To all the posters who helped me with the Zenoah G-23 prop question, your responses were greatly appreciated.
The big 1/4 Dr.1 made 7 very successful flights today, using the G-23 with an
18 x 6 prop. The engine is turning 6900 solid RPM, and the plane flies very well. It uses full throttle to take off, but it flies very scale-like on 3/4 throttle. I don't remember who told me to not underpitch the engine so I didn't have takeoff speed, but that was the secret! The 20 x 4 pitch prop was too much for the G-23 to turn, and just didn't make enough speed for a reliable takeoff.
Thanks again!
Dr.1 Gerald Dr.1 Driver "There's a Hun in the sun!"