DESIGN OPTIMISATION D
espite not havingmany participants, with just eight yachts taking part in total, the America’s Cup is one of themost competitive and technologically challenging international sports.With entry fees alonemeasuring in themillions of dollars, there’s a lot at stake and high-
rolling sponsors are difficult to please so getting the technology exactly right for gaining a competitive edge over the other seven participants is of crucial importance. To understandmore about what’s under the hood of these
surface-skimming technology power-houses, I spoke to Altair, the design optimisation and simulation company that works in partnership with the Royal Swedish Yacht Club’s challenger for the America’s Cup, Artemis Racing.
DESIGN CHALLENGES According to Altair, innovations in design and technology have essentially transformed the traditional concept of sailing vessels into the technical domain of aeroplanes.With sports sailing becoming one of the fastest andmost dangerous competitions on earth, fractional changes in design can easily translate into knots of difference on the water, which couldmean the difference between winning and losing, as well as between remaining safe and succumbing to disaster. Speaking about this latest challenge, Altair’s engineering
manager, David Durocher, compared state-of-the-art sailing to flying a plane. “This is not traditional sailing, it is flying. They no longer have a sailing crew but rather pilots,” he says. As such, Durocher saw immediately that the America’s Cup had
moved on fromits traditional roots of a high-profile racing competition, pitting wits andmuscle against each other, towards amore holistic challenge in which it has also become a highly competitive design competition, pushing the limits of physics and engineering.
DRAG REDUCTION At the heart of the innovations being deployed in the latest round of the historic yacht race is the “daggerboard”. A daggerboard is a kind of foil, a device well known in sailing for using hydrodynamic forces to lift the hull higher in the water to reduce the surface contact area andminimise drag. America’s cup teams have perfected the art of foiling to such an
extent that the daggerboards are capable of lifting the entire hull above the surface of the water so the vessel if effectively flying with theminimumpossible drag resulting fromcontact with the water. “The goal is tominimise the submerged profile of the boat,
since less dragmeans higher speeds. The daggerboard is a movable appendage to the hull, which can be stowed out of the water formanoeuvring or deployed beneath the water surface,” explains Durocher. According to Brett Ellis, the lead daggerboard engineer at
Artemis Racing, the design limits are being pushed all the time to maintain the advantage required to win the prestigious race. To do this requires the ability tomodel the behaviour of the board and to simulate different conditions. “We’re able to build a structural model of the daggerboard and a fluidmodel of the water and run 10, 100 or even 1,000 different design ideas on it,”Durocher says.
BENDING THE RULES Like all highly competitive sports with rich rewards, there has to be a rule book and the concept of the foil itself emerged in the past as the result of engineers pushing against the boundaries imposed by the rules. It’s a fine line between exploring the limits and crossing the line. I asked Altair to what extent these limits are pushed. “Engineers love solving problems and we’re always formulating
10 /// Environmental Engineering /// August 2017
a design optimisation problemwith some sort of limits or bounds on the parameters studied,” commented Durocher.He believes the rules should be viewed as controlling the edge of the design space and inmany cases, the best answers push the design parameters right up against their bounds. “All the teams are going to push against these edges and try to
find clever and innovative solutions sometimes well within the rules that aren’t necessarily obvious in the beginning, such as the daggerboard extensions, which are being used by New Zealand. I think you’ll always see adjustments and additions to the rules to try to keep things reasonable and focused on pushing innovation,
Plane
Jonathan Newell looks at the technology behind the “flying” boats competing in this year’s America’s Cup yacht racing event
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