America's Cup: The complicated construction of the Cup beasts: Foil tests with consequences

The first races of the new America's Cup yachts are eagerly awaited in the sailing world. But the road to functional monohull foils is a thorny one. The America's Cup organisers have now published a sensational video showing some of the major challenges. The designs were also subjected to stress tests in the laboratory. The consequences can be heard and seen. During the first tests of the OneDesign foils, the wings failed spectacularly under load.

Davide Tagliapietra from the Italian Challenger of Record Luna Rossa reports: "At 88 per cent of the maximum load, we heard noises and also received an acoustic warning signal. So we decided to stop the test and prepare the next one because there are areas that we can understand better in the next stage of testing." The breakage of the wing has prompted all teams to work together to find a new approach to wing design.

How the clever design minds of the America's Cup teams got the foils for the new AC75 yachts ready for use

The video shows the test scenes at the Italian Persico shipyard. "The loads and the pressure - we knew right from the start that this design would be a crucial component," says Horacio Carabelli from Team Luna Rossa. As the first AC75 yachts are due to be launched soon, it was crucial that the foils fulfil all requirements during the second test. This was carried out in May. Alessandro Franceschetti, Head of Structure at Luna Rossa, explains: "Only the full test programme can give the designers, boat builders and sailors complete certainty. Only then can a team give 100 per cent from day 1. The AC75 yachts are absolutely extreme machines. They develop and take on huge loads." Accordingly, the new foil arms were tested with a load of 20,000 kilograms - which is roughly comparable to the weight of 20 cars.

Guillaume Verdier from Emirates Team New Zealand explains: "This is a new type of boat architecture that has never been done before. We want to make sure that it works." The designers' basic problem: the foils have to be extremely light so that the future monohulls can lift out of the water quickly even in light winds. On the other hand, the foils have to be extremely strong in order to withstand the enormous loads that occur. Which - as testers, designers and constructors all agree after the successful final test - they are now ready to do.