Highly evolved design details made all the difference in the America's Cup final in Bermuda, we take a look at the winning ETNZ AC50
When Emirates Team New Zealand (ETNZ) launched their AC50 in Bermuda in mid-April, just six weeks before the America’s Cup Round Robin, they were the last to arrive and no one knew how quick the boat was going to be.
The team had done its early training alone in Auckland, away from too many prying eyes, and had elected to skip two rounds of practice racing with the other teams. When they did join in, Oracle Team USA and ‘sister’ team SoftBank Team Japan refused to race them.
But the team were sure they had a fast boat. Four days after launching in New Zealand, the crew had pulled off their first foiling tack.
The most glaring difference was their use of pedal grinders to produce power rather than traditional pedestal arm grinders. ETNZ’s sci-fi style term for their grinders was ‘cyclors’, cyclist sailors.
The idea had actually been tried before in the America’s Cup; Pelle Petterson used pedal grinders on the 12-metre Sverige in 1977. But ETNZ’s set-up now was very different: here it was part of a linked chain of innovations, the most obvious emblem of a radical approach.
Other teams countered that they had looked at this option but rejected it, but most people were still looking for clues on the outside of ETNZ’s boat when many of the most important secrets were hidden away on the inside.
The cyclors were fundamental to ETNZ’s stable flight and faster speed, but not quite in the way that people assumed.
One obvious benefit was the greater power output from using legs to pedal, but beyond this it left cyclists’ hands free and allowed the team to use a highly sophisticated system of fingertip control systems, and thus to use faster, less stable foils, and then to divide up crew roles so ETNZ could be sailed in a different way.
It all dovetailed. Firstly, the decision to have pedal grinders allowed ETNZ to produce lots of hydraulic power for the wingmast controls, the rudder trim controls, daggerboard rake and cant and board up and down controls. It was sufficient to cover multiple manoeuvres in a short time to go on the attack, where other teams may have needed more distance on the straight and level to accumulate enough hydraulic pressure.
High power output for a lower heart rate meant the cyclors could continue to pump enough oil when demands surged, for example on very windy days or ones when there could be three races in a row – as happened in of the playoffs. On a day when ETNZ was in total control, Dean Barker admitted that SoftBank Team Japan’s crew were “flogging themselves senseless.”
The cycling configuration allowed control systems to be distributed among the crew. So instead of the helmsman controlling several functions including daggerboard angles, ETNZ’s Peter Burling had rudder differential to worry about (the controls on the wheel), but otherwise could concentrate on steering the boat and working out tactics with input by wing trimmer and tactician Glenn Ashby.
As for the control systems themselves, this was the key to ETNZ’s ‘adventurous’, ‘aggressive’ design, because it allowed the team to use foils that couldn’t have worked otherwise. AC50 class rule states control surfaces can only be altered manually or by ‘electrical or electronic systems… initiated by direct manual input.’
ETNZ’s input may have been manual but the settings were controlled as near to an autopilot as the rule could be pushed. A programmable logic controller triggered electromechanical switches which controlled valves in the hydraulic system, a system that was “complicated, but well set up,” Glenn Ashby has said.
They weren’t alone in using such a system, but theirs was more sophisticated and better.
Dean Barker on SoftBank Team Japan, Jimmy Spithill on Oracle Team USA and Nathan Outteridge on Artemis Racing used a twist grip on the wheel to operate rake and cant controls, critical to stable flight. On Land Rover BAR, Ben Ainslie had controls at the wheel and an LED light array indicating target position.
But on ETNZ, daggerboard rake and cant was primarily in the hands of Burling’s Olympic crew Blair Tuke. Third from the back, he cycled with his forearms in carbon rests similar to triathlon aero bars. The system indicated the optimal setting and his input was, we have been told: “like following the bouncing ball”.
Glenn Ashby had a similar system for operating wing sheet, twist and camber, which could be operated from either side of the boat. There were no winches or ropes, unlike on other boats, and the wing could be pulled as well as pushed. The adjustments he was making were frequent and tiny, memorably described by Land Rover BAR’s Freddie Carr as: “like a hummingbird wing”.
Ashby’s control box also let him make all the adjustments for jib sheet, jib track and cunningham. All of these controls had back-ups so there were crossovers while crew were moving across the boat.
Pete Burling had a box near the wheel for trimming the wing, and Ashby had floor buttons for raising and lowering the boards.
So ETNZ clearly had finer controls and better man-machine interfaces. That made it possible to fly with faster foils, shapes that had less drag at lower speeds but as a result were less inherently stable.
“Like the Eurofighter, the most agile plane ever made – turn the computers off and you can’t fly it,” explains a rival team member.
ETNZ’s foils performed better over a wider wind range, and their package appeared better and faster in ‘high mode’, allowing ETNZ to point higher than Oracle upwind, and foil deeper downwind.
The distinct kink in their foils maximised draught and length within the arc allowed by the rule: ‘3.500m in any direction, measured along a straight line.’ They had less wetted surface area, too, something they achieved with a different build method, milled steel sheathed in carbon, which was heavier but allowed them to create a finer, slenderer shape.
And beyond the huge number of technical factors was the unflappable, cool-headed Peter Burling. Calculating how to play the shifts by himself played directly to his experience and talents.
“Their sailing technique, the way they are manoeuvring, how fast they manage to tack and how it is executed is different as well as the foils and systems. All this [contributes] to their speed,” observes Bruno Dubois, Groupama Team France’s sailing manager.
Still, there are mysteries, such as those lightning speed tacks. “How do they do it?” Dubois shakes his head. “No idea.”