DICKEYBIRD

How do you structures experts handle the spar placement on built up sweptback wings? I have scratchbuilt a few with mildly swept wings and was able to move the spar forward at the tip and rearward at the root enough to enable it to be perpendicular to the fuse center line and have a load path straight through. I'm helping a friend with a more radically swept design where I will be unable to do this. Is the best way to place the spars (with crossgrain shear webs) at the thickest point of the panels and add spars, perpendicular to the fuse centerline that tie into the main spars? We will of course sheet the center section with quality balsa and glass it with strong cloth cut on the bias. Any thoughts?

Flypaper 2

Put the spars in as you would a conventional wing. A V joiner wouldnt hurt to join the spars. Although I don't use one. I just use 6 oz glass, 1 layer or 2 depending on the size of the plane. Thats how my avatar plane is built.

Tall Paul

I try to avoid a swept spar. But when I can't, normal construction practices... sheeted center section, shear webs between the spars works weill.
I try for a continous sheeted center when possible. Seriously swept wings, such as a jet, get glassed with cloth also.

DICKEYBIRD

Thanks for the suggestions guys. Like Paul suggested, I had planned to sheet the center section with the grain running straight across but after I drew a front view of the wing and saw the amount of thickness change due to the taper and the amount the sheeting would have to bend, I nixed that. Looks like it will be conventional spars with full width shear webs between them, a perpendicular stub spar meeting the main spar at the 5th rib out and firm center sheeting with glass cloth as well.

Johng

My Feedback: (4)

THe Balsa Bandit from BVM is near perfection as far as swept wing construction goes. You build the wing panels with spars that run more or less at a constant chord location then build center spars perpendicular to the aircraft CL that transfer bending. The "trick" is in getting a super-solid mechanical joint between the outer wing spars and the center spars. Have a look:

DICKEYBIRD

Thanks John! I remember that shot from a magazine ad....you're right, a beautiful structure indeed. Plus it's a fully sheeted wing when completed....one STRONG mother of a wing!