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Smith Miniplane Rigging Question

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Vintageav8r

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Some members of this forum may remember the posting of my recently purchased SMP. One astute member pointed out that the wing appeared to have anhedral. What couldn’t be seen from the picture was that the leading edge was washed out several degrees while the trailing edge was flat. After loosening all the wing tie rods and resetting the front spar and leading edge to 0 deg dihedral and 0 deg sweepback, the top wing now has what I believe to be excessive wash out. Here are the numbers; top wing angle of incidence is, Left: 1.8 and Right 1.7. I’m guessing it probably should be 1.5 or even 0 for the top wing. The bottom wing angle of incidence is 1.8(L) & 1.5(R). All angle measurements were made with plywood templates made to the profile (within about 1/32”) of the 4412 airfoil as depicted in NACA TR No. 824 and measurements taken with both a smart level and an angle cube (to one hundredth of a degree - you just gotta love the technology). The wing’s actual airfoil section only loosely matched the template, except at the wing walk which is spot on. So, the measurements are probably only accurate within a few tenths of a degree if that. Ok, If you have read this far, here’s the problem; the left wing is washed out 2 deg and the right wing 2.8 deg. The bottom wing is not a problem because as you know its washout is adjustable by the interplane struts and the dihedral is about where it probably should be (as a matter of opinion). I see no way to adjust the washout of the top wing short of cutting and welding. And I’m not opposed to doing that. But, before I do, I wanted to put the question before the panel of experts. So, whadda ya think. Is there a way, or do I cut and paste?


Part of the reason I’m so reluctant to just start cutting is that this thing was built in 1967 and has flown almost 500 hours with several different owners. It’s hard to believe it’s been like this for all those years and hours. You’re going to ask how it flies. It does OK, cruses about 115 IAS at 2500’. The stall seems to me a little high at about 80 mph IAC, with little or no wing drop - very controllable. I’m hoping that I’ve missed something this panel would point out. Or say, quit whining and go flying.


Sorry for the long description and thanks for reading. Any and all comments would be appreciated.

Cheers,
E
 

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