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Hey Rappstar, how much will the way the rider's body affecting the airflow change the raw bike's aerodynamics. I'd imagine that is completely possible that riding knees in vs knees apart could affect the relative benefits of a P3C type cutout vs some other bike. Also, if I recall correctly, John Cobb once showed that when riding a softride it was better to go downhill in a tuck with your knees actually clamped to the top tube/beam but instead apart. The idea was that the air could reattack better behind the legs when apart than when together touching the top tube. Of course, this would not apply to a conventional bike, however it goes to show that rider position and style might also affect the aero benefits from one bike vs another, adding to or negating a particular bike's positive qualities?
It's certainly possible. I'm definitely not any sort of authority of rider/frame aerodynamics (frame aerodynamics are governed much more by the fundamentals of aerodynamics, whereas the rider/frame interaction is something where there is no real substitute for just going to the tunnel). But things could certainly be affected. For instance, Lieto rides very slack, so perhaps his legs are in a different position relative to the seattube than say Dave Zabriskie's on the P3C, where Dave is sitting way on the nose of the saddle. So this might, as a total guess, affect the airflow around the seattube, which might reduce some of the effectiveness of the P3C's shape there. If you go by the theory that the P3C is designed to be ridden steep, I'd also be willing to give Gerard the benefit of the doubt that they focused on the aerodynamics of a rider in such a position. I can imagine, though I want to emphasize that this is total guessing, that if the P3C is optimized geometrically for steep riding, it may also be optimized aerodynamically. The Trek is also designed to be ridden steep, but perhaps not to quite the same extent, so perhaps the aerodynamics of the frame work better with someone who rides slack. The geometries are close, but not identical, so it's certainly reasonable, I think, to infer that there may be a "right bike" for a rider based on fit, and then furthermore based on aerodynamics. I.e., if you know that 4 or 5 of 10 high-end bikes work with your position geometrically, you might further be able to refine that number down with windtunnel testing to the one or two bike(s) that are basically a perfect match. I believe they did this with David Millar's (tainted) World TT win. They built the bike entirely around him, both in terms of geometry, and in terms of tuning the aerodynamics around his position (at least, that is how I interpreted the article I read on the project).
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