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by spork
Mon Mar 23, 2020 7:18 pm
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

Incidentally, the Blackbird is supposed to be operating at El Mirage in Southern CA in early May if anyone is interested - assuming the lockdown is no longer in effect.
by spork
Mon Mar 23, 2020 8:12 am
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

How is it something of a low velocity can impart a greater velocity on something else? In the talk I gave I offered a few examples to try and illustrate how this can happen. Probably my favorite is the notion of pushing on the middle of a tall pole such that you move it at 5 mph. At that point the ...
by spork
Mon Mar 23, 2020 7:57 am
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

I personally think that yes wind could come from back of the blades in certain configuration (at least): with a very little AoA or ratio (or even 0% to illustrate), or at the very start, the wind is pushing the blade by tailwind, right? do you agree at that 0 speed step ? First off - sorry for my d...
by spork
Sun Mar 22, 2020 9:50 am
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

Not entirely sure why this is a theoretical discussion. Racers currently reach downwind VMG in excess of wind speed I think it's just a discussion about how that works, and what other possible ways one could do it. That means the only thing to define is how narrow you want to make this "direct down...
by spork
Sun Mar 22, 2020 6:18 am
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

So I have 2 questions: 1- what is wrong in your opinion in my analysis ? it works theoretically i think, and would like to catch where is the misunderstanding in your opinion. Maybe my explanation was not clear enough, on the word "surface" maybe. It's possible that I didn't understand it properly....
by spork
Sun Mar 22, 2020 1:28 am
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

Interesting you are all still arguing this thread...Without reading it new, I will add my bit. I don't think there's anyone left arguing it really. Just a friendly discussion. You can go dwfttw with a kite or sailboat for the same reason you can go upwind. Yes, with a sufficiently efficient craft y...
by spork
Sun Mar 22, 2020 1:23 am
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

Regis-de-giens - if I understand your analysis, I think you're caught in one of the very common misconceptions. The wind from behind never actually reaches the blades at all once we're going faster than wind speed. The reality is that the blades are now pulling us into new air that's in front of the...
by spork
Sat Mar 21, 2020 9:02 pm
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

>> Looking would have to be happy to ignore how it got to that steady state!!!! Exactly right. For purposes of analysis we can push the thing up to speed with a car. The question then is whether it can maintain that speed indefinitely. >> Could you please do the vmg for the 34th America's Cup Catama...
by spork
Sat Mar 21, 2020 4:04 pm
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

>> the energy input can only be from the existing wind but the forces involved at any given instant of time have to be analysed by including the accumulation effects of the craft's acceleration-velocity. This is not the case. We can look at the vehicle moving at any steady state speed without consid...
by spork
Fri Jun 28, 2019 8:58 pm
Forum: Kitesurfing
Topic: Downwind Faster Than The Wind - update
Replies: 342
Views: 33230

Re: Downwind Faster Than The Wind - update

knotwindy wrote:
Fri Jun 28, 2019 8:46 pm
Great vid, not a waste of time or boring at all.
Thanks!
I assume in the post above you meant “ ‘upwind’ mode, the big spiny thing acts as a turbine”?
Yes - that's exactly what I said (now that you caught it and I changed it :) )

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