BS: Slipstreaming what is the potential?

Subject: BS: Slipstreaming what is the potential?
From: Georgiansilver
Date: 22 Apr 04 - 08:39 AM

Flying in formation and slipstreaming, geese can fly 42 times further than flying on their own....they take turns doing the hard work at the front and are "dragged" for the rest of the way...Cyclists have been slipstreaming for years also as a means of conserving energy.
IMAGINE:- The potential of a flock of geese on bikes!!!!!!

Subject: RE: BS: Slipstreaming what is the potential?
From: Rapparee
Date: 22 Apr 04 - 09:03 AM

You'd have to be a goose to slipstream outside of VERY controlled conditions.

Subject: RE: BS: Slipstreaming what is the potential?
From: Bill D
Date: 22 Apr 04 - 06:24 PM

cyclists have been increasing their power thru sprockets and gear ratios for years...Imagine the potential of a school of tuna with pedals and shifters!

Subject: RE: BS: Slipstreaming what is the potential?
From: mack/misophist
Date: 22 Apr 04 - 07:05 PM

I'd never try it but I've talked to bikers who went 7 0r 8 hundred miles in a day, slipstreaming. That's motorbikers.

Subject: RE: BS: Slipstreaming what is the potential?
From: JohnInKansas
Date: 23 Apr 04 - 01:58 AM

One difficulty here is that "slipstreaming" bikers frequently choose large vehicles to "hook up to." Some truckers have NO sense of humor about this. The "potential" is sometimes "dead."

A group of bikers traveling together can get some significant drag reduction, particularly if they ride "in-line," or "in-echelon" like the geese do. It is necessary to adjust the spacing between riders pretty precisely for best effect, but you do "feel the sweet spot" if you get close to it. Contrary to the "obvious," even the guy in front gets a little help, although less than those following. It relates largely to the playoff between effective L/D (length to depth ratio) traded off against "interference drag."

For the "classic" analysis, look up the "Busman Biplane" ca. 1943 or so. Walter Beech used the concept in the "Staggerwing" Model 17 biplane, where the upper wing effectively "slipstreams" the lower (more forward) wing as airspeed approaches maximum - to get a few more knots out of a relatively puny engine.

Yeah, I know you guys were makin' jokes, and it's more than you wanted to know, but...

John

Subject: RE: BS: Slipstreaming what is the potential?
From: Georgiansilver
Date: 23 Apr 04 - 04:20 AM

JohnInKansas.   No my friend on the contrary. I was hopimg to get some factual feedback on this thread as well as the humour. It refreshes us all to learn something new. Best wishes.

Subject: RE: BS: Slipstreaming what is the potential?
From: GUEST
Date: 23 Apr 04 - 05:04 AM

...or as Van Morrison sang,

"If I ventured into the slipstream
between the viaducts of your dreams...

Absolute genius!

Subject: RE: BS: Slipstreaming what is the potential?
From: GUEST
Date: 23 Apr 04 - 05:10 AM

That last post was me, dianavan. I don't know why I'm a guest all of a sudden. Can someone clue me in?

Subject: RE: BS: Slipstreaming what is the potential?
From: Gurney
Date: 23 Apr 04 - 06:02 AM

You've lost your cookie. Go through the process of rejoining. Happened to me twice, and I don't know why.

Subject: RE: BS: Slipstreaming what is the potential?
From: Strollin' Johnny
Date: 23 Apr 04 - 07:21 AM

Don't know about genius, Dianavan! "If I ventured into the slipstream between the viaducts of your dreams" - sounds more like Van had been at the loopy-juice again, or some extra-stong stuff he got in Amsterdam. Shades of cakes left out in the rain! Or even 'Canyons Of Your Mind' (which you won't get if you're not British and a fan of The Bonzo Dog Doo-Dah Band)! :0)

Johnny :0)

Subject: RE: BS: Slipstreaming what is the potential?
From: mack/misophist
Date: 23 Apr 04 - 09:40 AM

Can't speak for the others but I wasn't joking. Kansas John got it dead right.

