im finishing up a stihl 2.8 in 43cc conversion engine that came out of a saw that was like new compression test was 160#
so i know it will run ok . im not sure what it will weigh but it similar to my friends q 42 in size and weight

so the big question is i want to build an 80 in or bigger magic 3d
ASSUMING its similar in power and weight to a q42 or us 41 does this sound like a reasonable sized plane for this engine?
also if you wanted unlimited vert out of one of those engines what would be a good rtf weight to aim for?

also the only real changes in airframe design im wondering is positioning the rudder further back (one of the 40 sized arf magic shortcomings imo). and swapping the semi symetrical airfoil for naca 0014 for better inverted perfomance ?

thanks for any input or constructive critisism
kevin

Instead of guessing, why not measure the static thrust with various props? Mount the engine on a a large board. Put dowel rollers under the board and measure the static thrust with a fish scale such as a Zebco Deliar. Pick the prop that gives the best static thrust. If the plane you intend to build weighs less than the static thrust, then it will be able to hover. The less the plane weighs than the static thrust, the better it will accelerate vertically.

The size of the wing will determine how slowly you can fly the model. Once you set the target weight of the model, you can calculate the wing area required to give it a wing loading in the range of 20 to 24 ounces per square foot (good for 3D). Having the wing area, when you pick an aspect ratio it determines the span.

Once you have a target weight and wing size, the trick is to build an airframe that is strong enough and light enough to carry the engine, fuel, radio, landing gear, flight loads, etc.

I'll give you some constructive criticism,. Your a lying thief. It's been nearly 2 months, and I have no plane. Just send my money back. You have no right being anywhere on RCU. If a moderator has a problem with my post, then help me with Kevin Carson/ Thief