On Aug 23, 1:00*pm, rektide wrote:
I'm looking at making a powered sailplane with a ducted fan and would
need at minimum 75HP. *I'd much prefer something closer to 120HP, but
I dont know what size and weight tradeoffs that would entail.

There is a Yahoo Group for using motorcycle engines in airplanes but
for the most part UL engines in the 40 HP + or - range are discussed.
The HD engine has been used but one person who used a newer engine in
a 701 pulled it and replaced it with a VW due to the vibration issues.
I think your best option may be one of the BMW engines that some
people in the Yahoo Group are beginning to use in their experimental
aircraft, it show's some good preformance features. One of the online
forums you inquired about that is very active is
homebuiltairplanes.com. I hope this little bit of information is
helpfull and look forward to reading about your progress.

Joe