bildan wrote:
.....
I've looked at the ducted fan issue and it looks like they can be
optimized to produce 8 -10 Lbs of thrust per HP in the 80 knot speed
range. The only airplane I know of that would benefit from that is a
glider tug.

9 lb of thrust at 60 kt takes 1.6 HP
Perhaps you had 30 kts in mind for 9 lb thrust per HP at 80% efficiency?

Brian W