Just an update .... this is our assessment and not that of an aero'engineerical type .... we dug up a digital micrometer and verified that the spar box was 60 thousandths too small to take the spar. Both spars measured out at 1.450 and the left box at 1.44 and the right box at 1.39, a full 60 thousandths too small. 60 is about the thickness of two thick plastic credit cards.
We tried various spreading techniques and the best we could get was another 10 which wasn't nearly enough. Vans recommended fix was to drill out the right 6-8 rivets on the front flange of the spar box and the lower 5 side rivets and then spread it open.
We started down that path and found that the flange on the right side had zero clearance to the lower longeron. That is probably why we couldn't spread it. The left side had at least 60 thou+ by eyeball. We suspect that this was done in assembly and that is why the box closed up. It took about 20 minutes to drill out the rivets and then we pried up the flange so that it would ride up over the lower longeron. Once that was done, we were able to easily spread the box to 1.470 and it was a done deal. Don't think we will even need to upsize the replacement rivets.
The long and the short and the narrow is that the right side spar box appears to have been assembled incorrectly but the fix was relatively painless.....(that said by the guy who didn't own the airplane )
Left Spar Box showing 1.45
Right Spar Box showing 1.39
This is the outside spar dimension on the standard micrometer with the internal set inside to show the physical difference between 1.45 and 1.39. The picture makes it look bigger than it was but it was easily two heavy credit card thicknesses.
Now note obvious gap between lower flange and lower longeron on left side.
Note there is zero clearance between the flange and the lower longeron on the right side. It actually popped as we pried it up before trying to spread the box again.
This is with the spar installed. Note how far the lower flange is pushed up over the lower longeron....looks like about 60 thousandths ...
So good call on Vans on the fix, poor quality control on assembly, but a relatively happy outcome. Some would say that's bad QC on Van's part but I am still amazed that the other 99% fits so well.... and it is experimental.
It's all good!
Still got the Grin