Installing the main wing bolts

The wings have been on for a while, but with temporary bolts.  This weekend was finally the time to install the real ones.  First concern was that the space in the fuselage center section was too big for the wing spar by as much as 1/16″.

I was concerned that when the wing bolts were tightened, they would either not pull this gap together or they would pull it together, stressing parts of the fuselage.  It turned out to be much ado about nothing–when I tightened some temporary bolts, the gap closed with minimal tension on the bolts.  It’s another reminder of how flexible this aluminum is (as well as how I shouldn’t worry so much).

Each wing spar has eight bolts: four 3/8″ and four 9/16″.  These bolt holes are really tight, which makes sense because they’re in shear, so any looseness would cause the wings to move.  As such, it takes some lubrication (LPS-2) and effort to get these things in.  That’s one area where the spar gap did cause a problem, since even that little misalignment made the bolts difficult to get in. To get around this, we tightened the temporary bolts, which closed the gap, then put the real bolts in one-by-one.  We had to hit them with a rubber mallet to get them in, which took a while to ensure we weren’t damaging anything.

This picture shows the first “real” bolt in (the large, gold one), along with some of the temporary ones.

Here’s a picture typical of the morning: me trying to figure out why a bolt won’t go in.

Almost done on the left side!  That lower, inboard bolt was the most difficult of them all.

Here I am getting started on the right side, with all the bolts laid out.

And finally, they’re all done.