RE: Sig 1/3 Spacewalker
Dr. Death,
I have seen several of these fly, and I think they fly scale like on a gasser around the 38-45 cc mark. A fellow has one at our field with a G38, and it flys very scale like aerobatics, and if anything, is somewhat overpowered. His is covered in cloth and painted. In my opinion, one of the great things about scale giant sized models is that they are flying on the wing, not just the engine. Now I am not an advocate to underpowering an aircraft, but a cub flying knife edge or having much vertical performance is not very prototypical. As with all aircraft, keeping them as light as possible will make them fly better, and definately improve glide characteristics, but putting a huge engine in one destroys scale effect for me. Greg Hahn had a wonderful article in MAN a few years ago ( don't remember the issue) where he described how to power a model based upon the full scale power to weight ratio. One of the real eye openers was that a G38 will fly a Ziroli AT6 very scale like, instead of using the stand by G62. I have seen a friends AT6 fly very well at 27 pounds using a koritz 40 cc engine. A lot of performance has to do with matching the prop to the airframe as well. I'd do some research, if you are going to try and power your model " scale like".
Hope this helps,
Bryan