This should have been a simple step. All that was needed was to clecko the E-904, E-903 and E-913 counterbalance ribs and skin together for a final drill. I did this per instructions, but I found some of the holes would not line up properly. Normally, I could open up the hole to 1/8 in and use an "oops" rivet (NAS1097), but some of the holes were almost 1/2D off. That would require going up to a 5/32 (AD5) rivet so that was not an option for me.
I contacted Vans support, but I was told it would probably just need to be adjusted to get it to fit. So I continued to do everything I could think of doing. I purchased some additional clamps that would hold the parts together with more force. I tried every combination of parts I could think of in the hope that I'd find a combo that would line up. Nothing worked. Using a drift pin to coax the holes into alignment just resulted in crushing the bearing surface.
After thinking about the problem for a while and taking some measurements, I saw there was a noticable gap between the counterbalance skin and the E-903 rib. It finally dawned on my what was wrong. The E-903 rib is a hydroformed rib. You can tell because the bend line is curved. Apparently, the tooling was a bit worn and the bend line is off. The proof? I measured a 0.050 in. gap between the skin and rib. The holes are about 0.050 in. off. That tells me the bend line is not where it should be. I need new ribs.
Assemble the counterbalance ribs for final drill.
No matter what I did I had some holes that were up to almost 1/2D misaligned.
After much measuring and thought, I concluded the E-904 ribs were bent improperly. Notice the gap.
