News Around the World
Making history at Weymouth Speed Week in October 1975 when ‘mustard baron’ Tim Coleman’s crew pushed their one-way proa Crossbow I to the max over the 500m course to set a new world speed record of 31.1kt. The following year saw the appearance of Crossbow II, another proa now with twin rigs, one per hull. Over the next four years Crossbow II steadily pushed up the record to reach a speed of 36.0kt in 1980. That, however, would be it for ‘normal’ sailing craft though it took the windsurfers six more years to break Coleman’s record with a run of 38.86kt in Fuerteventura in 1986. Things really took off of course with the creation of the first speed-sailing ‘trench’ in southern France. Kitesurfer Rob Douglas would eventually hit 55.65kt at another trench in Lüderitz, Namibia, before (at the same venue in 2012 but now sailing on the sea) Australian Paul Larsen finally reclaimed the best time for a ‘boat’ with the current record of 65.45kt. Yes, the SailGP F50s and AC75s are inching closer but only in bursts. A 500m average is a different animal
he landed in the America’s Cup when the great European aeronau- tical company decided to enter the American market. Without adver- tising it they began a collaboration with Team Oracle for San Fran- cisco 2013; then in the following edition in Bermuda they extended the agreement by supplying the US team with a more sophisticated ‘bolt-on’ engineering support package. As part of this co-operation Bailys’ consultancy was asked to
develop a new broader foil design tool, something that would be able to tell quickly if a particular concept was moving in the right or wrong direction. Oracle were very good at detail, but they needed this tool to filter different designs and speed up the process. Come the last Cup and with Oracle no longer taking part it was
American Magic who continued the Airbus connection in the America’s Cup. For Bailys everything then became much simpler, as then American Magic lead designer Marcelino Botín kept the core of his design team in Santander. The geographical proximity contributed to a closer professional relationship and Botín asked Bailys’ company to permit his full-time involvement with American Magic. After Auckland Botín suggested that the pair collaborate again, but this time as an integral part of the team… but now the Alinghi Team! Seahorse: Has your work changed a lot by being inside the team? Nicolás Bailys: Last campaign I already had a very direct relationship, but this time it is different as I am a member of the team itself and also the design team is at Alinghi’s own base. Being altogether and having the boat here is very important. You can go to the ship to see something you have on the screen in the office, you see it better, you touch it… it’s more direct. On the computer everything is scaled down, then on the boat you see this huge 4m foil. You get closer to the physical reality, because you directly expe-
rience things like construction and maintenance. They explain things about maintenance and robustness that I didn’t know and did not consider in my design work. Together we now use their inputs to improve the foils for their needs, but without affecting the foils’ performance. That communication is becoming super important. SH: One of the significant AC75 rule changes is the increased size of the foils. NB: There are a couple of big changes to the foils. One is the ability to position the foil a little further forward or aft, and the other is its dimensions which are limited by a box that has changed with the
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new rule. We have gained in wingspan, increasing from 4 to 4.5m and they can also be a little deeper. With this the boat will be more comfortable than before sailing at 6kt speed. The dilemma is how much to reduce the total surface of the foil
so that it still lifts better but does not suffer the increase in drag that that half metre extra span could entail. It is a key parameter in the resistance of the boat; aircraft designers also try to have the wings as long as possible, and have a problem similar to our mea- surement box because the airports restrict the total width of planes. SH: The total weight of the boat has been reduced… how does that influence the foils? NB: It’s another big change, and the trend is to take some of that extra weight out of the foils. The bulbs will now be lighter and not as artificially distorted as before. The original rule said that when the boat capsized the weight of the foils must be sufficient to right it, driving the weight and the centre of gravity of the foils. It was unnatural that in such a light carbon-built boat it had foils with a very heavy steel structure; not only that but also holes in the steel to fill with lead to weigh them down even more. With the new rule this area can be made lighter and for the engineer more elegant. SH: Will we still see very different foil profiles as in New Zealand? NB: The design of the profiles is heavily driven by cavitation. Aircraft have similar cruising conditions throughout their flight spans and so have to be efficient with a fairly similar geometry when they fly, except for getting lighter as they consume fuel. The AC75 sails at very different speeds but the weight is always the same, so the foil needs to ‘adapt’ with speed. The way to optimise the curvature of the profile is with the small
flap to achieve more or less lift when sailing slower or faster. This means that with different flap angles the foil must be very efficient with different geometries. The design of the profiles is very much based on that, so we are
not talking about a fixed profile but one that varies with the movement of the flap. It’s a mixture of things that you put in a shaker, shake it and you get the profile that you think is best! The height of the foil controls the balance of the boat, thus varying
its horizontal angle. You always have to generate a vertical force very close to the weight of the boat, and depending on the angle you will have the horizontal force that compensates for the thrust of the sails and so controls the heel. It is a choreography between foils and sail
JONATHAN EASTLAND/ALAMY
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