I bought another motor and have 78 flights on it now. Approaching 6 gallons. Running redline now at 40:1.
Have it at the St Clairsville contest this weekend thanks to Mark Hunt getting me the templates to be able to make another canopy after losing my original in the corn field.
Started running the apc 21x10 wpn this week. Turned 6700 when I tached it. That's on a 29" pipe. Planes not super fast but pulls like a mule and doesn't stop. Originally bought this prop to try on my YS 175 which turned it at 6300 the only time I ever tached it.
Bob Kane had a radio shack db meter with him, so we took it out and ran it up and got a reading of 93db over grass. Engine is hard mounted on a balsa, ply, foam airframe. I realize this isn't the most accurate meter in the world but it does offer some encouragement. We have the D4 year end meet at Muncie end of September and we're going to try and get the same sound meter used at the nats and get a good reading. Will try the 20.5x10 also. I did the sound testing for masters at this years nats, so I have a pretty good idea how this will compare to the other setups.
The sound factor has always been in the back of my mind. If it couldn't be used at the nats without penalty, then it wouldn't be overly useful to me as I like to fly there every once in a while. If it's successful, I can't think of any other argument that gas power isn't a realistic alternative for competition. Biggest problem would be finding an airframe.
RM,
The engine turns the 21x10 wpn okay. It is a little happier with the 20.5x10. On my set-up I get just about 7K using avgas. Premium gas will get another 2-300 rpm which is totally unnecessary. The extra 2 1/2 mm of stroke (compared to all other 30-35cc engines) gets you a lot of torque. The engine puts out similar power to the 185. And neither engine needs to run at full revs....ever....for any maneuver.
A soft mount will drive the sound down to around 90-91. The balsa/ply plane is the quietest test bed for IC
The larger disc area of the 21" should produce n even slower downline. The 20.5" results in quite the slow line though.
YS throttle response is a little better than the run of the mill Walbro throttle. Wish OS would develop a better carb for the 33. They did for their 15. But I doubt that will happen anytime soon. Just not the money in IC engines for Pattern to warrant the R&D. Unless OS wanted to go head to head with YS 4 strokes which won't happen. It's taken YS decades to get the throttle system they now have.
At the end of the day, the GT33 is a great sport engine adapted to Pattern. It's inexpensive to own and operate and gas just doesn't need bearings every 100 flights or rebuilds every 400 flights. The fact that it is pretty close to par with the thoroughbred YS is either genius or dumb luck. Had it come out in 2000 when the 140RX was all the rage it's simplicity alone would have bypassed everything else.