The America's Cup: Nerves, Skill and a Lot of Computers
This year's America's Cup will be remembered for Oracle Team USA's jaw-dropping comeback against Emirates New Zealand, but it should also be remembered for the huge role computers have come to play in the competition.
Thu, September 26, 2013
IDG News Service (San Francisco Bureau) — This year's America's Cup will be remembered for Oracle Team USA's jaw-dropping comeback against Emirates New Zealand, but it should also be remembered for the huge role computers have come to play in the competition.
The teams raced 72-foot twin-hull catamarans that are so fragile and finely tuned that they have more in common with Formula One race cars than traditional sailboats, and they made this competition on the blustery San Francisco Bay both exciting to watch and dangerous for those taking part.
Long before the boats hit the water, the teams used powerful computers to model small changes in their design and extract maximum performance. It's hard to overestimate the role computer-aided design tools have come to play.
Nick Holroyd, technical director for Emirates Team New Zealand, has been doing America's Cup races for 18 years. In that time, he said in a recent interview, New Zealand has gone from "almost 100 percent physical testing," where design changes were tested in wind tunnels and water tanks, to this year's competition, which was "the first where we've done basically everything using computer simulation."
In years past, he said, teams did three or four "tank sessions" a year, allowing them to test about two dozen hull designs. With high-performance computers, they can now test 300 designs in the same amount of time, and with greater precision.
This year's boat class was so sophisticated it's not surprising that computers played such a critical role. The catamarans have a towering, 131-foot wing sail made from a lightweight, carbon fiber frame, covered with plastic sheeting only six times thicker than kitchen wrap.
The sail has flaps like those on an airplane wing that are adjusted to maximize performance, and the boats are at their most spectacular when they lift clean into the air and hydrofoil at speeds approaching 50 mph, held aloft on retractable keels, or "dagger boards," that descend from the center of each hull.
In the run-up to the race, the teams make modifications to the shape of a hull or the size of a rudder and model its effect with computational fluid dynamics. They plug hydrodynamic and aerodynamic data into a velocity prediction program that shows the effect the change will have on the speed of the boat, its angle of heel and other variables.
"When you work in a physical tank, you can look at the wave patterns around a hull and you can get a really accurate drag number from the gauge, but it doesn't tell you a thing about why one model is better than another," Holroyd said.