Flexifoil wobbles on my nerves

In article <1mo4pb$hvc@info2.rus.uni-stuttgart.de> martin@mecha2.verfahrenstechnik.uni-stuttgart.de writes:
>I have a rather small FlexiFoil kite (approx. 80 cm span) which
>does something I don't like:
>It does not keep it's angle of attack constant, but "wobbles"
>up and down when the wind load is getting stronger.
>The frequency of these changes in angle of attack is about 5-10 Hz.
>To me it looks like separating flow at higher alfa -> lift is
>dropping -> reduction in alfa -> flow reattaches -> higher alfa ->...
>Is there a trick to avoid this (adding lead to the lead-ing :-)
>or trailing edge or something like that) ?
>The larger FlexiFoil seem to have no problems with this phenomen.

You probably have sand or dirt inside the sail.  I had some sand indside one
of mine once and observed the exact same behavior.

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