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Re: Wind-assisted vs wind-resisted speed

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  • Andy Coggan
    [I asked Andy to repost with an explanation of CdA, yaw and bluff, but he did not reply.--Moderator] I m not sure why you focus exclusively on the pure
    Message 1 of 6 , Jan 4, 2006
      [I asked Andy to repost with an explanation of CdA, yaw and bluff,
      but he did not reply.--Moderator]

      I'm not sure why you focus exclusively on the pure head/tailwind
      situation, since obviously that would occur only a tiny fraction of
      the time. In any case, as I pointed out to Greg Atkinson
      offlist, it is possible for at least a cyclist on an out-back or loop
      course to be faster under wind vs. no-wind conditions. This is true
      since CdA tends to vary as a function of yaw angle (i.e., cyclists
      do not behave like purely bluff bodies). Specifically, if the
      reduction in CdA due to a crosswind is greater than the increase in
      effective wind speed, then less power is required to overcome wind
      resistance, or conversely, a given power output results in a higher
      speed. You can show this yourself using "elementary first-order
      differential calculus" using the model of Martin et al., but in fact
      Chet Kyle already did so (in a paper in Cycling Science) well before
      that study was published.
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