• The afterguard on ETNZ. Photo Chris Cameron/ETNZ.
    The afterguard on ETNZ. Photo Chris Cameron/ETNZ.

At first glance, you might think there are no similarities at all between a traditional soft mainsail and the giant, 131ft wings being used on the America’s Cup 72 foot catamarans.

While the construction methods are very different, in some ways the trimming techniques – getting the best VMG for the boat – have similarities. For starters, if the trimmer isn’t in total tune with the conditions and with his helmsman, the boat will round up in a gust and fall out of the groove. There is also a lot of symmetry between the two sails on the boat, with one needing to balance the other for perfect results.

To find out more about how these amazing machines are made to go fast, I spoke with Emirates Team New Zealand wing sail trimmer Glenn Ashby.

Glenn is a sailmaker by trade and one of the most experienced multihull sailors in the world. As well as his silver medal at the Beijing Olympics with fellow Australian Darren Bundock in the Tornado class, Glenn has won 14 world championships across three classes, including eight A Class World titles.

The Benefits

The AC72s are sailing at twice the speed of the wind. They are so fast that the apparent wind is always forward of the wing – effectively they create their own sailing conditions. So what is it about a wing that is so superior to a soft sail?

Says Glenn: “The beauty about the wing is that they are just so clean aerodynamically through such a big range of conditions. With the 72 footers that we’re sailing now, you would struggle to get the boats around the track with a soft sail. You just couldn’t physically move enough sheet to sail a boat accurately enough around a tight course. With the wing you can effectively turn them into any aero shape or aero loading that you want to.

"That’s where the wing is the golden piece of these boats. Without the wing you’d need another five or six people on the boat to make it look the same around the track because the wings are so user-friendly and easy to use, resource wise.”

The Shape

Like a traditional mainsail, there are times when you want power and there are times when you want to minimise drag. The fine tuning that is possible with the wing is what makes it so effective.

Glenn explains: “I’ve got foot buttons to control the twisting and camber of the wing, which is the overall power source, or outhaul effectively, of the articulation between the angle of the overall shape - the angle between the front and the back parts (of the wing). Obviously the more camber you have the more drag you have, but the more power you have as well. It’s just like sailing with a baggy main.

“I’ve got a winch which is just a 1-to 1-sheet going directly from the winch to the clew of the wing. What I’m doing is adjusting the twist and the camber for the most clean aerodynamic package that gives you the most amount of thrust forwards. If you’re too flat or too twisty, similar to a normal mainsail, you’ll be low and fast, and if you’re overstood or deeper you’ll be higher and slower. So it’s generating that balance between going forwards and staying high.

“Because the wing is so aerodynamically efficient, you can really drive hard off the lower part of the wing and you can actually get to the stage where you’re inverting the top part so the aerodynamic force is actually going to windward.

“The head of the wing reduces drag a little bit but also means you can lower your centre of effort and drive harder off the bottom of the aero package - the wing and the jib - but also means you get a slight righting moment as well which obviously helps you go faster forwards.”

Glenn says that Oracle and Artemis don’t have a twisting wing element so their inversion of their W2 flap or aft flap is generally greater than ETNZ, but the overall loading is very similar so the performance should be fairly similar.

“We’re hoping as a team that our wing design is good, being able to twist that front part of the wing. Upwind it’s probably not a massive advantage but downwind it will give us a range of modes we can sail, make a ‘soaky’ mode possible a bit more than the other guys. But we’ll have to wait and see."

Beating’ Downwind

Because of the incredible speed of the AC72s, even when the true wind is behind them the apparent is well forward of the beam. And that can make things expensive as Glenn explains:

“You’re basically sheeted in exactly the same position downwind as you are upwind so we wear out the wingsheet – we only get a bit over a day out of a thousand dollar wingsheet. It’s wearing in the same spot all the way round the track, reaching, upwind or downwind, except for the mark roundings and the pre-start where you might get a little bit outside that.

“The clew of the wing is very much in the centreline of the boat and the jib is also sheeted in the same position upwind as it is downwind because your apparent wind is in almost exactly the same spot. It is pretty crazy!”

Glenn says that often the trailing edge of the wing will be pointing directly into the true wind so he’s effectively bending the wing 180 degrees from where it would be if the boat was stationary, where the W2 would be facing directly into the true wind.

The effect of this constant “beating to apparent windward” at high speed has caused the headsails to get flatter. Development of the boats – the wings, daggerboards, rudders and fairings - has made the whole package more efficient, Glenn says,  so they don’t need as much ‘grunt’ such as Code Zeros or baggy jibs to get  downwind quickly.

Role of the Jib

When racing against Luna Rossa in the round robin stage, ETNZ broke their jib halyard. Instead of being the disaster it would be on a conventional yacht, they continued without it and on some legs actually sailed faster than the Italians. So, as the headsails have shrunk considerably in size, are they really necessary at all?

