Center section
Next up is the center section bulkhead. I spent a little time digging out parts that came with the wing kit for the center spar section that makes up the backbone of the airplane. These parts are match drilled at the factory with the spars in the wings. I started out with opening up some pre-punched holes for snap bushings with a unibit. It is a bit of a scary operation to go after this beautifully anodized assembly that is matched to the wing spars (no easy replacement) with a unibit to 5/8″. Don’t just measure twice and cut once, but think three times and drill once here.
Then I assembled the uprights (fore and aft) using the close tolerance bolts to line things up. I measured the bolts and found one that was .0005 smaller than the rest. I used that one and one other to line up the parts. Match drill after everything is lined up. Next up was the shear blocks. I aligned these with close tolerance bolts and back drilled them by hand. Looking back, I probably would have just marked them with the back drilling process and then transferred the drilling process to the drill press. i.e. my by-hand drilling wasn’t perfectly square, but will be just fine.
I also match drilled the control pivot brackets (pictured) via the above concept. Then the brackets were trimmed per the plans on the band saw. Oh, yeah, don’t forget deburring both sides of any holes that are drilled. Next is to prepare and assemble nutplates on the top edges of the center section…
