I came across a pretty interesting article in Wired Magazine the other day. The crux of the story surrounds whether or not it is possible to construct a vehicle, powered only by the wind, that can outrun a balloon propelled by the same wind. It’s solution was based on the fact that a sail will generate thrust like an airplane wing. Personally, I didn’t know that it was true that a sailboat tacking in the wind could actually go faster than the wind (so long as it’s travel vector is not parallel to the wind). Anyway, this guy Rick Cavallaro decided to adapt the tacking method onto a vehicle that could travel dead downwind, powered only by the wind and go faster than the wind. The key was visualizing the sail in a different way, until you realized the required motion was that of a propellor. The following images are described well in the original Wired story.

The outcome of his design proved to slowly start turning the propellor by wind power alone which turned the wheel’s driveshaft. Ever so slowly, the vehicle began moving until it reached the zero wind condition and then surpassed the wind by a more than significant margin repeatedly in multiple trials. In fact, the tests had to be stopped because their vehicle which was constructed of carbon fiber and bicycle components couldn’t handle the continually rising torques imparted by the wind (measured as equal to that of a Corvette engine). Nevertheless, the experiment proved a wind powered vehicle could outrun a floating object pushed by the same wind.