So what one ends up with is a wing with the main spar at the thickest part of the wing, two light-weight closing-off spars front and back, and ribs made entirely of foam (the wing surface bonds directly to the foam, so no need for strips to be bonded to each rib). The wing should be incredibly stiff, and by correctly calculating the number of CF rods, one could build it to any G rating.
- Bond carbon fibre rods directly to the plywood along the thickest part of the wing. This will be the spar cap.
What serves as the spar web ( transferring the loads between the top cap and the bottom cap)? If I'm picturing this right, you'd have just the foam ribs and an indirect path through the closures at LE and TE.
It is the spar web (which joins the top spar cap, which is normally in compression, to the bottom spar cap, which is normally in tension) that gives the spar stiffness. Without this, you've just got very flexible top and bottom caps.
Also, the only thing to keep them from buckling (under compression) is 1mm ply to hold them straight. Maybe that's enough, I don't know.