Electric?
 

Maybe a bit low HP at the moment for general aircrafts, but a motorglider (RV-11?) with this motor would probably work? :)
http://www.electraflyer.com/

Buy one here....
 

An electric self-launch sailplane is already on the market...

http://www.alisport.com/eu/eng/silent_b.htm



gil A

Another one
 

The Antares 20E has been flying about a year now.
link: http://www.lange-flugzeugbau.com/htm...tares_20E.html