There is a jet-powered sailplane called Prometheus built at the Swiss
Federal Institute of Technology in Zurich sometime in the seventies.
I couldn't find much on it on the web. Only this: Its a side-by-side
double seater with two jet engines with about 900N thrust each gives
the Glider a 6m/s (12kts) climb at 200km/h (108kts).
Seems slightly overpowered to me.

In the meantime they have cut off quite a bit of the wings and are
testing so-called winggrids as an alternative to winglets.

http://www.fva.rwth-aachen.de/jahres...mertreffen.htm
somewhere in the middle
and
http://home.arcor.de/luftpiraten/luf.../glos_w00.html
under Winggrid