So here's the current status:
humber claims that Drela's statement does NOT support the case that the balloon goes the speed of the wind or that it supports the treadmill being equivalent to a road with a tailwind.
From the linked post:sam_sam. The complete question this time.
Stick to the premise, wind powered, not multiple HP treadmill power. Once you attain wind speed there is no more power available. You can't even attain wind speed because of friction/resistance. Trying to grab traction power from the inertia of rolling over the ground or water adds even more resistance.
Questioner;
Stick to the premise, wind powered, not multiple HP treadmill power.
(1) Quite clearly, the question excludes treadmills.
(2) He claims that winspeed is not possible. Nothing to do with the validity of the treadmill.
Dr Drela: ( not in direct reply, but after several other comments. You know how that goes. Would you use this thread as a factual reference?)
Hmm. I think this statement identifies one major misconception which causes so much confusion: The idea that "the wind" provides the power. It doesn't, at least not to all observers.
(3) Here he alludes that the wind may power a vehicle directly as in a glider, or between two media, say the air and ground.
An observer in a hot-air balloon always feels zero wind, so to him the concept of "wind power" seems strange. To him, the DDW cart is clearly "ground powered", by the ground moving past the balloon.
(4) The hot air-balloon is an example of being driven by the media itself. Thinking that "zero wind" means zero power leads to a misconception referred to earlier.
That he says "feels" zero wind, does not mean that he agrees that the balloon is traveling at windspeed. He is a scientist, a recognized expert talking to the public. That is figurative. You must accept that, unless you think that Dr Drela believes that balloons cannot travel slower than the air (you feel it then too, right?)
Here he makes it clear:
It's better to say:
Sailboats, iceboats, DDW machines, Dynamic Soaring gliders, are all powered by the velocity difference between two media.
This works because a velocity difference is the same for any observer, regardless of his own motion.
Yes, relative velocities. Everyone here knows that.
Some examples of the two media, for specific machines:
DDW cart, land yacht: Airmass and ground
DDW boat, sailboat: Airmass and watermass
DS glider, albatross: Airmass above and airmass below a shear layer
This is the correct view he uses to clear up the misconception.
He replaces simple "wind velocity" with airmass, watermass, and shear layers, and which is appropriate for each vehicle or mode.
Compare this with Spork's view. Anything that moves in the wind, or has wings or moves in anyway relative to another, is evidence for the treadmill
BUT..... He is also sure Drela never said what I quoted directly (as a cut and paste). humber thinks the statement supports his own argument, but is now on a mission to prove Drela never said it.
No, I said that we should see all of the other comments in the thread, to see that you had not taken it out of context, or ignored other remarks that do not support your case. You just did it in that in answer to my remark when you misrepresented me.
You did also misrepresent Dr Whiteman. Given that all academics disagree with you, I thought it likely that you would do so again, and it seems that you have.
And he refuses to respond to my assertion that 2+2 = 4
Addition is one mathematical axiom that can be formally proven. You can't do that, yourself of course, but you can count like a child.
Good, more rope to hang you, as always.
