Regarding the glue joints ribs to spars: The only real purpose of the wing ribs is to support the fabric and give the proper airfoil shape for efficient flight and to hold the two spars parallel at the proper distance apart. None of this has much of anything to do with the glue joint; it totally depends on the strength of the wood rib itself. Where the real important strength is in the spars themselves, held in position by the struts and root anchor bolts and the anti-drag cross-bracing tubes to prevent parallelogramming. None of this relies on the glue bond, which only helps keep the ribs in relative position on the spars. I do believe a wing built without glue, with just the shrunk fabric to hold the ribs in place would safely fly. Of course over time the small relative motion between ribs and spars and fabric would cause chaffing, wear and eventual failure.
Just going back to the worry about the wings and the type of construction used in them, I have an old picture from when Avid did stress testing on these wings. Of course Kitfox uses the Avid wing design in their planes as well. Hope the type below the picture is readable. At any rate, Avid tested the wing to 5.7 G's with no negative effects. As you can see in the picture, the fabric wasn't on the wing and I would think that would also make it somewhat stronger as well. I think the newer Kitfoxes have a stronger stiffener inside the spars also. Take care, Jim Chuk
Re: Buying a used kitfox
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