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Downwind Faster Than The Wind - update

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spork
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Downwind Faster Than The Wind - update

Postby spork » Sun Nov 15, 2009 8:59 am

Some of you will probably remember the brainteaser I posted long ago, asking if it was possible to build a wind powered vehicle that will go directly downwind, faster than the wind, steady state.

We built a few of these vehicles, and demonstrated them primarily on treadmills. But some folks didn't believe that working on a treadmill meant it would work outdoors. So a buddy and I decided to build a 250 lb vehicle with a 16 foot prop, that carries a driver. We're hoping to test at the Alameda Naval Air Station in April. It would be great to get locals there to witness.

You can see our progress at www.fasterthanthewind.org

ETA: We let the BUFC loose on the lakebed at Ivanpah, NV. We were pretty excited to do better than 2.5X windspeed directly downwind. These are not official results, but we're now preparing for an official record run.

Some videos from Ivanpah:

First run: http://www.vimeo.com/10476453
Second run: http://www.vimeo.com/10477373
Last run: http://www.vimeo.com/10476216
Last edited by spork on Sat Apr 10, 2010 7:00 am, edited 1 time in total.

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Peter_Frank
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Re: Downwind Faster Than The Wind - update

Postby Peter_Frank » Sun Nov 15, 2009 7:30 pm

I dont get the issue ?

You want to go straight downwind, having the wind drive the propeller, and go faster than the wind ?

Or what ? (as I cant see above to work in any way...)

Whereas, going on a broad reach almost straight downwind, would give a sideways air composant, that should make a really efficient propeller vehicle to be able to run faster than the wind, and maybe even faster than the wind regarding downwind vmg - which in itself is a really interesting and not easy feat :thumb:

Curious now :D

Kindly, Peter Frank

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Re: Downwind Faster Than The Wind - update

Postby spork » Sun Nov 15, 2009 8:29 pm

The cart goes straight downwind. We're shooting for 2X windspeed. But the wind doesn't drive the propeller as a turbine. Instead the prop is geared to the wheels. So the wind pushes the cart downwind, the wheels cause the prop to start turning, and it pushes the cart beyond wind speed. The "secret" to the whole thing is that, while the cart is going straight downwind, the prop blades are not. They are on a continuous broad reach as you suggest.

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Re: Downwind Faster Than The Wind - update

Postby ThickAir » Sun Nov 15, 2009 8:50 pm

Awesome!! Good luck with the build, Spork.

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Re: Downwind Faster Than The Wind - update

Postby spork » Sun Nov 15, 2009 8:54 pm

ThickAir wrote:Awesome!! Good luck with the build, Spork.


Thanks. This is based on exactly the same principles as the little carts we've built and demonstrated on the treadmill:


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Re: Downwind Faster Than The Wind - update

Postby ryansurf1 » Mon Nov 16, 2009 4:30 am

I dig it....

Love to see people with a few extra dollars... a few hours...and an idea that people say 'can't be done'.

The little cart was cool but the best part of the video is where you say 'Spoork',

I hope the German guy who is vehemently opposed to the concept shows up to the test run :lol:

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Re: Downwind Faster Than The Wind - update

Postby spork » Mon Nov 16, 2009 4:40 am

ryansurf1 wrote:I dig it....

Love to see people with a few extra dollars... a few hours...and an idea that people say 'can't be done'.

The little cart was cool but the best part of the video is where you say 'Spoork',

I hope the German guy who is vehemently opposed to the concept shows up to the test run :lol:


The German guy (waker) was the only guy to ever take me up on my bet. A few days later he emailed me privately asking to be let out of the bet - after having ridiculed and insulted us for months. We'd love to have him there. But I strongly doubt he, or any of the other skeptics, will show. I don't think they're prepared to have their faith shaken.

Incidentally, the one with a few extra dollars is Jobe Energy. I doubt if we'd do this without their support. But it is taking a whole lot of hours. We intentionally scheduled it for the non-windy season :D

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Re: Downwind Faster Than The Wind - update

Postby Vin Stefanelli » Mon Nov 16, 2009 4:58 am

takes apparent wind to a whole nother level!
the H-N-L!
will the full size device
be able to change the blade pitch on the fly?

does the prop switch directions
when it passes the ambient windspeed?

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Re: Downwind Faster Than The Wind - update

Postby spork » Mon Nov 16, 2009 5:29 am

Vin Stefanelli wrote:takes apparent wind to a whole nother level!
the H-N-L!
will the full size device
be able to change the blade pitch on the fly?

does the prop switch directions
when it passes the ambient windspeed?


The prop always goes the same direction. It's driven by the wheels from the very start. It acts as a bluff body until it gets spinning fast enough to develop lift over the blades. At this point we plan to have the pitch "ground adjustable". But we may change that if needed to improve the acceleration. Our plan is to have a long enough runway that acceleration won't be too great a problem.

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Re: Downwind Faster Than The Wind - update

Postby Kamikuza » Mon Nov 16, 2009 7:58 am

Very cool! Keep us updated, yeah?


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