SB..your plane looks SUPER[:-]!!
Remember that the engine will lose torque when the exhaust pressure leaves the cylinder early...but you gain high rpm ability.
So......your engine will become very critical about the amount of diameter it will turn. You have an airframe that should be clean enough and small enough to make a 8+ inch diameter prop work if the rpm is there. The real work isn't just doing the engine mods. The real work is finding the correct prop that compliments the engine mods. With a high timed speed engine [180 degrees or higher] you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
Thanks for the compliment Chuck !!!
I hope you mean about it wont be able to run bigger props like 11x7 APC , or do you mean the 9x10 APC could be too much load to this displacement after raising the timing???
I don't pretend to use something under 9'' in diameter for this airframe. Im not sure if a 8'' long prop would be enough to overcome the drag of this model.
I'll be careful after doing the first 5Â° timing job , if no gain there , I probably wont make any more raising timing.
I have never played with any engines larger than .50 sized for speed so I can't tell you about which sized prop will work best for you. All I can say is that 9x10 sounds large to me, but it might be just fine.
My comments are to be taken as general advice. When you want more speed from a 2 stroke engine, you must do mods that raise RPM.
With mechanical engineering, every time you try to improve one aspect.....you make another aspect worse.
If you are serious about speed, it has been proven that 180 degrees of exhaust duration is the STARTING POINT for a properly designed full wave pipe to be able to do it's magic. The trick is to find the best combination of propellor characteristics to fully take advantage of the narrow power band that a high timed 2 stroke engine has. If you expect the perfect propellor is just a phone call away....it might be, or it might take a lot of trial and error to find the prop that marries your engine to that airplane just like a wedding ring.
you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
A piped engine with high timing [+180 degrees] is a supercharged engine and it will behave like a weight lifter trying to impress his new girl friend if you go for too much load too soon.
It is capable of developing more power. stress and heat than the parts can tolerate..but only for a run or 2.
Piped engines below 180 degrees timing don't hit resonance as brutally..so they don't have the same handling precautions. They have more margin for error