Winning Ways

Design and construction of the new
ILC 40 yacht "AeroSail Anemos"

Improving on a winning formula can be quite a challenge. But standing still in a fast-changing environment - like modern racing yachts - means falling ever further behind. The "AeroSail ASTRO", the the ILC 40 yacht built last year by AeroSail, has shown in various races that it is one of the best and fastest yachts on the sea today.

The developement and construction of the new ILC 40 yacht was an ambitious task for the AeroSail design team. AeroSail was looking to demonstrate amongst other things that it now has the capability to carry out such a project by itself. Needless to say, it is a big help to be able to draw on tried and tested past achievements. So one of the first tasks in the development was to review all the experience gained with "ASTRO", with a rigorous analysis of all weaknesses.

"ASTRO" had showed itself to be slightly below par at average wind speeds. A closer look was taken at this in water tank tests in the VWS test facilities in Berlin. Heiner Meldner's AeroSail design team then defined the lines of the hull of the new boat on the basis of these findings and honed the finer details with reference to the predicted IMS speed regulations. The hull structure and the deck layout too were subjected to critical scrutiny. In co-operation with Daimler-Benz Aerospace, finite element techniques and numerical optimisation methods were used to come up with interesting solutions for making the hull lighter but even stiffer.

By early November, the ILC 40 class rules for the coming season were largely in place, so that by mid-December the green light could be given for designing and constructing the new yacht. It is now a matter of implementing the targeted improvements within the short time span available. The risks of each particular measure have to be weighed very carefully against the expected advantages. In one significant departure from the design of the "AeroSail-ASTRO" for example, the hull and the decking are to be made of high-strenght carbon fibre, since this material is at last no longer unduly penalised by the regulations.

The most striking feature of the new AeroSail ILC 40 yacht "Anemos" however is the dramatically leaner stern. Particularly at the extremities it is vital to shed every ounce of unnecessary weight. All feasible scope for savings here was exploited. The high rigging stresses which act on there areas are counteracted exclusively by stress and strain forces, which should give high rigidity.

New directions are being taken in construction too. For the first time, the complete structure is taking shape in three-dimensional form on the computer, and the moulds for the hull and deck can be produced directly from this on a 15 x 4 m milling machine. As in aircraft manufacture at DASA, longitudinal members and reinforcements can be integrated with, and built together with, the hull. As well as the much greater dimensional precision, this procedure should result in a reduced structural weight and an overall improvement in the qualitiy of the individual parts.

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