Re-adjust what you imagine when you think of a fast sailboat. Forget the floppy sails, majestic prows and guys scurrying around in silly caps. Those would fly off on a C-class catamaran. Hell, the boats even fly.
C-cats, as they’re affectionately known, are the most efficient wind-powered vessels on water. They’re light, weighing about as much as their two-person crews. And, because they’re designed by aerospace engineers, they leverage every hydro and aerodynamic trick possible to make speed. Instead of one hull, you get two; and instead of a sail, each one of these boats boasts a rigid wing sticking straight up from the deck. No surprise, then, that they can fly on the water. Literally.
The wing sails, usually about 12m tall, can convert even the weakest breeze into impressive nautical thrust. But when there’s high wind, you have to hold on for your life.
Fred Eaton, the Canadian who helms the defending champion, Canaan, explains: “At 10 knots, it’s an incredibly smooth and happy experience on the boat. At 15 knots, it’s a complete handful. At 20 knots, you just want to go home. At 25 knots, the boats take off – physically take off – from the water.”
The predicted conditions this for this week’s International C-Class Catamaran Championships off the coast of Newport, RI? Some rain with winds up to 25 knots. [Editor’s note: As of right now, the winds are too strong for racing, and the event has been postponed to prevent the boats from going so fast that they travel back in time and totally screw up history.]
Winged sail boats are seeing something of a popularity boom recently. The ship sailed by the BMW Oracle team in this year’s America’s cup, USA-17, used a behemoth 68m wing in competition. And the Sauter Formula Zero Solar Hybrid Megayacht has solar cells attached to its gigantic rigid wings.
C-cat races have been around since the 1960s, and rigid sails started to emerge in the early ’70s. Over the years, designs have improved, and numerous international races have been held. The big prize, which one lucky team will take home at the end of this week, is known as the Little America’s Cup. It’s skipped around the globe between teams from Britain, Denmark, Australia, the United States and Canada. And the honour of who has the craziest, most over-engineered boat, is almost as desperately sought.
The beauty of the C-Class is that there are very few design constraints, leaving engineers room to experiment. The catamaran must have two identical hulls and be sailed by two people. It must be 7.6m long, 4.3m wide, and the area of the sail must be 28sqm. But that’s it. There is no minimum weight, no material that’s off-limits. The rest is open to interpretation.
That’s where the wing came from. Because engineers had no rules, their thought process went something like this: We need the lightest hull possible. We need the tautest sail possible. DRAT! To make the sail hold its shape in the wind, we need a heavy mast and a bunch of high-tension wires (forestays, if you’re in the know), which would put too much pressure on our super-lightweight hulls. EUREKA! We can combine the mast and sail into one rigid piece – a wing! – that holds its shape due to the nature of its materials and construction, eliminating the need for a heavy mast or forestays. Woop Woop!
Norman Wijker, head of the British team Invictus, explains that winged sails feel substantially less drag than conventional canvas. This lets C-cats sail attack the wind at sharper angles as they tack, zigzagging upwind. And sailing downwind in a C-Class is true aerodynamic magic. Usually, a boat with the wind at its stern (back) simply catches the wind in its sails, never moving any faster than the speed of the gusts. But in a C-cat, sailors deploy flaps (just like on an aeroplane wing) to keep air flowing fast even when apparent wind (the breeze you feel) is low. Sailing directly downwind will never give you much speed, he says, “but by tacking downwind, we can sail faster than the wind.”
But it’s not just wing design that wins races. The crew’s familiarity with the boat and the wing’s controls are crucial for performance. This race’s underdog is the British team, which will be using this event to debut its new, more aerodynamic wing. That said, Wijker believes his team has spent more time on the water than his competition. This could count for quite a bit in a race where split-second decisions and precise handling of the controls are crucial.
Indeed, C-Class catamarans are beyond responsive, says Steve Clark, leader of the US team, pointing out that small differences in wind velocity across the race course have larger than normal consequences. “Large leads can vaporize in seconds,” he says. That’s something Clark knows quite a bit about: His squad’s new boat, the Aethon, was damaged during pre-race testing, so the US team was forced to enter an older boat, the Cogito, into the competition. It’s no slouch, having won the Cup in 2004, but it’s just one more piece of evidence leading to the conclusion that sailing – no matter what sort – is a fickle sport.
Whether your boat is old or new, “you can’t see the wind, and it doesn’t blow consistently,” says Clark. “You have to be able to pick out the clues that tell you what is going to happen next and position yourself to take advantage of it.” “Keeping the boat going fast and going in the right direction is the challenge of all sailboat races.”
Kate Greene is a science and technology writer based in San Francisco
Photographs courtesy Team Invictus Ltd.