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## Wind-Powered "Greenbird" Seeks Land-Speed Record38

Mike writes with this tantalizing excerpt: "Dale Vince of Ecotricity and engineer Richard Jenkins are setting up on the salt flats at Lake LeFroy in Western Australia, hoping to catch the right breeze and break the wind-powered landspeed record of 116.7 mph in their sleek wind-powered vehicle, the Greenbird."
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## Wind-Powered "Greenbird" Seeks Land-Speed Record

• #### Faster than the wind? (Score:1)

Can someone explain how they could travel 3 to 5 times faster than the wind is blowing? I'm thoroughly confused on how that's possible. Is the vertical wing producing less air pressure towards the front providing forward momentum?
• #### Re:Faster than the wind? (Score:4, Informative)

on Thursday August 21, 2008 @02:34PM (#24694095)

I hate to do this but...

>;-)

.haeger

• #### apparent wind (Score:2, Insightful)

by Anonymous Coward
• #### Re: (Score:1)

The vertical hard sail is actually a wing, just like an airplane wing, there is a high pressure side and low pressure side when air flows around it. I would imagine the most challenging part of the drive is jump form going slower than the wind, where the sail is presumably acting like a sail, to going faster than the wind, where the sail acts as a wing.

Bah, who am I kidding, they're just going to pull it behind a truck until they get it up to above wind speed. They're only looking for the big number at the

• #### Re: (Score:2)

the sail is presumably acting like a sail, to going faster than the wind, where the sail acts as a wing.

Soft sails act as wings too, unless you're on a run. So really it is acting as a sail all the time. And a wing.

• #### Re: (Score:1)

They're traveling across the wind, not just being pushed straight forward by it. Think of a racing sailboat keeling over to the side--clearly it's not being pushed from behind (or at least, not always).

• #### Re: (Score:2, Informative)

Being a sailor, I get that queston quite often. The explanation is simple and appears to be a bit contradictory; the sails generate lift from the wind created by the boat's own movement. If you are familiar with vector addition, it is trivial to see that the resulting "apparent wind" is the "true" wind (the wind speed and direction as seen by a stationary observer) added to the the speed of the boat, both which are vectors with different angles.

This is also the reason why iceboats (and probably also the "bo

• #### How does it go? (Score:1, Funny)

It doesn't have a sail. How does it go?
Someone tell me how stupid I am.
• #### Re:How does it go? (Score:4, Informative)

on Thursday August 21, 2008 @03:17PM (#24694863) Journal

Really stupid ;-)

Just kidding, of course. The thing does have a sail, but it might not be obvious to the uninitiated. It's that thing that looks like a vertical airplane wing. As you may be aware, the sail on a modern sailboat functions much like the wing of an airplane. The rigid sail on this landsailer is actually much more efficient than a cloth sail.

• #### Re: (Score:2)

Yeah, I thought someone had stuck a R/C glider onto the roof
• #### Re: (Score:2)

The rigid sail on this landsailer is actually much more efficient than a cloth sail.

This has been tried on boats too. From Wikipedia: [wikipedia.org]

Two Stars and Stripes cats were built, one with a conventional soft sail (Stars and Stripes S1), and the second with a hard sail (Stars and Stripes H3) built by Scaled. The hard sail proved faster and was used in defense.

After the 32nd America's Cup, the hard sail yacht was bought by Mexican yachtsman Victor Tapia and sails in Mexico. The soft sail yacht was bought by Steve Fossett and used to set speed records in various yacht races.

Yes, "Scaled" refe

• #### Re: (Score:3, Informative)

I wonder why that design hasn't become more popular. I suspect it was made illegal for racing.

Rigid sails are extremely inflexible compared to their soft counterparts. Every wind needs its own sail shape; different wind speeds, directions, wave heights, etc. all require different shapes. There is no rule against rigid sails, it's just too hard to bring dozens of huge metal foils on a boat.

• #### Re: (Score:2)

"There is no rule against rigid sails, it's just too hard to bring dozens of huge metal foils on a boat."

besides which converting a modern ship from diesel to sail powered is very hard, that's why they're using kites, which can easily be added to a conventional freighter, to reduce the fuel consumption. http://www.treehugger.com/files/2008/03/beluga-skysails-cargo-ship-kites.php [treehugger.com]

PLUG IT IN!!!

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