Err, they made it go faster than the wind downwind.. Interesting! The boats I read about did not pull that one off, but there is less drag from the wheels compared to a hull or two.
So Jake, what is the explanation? Or do we need to call inn Wouter?
Heck if I know. I haven't had much time to ponder the treadmill trick, but I'm having a difficult time figuring out the physics of it. It would seem to be a perpetual motion machine if it can climb a hill without any external source of energy...I suspect that there was some airflow behind the cart on the treadmill helping to push it forward...but I don't doubt that it can move faster than the wind downwind.
You absorb energy from the wind by redirecting (slowing down) the molecules of wind as they go by. You can absorb a fixed amount of energy this way. If you're resistance to motion is less than the energy that can be extracted from the wind, then the craft can move faster than the wind that's powering it. Sailing craft have demonstrated (easily) the ability to sail faster than the wind at certain angles...the blades of the prop help maintain those beneficial angles while the vehicle can be moving in any direction.
