The View from a Moth - Sail Magazine

The View from a Moth

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Every fledgling has a first flight, but it comes more naturally to our feathered friends than to sit-down sailors who took centuries to achieve liftoff. When it happened, though, it happened big. Foiler Moths—11-foot experimental dinghies with hydrofoils on their rudders and centerboards—have gone from controversial to winning their class worlds. To find out what its like taking that first “flight” we went straight to the source: 2009 Moth world Champion and Rolex Yachtsman of the Year, Bora Gulari.

It’s a bit counter-intuitive, Gulari said. People tend to want to sheet in hard, but to get up on the foils, you actually need to ease the sheet and bear away. “Speed is your friend, and then it’s almost automatic,” he said. “The boat jumps up about two and a half feet out of the water. Everything goes silent, and the speed jumps from 6 knots to 16. You trim instantly, add vang tension to flatten the sail, and you keep your weight forward. At about that point people start giggling and s--- eating grins are inevitable.”

Unless, of course, you crash.

Well, you could still come up grinning. “I’m barely in control most of the time,” Gulari said. “I love it.”

Not that crashing is a problem for this guy anymore. In 2009, he owned the Worlds.

The Moth began as a development class in the 1920s, but the boat’s future was looking dim circa 2000, when a few adventurous Aussies began to experiment with methods to fly the hull clear of the water. Aboard today’s boats, the centerboard foil is equipped with a set of trailing flaps that are controlled automatically by a pivoting sensor arm, or wand, on the bow. Under sail, when the hull and wand are immersed, the water presses the wand aft, which activates the flaps through a pushrod, producing maximum flap deflection and maximum lift. As the hull rises clear, the wand falls down and forward, easing the pressure on the flaps and reducing camber, while the higher speed produces the necessary flow to maintain lift.

At the transom, the rudder is mounted on a structure that extends behind the hull—spreading the base improves stability—while the rudder foils are adjusted to control bow-up/bow-down angles when sailing up or downwind or in response to a changing breeze: a twist of the tiller extension does the trick. Because the aforementioned wand is off-center, winning form also requires a tweak for different tacks.

According to Gulari, riding high out of the water is good, for minimum resistance, unless you ride too high and the foils lose their bite, and then you crash back down. “Once you’re foiling, your righting moment increases as you heel to weather,” Gulari said. “You get a significant increase in power and better performance from the foils…The people who crunch numbers tell me it’s about 22 degrees.” That would be upwind. Downwind, the angle of windward heel is less.

Tacks are more violent than gybes because the boats are so light. In Gulari’s words: “Stay flat, get to the new high side quickly, ease the main and finish the turn hard. For gybing, I tell people to think about riding a motorcycle. Unlike non-foiling boats, this one has to lean into the turn. That way the hydrofoils are constantly developing positive lift. It’s very much the way an airplane rolls into a turn with the pilot pulling up on the stick. Once you figure out the heel angle, the next is the rate of turn. The boats are going so fast that centripetal force is very real. The more you lean into the turn, the faster you can turn and transition your weight to the new windward side.”

To maximize his boat’s performance, Gulari works with the likes of Seattle-based naval architect Paul Bieker, who designs his foils. One recent iteration cut the wetted surface of the foils by 20 percent and increased upwind speed by as much as a knot at the price of being “a little harder to sail.”

Moth sails are cut with induced camber to hold shape under tension, even in light wind. It’s much like a windsurfer sail, with flat upper sections that are more about reducing drag than creating power.

A Detroit native who “slept on floors” in Australia to learn from the pioneers, Gulari practiced like a demon to get where he is today. From his first foiler ride to winning the Worlds at the Columbia River Gorge last fall took 26 months. “I had sailed 49ers for six years,” he explained. “I just wanted to go faster.”

With speeds regularly hitting the mid-20s, and a world-record run of 30.31 knots last September, it appears he’s gotten his wish.

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