“In the really light air you need all the power you can get,” Glenn explains. “Then you get to a crossover when the boats are going so fast and they’re so efficient in not a lot of breeze that the only way to become more efficient is to shed sail area, which is ultimately drag, so we’re putting smaller and smaller front sails on and we’re at the stage now where we’re effectively sailing around the track wing alone.”

But Glenn says the jib still has a vital role to play, especially in the balance of the boat both upwind and downwind. “It’s definitely a big help in the manoeuvres, there’s no question there, but it’s a really good balancer for the boat and it gives you a really good wind indicator of how you’re sailing.

“You can see what’s happening on the jib very clearly, where the wing can be sheeted on or let out or one way or the other and all the tell-tails will still flow. So you’re looking at the headsail to see how you’re trimming the wing.

“The main thing (with the jib) is it balances the boat nicely for upwind to downwind, just with the loadings we have on the boat. Without the jib the wing sees a huge amount of side-load so when you do sail wing-alone it’s structurally quite a nervous time for the wing engineers and the structural guys because the boat’s been designed to share the load between the jib and the wing. When you are wing alone, it’s quite a nervous time and you’ve got to juggle the loads more accurately.

“We’ve tested wing alone and the various jibs so when the jib did decide it was going to come down you could pretty much clock straight into your setting and you know that you’re going to be reasonably safe to get the boat around the track. But certainly it makes the boat a lot harder to sail because your centre of effort goes up quite a lot higher because you don’t have the jib in front and the boat becomes a lot more tippy and harder to sail forwards."

Sailing Fast

It’s often said that women are excellent on “strings” in a keelboat because they are better at multi-tasking than we males. But if you think having to coordinate ‘kite up, topper up, downhaul set, jib down, outhaul eased’ is a task, try sitting in Glenn Ashby’s spot for nearly an hour.

“I’ve got six or seven buttons that I operate plus the sheet. Most of the buttons that I’ve got are on the floor so I can do them with my feet so that leaves both hands free for trimming the sheet.

“The mainsheet is like a traveller, you’re barn-dooring the boom - opening and closing the two wing elements which obviously affects the whole wing. The twist function is like a Cunningham on a standard multihull or high-performance boat where by pulling the Cunningham on you’re flattening and twisting the sail by bending the mast and soaking up the luff curve and letting the top hang open. You set the wing up to twist more or less and in different areas depending on what conditions you’re sailing in and what mode you’re wanting to set the boat up in.

“It’s all done with control arms and a hydraulic ram. We’ve got a couple of hydraulic rams that are connected to a control panel at the bottom of the wing. The control arms take the load, the ropes from there go down the inside of the wing to the control panel and attached to the control panel is the hydraulics which you operate from the cockpit. By altering the hydraulics you can adjust the quadrants effectively and that adjusts the lines which affect the control arms which makes the wing twist or stand.”

It’s sounds easy when you say it fast!

Who Does What?

To perform a foiling gybe, where the boat goes across the wind without coming off the foils, is the ultimate manoeuvre on an AC72 and can gain or lose hundreds of metres. It requires incredible teamwork from all 11 crew, and especially among the three in the afterguard; trimmer Glenn Ashby, helmsman Dean Barker and tactician Ray Davies.

Glenn explains the procedure when Dean Barker counts down to the gybe: “Ray will go down to leeward and put the wing sheet in the self-tailer on the leeward side and as we’re entering the gybe I’ll start the transfer and click the guys (the grinders) into the hydraulics with a button.  Just as the load starts to transfer from one side to the other I’ll be crossing the boat. The grinders have got full control of the camber transfer in the gybe, and the tack for that matter. I’ll go across and do a final adjustment of the camber to either stop it or continue it to where we need it to.”

The procedure for the wing trimmer is therefore very similar to a headsail trimmer on a traditional boat, who releases the sheet at the appropriate stage of the tack, then crosses the boat and makes the final adjustment in or out depending on how efficient his winch man has been. But on the AC72s three people, including the helmsman, have to travel 14 metres across the boat and someone needs to be in control of their functions while they are doing so.

“So Ray gets the wing sheet set for the new gybe, I come across and grab it just a few seconds afterwards, then Ray will take the wheel and then Dean can cross. I’ve got the sheet then, so we’re in total control of the gybe.

“Tacking, I’ll go down to leeward the majority of the time and get set up and actually pass the sheet over to Ray who’s next to Dean, we’re all quite close. So I’ll go across and get set up for the hydraulic transfer for the guys to click in and then the big guys come over and start trimming the sheet.”

Grinders at Work

Glenn says he relies heavily on the grinders to give him the grunt he needs to trim the wing accurately.

