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