RE: th fun 51 and muffler problems
First of all, use sticky weights up front and set it to the proper CG point (use the manual to tell you where that balance point is). If it's slightly nose heavy for a maiden, that's a good thing. You want a nice, safe, and uneventful maiden because that's when you will set your initial trims to make sure it flys straight and level with hands off.
Once you do that, you can "tune" it to fly the way you want it to fly by adjusting either the amount of weight up front (removing some of the stick-on weights).</p>
Regarding the engine, someone will have to chime in for the power relationship between the two engines. I only know about the LA engine, and it is not a power house, but is very reliable.</p>
Now as far as the muffler is concerned, well, if I recall, the muffler bolt, the one that goes through the muffler, actually screws into the rear of the muffler and that nut is a check-nut that keeps the whole thing from coming apart. So, remove the check nut, then unscrew that bolt from the muffler and it should come apart.
What's the reason you want to take it apart? To remove the baffle? I don't suggest you do that. You may lose valuable pressure for your tank pressure system, and you will increase the noise. Noise does not equate to power. You won't get much more out of it if you remove the muffler baffle. Some claim 800 to 1000 RPM but I find that slightly over-rated. You may get more RPM but, again, that equates to more noise, and I go back to my original comment about noise does not equate to power.</p>
Just my little advice for you to consider.</p>
Prop wise.. well, get something that will spin up, give you good running RPM, and will fly the plane the way you want it to fly, given the limitations of the engine choice you have made. Bring a few props of various sizes and try them. No one can give you an actual recommendation for a particular prop, you have to work with it to see what will suit your needs. I would start in the 10" diameter at most for this engine, perhaps a 10-4 to start out with, or even a 9-6 or something on that order. But, I'm sure someone will come in and give you a more specific recommendation for that engine.</p>
CGr.</p>
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