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Post by alancalverd on Dec 19, 2013 20:29:59 GMT 1
Sailing into the wind is fine, as long as it is a true wind, i.e an external source of power. The problem with the "wind powered car" is that it is supposed to generate an apparent wind by using its internal power source, and that's where physics says "no".
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Post by jonjel on Dec 20, 2013 12:05:05 GMT 1
Alan,
As someone who has spent a great deal of time messing about in boats I can't quite see how you can sail directly into the wind, true or not, other than by tacking. If a steady wind is blowing from the West you cannot sail directly West.
The machine my friend made was not strictly a sailing machine, just wind powered. He would ask his students if they thought it was possible to sail directly into the wind and when they all said no produce it from under the desk.
But I agree with you on the wind 'powered' car. The car would probably be more efficient if it was less wind resistant and relied entirely on batteries.
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Post by alancalverd on Dec 21, 2013 1:26:27 GMT 1
Sloppy use of the word "sailing". Clearly if the lift force of a static aerofoil is the only driving force on any vehicle or vessel, it can't sail directly into the wind. But a rotating aerofoil (i.e. a windmill) can transfer power to another device - be it a wheel or a propeller - to produce forward thrust.
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Post by principled on Dec 21, 2013 12:43:45 GMT 1
Alan If we are talking about going directly into the wind, then forward motion would only occur if the total resistance (rotating aerofoil + vehicle rolling resistance and aerodynamic drag) consumes less power than that produced by the turbine. I accept, however, that the aerofoil would assist whatever other power train device is used and thus save energy. In having a look at aerofoils, I came across this. Does anyone know if there have been any takers? www.ladeas.no/P |
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