Back in April, I and my buddy bought a couple of ARFs from ARF MFG (same as GoldWing) named 20cc Sbach 340. At that time the model was undocumented even on GoldWing's website so we took a risk. The model has subsequently been released in the West through Troy etc.

When I did an unboxing, I was pretty appalled by the quality or rather the lack of it. The fuse was ultrathin ply, the wing didnt seem to have a spar etc. However, having bought it we had no choice. In the meantime, I developed back problems and stopped flying. My buddy however, went forward with reinforcing it- he birch ply laminated the fuse upto the wing tube, rest of it he balsa sheeted almost all the way to the tail on the fuse sides. The bottom of the fuse was just stringers. Since we have a rough and ready field and transportation, that has to be reinforced. Initially, I thought it was soft balsa stringers but it turns our to be much stiffer birch or something. He glued CF strips on the sides of the stringers and then pasted further birch stock on top, but lets the structure as stringers. He went ahead and flew his model with a 120ax and ended up adding a lot of nose weight (he says its 300-400g but I feel it may not be that much). It turned out to be an excellent 3D model and fairly sturdy- he has had a number of deadstick plop downs and hasnt broken too much.

Now its my turn to start building mine. I made templates for the reinforcement sheeting so I can sut them easily. Typically I would use 1/8 midwest ply to reinforce but that adds a lot of weight. My buddy suggested to balsa sheet most of the model and restrict ply only to the fuse upto the wingtube which includes the motor box and sides of the model (where the original ply bends out when only trying to install the wing).. I am not comfortable with leaving the bottom as stringers and will sheet that too between the stringers. Now all of this will add a lot of weight if done in ply (his is already 5KG). Secondly, I intend to go gas on the model and he is suggesting to put in a dle30. My question is, how much stiffness and strength will balsa sheeting add? Alternatively, what should I do? Should I consider CF plates instead of ply / balsa?

Ameyam