Originally Posted by
RChung
Sorry, I used a book marked site that I just pulled up as I was typing that.
http://www.cyclingpowermodels.com/Cy...odynamics.aspx
Originally Posted by
RChung
I haven't done this, no. Andy Coggan has done this and I believe he's reported that the direction is less precise than the wind speed (that's not hard to believe; others who have tested the Kestrel units also say this). That's why I mentioned (as part of my full disclosure that you won't get from most people) that the guy who was doing this wasn't relying on the Kestrel to give him direction, only speed; and that he was doing this up and around an athletic field; and what the terrain looked like. And that's why I describe his results as "reasonable but not validated." Of course, to tease out small deltas in yaw you need pretty high wind speeds so the pressure differential is big enough to measure; when the wind speed is low the wind angle is both harder to measure and, thankfully, less important. That's about the only nice thing about yaw measurement: the situations when it's hardest to measure are also the situations when it's least important.
AC is right. Those Kestrel Units are remarkably unstable when it comes to direction. And I agree with the rest of this.
Originally Posted by
RChung
Um, I can't say, other than that you're exactly right and the correct way to do this would include exactly the kinds of calibration you're talking about.
What I can say is that I have a day job that I like, I'm not selling anything, I haven't invested any money in any device, I wish the best of luck to anyone who's attempting to make any similar device, I haven't charged anyone any money for anything I've done on this, everything I've written on this is either in the public domain or licensed under Creative Commons, people often ask me to look at something and I answer as best I can, and that I've received a really nice bottle of wine and a free dinner for this stuff -- and that makes me happy. [Edit:] My wife thinks I'm nuts and she says if I charged for this I could afford to visit a wind tunnel.
I've always been a fan of VE, and have done quite a bit of it myself. I've even gotten good enough that I was able to validate a VE helmet test almost spot on with a test at the tunnel (0 yaw). I recommend it to everyone who comes up to me and asks "Hey, which is faster, X or Y?" I'll even give them a detailed explanation of how to do Bowl Testing,( my preferred method of VE testing.) Of course, I always tell them that it's only part of the story, but it's a great start to it, and can give you some insight into what's working and what isn't. So, for that, thanks for bringing it to the cycling community. And like you, I have a day job, and don't make a living doing work at the tunnel, I do it because it's interesting and fun. And like you, my wife thinks I'm nuts for taking days and days of vacation to run around trying to learn about this stuff.
