America's Cup: 50 knots and flying

Team New Zealand could be in line to crack the 50-knot top-end speed barrier off Bermuda but it won't be easy, warns skipper Glenn Ashby.

The development race in the America's Cup remains alive with just under a month to go before the regatta.

Given the swift rate of development seen in this Cup cycle, event chief Russell Coutts raised the possibility at the weekend that the magic 50-knot speed barrier could be broken in this year's event.

The 50-knot mark, which equates to about 93 km/h, is a wall the teams have struggled to break through since the introduction of foiling technology to the event in the last Cup cycle. Coutts believes some teams are inching ever closer.

"The revolution with this America's Cup has been quite incredible ... a lot is still changing. It's too early to predict who's going to be strong in this America's Cup but the performance of the boats is incredibly impressive. We've certainly seen speeds of 47 knots, some even at 48 knots, so we're getting close to that 50-knot speed barrier," Coutts said in his regular video update.

Team NZ skipper Glenn Ashby said it was tough breaking 50-knots.

"At those top-end speeds you run into a bit of a wall where you need a lot more thrust to go just a little bit quicker. It's the same as driving a car or motorbike fast, you sort of get to the stage where if you're doing 250 km/h it's really hard to get to 255. You need a whole lot more horsepower to do that extra 5 km/h. It's a similar sort of thing with the drag on the foils, you need a lot more thrust, a lot more wind to just go that little bit faster in those top end conditions," said Ashby.

"If you did some super cavitating foils I'm sure you could keep going right through past 50 knots, but you'd be pretty slow around the rest of the track," he said.

Ashby said the biggest area of speed gains lies in the boat's performance in lighter air, with the new high-tech America's Cup class catamarans sailing at close to three times the speed of the wind.

"These boats are incredible, the performance you can do in light airs really the amazing thing. In 7, 8, 9, 10 knots of breeze you can be up over 30 knots at times," he said.

Up to speed

34th America's Cup (sailed in 72ft catamarans)
Top speed in 34th America's Cup: 47.57 knots in 21.8 knots of wind (Team New Zealand, race 18).
Average downwind speed: 32-37 knots.
Average upwind speed: 16-21 knots.

35th America's Cup (sailed in 50ft catamarans)
Predicted top speed: 47-50 knots.
Predicted average downwind speed: 38-43 knots.
Predicted average upwind speed: 23-28 knots.