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The slipstream...

Old 08-19-07, 12:35 PM
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joonbog
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The slipstream...

Hi there...I have to do a concept presentation for an interview and want to present on the concept of using the "slipstream" in cycling. Does anyone have any creative ideas about how to teach this concept, links to information, or activities that could help me with this presentation?

Thanks!
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Old 08-19-07, 01:11 PM
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Hmmmm.

Google: Results 1 - 100 of about 565,000 for drafting cycling. (0.24 seconds)

READ ME

The rest is up to you.
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Old 08-19-07, 01:12 PM
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If by "slipstream" you mean "drafting" another vehicle to gain
speed know this...........Drafting is not only stupid it's deadly
to those idiots who do it in addtion to being illegal.

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Originally Posted by krazygluon
Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?
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Old 08-19-07, 02:08 PM
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Ok...

Aerodynamic drag (in terms of power required to counter it) on a bicyclist varies as speed cubed. Speed in this case is speed through the air (in your direction of travel), which is lower than your "road speed" if you have a tailwind, and higher if you have a headwind.

When a bicyclist rides through an airmass (with a speed not equal to that of the bicyclist), the air surrounding the bicyclist will be accelerated in the bicyclist's direction of travel - he is setting air in motion, pulling it along. The power required to set this air in motion is the power required to overcome the wind resistance.

Behind the moving bicyclist will be a mass of air moving along with him, but not quite at the same speed. Towards the sides of this rearward-pointing "cone" of dragged-along air, the speed of the air will be gradually lower until at some point, it will be the same as for the unaffected air. The same is true in the rearward direction, so at some point behind the bicyclist, air will return to its normal state, and be effectively unaffected.

If second bicyclist rides closely behind the first, he will be moving along inside that accelerated mass of air, and will see a reduction in relative air speed for himself. This translates to a lower power required to maintain any given speed.

Since power required to overcome aerodynamic drag varies as the air speed cubed, even a small reduction in relative air speed will make a big difference in the power requirement for the second bicyclist. Another factor to consider is also that the faster the first bicyclist rides (and/or the greater the headwind), the greater the reduction in drag for the second rider will be.

The cone of accelerated air behind the first bicyclist will be deflected to the side in a crosswind, so the actual sweet spot could very well be at an angle behind the first, requiring a staggered position for a trailing bicyclist.

The effect of drafting increases as the distance between the two bicyclists decreases. At a sufficiently low relative air speed, the drafting zone is too small for another bicyclist to fit into, and virtually no benefit comes from drafting.
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Old 08-19-07, 05:12 PM
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Originally Posted by Tightwad View Post
If by "slipstream" you mean "drafting" another vehicle to gain
speed know this...........Drafting is not only stupid it's deadly
to those idiots who do it in addtion to being illegal.

Yep but is a good way to set speed records...

Aaron
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"Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred
Which one would you rather have under your butt at 30mph?"
_krazygluon
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Old 08-20-07, 01:13 PM
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Originally Posted by wahoonc View Post
Yep but is a good way to set speed records...

Aaron

Yes, it sure is.....BUT.... speed records are set on closed courses with pro's
all around and riding. Idiot's need not apply.
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My preferred bicycle brand is.......WORKSMAN CYCLES
I dislike clipless pedals on any city bike since I feel they are unsafe.

Originally Posted by krazygluon
Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?
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Old 08-20-07, 01:15 PM
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Originally Posted by Tightwad View Post
Idiot's need not apply.
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Old 08-20-07, 03:29 PM
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There's a Mythbusters episode where they presented this concept fairly well. Even though their "plausible" conclusion was way off the mark!

Anyone have a video of John Howards 152mph record run?
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Old 08-20-07, 04:56 PM
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Originally Posted by joonbog View Post
Hi there...I have to do a concept presentation for an interview and want to present on the concept of using the "slipstream" in cycling. Does anyone have any creative ideas about how to teach this concept, links to information, or activities that could help me with this presentation?

Thanks!
mythbusters
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Old 08-20-07, 05:10 PM
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I always liked the poster (think it's www.despair.com that markets it) that has a picture of geese flying in a "V" formation. Caption: "Geese flying in formation use 30% less energy than flying alone. Which proves even Nature values laziness."

I might have the caption slightly off, but you get the idea. Maybe not what you're looking for in an interview, though.

Minstrie
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