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5592[ksurf] Re: big fat boards

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  • KiteBoard@aol.com
    Oct 2, 1999
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      In a message dated 99-10-02 10:00:24 EDT, burgy@... writes:

      << I'm thinking of putting some concaves in to generate grip & lift, any
      words of wizdom regarding that? >>

      You'll probably find that while they may generate "grip" & lift, they also
      generate extra work (to build), weight, drag, & directional stability (hard
      to turn). Flat is fast & loose, and easy to build.

      << get 2 fins & attatch them to the board at say 45deg with the tips pointing
      to the outer edge of the board so its semetrical along its middle.
      would the side ways lift generated by these fins cancel each other out giving
      only vertical lift or would the turning moment generated by both these fins
      be in the same direction making this idea a non starter? >>

      With symetrical foil shapes, & centerlines both aligned with the board's (no
      "toe", in or out), the horizontal lift will be in the same direction (upwind)
      for both fins, since they will have the same angle of attack (when viewed
      from above), so they won't cancel each other out. They may or may not create
      vertical lift, depending on their angle of attack when viewed from the side.
      Depending on where the fins are located longitudinally, the vertical lift may
      just add to board drag, by changing its angle of attack to an innefficient
      angle (fins lifting tail reduces board aoa & increases surface contact).

      Personally, if I was to experiment with board width & fin size*, I'd leave
      the other factors on the "fag packets" for now, & just use a plain flat
      bottom & vertical fin(s). Otherwise you won't know if your new board works
      great because of the concaves, fin size or dihedral, or board width.
      *which I think is a good idea

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