed very, very high. If you don’t sail at the correct VMG [velocity made good: a measurement of time to cover a distance between two points] then the boat is only as fast as any other good 12-Meter. You need to lift the boat up 3°–4° higher. We discovered that the boat maneuvered very, very well. The waterplane area was a lot less, and there was free-flow around the hull because the keel chord at the top was so short.

“There was an Australian Cup event just prior to the boat going to Newport, with three or four other 12s participating. The Americans should have realized something new was going on, because Australia II won all of those races by minutes.

“Later, in the finals at Newport, after four races, Dennis Conner in Liberty was up 3–1. Dennis is a shrewd sailor, one of the very best. In the next few races Australia II won by three minutes and more. On each windward leg she was far ahead. It went to the final seventh race, in light, shifty conditions. Again the Australians were behind, except for the second-to-last leg, downwind, when Dennis didn’t cover Australia II. Dennis went over on the port side of the course and Australia went to the starboard side. Dennis should have jibed and covered. When they came down to the bottom mark Australia was ahead by something like 30 seconds, and won the race by 45 seconds.”

—Dan Spurr

From the article, “The Hydrodynamicist” by Dan Spurr in Professional BoatBuilder, Issue No. 121 (October/November 2009). All rights reserved.