- Nov 29, 2008
- Belleville, Ontario Canada
Ya, that's the thought anyway, bolt a metal wing to a wood fuselage. Mainly because I need a three piece wing and that is easier in metal I believe.I just want to make sure I understand... you're building a metal wing to attach to a wooden fuselage?
If it's a wooden wing, just build the center section with the dihedral break like you would at the middle of any one-piece wood spar. Attachment stays the same. When doing the design, don't forget that there is an axial component along the spar due to lift and your shear web design will need to account for this.
If you're doing a metal wing, I think BJC has the ticket--split at the middle, and spliced together. With the two-bolt attachment, shear will be zero between the bolts (assuming the wings are loaded evenly) but bending moment will be at its maximum value between the bolts. Therefore the splice at the middle will need some attention to carry the moment, but you could treat it similar to the design of an ordinary wing panel joint (heavier here because of the high moment) or you could make the caps using built up 1/8" curved "straps" (RV style) or by curving the angle as BBerson suggests.
You might also look into @Will Aldridge's SpitSairWulfStang project--it had a curved spar for a in inverted gull, but I don't remember the material or details.
Will's Corsair/KR2 wood center section looks great too but can it be up-sized for 2500 lb. gross weight . . . ?
The other problem with wood is the spar becomes really wide at required strength. The Jurca spar is 10" wide and since the wheels must fit ahead of the spar, the spar has to be very far back in the wing. Being wide means the center of strength/stiffness is even further back. Hate to bore you with all this but an expert advised me to get the spar narrower if possible for structural divergent reasons. I've had it re-designed in carbon fiber even which is great - only 1.25" wide but still one piece. I'll attach a pic of how far back original spar would be. A metal spar would be narrow too.