Iceboats can hit 60 or 70 mph without breathing hard

I hear that ice-sailing boats can travel faster than the wind that propels them. How can this be so? The aerodynamic principles governing their motion must then apply to ocean vessels too, no? — D., SDSU

Why, yes. Windsurfers, sailboats — and also when Cujo sticks his head out the car window and his ears fly back and his dewlaps flutter like chattering teeth. But iceboats have very little friction or drag — no water tugging on a hull — so they can better exploit the aerodynamic principles. Iceboats, which are basically crossed sticks with sails and skatelike runners, can hit 60 or 70 mph without breathing hard; 143 is the current record. While the best catamarans can go twice the speed of the wind, depending on whom you believe, iceboats move three to six times wind speed.

Anyway, iceboats are powered by the ordinary wind we hear about every night on the 11 o’clock weather report and also by “false” or “motion” wind generated strictly by the forward movement of the boat. When the real stuff combines with the fake stuff, the wind strikes the sails at yet a third angle called the “apparent wind.” Say the true wind is blowing at 12 mph directly from the right; when your boat also reaches a speed of 12 mph, you have a motion wind of 12 at a 90-degree angle to the true wind. The resulting apparent wind is 17 mph at a 45-degree angle. All of this is going on while the fool at the helm is only inches from the ice, magnifying the sense of “apparent death.”

The faster the boat goes, the stronger the false wind and the closer together the false and apparent winds approach each other; this makes the iceboat go still faster. Air moving past the windward side of the airfoil-like sail creates a low-pressure area on the lee side, which tends to pull the iceboat forward. And because iceboats are pinched between the wind on one side and the grip of the runners on the other, they accelerate like a grape squirted out of its skin. Got all that? I think it’s time to head for land and have some cocoa.