July 4, 2007
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I finished the last of the structural welding with the attachment of the spar attach fittings. Although these fittings were much easier to weld than the gear fittings, I did learn some tricks. Like many things, if I would have known then what I know now it would have been a lot easier. Pictures and captions below should make it clear.
This first picture is of the jig I used to align the fittings. The jig is made from one inch square tube from Harbor Freight. The distance from the holes to the bottom of the horizontal tube is the same as from the wing attach point to the bottom of the spar. I used this jig to grind and tack weld all four fittings in place.
After checking the measurements, I found the right front fitting to be off about 1/16″. I realized that the 1″ square tube is not large enough for the fittings. The plans do not show the dimensions, but the spar fittings have an open dimension of 1 1/16″. So, if you use square tubes you will need to weld a washer to the face of the uprights and grind to finished size of 1 1/16″. Then, weld to the horizontal. I didn’t do it that way and decided I needed to be very sure of the fit, so I made a couple of “short wings” to the exact dimensions of the spars. I planed some birch ply to the .090 used on the face of the spars and made the dimensions exactly the same as the end of the spars will be. The picture below shows the finished “wing”
Below are both wing jigs with a couple of ribs just to get an idea of how this will all look.
Next, when I fitted them to each side, I found I hade some alignment issues that the tube jig did not show me. I removed the front right fitting and repositioned, and heated and bent the others a bit to get everything to fit. When I was satisfied, I heated the fittings and formed them nicely around the clusters and finished the welding. When finished, my “short wings” fit very nice! This may have been a bit of overkill, but I wanted it as close to the plans as possible. When everything checked out, I loaded it into my trailer and brought the fuselage to a friend who is a EAA Tech Consoler for a good once over. Passed with “flying” colors!
Finished rear fittings:
Finished front fittings:
Loaded up and off for an inspection, We passed!
Comments (2)
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