“As far as sheet versus twist control and camber it’s about 50/50 usability. You’ll be using the twist and camber or the hydraulic functions about half the time that you’d be using the sheet. Although you’re moving a lot of sheet you’re using your twist controls and camber controls pretty much constantly around the track. Even on a relatively steady day you’ll be doing fine adjustments to try to eke that little bit of height and that little bit of forwards.”

This means the grinders, who provide the power to the winch and the hydraulics, are working constantly. Artemis grinder Craig Monk told me he was grinding about 80% of the time, as opposed to about 20 or 30% on a traditional America’s Cup boat.

Glenn says that when watching the AC72s it’s quite hard to work out who is grinding for what function. “The boats are hugely resource hungry as everyone can see. The big guys are really the engine department. Without them working you’re not getting the maximum performance out of the boat, so they’re definitely the key to making the thing go forward.

“The athleticism they have is unbelievable. They’ve got to be big and strong but they’ve got to be able to grind hard and fast at different times and there’s so many functions, like boards up and down, wing controls, jib controls, we’ve got a self-tacking jib with a car that we can adjust - there’s a huge amount of functions.”

He said that James Dagg, the ETNZ headsail trimmer, will often be a couple of pedestals back from where he’s normally sitting to jump on the handles and assist. “Basically anyone and everyone who’s got a spare two seconds will be putting in for whatever’s going to get the boat around the track the quickest. So quite often he’ll be top-handling the jib but he’ll spend a lot of time in manoeuvres on the pumps with the big guys.”

Even though there is only room for eight grinders on each side of the boat – four coffee grinders with two men per set of handles - Glenn says you can have people on the other side of the boat grinding too, so there can be up to 10 people on the winches at one time. “If you’re flying a Code Zero, for example, you’d have everyone except the guy steering, and probably if you could you’d have him on the handles too.”


Glenn says the teamwork required reminds him very much of the Tornado days with Darren Bundock and he understands why the unique partnership that Nathan Outteridge and Iain Jensen shared on their 49er translated into AC sailing. They are famous for each doing their own job – Jensen tunes the sails to make the boat go fast and Outteridge decides where to put it on the course.

“The relationship that I have with Dean (Barker) on the 72 footer - you’ve got nine other guys who all have to work exactly in sync to get the boat around the track, but that relationship between the wing trimmer and the helmsman very much has to be in sync and we’ll be talking constantly.”

During a race, it’s a three-way communication between helmsman, trimmer and tactician.

Ray Davies scans the course and keeps an eye on the opposition, and he will tell Dean Barker and Glenn Ashby what mode they should be sailing in.

 “Ray will say ‘Happy to sail slightly faster numbers here’ or ‘Happy to take everything you can in height for the next 20’. By giving Dean and I a bit of heads up on what he’s wanting to do, we can make the necessary gear changes.

“In my case, it’s not just an ease on the sheet that will get you down, it can be a twist adjustment, a camber adjustment and a sheet adjustment all happening at exactly the same time. That’s how we change gears and let the boat go forwards depending on whether you want to go fast or high. If you get it wrong it’s exactly like a double-handed boat or a 49er - if the crew’s not on the same page as the skipper it can go bad really quickly, same on the F18 or the Tornado.”

Winning Moves

Traditionally in the America’s Cup, the faster boat wins. Both are crewed by the best sailors in the world, so mistakes are rare. But Glenn offers hope to spectators who don’t want to see a procession like we witnessed in the round robins when ETNZ clearly had a boat speed advantage over Luna Rossa.

“The opportunity for gain and loss in this Cup is much greater than it’s been. A bad gybe can cost you 150 metres where a bad gybe in the earlier boats might cost you half a boat length if you had a real shocker.

“You only need one button not to work and it can shut the whole boat down. The boats have an absolute plethora of hydraulic functions and hydraulic valves and cylinders and rams and manifolds and all sorts of bits and pieces that could go at any time. Then there’s the electronic side.

“If you ‘lift the bonnet up’ and have a look underneath at the internal workings of the boat you just shake your head and go ‘oh crikey I’m going to just shut the lid and not think about it when I’m sailing’. That aspect - degradation and parts wearing out and when do you change them? The stuff’s loaded hard and works hard all the time. There are valves and rams working at their absolute max pressure every day and it does take its toll for sure. Because of the speed the effective wind pressure is equivalent to more than 60 knots - not only the sails but the boat has to survive in that.”

All four syndicates have stacked their sailing teams with incredible talent – Olympic gold medallists, world champions, round-the-world racers and previous Cup winners. After speaking with Glenn Ashby, I left the ETNZ base with a better understanding of why these men are paid the big bucks.

There is no “set and forget” function on the AC72. During every second of the race, there are 11 men on each boat working in unison to trim the wing, trim the jib, perform each manoeuvre to perfection and to put the boat in exactly the right position to win the race.

Wouldn’t it be perfect if the two boats in the final are matched for speed, so that ultimately the Cup is won by the 11 men who sail better?

- Roger McMillan in San Francisco

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