Hi Michael,

indeed, SL12 includes a reference to turbulator tape in front of the control surfaces. Especially in case of the rudder, this helps to reduce the lack of rudder authority that most Astir. Turbulators on the suction side in front of the ailerons also seem to improve aileron authority on some gliders, like the ASK21.

However, the drawing that Grob released in the 80s and which the Aerokurier article refers to, includes additional specifications for turbulator tape on the pressure side of the Eppler airfoil. These are not part of SL12. When following these instructions, the tape will not be right in front of the aileron gap as shown in SL12. It will be a few centimetres further upstream..

Regards
Christoph