For the foot launch capable glider plane “Archaeopteryx“, built by Ruppert Composite in Switzerland, Karl Käser improved and measured the airfoil. The specific characteristic of this design was the consideration of its construction method. The wings of Archaeopteryx are covered with fabric.

Due to the fabric, there’s an additional concavity during flight between the ribs. The exact shape of the airfoil during flight is only given at the ribs. For the project the positions of transition had to be determined during flight using sensors of the IAG of the University of Stuttgart on the prototype.

This was followed by wind tunnel tests of the skin deformation using different coefficients of lift. The problem was generalized that much, that calculations with XFoil were possible and that the airfoil could be improved as necessary. With that new wing design the laminar boundary layer was stable beyond the beginning of the fabric.

Specifications Archaeoptreryx

Span 13,6 m
Empty mass <55 kg
Max. load 100 kg
min. sink rate 0,51 m/s
Best glide 1:28