On Thursday, April 30, 2015 at 12:19:05 PM UTC-6, Blake Seese 9V wrote:
Hello,

Does anyone have any information on applying turbulator tape to the wings of a PIK 20 B? Can any improvement in performance or handling be gained for this airfoil?

Thanks!

3Y
Formerly 9V

All,

I found this on the web from Udo Rumpf:

The FX67 15%&17% was designed to be a naturally transitioning airfoil. In early wind tunnel test it looked to be a winner and was used on some of the first 15meter flapped gliders. As it turned out it was not as good as the designers hoped.

The FX67 has a steep pressure drop and a very pronounced pressure recovery, due to the high camber and the general layout of the airfoil. Also the separation bubble was not understood very well at that time. The leading edge is relatively sharp, which further makes the airfoil intolerant to gusty conditions, like very turbulent thermals. The back 45% of the chord is very sensitive for the turbulent flow to separate. That is why I think in smooth conditions that airfoil performance better.

The FX 67 15% Is used on the Mini Nimbus, Mosquito and our HP-16s, '18s and RS-15s.

The Pik20 and the LS3 use both the FX67-15%&17%

The Performance can be enhanced by first: making the airfoil accurate in both shape plus or minus 2.5% and waves within the .002"-.004" tolerance and second installing a turbulator on the top at about 52% chord. I would use 3/16" cylinder dots about .040" high and spaced 1.25" apart. Within 1.5" down stream due to the 35 deg. wake the "top" surface will be awash in turbulent attach flow, at higher speed the effect will take a little more distance..