Call me dense but . . .
. . . can someone explain how it can go faster than the wind that is pushing it?
So how's this for emissions-free motoring? Greenbird Greenbird: record breaker Called Greenbird, the hi-tech land yacht is the brainchild of British engineer Richard Jenkins and last week it snapped up the word land-speed record for a wind-powered vehicle at Ivanpah dry lake in Nevada with a top speed of 126.1mph (202.9kph …
It may be completely useless as a form of transport, but if we are to take the form follow function rule as defining beauty, then this is just what this is. It is, asthetically speaking, gorgeous.
Well maybe I'm a bit harsh when I say it's useless as a form of transport, possibly ships might use rigid wings as a means of reducing fuel consumption (I think some companies were experimenting with the idea).
..... and there's a plentiful supply of constant wind,
and the wind is always blowing from the right direction,
and there are no buildings to block the wind or create turbulence,
and there are 10 meter wide carriageways,
and you don't need power for heating, indicators, lights
and you don't need to carry goods!
... and there's a plentiful supply of constant wind,
and the wind is always blowing from the right direction (for all drivers),
and there are no buildings to block the wind or create turbulence,
and there are 10 meter wide carriageways,
and you don't need power for heating, indicators, lights
and you don't need to carry goods!
"can someone explain how it can go faster than the wind that is pushing it?"
Google "Greenbird" go to their site and click on "How it works". BTW, there was a post and comments on this wind-powered "faster than the wind" on Good Math, Bad Math a while back (http://scienceblogs.com/goodmath/2008/12/the_real_bozo_attempts_to_aton.php) where MarkCC, to his credit, apologised for calling the guys who demonstrated such a "faster than the wind" device bozos when he himself just didn't understand how it worked. The subsequent comment thread (and the threads in his previous posts on the subject) do a lot of explaining about how this works, including the math if you're into the nitty gritty.
If the machine had been "sailing" with the wind directly behind it, then it could, indeed travel no faster than the wind speed. Paradoxically as it might seem, the highest speeds are attained with the wind arriving approximating to 90 degrees from the direction of travel. The aerofoil shape generates "lift" which provides a force that propels the vehicle (or boat) forwards.
It doesn't go directly downwind but at an angle to it. The apparent wind then becomes the vector sum of the craft's motion plus the wind's. This new vector can have a scalar velocity greater than the original wind itself. Since the craft is propelled by the apparent wind, it effectively generates its own wind and sails in that.
If you observe (say) America's Cup racing you'll see that the boats are always sailing about 45 deg to the wind, both upwind and downwind. This is the most efficient angle. To understand it fully, do a google for Polar Curves and Velocity Made Good. Some good stuff at Sailplanner.net.