In my opinion there is nearly no room for further improvement of sailplane
performance measured by e.g. max. L/D.


Wow, how many times has THAT old line embarrassed someone in the past?
(rhetorical..)

Perhaps this may be true for CURRENT traditional materials and
established dogma, but besides Windward Performance (who now has the
DuckHawk turning from a 'paper airplane' to a flying machine) who
makes eintire gliders out of PREPREG carbon, you will only find an
occasional aileron or rudder made out of this VERY UNDERUTILIZED
spaceage material. Considering that prepregs have appx double the
strength of the traditional wet layup construction that just about
every composite glider is made with (including the lovely Dianna 2), I
see much room for improvement in ALL aspects of soaring performance
enhancement. And this is even with materials that have already been
discovered (but as mentioned, other than some fancy trim parts have
been studiously ignored by 'most' designers).

In case the significance of what double the strength to weight ratio
means when applied to sailplane structures is not grasped by someone
out there, it is this: The structural minimum just got that much
closer to the aerodynamic optimum. Personally, I see no end to
improvements since our materials will continue to advance, thus
continuing to push the all important structural minimum closer to that
(also ever advancing) theoretical aerodynamic optimum.

How about once carbon nanotube fabric is available, then in prepreg
form? Still no room for improvement then?

Paul Hanson

"Free your mind and your a$$ will follow"--George Clinton