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Arc Tuning - Tip Twist

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  • Greg Walsh
    Hi Arcers Below is a copy of a post from the Foildesign group about tuning the amount of twist in the tips of sled-foils. It refers to the internal bridle line
    Message 1 of 1 , Sep 4, 2001
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      Hi Arcers

      Below is a copy of a post from the Foildesign group about tuning the
      amount of twist in the tips of sled-foils. It refers to the internal
      bridle line you can see running from the tips to the LE of the Arc.
      Thought you might be interested.

      "Hello Sled Enthusiasts:

      A number of people have commented that their experimental
      sleds didn't fly due to collapsing tips. One fix is to move the
      towpoint aft along the tip until the collapsing stops but that often
      results in a kite that won't fly up well overhead. Another fix is to
      reverse 'wedge' the kite but this is basically the same as moving
      the towpoint.

      Here is a simple fix that doesn't markedly effect the tow angle of
      the center lifting section but quickly cures collapsing tips. I call
      them tip twist adjusters.

      1) You will need a large needle and some extra flight line or
      similarly sized line.
      2) Lay your sled out flat (belly up) and with a straight edge draw a
      diagonal line on the inside (lower) skin from each wingtip's TE to
      a point on the leading edge about 1/4 - 1/3 of the span from the
      tip.
      3) Secure the line at the leading edge point and very loosely sew
      it along the line so that it emerges at the wingtip TE. Do this on
      each side. (You only need to make a stitch at the profile seams
      and center of each cell.)
      4) Then adjust the length on each side to induce tip twist in your
      kite. Start out with them loose and fly the kite. Then take them up
      a cm or so at a time equally on both tips until the kite ceases to
      collapse.

      You will make what seemed like a totally useless and frustrating
      kite into a perfectly flying and more than likely, fast and stable
      sled.

      Beats starting over from scratch... Turns out one of my early
      designs is also one of my best fliers with this fix.

      Good Luck!
      Wil"
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