I recently posted an question regarding me building a large scale aircraft. The problem was that I didn't research engines too much. The engine requirement is a minimum of 3.7ci. That's an enormous (and enormously expensive) engine. I had very few people who recommended anything other than a Zenoah G62. I had asked about converting a 3.2 ci chainsaw motor that my father in law has(and hence it's free). Only one person encouraged me to go this route.

I'm still fairly against paying more than $300 for an engine. So I'm trying to come up with alternatives. Maybe I can make the plane out of lighter materials and thus require less engine to run it. My first thought was carbon fiber. Wow what a mistake that was. The sheer cost of c/f makes the engine purchase seem cheap. Then I thought about fiberglass. Has anyone ever done any r/c work using fiberglass. Both my brother and father are very skilled at fiberglass work and would be able to assist. If the wing spars are made of plywood, couldn't they be made of very thin balsa wood (for form and flatness) then coated with a sheet of fiberglass and epoxy (for the rigidity and strength). Or would the added weight of the fiberglass/epoxy equal the total weight of the plywood?

I'm a newbie at r/c plane building and am requesting some experienced opinion on this. I look forward to your replies and getting started on this plane.

Mark

FACT....Almost all RC engines started life as chainsaws....RC engine manufacturers don't like to acknowledge this...The cylinders, pistons, cranks, and carbs are all chainsaw parts...They machine a crankcase and hub and call it an airplane engine...Converted chainsaws are every bit as good as any of these...Some manufacturers make their own cranks also...Almost all use the same Walbro carbs, and an aftermarket ignition...
It's quite possible that some do some porting in the cylinder, but so far I have not seen any..
Except for some of the Precision Eagles and/or others sold as racing engines....

You should be able to find a Quadra 52 very cheap. You can usually save some weight by discarding heavy wood for lighter in some areas, cutting holes in wing ribs, routing spars at the tips, ect. Composites can be light but usually requires carbon and a lot of skill to keep the weight down, epoxy is very heavy, and the material is expensive. Making good chainsaw conversions and building light airframes takes time to master, and there is also that flying part on top of that. Few people can do it all, and very few can do it all well. Just build the airframe as straight as you can and keep looking for an good engine deal.