A wind-powered vehicle that can travel twice as fast as the wind itself
<i>> The secret to Blackbird, Cavallaro explained, is that once the wind gets the vehicle going, its wheels start to turn the propeller blades — they're connected to the blades by a chain. As the vehicle speeds up, its wheels turn the propeller faster and faster. The propeller blades, in turn, act as a fan, pushing more air behind the land yacht and thrusting it forward.</i><p>That's a terrible explanation - no wonder people doubt the system would work!