weirdasses do ride them. theyre always giving you that pedi-smile and they cant steer worth poop.

I remember reading that the Varna Diablo II (http://www.hi-id.com/?p=553) - the vehicle used to establish some of the past land speed record has a CdA of just under .15 and that other versions of the Varna which also compete at Battle Mountain (mostly designed by George Georgiev) are about .16.

I think he uses pictures to establish frontal area, but not sure what exactly he does to calculate his CdA numbers.

A couple of years ago, Mr Georgiev seemed to think that a CdA of .14 was possible with improvements of the current design. The new vehicle (Varna Tempest) is probably around there CdA wise (82.819 MPH 1/4 mile avrg. speed and 56.295 MPH 1 hour effort this year)
http://timetogetnaked.com/...2009/07/dsc_6575.jpg

A camera-and-screen solution could theoretically lower CdA even further - but handling and tyre blowouts are a major issue at these speeds.


I am pretty sure you can contact George Georgiev and, if you explain who you are, he'll probably be happy to tell you more about his methodology.

Sam Whittington, the guy who rides Mr. Georgiev's vehicles, is a former national level Canadian track cyclist. I am pretty sure he has a good idea of the power numbers during his record attempts and will be happy to share some files with you.

they are in fact, often weirdos

but in a good way I think

not we like aren't

You'll have a hard time finding power numbers for riders in those record attempts. Top speed is a function of both power and drag and we know the drag is lower (though how much lower is also hard to know) so it's not clear what happens to top end power.

I've just spent some time asking on recumbent forums how they measure aerodynamic and rolling drag. I wasn't asking what that drag was, I was just asking how they do it. In general, they don't and several people got angry that I asked. The consensus was that measuring was either impossible or impractical or useless.

[Edit:] BTW, I wasn't criticizing that point of view -- I was surprised by it.

I don't know - it just looks like even with total CdA (m2) of .10-11, Sam needs to make upwards of 3000W for the last 10 sec. - kind of a tall order even for a national level sprinter.

Actually, it's quite easy to find that sort of data, the HPV world is filled with very smart people approaching design in a very scientific way, measuring everything. But maybe the problem is (and that would be a general problem) that you're trying to find useful info on a forum. If you check the IHPVA newsletters, or old issues of Cycling Science, then you will find drag numbers, wattages, etc.

the HPV world is filled with very smart people approaching design in a very scientific way, measuring everything.

Slightly off-topic but super-interesting is the book "The fullness of wings" about the Daedalus project. The research done there on nutrition gave birth to Shaklee energy drinks, and eventually to the pro cycling team of the same name. But more than a tech story, it's a very well-written human story.

You're surely right about asking on forums. Nonetheless, this was the forum that is frequented by several of the builders making record attempts, and I wasn't looking for the data, I was asking how they did it. I've checked all the back issues of the IHPVA.org journal but only a couple from Cycling Science and I didn't see much info about testing methods and protocols, especially in the field.

I don't think your survey is really typical of the way the serious competitors approach such questions. For example, Lim learned of the regression approach from those in the HPV world, and HPVers also were the first to measure relative wind speed (and direction) with instrumentation on the bicycle.

no one admitted to testing rolling drag.

Considering the speeds that are achieved, I'm not sure that low Crr should be one's first consideration when it comes to choosing tires. ;-)

Considering the speeds that are achieved, I'm not sure that low Crr should be one's first consideration when it comes to choosing tires. ;-)