Sir Ben Ainslie explains how the AC75’s control systems work in the latest episode of our America’s Cup podcast

The systems that control the aero- and hydrofoils of the new AC75 are covered by some of the most complex parts of the America’s Cup Class. The section on control systems takes up 12 pages of the 67-page rule.

There has been a major philosophical change from the 35th America’s Cup, when all the power to adjust the wing, sails and hydrofoils had to come from the crew. In the coming America’s Cup, the AC75 rule requires the sailors to power the control of the soft wing mainsail and the headsail, along with legal rig adjustments like the runners, but allows electric batteries to power the hydrofoils.

“We’re given a minimum number of batteries,” explained Ben Ainslie. “We’re allowed more but that’ll add weight and because it’s so tough to build these boats within the maximum weight rule, we really don’t want to do that. So once again, it comes down to having super-fit sailors and efficient control systems so that we can really push the boat to its limits.”

But designing and building efficient control systems is a huge challenge. There are many competing requirements to be balanced in every element of the control systems and deck layout. “This is something that’s a really interesting focus for all of the teams as we’re coming into the design of the second boat, the race boat, and trying to work out just what the requirements of the crew are for this style of racing,” said Ainslie.

Return to grinding

What we won’t see is any more cyclors: the rule has been designed to keep them out, and force the use of traditional grinding pedestals. “I think it’d be hard to find a way around that, but it doesn’t mean that there isn’t a lot of interesting work being done to work out how best to optimise the power of the sailors.”

This work will reach into many areas, and some of them will be obvious, like the position of the grinding pedestals. It’s not just about power and efficiency, the position of the crew changes righting moment and the hull centre of gravity and impacts the potential top speed.

Others will be more subtle, hidden in the hydraulic engineering and plumbing deep inside the boat. And between these two extremes will be what’s now called the HMI – the human machine interface.

Back in the good old days this used to be the steering wheel and the sheets. The AC75 still has a wheel, but that may only be because the rule mandates it. The rest of the HMI is more likely to be a box of electronics with more than a passing resemblance to a games console. These will be on deck, but the teams will be doing their very best to stop the opposition and the fans seeing them.

“Last time the rules tried to prevent the control of the boat by an autopilot,” explained Ainslie. “However, the rule only forbade direct control, and so that effectively left a loophole that allowed an autopilot to display its output.

And by that I mean what the autopilot thinks the foil should be doing to optimise performance, and the sailors [were] then able to control the foil to mimic that output by following a dot on the screen.

“This time around the Kiwis have reinforced the original intention to stop the boats being sailed by autopilots by delaying the instrument data that appears on the displays. It goes through what we call a media box. So there’s a short time delay there. So even if you were to run an autopilot and show its output for the crew to follow, it would be a second or so behind the action, and that’s a long time in a foiling boat.”

The enforced delay in the data appearing on the crew’s displays, or Crew Information System (CIS) as it’s called in the rule, is combined with a lot of other detailed rules designed to prevent the CIS from knowing anything about the boat state. It’s all intended to prevent teams from running an effective autopilot.

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Even slicker

The outcome is that crews will need even slicker ways to control the systems that control the boat. That’s why everyone will be so protective of what’s on those games console-like screens.

“We do rely on guidance. We’ve talked about autopilots that are not allowed under the rules, but there are certain prompts which help the key people in those trimming roles and steering roles to maintain the boat’s optimised position or trim.

“Then it’s around your natural instinct as a sailor. It’s the choreography of the whole team that will keep this boat sailing fast and racing well. It really comes back to a full team effort.”

Sir-Ben-Ainslie-Team-Principal-and-Skipper-headshot-bwAbout the author

Ben Ainslie is the most successful Olympic sailor of all time, and Team Principal of the British America’s Cup challenger. INEOS Team UK will be challenging for the 36th America’s Cup in New Zealand in 2021. Each month he talks to Mark Chisnell about the innovations and technology behind the new AC75 foiling monohulls.