Subject: RE: BS: Slipstreaming what is the potential?
From: saulgoldie
Date: 23 Apr 04 - 12:48 PM

If you are a confident cyclist, slipstreaming is a positive gas! I have (a few times, only) "drafted" behind a large vehicle--truck/bus--as it pulled away from a traffic light. I rode them suckers up to bout 50 and for perhaps 1/2 mile when I either ran out of gear or nerve, depending on the situation. It is very heady, but I do not recommend it for any but the steel-nerved. And if the wrong person is watching, you CAN get a ticket. Following too closely, wreckless driving, something like that.

In another situation, I spent much/most of my (solitary) double-century riding a line. My group finished in just over 14 hours. But we certainly would not have been so chipper at the end, nor would we likely have finished so fast if we had been riding "normal" group ride style, side by side.

In short, at slower cycling speeds, one's energy is used mostly to overcome friction within the bike, and some gravity. As one approaches about 22 miles per hour, the energy drain shifts to wind resistance and increases either geometrically or exponentially, I fergit my physics. This is also why many racing cyclists tend to be shorter--less body to resist the wind, and easier to tuck in behind another cyclist, regardless of their size.

Hope I didn't bore you.

Saul

Subject: RE: BS: Slipstreaming what is the potential?
From: JohnInKansas
Date: 23 Apr 04 - 05:34 PM

For cyclists, the straight in line group is probably most efficient. The basic drag on an object is proportional to air density (less at high altitudes), proportional to "frontal area" (scrunch down low), and proportional to the square of the airspeed (v*v). Double the speed, and you have 4 times the drag. The other factor is a "drag coefficient" that depends on the shape of the object. You usually get the Cd from wind tunnel tests, but it's smaller if the object is "long" in proportion to its thickness.

If two riders are close enough so that the air doesn't "get between them" mother nature thinks they're one longer object, so they have a better "combined" Cd. The faster you go, the longer the gap can be, but it's often smaller than is comfortable unless you're alert and experienced.

At speeds below 10 mph or so, you'd have to be very close (and the effect would be small). Unfortunately, since things like stopping distance and maneuverability also go with the square of the speed (it's the kinetic energy that counts) the "allowable gap" for slipstreaming doesn't increase as fast as "space needed for feeling safe" does. You feel the "need" for increasingly more space as the speed goes up, and the increase in space that works doesn't increase quite as fast. Some skill and experience is needed.

When you follow a large vehicle, you're not really slipstreaming. You're just following a windbreak that reduces the local airspeed you're riding in. NO points for technical sophistication for this. It's just lazy - and usually dangerous.

When two riders align themselves to join the flow around their "connected" shapes, both riders get a reduction in Cd that makes it easier to get, and maintain, speed. As with formation flying or good sex, both participants must be willing and know what they are trying to do. Both must participate. (And they must trust each other not to crash and upset the flow.)

John

Subject: RE: BS: Slipstreaming what is the potential?
From: GUEST,.gargoyle
Date: 24 Apr 04 - 12:05 AM

For over a decade now.....those in the know....have been slip-streaming the net.

The media is fed various "bit-steams" from the government and private-enterprises .... but....the masses are asses.

The "real community" continues to opporate...cooperate...syntilate...facilitate.....low, low, low, under the govt's, nets, radar.

Napster, Krapster, Morph, Dwarf, Lyme, Slime, KaZaa, WaXaa......for all the ones the government blames....there are 1000 more without the populus names.

They want to feed on paranoia.....the truth is ...with 10 hundred, thousand, billion, trillion, gigilion and their ability to hard wire, fire, fryer, wired-ya....they do!!!

Unless....your are adopted, conopted, synopted into the brotherhood, of "THE community."

In which case...you are dead-meat hanging in the API locker beside the bacon/hog-back offering.... next week....for the masses...who are asses....who are living in your very own neighborhood and don't even wear a visible snout....nothing to shout about.

Sincerely,

Gargoyle

Subject: RE: BS: Slipstreaming what is the potential?
From: Strollin' Johnny
Date: 24 Apr 04 - 05:51 AM

Eh?