America's Cup 2017: Team New Zealand's light air speed will be worrying its rivals

The secret is out: Team New Zealand has a very fast boat in light wind conditions.

The Kiwis embarrassed Sir Ben Ainsley and his British crew on Friday (NZ time), leading by over six minutes heading into the last mark before Ainsley called it quits.

The result leaves the New Zealanders guaranteed a semifinal spot and their opposition praying for the Bermuda wind to pick up quickly.

What was crystal clear about Friday's racing was the New Zealand boat's ability to move quickly through light air manoeuvres; the Kiwis the only boat on day five to avoid any significant time off the foils.

Team New Zealand blows away BAR in light winds

Skipper Glenn Ashby noted how important slick crew work, along with expert boat design, will be in deciding races that are sailed in under 8 knots.

"In these light air races it can really come down to manoeuvring," said Ashby

"The boats are extremely tricky to get wound up and come out of a manoeuvre. While you can look comfortable going in, it's actually the exit that can be the difficult part.

"We were fortunate that we were able to pull off that first jibe reasonably well today and keep the boat on its foils a little bit longer than what the British did."

All four of the day's races were contested in conditions that barely tipped the 10 knot mark and, Team New Zealand aside, all crews experienced moments of panic.

Ashby said they expect similar conditions as the regatta plays out, and judging by the latest results, the Kiwis will be praying for calm air in the Great Sound.

"It's tough going," said Ashby. "We haven't really seen a lot of it to date. We possibly may see a bit more of it in the future, but it's certainly difficult to sail the boats in those conditions and keep the boat on the foils."

Team New Zealand helmsman Peter Burling said Thursday's (NZ time) unexpected day off due to inclement weather was a blessing, as the shore crew were able to make a few minor tweaks to the boat, which paid dividends.

"One of the things that was really exciting for us out there today was even though we didn't race yesterday we still learnt a lot out of it," he said.

"We made a few changes overnight and we are really happy with how they are going.

"We have put a lot of work into our light air setup and it's really pleasing to see we are somewhat on the pace."

BAR skipper Ainsley said despite a crucial error just before the first mark, which saw the Brits go from a slight lead to a one-minute deficit, the speed of the New Zealand boat would have been too much too hold off.

"In all fairness, they [Team New Zealand] were going really well in those conditions and they more than likely would have found a way past us anyway, but it would have been nice to make things a little bit harder," he said.

Racing continues on Saturday (NZ time) with New Zealand facing both France and Japan before the grudge match against Oracle on Sunday morning.

Newshub.