Some time ago there was a discussion about influence of (thin) airfoil on
climb performance of sailplane. I am not a regular reader of the group, so
my post is slightly delayed.
Influence of airfoil characteristics on climb performance and final
cross-country speed was the main objective studied during design of Diana-2
sailplane. The paper on this subject was presented at OSTIV Congress and
published in Technical Soaring. The paper can be download now from
http://www.dianasailplanes.com/Tech_Soar_KK.pdf
May be someone will find it interesting.
In my opinion there is nearly no room for further improvement of sailplane
performance measured by e.g. max. L/D. But there is a relatively large
space for improving final cross-country speed by better utilization of
thermals. Diana-2 was just an attempt to perform this.

Krzysztof Kubrynski