We have had a number of discussions of bending-beam spars over the years, here are two:
https://www.homebuiltairplanes.com/forums/showthread.php?t=20232&highlight=bending+beam
https://www.homebuiltairplanes.com/forums/showthread.php?t=7248&highlight=bending+beam
I am assuming that torsion and drag loads are carried through pinned fittings at the wing roots that allow each wing half to flap up and down, it's the bending beam center spar that prevents them from flapping. My specific question is on various ways to connect those two wing halves and that center spar. Logically, here are a few I can think of:
1) One piece spar, no break at all
2) Centerline break
3) Breaks at both wing roots
4) Horizontal overlap (spars and wings staggered slightly fore-and-aft)
5) Vertical overlap (bottom spar cap attached to one wing, top spar cap to the other)
1) is certainly lightest, but I want to keep the wing panels within the size of a 20' shipping container and that makes for an awfully short span unless you go with a 3-piece wing, probably not worth it for normal light aircraft aspect raios.
2) is probably heaviest as the fittings are highly-stressed, but with no overlap you gain more wing span for the same panel length, which may be a useful trade off.
3) seems structurally inefficient with two sets of highly-stressed fittings as well as being awkward to assemble/disassemble.
4) seems doable if you don't mind a tiny little bit of asymmetry but I am not sure if it's worth the complication compared to 2).
5) seems like an interesting option but I am not sure if it's worth the complication compared to 2) either.
My thoughts are based on eyeballing, nothing more, so a more educated opinion backed up by actual math would be a big help.
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