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Old 11-04-2010
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Quote:
Originally Posted by JohnRPollard View Post
the prop blades are not acting as sails to propel the vehicle.
What do you mean by "acting as sails" in physical terms? In terms of aerodynamics they are acting excatly just like sails on a broad reach with a downwind VMG > wind speed. This animation shows this very nicely:
youtube.com/watch?v=UGRFb8yNtBo

Quote:
Originally Posted by JohnRPollard View Post
In other words, there are no sails that use the apparent wind or benefit from its effect,
What do you mean by "use the apparent wind or benefit from its effect" in physical terms? Every airfoil (sail or propeller blade) can create an aerodynmaic force if it experiences relative air movement (apparent wind).

Quote:
Originally Posted by JohnRPollard View Post
Just the opposite with this vehicle. In this particular type of windpowered vehicle, it is actually advantageous to have apparent windspeed drop to zero
Note that the apparent wind at the rotating airfoils never drops to zero

Quote:
Originally Posted by JohnRPollard View Post
The new apparent wind (now a headwind) and the prop thrust begin to work together to complement eachother.
What you mean by "work together to complement eachother" in physical terms? Thrust is a force while apparent wind a velocity so you don't make much sense here.

Quote:
Originally Posted by JohnRPollard View Post
From what I can gather, the controversy surrounding this vehicle and what it demonstrated has less to do with the concepts and more to do with how poorly they were expressed/explained. Unfortunately, proponents consistently employed oddly chosen terminology,
Actually I find your terminology very odd and unclear.

Quote:
Originally Posted by JohnRPollard View Post
and made the mistake at the outset of implying that there was a connection between this vehicle and the sport we know as sailing. There is not.
The analogy to sailing is only useful to those who actually understand the physics of sailing.

Quote:
Originally Posted by JohnRPollard View Post
This vehicle would be more analogous to a wind-powered "motorboat". On the water, you'd build it with a pointy bow and a lot of surface area at the stern, and paddle side wheels. The paddle wheels would be connected to an underwater propeller via a geared transmission. As the boat began to move downwind, the paddles would spin due to resistance in the water and they would in turn drive the propeller and produce thrust.
So you want to harvest power from the water(via paddle wheels) and transmit it back to the water(via underwater propeller), and hope to create forward thrust by this? Good luck with that!

Sorry, this is not how this vehicle (and sailing in general) works. Just like any sail boat this vehicle takes energy from the velocity difference between two different media.
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