well my th fun 51 is tail heavy by about.5 an inch, if i add1 oz of weight up front it will balance fine. my question is is it close enough?
ill add the weight at first for maiden. just want some info on the cgfrom someone who has/had one. i did extend the rudder/elevator by an inch

now for the engine. is a os fp .40 (bushing engine)even cose to a os .40 la engine in power terms?
also is a 11x4a good torque prop for such a small/weak engine or could i use a 11x5?

i am also having a problem turning the back section of the muffler.
the front screw will not turn, i can get the backnut*** off.
if i run the engine for a little and let the muffler heat up will that help?

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>

</p>

i just want to move the exhaust outlet so its not blowing on the fuse (pointed directly at fuse), the problem is that it will not move. i took the backnut*** off , tried to move it, nothing, so i tried to loosen the screw in the front of the muffler but it would not turn what so ever.

i put an 10x6 on it and it seemed to spool up fine. im going to test it now.

edit

ok well i just went out and tested the engine. it is an airbleed carb and im still getting used to tuneing it.
i dont know if this is a problem, but it will not run unless the throttle is 1/4 open (are airbleed carbs like that?). it will transition fine and has a lot more power than i was expecting (good thing).
i think i may have a leak somewhere, because if i keep my hand behind the prop i get the "cooling" feel of methanol, and i notice i am getting slime where i wouldnt expect any. although since the muffler is pointing strait at the fuse that may be creating some funky airflow throwing slime all over the plane. i am going to check for leaks anyways
ill run the engine again and cover the muffler w/ a rag and see if i still get that cooling feel, if i do then i know i have a leak.

i also tried to turn the muffler once again, letting it heat up, but that screw still will not turn.

i just remembered, when i pinch the fuel line it dies within a second (the richest setting or the leanest doesnt matter), however on the richest setting the engine will stumble as it goes to WOT.

well i took it out for the maiden. it flew much better than i thought it would, it required only a click of up elevatorto fly hands off (to my amazment).
from a performance standpoint the plane is amazing for only costing $75 (for the airframe) it took about 25 hours to complete. the plane can fly amazing slow, w/ flaperons i bet i could walk beside it. my dinky engine will pull it around fine at 1/4 throttle, although it only has about 150 foot vertical if you are putting around at 1/4 throttle, gun it, andinstantly go vert. which isnt horrible. IMHO the 11x4 was not as good as the 10x6 (under proping it) , i think this engine will be able to handle a 11x5. i will try it this weekend.
if you have a bunch of old servo's, are looking for a beater plane, and have a old .40 or .47 this is the plane to get
i also had 2 oz up front, it was nose heavy and i will take .5 off at a time and see how it performes