DDWFTTW - Directly Downwind Faster Than The Wind

[Rick Willoughby]

Originally Posted by InetRoadkill

Present a general set of equations describing your device.

There are two papers that Mark Drela produced that I included at post #3 on this thread that gives the generalised equations of motion and energy balance. These are actually for a boat using a water turbine to power the prop. To apply them to the buggy situation you need to equate his turbine and transmission efficiency to my generator efficiency. Other than this the boat and buggy have the same generalised set of equations.

I expect as you are a pilot and all you will at least know of Mark Drela.

Rick W

[spork]

Originally Posted by Rick Willoughby

I expect as you are a pilot and all you will at least know of Mark Drela.

I doubt it very much. But I'm sure he's familiar with Google.

[Richard Atkin]

A wind tunnel test will show you guys where you went wrong in your equations.

Sorry to drag up an old thread....couldn't resist

[spork]

Originally Posted by Richard Atkin

A wind tunnel test will show you guys where you went wrong in your equations.

Actually, both the outdoor tests and treadmill tests show that we were exactly right with our equations. If you understood the concept of going downwind vs. upwind, you might realize how silly it is to suggest testing this in a wind tunnel.

Perhaps you don't understand how a wind tunnel works. It's like a tunnel - for lack of a better word - with wind in it. It really isn't likely to be able to show us where an equation went wrong. Of course if you even thought you knew what you were talking about, you could try and show us where our equations went wrong.

Sorry to drag up an old thread....couldn't resist

No worries. If you want to go that far out of your way to be wrong - be my guest.

[Richard Atkin]

Hi Spork. My point is, you need to be able to make very ACCURATE measurements to provide the proof in a real-world test. You will need a highly controlled wind source to eliminate variations, and when you discover your theory doesn't work, the result will encourage you to look for the flaw in your equation. I can't be bothered because I already know it can't work. I was just offering a challenge. If someone can prove it does work, that person should recieve the Nobel Prize.

No sarcasm intended.

[spork]

Originally Posted by Richard Atkin

Hi Spork. My point is, you need to be able to make very ACCURATE measurements to provide the proof in a real-world test. You will need a highly controlled wind source to eliminate variations, and when you discover your theory doesn't work, the result will encourage you to look for the flaw in your equation.

And yet we've already done the tests that show it DOES work. Putting the cart on a treadmill provides a perfectly controlled wind source. Using a tell-tale on a pole is all the instrumentation needed in an outdoor test to show the cart is going faster than the wind.

I can't be bothered because I already know it can't work.

Interesting - you just "know" this without even understanding the equations and arguments presented. Of course knowing everything is the greatest impediment to learning anything.

I was just offering a challenge.

I guess I missed it. What is the challenge exactly?

If someone can prove it does work, that person should recieve the Nobel Prize.

Unfortunately that just shows how poor your understanding of this thing is. There will be no Nobel prize for this simple brainteaser.

No sarcasm intended.

I understand no sarcasm is intended. Was the stupidity intended?

[spork]

Hey, here's a challenge for you:

I'll bet you $100K that it does work. I presume you could be bothered to take my $100K - no?

Do you really KNOW it can't work? If so, take my money.

[spork]

Incidentally, if you want to understand how and why this thing does work, rather than simply tell me that you think it shouldn't, I'll be more than happy to explain it.

[Richard Atkin]

are you prepared to enter the bet?

[FAST FRED]

"I'll bet you $100K that it does work."


I would be happy to hold the CA$H for this contest!

No ca$h in ADVANCE , not a serious challenge .

FF

[Stumble]

Tell you what, if you guys really want to make this bet I will hold the money in my clients escro account, and hold it for the winner. Though it may be better to find an attorney in Vegas to do it for you.

[spork]

Originally Posted by Richard Atkin

are you prepared to enter the bet?

Of course I am. That's why I offered it. And yes, we both have to put up the money up front. And no, we're not going to leave it with someone we've never met on the internet. We will put it in a joint escrow account.

Sounds like you're up for it?

[Rick Willoughby]

Originally Posted by spork

Of course I am. That's why I offered it. And yes, we both have to put up the money up front. And no, we're not going to leave it with someone we've never met on the internet. We will put it in a joint escrow account.

Sounds like you're up for it?

Spork/Richard
Is this one for boat or land based vehicle?

Spork
Did you ever collect on your land vehicle bet?

Have you progressed with the version you can ride?

Rick W

[spork]

Originally Posted by Rick Willoughby

Spork/Richard
Is this one for boat or land based vehicle?

The original post is yours, and it mentions both a boat and a land vehicle. Richard seems to think the concept is fundamentally flawed, so either one succeeding should suffice to prove him wrong. As I've made several of the land variety, that's what I would be inclined to have decide the wager. Of course there is no theoretical reason it can't be done with a boat, but it'd clearly be more difficult.

I think I've managed a tack on my kiteboard with downwind VMG faster than the wind (as recently as 2 days ago). But I wouldn't bet on it - at least not until I convinced myself.

Spork
Did you ever collect on your land vehicle bet?

I'm not certain which one you're refering to. I've offered this, and similar, bets MANY times. There was only one guy that I recall that ever seemed serious about taking me up. He was in Germany, and wanted a bit of time to raise the money from people that would obviously be well paid for their investment. It seems they insisted he dig a little deeper before they invested with him, and he emailed me off the list asking to be let out of the bet. He claimed that he tried it himself, and found to his surprise that it actually worked. I suspect he did not actually do this, but did become convinced by someone rational that he was about to lose $100K. He was one of the most beligerent and insulting critics we've ever had.

Have you progressed with the version you can ride?

You can never go wrong betting on my laziness. We've done some design work and found the key components. JB and I also presented this as a seminar at both Stanford and SJSU in the interest of finding some Aero students that might be interested in taking it on as a project. One student came forward, and is trying to find 3 more for his team. I somewhat doubt that'll get any traction. I've suggested to JB that maybe we should just suck it up and do it ourselves once the kitesurfing, hang gliding, paragliding season ends (and I get bored). Perhaps we'll do that - but you'd still be pretty safe betting on my laziness if history is any guide.

One thing is for sure... if someone actually puts up the money for this bet, I'll run out and build a full-scale version in a hurry. We figure it'll cost a couple grand, and I'm an unbelievable cheapskate (which should be a warning to Richard - I would NEVER put up $100K on a bet that I might lose).

[Rick Willoughby]

Originally Posted by Richard Atkin

A wind tunnel test will show you guys where you went wrong in your equations.

Sorry to drag up an old thread....couldn't resist

Richard
Before you jump any deeper into this you should Google DDWFTTW. Also take a look at Mark's equations in post #3 and check on who he is if you do not know.

What you are challenging Spork to is not particularly difficult to demonstrate on land.

Most people have difficulty appreciating that the blades become a propeller driven by the wheels - the opposite to going upwind. What you are arguing is the same as saying an aeroplane cannot produce any thrust in a tail wind - it is nonsense.

Rick W