I am no expert but what does the treadmill experiment really prove?
If it was actually going down a real hill, the wheels would build up some resistance when transferring power to the propeller right?
But the engine of the treadmill is so powerful that it just overrides that resistance and the difference is probably what makes it go forward.
Does that make any sense?

Now if it could drive of the treadmill and just keep on going I would be impressed.

apparent wind, duh!
Oh did I mention the NACRA 20 sucks?

I can't see the video or pictures that Jake posted but Tawd is on the right track here.

A wind mill car (or trimaran as shown in the movie Water World) can indeed "sail" straight into the wind. Just make sure that the gearing between the driven shaft of the wind turbine and the drive shaft to the wheels or screw is large enough.

The minimal gearing required is the same as the ratio between the orthogonal forces acting on the windturbine blades. The ratio between the force that makes the turbine turn (perpendicular to the airflow) and the one that tried to bend the turbine blades backwards (parallel to the airflow).

Any gearing higher then that (and sufficiently large to also overcome other parasitic drag factors) will see the craft move directly into the wind.

A Darrieux windturbine design would be very attractive solution for such a craft. Look it up on wikipedia. This design doesn't require the turbine to be aligned to the wind in any way. (water world tri had on of those and that was actually a brilliant idea)

Wouter

Wouter,

here is a link to the youtube video that started the current discussion.

http://www.youtube.com/watch?v=xHsXcHoJu-A&feature=player_embedded

If you can see the video, it looks like the car builds its own energy and accelerates.

The point of the demonstration was to show that a vehicle can "sail" faster than the wind dead down wind (DDW)...and this one does. What stumped me was that the vehicle outruns the treadmill and that there was no visible sign of energy being added to the car to keep the propeller turning. Some of you undoubtedly saw the right things right away.

The propeller is pushing the vehicle forward against air that is not otherwise moving. The treadmill is pushing rearward on the cart, but the propeller is pushing harder against the static air and this imbalance is what allows the cart to move forward but still draw energy from the treadmill.

In a real world scenario with the cart moving on an open road in still air it would have an apparent wind and would have much less traction with the air ... so it would never be able to self sustain speed. However, put some wind at the back of it...and enough to get it to a certain speed, it's capable of pushing itself off the air and move faster downwind than the wind is blowing. This is exactly what the treadmill is demonstrating...that it can move faster than the still air.

Oh! I see! The alchemy demonstrated will restore lost beach access. Wonderful! Where do I get one?