> I do keep thinking that in combination with a front fender extension like > Jan has talked about, a fitted back section of the front fender could direct > the air as it comes off the tire/rim so it flows behind the fender rather > than behind the tire. Somewhat like Zip's idea in integrating the shapes of > their aero tubular rim and their own tubular tire.
The bigger issue is separating the tire tread from the oncoming air stream. The top of the tire is moving forward with twice your road speed. By putting a fender between tire and oncoming air, you reduce that speed by half. (Now the tire rotates at bike speed against the air inside the fender, and the oncoming air stream hits the fender at bike speed, too.) And since air resistance goes up by the square of the speed, you gain something. For this to work, the fender must extend beyond the top of the tire, otherwise, you probably gain little, or even act as a funnel directing more air onto the tire. Racing motorbikes all have fenders on the front wheel, not to keep the rider dry, but to improve aerodynamics. Regarding dimples (and I understand that Allan was tongue-in-cheek), I don't think you get boundary layer adhesion on bikes, as they vibrate too much. At least that is what recumbent builders have found with their fairings. (That is why dimples on rims probably offer no advantage on the road, even though they work great in the wind tunnel.) Jan Heine Editor Bicycle Quarterly http://www.vintagebicyclepress.com Follow our blog at http://janheine.wordpress.com/ -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
