re: [CR]Aero fenders, now bogus metaphors

(Example: Framebuilders:Pino Morroni)

Date: Wed, 18 Jun 2003 20:42:04 -0400
From: "HM & SS Sachs" <sachs@erols.com>
To: heine@mindspring.com, classicrendezvous@bikelist.org
Subject: re: [CR]Aero fenders, now bogus metaphors


Jan Heine wrote,

"About the aerodynamic advantage, as I said, it's anecdotal evidence. But nobody has proven the opposite, either, that fenders slow you down." <snip>

Without criticizing Jan, I'm using his post to try to express a bit of surprise about this thread: I didn't see anyone complaining that high-speed aerodynamics have rather little to teach us old guys who piddle at speeds usually less than 25 mph (40 kph or so). Aerodynamic drag follows a power law, increasing as the square of speed (if I recall correctly, with the power required going up with the cube). Again, if I recall correctly, below about 20 mph tire flex and parts friction are larger than aero drag, but aero picks up and comes to dominate quickly. At least for my riding, I'm content to value (or not) fenders for keeping the mud off me, and even to ignore whether at some given speed climbing a specific grade the extra weight of the fenders might be greater than any aero benefit at that speed. Easy for me to say: I don't climb very quickly. :-)

So, Jan, the argument doesn't have to be anecdotal; the physics is understood and there are some data on rider drag -- although I have not seen anything on drag between fender and tire as a function of clearance, tire roughness, etc. It makes my head spin.

harvey sachs mcLean va

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