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America's Cup: Tom Whidden reflects on the winning of AC36

by Sail-World.com/nz 20 Jun 15:43 BST 20 June 2021
Emirates Team NZ and Luna Rossa in the prestart- America's Cup - Day 2 - March 12, 2021, Course E © Richard Gladwell - Sail-World.com / nz


Three times America's Cup winner and President of North Technology Group, Tom Whidden, shared some insights into the 36th America's Cup during a Wednesday Yachting Luncheon hosted by Ron Young of St Francis Yacht Club, San Francisco. Young covered America's Cups from 1988 to 2010.

Whidden was a tactician and initially trial horse skipper for Dennis Conner, winning the 1980 (Freedom), 1987 (Fremantle) and 1988 (Big Boat).

Much of the early interview, told in Whidden's laconic style, covers his early days in the 12 metres, when he part-owned Sobstad Sails before joining Dennis Conner and then going to North Sails.

Whidden is now CEO of North Technology Group, the umbrella corporation for North Sails, Southern Spars, and Future Fibres. The three companies have worked across all the past and current AC classes giving Whidden an insight from the conventional 12 Metre and IACC America's Cup classes through to the wingsailed foiling America's Cup catamarans - the AC72 and AC50 - and now the AC75 foiling monohull.

"Nothing has really changed about the America's Cup", he says, looking back over the last 40 years or so, "except the speeds are much more."

"At 40kts and 50kts, there are a whole new set of issues. The AC75's need to be able to get to foil at low speed and then get onto flat shapes and low drag at high speed.

"But it's still all the same - just trying to make one boat go faster than the other."

The aero package matters a lot in America's Cup boats of all types and sizes, Whidden continued.

"In the A75, they are trying to go from a windspeed of 6.5kts to 23kts or more at the top end. Imagine what the sail differences must be from going 10kts through the water and 50kts.

"What we learned was how to prevent deformation."

"How to make the best layout, so the sail doesn't deform. And how to make it go from the flattest shape you can imagine - almost 0% camber - to as much camber as you can possibly get - say 15%."

"Back when we were using a rigid wing back in the America's Cup in 1988, it was fantastic because you could go from 0% camber to 20% camber. But how do you do that with a soft sail?"

"This time, the teams did a great job using internal battens, a rotating mast that could also twist, and a double skinned mainsail.

"They, and particularly Team New Zealand, figured out how to make the sail go from almost board flat, up to 15% camber. They got almost to the point where the soft mainsail was almost equal to a rigid wing."

WYL Moderator Ron Young asked how much different the shapes were on the windward and leeward sides of the double-skinned mainsail?

"They weren't wildly different, but because they were somewhat different, they generated incredible lift and efficiency", Whidden responded.

"Amazingly, there is a patent from around 1929 from one of the Herreshoff's on the double sail idea. They had a mast drawn with two tracks on the back of it. A "D-section" mast and double skinned mainsail.

"I don't think he ever imagined carbon battens in the middle, nor did he imagine virtually stretch proof skins. He probably didn't imagine so much adjustability of batten tension and skin and leech tension.

"The carbon battens are adjustable and do allow you have a little fuller shape on the leeward side of the mainsail than the windward side.

"That provides a shape more like an aeroplane wing or a rigid sailboat wing and has made these boats really efficient.

Whidden says the battens can be adjusted independently, "but each team went about it a little differently, and the camber can be adjusted for the change in apparent wind speed across the boat."

"What is interesting is that [in Auckland] there were a lot of different jib sizes, for instance. That is simply because, for every 2kts of windspeed, they needed a different sized jib."

"The jib is used for power when the AC75's were trying to foil, and manoeuvrability around the starts and the tacks.

"Pretty much for the rest of the time, it was in the way. It's drag. So you will see the jib being made fuller when they need power, and then they make the sail as flat as possible once they are up to speed."

Kiwi's Cup dominance

"If you drill down into what their success is, it is so many things," Whidden replied in response to a question from WYL host Ron Young as to why the Kiwis had been so dominant in the America's Cup.

