If you can go downwind 3x faster than the wind, can you turn and go perpendicular to the wind using this mechanism? Can you turn again and go directly upwind?<p>At a multiplier of 3x windspeed, it seems like the fact that there's wind at all is irrelevant other than to get off the starting line. You're generating your own wind power by pushing the propeller through the air. Is this correct?<p>Because if this works other than directly downwind, you have a perpetual motion machine - scale up, drive in a circle, and hook a dynamo to a wheel. Which makes me think I've neglected something somewhere...<p>Edit - from the Wired article:<p><i>"Skeptics think that the wind is turning the prop, and the car is turning the wheels, and that's what makes the car go," Cavallaro said. "That's not the case. The wheels are turning the prop. What happens is the prop thrust pushes the vehicle."</i><p>OK, now I'm really confused. I thought the prop rotation was screwing through the air slower than the relative airspeed and driving the wheels - now you're telling me that the wheels are spinning the prop to produce forward thrust?<p>If he can go from sitting still: wind speed -10, ground speed 0, to W0/G10, and accelerate up to W20/G30, what happens if the wind drops to 0 mid-run? Can he keep going at W20/G20, isn't that easier than W20/G30?