Originally Posted by
Steamer
It is relavent (in my mind at least) because you gave no explaination as to why you need / want this information. I hope it is more than intellectual curiosity. I have not bothered to do such a test because I don't care what my CdA is one little bit. From plenty of riding experience I know my hiracer bent has a signficantly lower CdA than any of my DFs do. Exactly how much better is a detail that doesn't concern me. For most of us with limited time and money to devote to our leisure activities, the time it would take to determine CdA would be better spent doing a hard training ride (assuming the ultimate (though indirect) goal of such a coast down test was to go faster). Once I have my CdA determined with painstaking accuracy, what do I do with that info exactly? If I am trying to understand the effects of a particualr aerodynamic enhancement (fairing, disc wheel, whatever), a reasonably well done coast down test with and without the enhancement will reveal the relative improvement of such an enhancement, and that is ususally more than enough info needed to make a decision about whether to use that particular enhancement on a given ride / event.
Man, you guys sure are suspicious. I feel like the honest traveling salesman who came through River City right after Harold Hill. I've been upfront about my interests, both here and on the recumbents.com forum: I'm interested in figuring out how to improve the current methods of estimating cycling drag (both aero and rolling) from field tests. I have no ulterior motives. I'm not selling anything, I'm not trying to get anyone to test any method I've developed, I'm not writing a book, I'm not developing a fee-for-information web page, I'm not trying to screw up your recumbents by feeding you bad information, I'm not trying to steal anyone's recumbent or streamliner designs, I don't have a financial interest in any power meter or software company, and I'm not trying to convince anyone to do CdA estimation (except maybe that one guy who was wondering whether to fair his steerer tube). I was somewhat surprised that so few of you measure your drag (as I've said several times, my a priori expectation was that a group of dedicated enthusiasts with a lot of technical knowledge would have figured out clever ways to do this) but I'm coming to the realization that you don't. That's okay. To that list above add this: I'm not trying to make anyone feel bad because they don't measure drag. If you're happy with what you've been doing then I'm happy for you, too. I happen to operate in a world where after an hour of racing six seconds can cover the top three spots but if you don't there's no need for you to estimate drag with the kind of precision that we do. (But if you don't need to and you haven't even tried it, don't tell me it can't be done).
But this has nothing to do with my original question: if anyone here has measured his CdA, how did you do it?