America's Cup win for BMW Oracle; mission accomplished for HDS

[Source: HDS] On February 14th, 2010 in Valencia, the black trimaran of the American Challenger, BMW ORACLE Racing, equipped with a wing of 68 meters, beat the catamaran of the Swiss Defender, Alinghi, to win the 33rd America’s Cup Match. Many talents from the French marine industry (sailors, naval architects, technicians and engineers) contributed to the development of what just might be the fastest racing boat of its size ever built. Among them, experts from HDS have shared in this technological challenge and contributed to the birth of the largest wing ever built for a sailing yacht.

In nearly twenty years, HDS, the company from Brest has written some of the most beautiful pages of modern sailing history. Specialists of structural engineering, these “men living in the shadows” follow the sailors and their teams in the design of always larger, lighter, more reliable and more efficient yachts.

From the Vendée Globe monohulls, to multihulls such as Groupama 3, Banque Populaire V or the Hydroptere, this team led by Hervé Devaux has collected no less than five records in 2009. This same team, internationally recognised, has also been involved in eight editions of the America’s Cup, which is a different world, where design and creativity have no limits.

Summer 2009, Anacortes (USA), apparent structure of the main element of the wing. The lower part is used as a mast and all the vertical parts stiffens the profile and is then covered with a film used in aviation. Photo copyright Steven Robert/HDS

Multihulls - a new challenge for the cup
The legal battle of this 33rd America’s Cup has often overshadowed the sporting side of the event and has also forced the designers into a ' no mans land' of constantly changing deadlines, different venues and new timelines.

In July 2007, BMW Oracle Racing challenged the Swiss Defender. The U.S. team then began work on the design of a maxi trimaran and called upon the French firm of architects Van Peteghem-Lauriot Prevost and HDS for the design. Both are widely recognised as leaders in the field of multihulls. Hervé Devaux, Aurélien Miller et Steven Robert then join the adventure. The latter remembers: “We knew that, potentially, the racing could have started one year after that initial challenge, so we had to work fast. We extrapolated what we knew (Orma trimarans, Groupama 3 ...) by scaling up to a 90-foot beam. We determined loads and defined the structural concepts of the yacht, masts and appendages. Legal proceedings were continuing and we gained more time to conduct a real development campaign. The measurements of hundreds of sensors were analyzed in order to optimise every element. Every kilogram saved was invested in new systems to improve performance. From a versatile boat - a good 'all-rounder' - we went to a pure racing machine. With modifications to the floats, bows, masts and appendages, the trimaran had already gone through several significant changes before the wingsail arrived.”

An early manuscrit of Hervé Devaux's drawing during the wing lift arm's design. Photo copyright Hervé Devaux /HDS

The wing is the thing
In 1988, the American catamaran Stars&Stripes beat the massive monohull KZ1 from New Zealand - in large part, due to a rigid wing sail. The BOR design team, under the direction of Kiwi Mike Drummond, was seriously thinking about the possibility of integrating this concept, this time for the trimaran. “We joined a small team with Hervé, developing the first steps of the secret project of the wing” continues Steven. “The ‘go-ahead’ was given on the 1st April, 2009. I then moved to the production site of Anacortes (USA) where nearly 70 boatbuilders were involved in the project. All day, I supported the engineering and in the evenings I would finalise some of the designs! After five months of construction we assembled the wing in San Diego. Those of us who saw the birth and development of the wing sail were beginning to get accustomed to its size... but when on the 10th of November the two cranes lifted it for the first time and it was attached to the boat - that was a very special moment. The boat was already flying a hull later that same afternoon and the sailors returned to the base with a big smile… We already had some of our answers.”

From an initial 60 meters, the wing was then extended to 68 meters, for an overall surface profile near 650 square meters, more than the double that of a Boeing 747 wing. The sail consists of a main wing element and eight moving flaps. No less than 450 carbon/nomex sandwich panels and reinforcements straps have been assembled, representing nearly two kilometres of tapings.

Mike Drummond (NZL, BOR design team dir.) and Jean-Marc Normand (FRA, shore team) conduct some tests with a Class A wing in San Diego. Photo copyright Aurélien Miller /HDS

10 times less loading
Despite its construction and the huge logistics involved in using the wingsail, this prototype is a beacon of simplicity. “The wing simply replaces the mainsail. So we get rid of the issue of mainsail leech tensions, mast/boom links and all the systems involved in controlling the shape of such an enormous mainsail. The optimal shape exists on the wing without any effort. In light conditions, it generates about 2.5 tons of loads on the platform compared to 20 to 25 tons for a conventional rig - a ratio of 1 to 10 with about an equal weight,” explains Steven. “To cover the frames of the wingsail, we chose a film used on aircraft, for example, which perfectly shrinks over the frame when heat is applied. It is ultimately that film tension which has guided us in our calculations to design the skeleton of the wing more than the forces generated by the aerodynamics loads.”

Exchange of expertise
In this campaign, the boundaries between the “French world” of multihulls and the Anglo-Saxone, monohull culture of the America’s Cup have faded, allowing designers to mix their knowledge and exchange ideas. “For HDS, this experience has put us in an international mode, making us experience other design methods and manufacturing techniques. We have, I think, sometimes guided the team to more pragmatic choices as we usually do with projects having smaller budgets and where we find similar constraints of time,” says the 31-year old engineer “From a personal standpoint, this was also an opportunity to experience the daily life of a team and to win the America's Cup in my first campaign!”