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Wing It! A closer look at the AC45 Winged Sail

June 21, 2012 by Sail1Design Editor Leave a Comment

By: Judith Krimski

It takes a monumental team effort to design and build the winged sails that grace the AC45 and AC72. When Team Oracle decided to go with the winged sails for the 34th America’s Cup they tapped Rhode Island native Scott Ferguson, a naval architect and veteran designer of America’s Cup competitions and the Volvo Ocean Race to name a few. Scott is also notable for his accomplishments on the Laser Masters circuit where he’s was World Champion in 2009 and 2010.

I was especially curious about the winged sail so I decided to go to the source with my questions. Here’s what Scott had to say.

How did you come to be involved with this latest AC campaign. What is your role?

I was part of the previous campaign for the 33rd Cup in the giant multihulls, and was asked to return in same role of managing the Rig Design. By the time I was signed up Oracle were undecided on the multihull/monohull question, wing or normal mast, so as it turns out I am working again on the design and engineering of the wing managing a group of 4-5 other designers.

How is the winged sail constructed? What are some of the key features as far as trim controls and sailing that make it different from a conventional sail?

The wing is constructed primarily of carbon fiber, foam, nomex cores. The front and back 2 or 3 panels we refer to as ‘elements’. The front panel is the Main Element and the aft one is the Flap Element . These Elements have hinges much like an airplane that allow you to control the depth and top to bottom twist of the wing. The twist is controlled at 4 or 5 vertical heights over the span of the wing and at the bottom of the wing there is a traveler that controls the angle of the entire wing relative to the boat.

A conventional sail requires a tremendous amount of sheet tension to control the sail shape and twist. Generally, to get the correct shape and twist in the middle of the sail means that the top of the sail is too closed down and therefore inefficient compare to the wing.

How much does the wing weigh?

1325kg (2922lbs) all up

Russell Coutts has said that the AC45 is a challenging boat to sail. What are some of the challenges mono-hull sailors face when learning the boat?

The AC45 is still a sailboat so most of the same basic rules apply. The biggest differences compared to most mono-hulls are the top speeds and wider tacking and jibing angles. During a tack or jibe the boat comes almost to a complete stop so there is a premium on minimizing tacks and learning to get up to speed quickly after a tack or jibe. As a monohull guy myself I made the transition to an A-Class Catamaran last year. I am still learning the go-fast subtleties, speed is king so you do not want to pinch upwind or get caught too low downwind. It has been challenging but quite a lot of fun to learn a new one design class, again, it is still a sailboat.

What about designing the original AC45?

It was a fairly rushed project. For the 45s we had to design a boat and a wing in a short period of time last summer and into the fall. It’s not just for our benefit, but to get the whole cup competition kick-started. I’m pretty proud of the fact that the boats look exciting, they’re responsive, and they’re fast. It’s good to see them out actually competing now.

Everyone has watched the youtube video of Oracle’s capsize in San Francisco. How do you repair the wing when it’s got a big hole in it?

Russell was quite lucky to go through the softer part of the hard wing! The softer areas are made from a polyethylene film very similar to the plastic covering used on most items you find in the grocery store, and a lighter more specialized version of the shrink wrap used to cover your boat during the winter. It is easy to apply, and shrinks to a nice tension using a heat gun.

Which would you rather sail—the AC45 or the AC72? How about those vs. the laser?

The AC72 has about 5 times the power (righting moment) of the AC45, and will be a handful on San Francisco Bay this summer, but I am looking forward to the first sail. I have a laser here in San Francisco that I still like to sail ….. nothing like 40+ boats on a line.

More about Scott:

Scott Ferguson holds a Bachelor of Science degree in Naval Architecture from The University of Michigan where he was also a three time Collegiate All-American in sailing.

Scott has worked in the marine industry since 1984 and established Scott Ferguson LLC in 2000. He has become a specialist in the design of carbon fiber grand prix racing spars and brings not only his years of technical experience to the table but also a long resume that also shows his talent around the race course.

Thanks Scott and good luck to Team Oracle, 34th America’s Cup defender. For more information or to contact Scott click on the link to his website.

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IMAGES

AC45 sail catamaran in action
SailRaceWin: America's Cup: AC45 Wing-Sailed Catamaran Under Sail in Auckland
AC45 catamaran yachts competing in the Newport ACWS
AC45 Series 2016 @Portsmouth: BAR 1st
The AC45 foiling catamaran of Oracle Team USA during practice racing at the America's Cup World
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