Breezy... is there a wind-powered car in your future?

Sept. 7, 2008

Sails were the main propulsion power for transportation for thousands of years. Pecos Bill, that American folk hero, was said to sail across the American plains in a square-rigged prairie schooner. Pecos Bill’s land ship was depicted in a Disney movie. But what if you could actually sail across the land?
The fastest any human being had ever traveled back about 1910 was on an ice boat. An ice boat, rattling along on a smooth, frozen lake, can reach speeds of over 90 miles an hour. On a broad reach, the wind amid ships, a sailing craft can exceed the wind speed.
Of course, the ice boat speed was soon surpassed by racing cars. The fastest land speed record was achieved by Campbell in the Bluebird, a jet-powered fuel-gulping monster blasting along on a salt flat.
The existing wind speed record for a land sailing craft is 115 miles an hour. Now a couple of eco-friendly Brits, remembering Campbell’s Bluebird, have named their vehicle “Greenbird” and plan to test it on a salt lake in Australia.
A sail is really a vertical wing. Of course, Greenbird doesn’t have a cloth sail. As any sailor can tell you, a sail is an airfoil shape. Because cloth is flexible, as the wind increases, a cloth sail changes its shape. For maximum efficiency, the airfoil has to be rigid. On a boat, sailors control the shape with a flattening reef or a vang that pulls the boom down to maintain the shape of the cloth. On an airplane the amount of lift is boosted at low speeds with flaps that change the shape of the wing.
Dale Vince and engineer Richard Jenkins have developed the Greenbird prototype and plan to sail it in Australia on Lake LeFroy, a 500 square kilometer salt lake in western Australia. That is, they’ll try it when the surface is totally dry. Lake LeFroy turns to mush when it rains. If it’s dry enough they expect to travel up to six times the wind speed, so in a 20 mile an hour breeze they could theoretically make 120 miles an hour with Greenbird.
Vince thinks wind-powered cars are the wave of the future. That might be well and good if we all lived on a flat-bottomed salt lake, but I can’t imagine tacking westward on the Interstate against the prevailing wind at any speed. We have trouble enough with drivers who weave in and out, racing between lanes on the I-75. There’s also that problem of clearance under bridges. Overpasses are just high enough for 14-foot-high semi trucks to slip under. The vertical wing of a wind-powered car would have to be lower than 14 feet. My 22-foot sailboat has a 24-foot mast on top of the hull. We do not tow it down the highway with the mast up.
Perhaps their wind car is intended strictly for crossing the hundreds of miles of the Australian Outback.
It is an entertaining thought. Leave it to the Brits to come up with an idea like this. Remember, it was the English who were so keen on a man-powered airplane. Eventually, a skinny guy peddling madly a few feet off the water made it across the English Channel to France, arriving winded just at the shore. The Mylar-winged Gossamer Condor made it, too, powered by solar panels that ran small electric motors. And of course, it’s a Brit who is building a space ship for passengers to ride at $200,000 for a sub-orbital flight. That’s not exactly a trip to the moon or even to New York City;
If Vince thinks we’ll actually be able to commute with wind-driven cars, he’ll have to make better sailors than we have drivers today, and point no highway upwind. Pecos Bill with a square-rigged wagon could run only downwind. The sailors in clipper ship days depended on the trade winds that blew in one direction in one season and reversed in another, which meant only one round-trip a year. That won’t do on your daily trip to the office.
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