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Mess with your minds: A wind powered craft going faster than a tail wind speed.
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Labrat101:
I gave the formula for the thrust and kinetic power of a propeller. 
But he ignored it completely.
 
CatalinaWOW:

--- Quote from: IanB on December 30, 2021, 09:33:59 am ---
--- Quote from: MikeP on December 30, 2021, 09:13:34 am ---Friends, I found this thread by accident. There appears to be no consensus. 54 pages is beyond my strength, but I saw the film. This is incredible! New horizons are before us!
--- End quote ---

Certainly there is consensus. A set of equations describing how to design such a vehicle has been put together using established principles of physics, and accepted as correct by qualified professors of engineering. Both full size and scale models have been constructed and shown to work.

This was first done as long ago as 1969. Reference here: https://projects.m-qp-m.us/donkeypuss/wp-content/uploads/2009/06/Bauer-Faster-Than-The-Wind-The-Ancient-Interface.pdf

--- End quote ---

Thanks for the paper.  A clear and coherent description of why it works. 

Most importantly a set of equations that properly represents all elements of the system.
electrodacus:

--- Quote from: Kleinstein on December 30, 2021, 10:13:43 am ---
When going at a very low speed, that is low RPM on the pedeal on will not be able to get 300 W. The driver has the same problem as the vehicle: it is hard to get the same power, as the forces have to go up.
The problem why going 1 km/h again a 40 km/h head wind with a normal bicyle is not possible is not because the 300 W are needed, but because it is hard to produce even 30 W at such a low speed, as this needs very high force.
The is just not enough force to produce 100 W at a very low speed. So if the magic (..)³ expression would be true one would never be able to start from a stand still aginst any headwind. One allways starts with infinitesimal low speed and thus infintesimal small (essentially zero) mechanical power.

There is no need to repeat the supposed formula for the maximum available wind power for the moving vehicle. Without a good source or maybe an acceptable explaination this is worthless like repeating "The earth is flat.".

The (w-v)³ type equation is not only withput a good source, but in addition also proven wrong (see above).

--- End quote ---

Why can you put 300W and go at low speed when climbing a hill ?
Why do you think driving in head wind is any different in that regard?
The bicycle speed will be low but your gear ration can be set so that your legs move very fast thus even with low force needed at the pedals you can still produce 300W
There is a limit based on when the traction wheel will start to slip but 300W even at 1km/h is possible on a bicycle.
You do not start with an infinitesimal small amount of power you just have this wrong.
Have you not seen the (w-v)3 in enough places ? It is basically everywhere.
But more important that that the equation works and produces the correct results as seen in any real test.
PlainName:

--- Quote ---But more important that that the equation works and produces the correct results as seen in any real test.
--- End quote ---

It doesn't, simple as that.
electrodacus:

--- Quote from: Domagoj T on December 30, 2021, 10:49:16 am ---Don't worry about my feelings, I'm a big boy, I can handle it. Will I'll have no clue what you would have said because you think I have reduced mental capability or because you just can't provide an argument?
You keep saying that at wind speed a sail has no power, yet when I give you an example of sail traveling below wind speed, you deflect and avoid.


So let's focus not on generic, but on this specific example.
And yes, this vehicle does have an external energy source - the wind.

--- End quote ---

I do think people mental capabilities are very different.
There is no wind power available to a sail vehicle traveling at wind speed. There is of course plenty of power available to a sail traveling below wind speed. The slower it travels relative to wind speed the higher the available wind power.
It is clearly seen form the equation that I constantly post here.

Pw = 0.5 * air density * area * (wind speed - vehicle speed)3

I even provided examples. Maybe you got here more recently and did not see them but here is one example just for you

area 1m2
air density 1.2kg/m3
Wind speed 20m/s
Vehicle speed:
a)0m/s
b)5m/s
c)10m/s
d)15m/s
e)20m/s
Wind power available to vehicle
a)4800W
b)2025W
c)600W
d)75W
e)0W

 
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