Thread: Discussion 50% Christen Eagle
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Old Nov 20, 2012, 03:57 PM
packardpursuit is offline
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Hope wing plan photo shows need for jigging ht. change. The wing changes geometry at point of wing sweep(#3 rib from root). Since the airfoil doesn't change, nor does the straight alignmernt of the continuous spar line, the top/bottom spar flanges now have to conform to their new relative positions on the first two ribs. Front spar flanges get closer together, rear spar caps grow slightly apart, the closer either is to root. This affects only the first two root bays. the spar flanges are merely following the rib surface as the airfoil is being sectioned on a NON * NORMAL tangent. Bad design in that it's hard to keep everything aligned and as the plan says is "approximate" by negative 2.5 mm at front spar and 2.5mm + at rear !!

I suspect that the spars coud have changed direction at point of sweep change with sufficient overlap joint to provide adequate bonding of the spar segments. There are a number of other such joints in other areas of the model. No reason to think those types of joints would fail, even in the wing! Besides this is not as highly stressed as lower wing (which AFAICT carries nearly all the flight loads) and there is also the additional strength imparted by functioning flying/landing wires. I wonder how the geometry change is handled on the real plane? Will be finding out soon enough.
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