"It's so many things," says Whidden rattling off a long list.

"It's culture. It's leadership. It's how to manage. They employed AI [Artificial Intelligence], this time. They have the best simulator. They apply technology probably better than any of the teams. They are a small team. They are cohesive. They are very budget-constrained, but they spend their money well.

"You could argue that many of the teams spend too much money in too many different areas without enough focus on the big decision making from a cost-benefit point of view.

"We kid about the kiwis having broad shoulders because they have a chip on both! But it's not the case. They are intelligent guys, they work hard, they're serious, but they have fun. It's a great culture. And on top of it all, they are great sailors.

"The Royal New Zealand Yacht Squadron are now the second-winningest yacht club in the world behind the New York Yacht Club. That will be a hard one to beat. But I would never count them out."

Brit's speed issues

"Ben Ainslie's team sailed the Round Robin phase better than anyone else. I think they won every race.

"But they knew from the beginning that they had a bit of a speed issue. I think one of the problems was the bustle they had down the middle of the boat. It wasn't very hydrodynamically efficient. It didn't get them up on the foils as easily as they would have liked and probably gave them more [aero] drag once they were upon it.

"If they had the chance to do it again, I think they would have had a bustle more like Prada's, which turned out to be the better bustle.

"With the flat part of the bustle, but I think their thinking was that the boat would get up on that in marginal foiling condition and lift off to the point where the foils started working more quickly. They never really made that work, so not only was it drag when they were down in the water, but it was also aerodynamic drag when they were up out of the water.

The bustle is important because you have very little lateral resistance when the boat is in the water. So if the wind is hitting the sails and pushing it sideways, then the AC75 loses its ability to get up on the foils.

"The bustle acts a little like a keel in marginal foiling conditions.

"Its second function is to make the boat stiffer, so it is like a big I-beam, carrying big forestay and backstay tensions.

"The third function is so that if you can close down the endplate with the water. Ideally, you fly about 6" above the water, and then you get this endplate effect from the bustle. The mainsails are right down on the deck, and the bustle itself is closing the gap between the windward side and the leeward side and end-plating on the water."

"Prada had very good manoeuvrability. They had a high gear and a slow gear that they made work better than the other teams, but ultimately I think the speed of Team New Zealand was just too much.

Whidden says the Kiwis had "a very clean boat, with a bustle designed to be almost down on the water."

"There is a tunnel down the centre of the deck, and they had the sails down in that tunnel. You could say that maybe that wasn't the most efficient, but it was much better for the crew work."

North Technology supplied sails, spars and rigging to three of the teams. American Magic used only the rigging package supplied by Future Fibres, which was compulsory as a standard item.

"The Aero package we build is everything above the deck. At Norths, we call it the engine above the deck," Whidden explained.

"We model the mast, sail and rigging together. They are all interactive, and each depends on the other for maximum efficiency.

"The shape of the main is dictated very much by the shape of the battens and the mast. The jib being in front of the main changes the airflow of the mainsail.

"And of course, the rigging is there and is drag, so we try and make that the lowest windage and least stretch possible."

What's great about working with these teams is that you work with really smart people in an environment of learning that can't be had in any other racing venue. I have learned that if a guy who works for a team, or even a sailor on a team, if they say something, then it's probably right.

We, as a company, very much embrace ideas from outside the box. The two biggest technologies that we have employed in sailmaking are 3DL and 3Di. We bought both of those from the outside. They probably couldn't have been developed properly on the outside. In bringing them in-house, we were the ones that developed them, but the ideas came from outside.

"Our success has been from working with these people and these teams, having a complete desire to interface with them, and learning from them while they are learning from us."

"This interaction or iterative process is what makes us different from everybody else."

"It's worked out great for North and for me. We have a wonderful team who never stops learning and never stops teaching. My son jokingly introduces me to his friends, saying, "my dad did OK, for someone with a full-time summer job!"

"I don't know if he is disparaging me or just jealous, but we have a good laugh about it!"

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