Realign LH and RH rib 10 main spar attachment flange connection

Like several other main spar rib attachment flanges, bend tolerances had to be compensated for by upsizing and recentering the 4mm rib holes. In so doing the need for forcing or cleaning skin rivet holes and/or the occurrence of oil-canning is avoided. The pay-off of doing this has already been evident, and it was noticed that rib 10 (RH wing) was similarly affected. A jig was constructed to position the top skin 5 precisely in relation to the main spar, as before.

The original rivets were removed some time ago, prior to rivetting the bottom skins. It turned out the LH wing required upsizing only a couple of rivets near the bottom skin, which effectively served as the jig. The jig mentioned above was used to confirm the correctness of the existing alignement at the top side.

The alternative to upsizing was to elongate the 4mm rib holes. Sling has advised this is the default approach in production, unless the elongation exceeds 1mm. I have elected to avoid this, at considerably more effort. In this sense my approach of upsizing represents a step-up in build quality, perhaps. The other huge pay-off is the avoidance of skin rib mismatches, which from other builder's accounts results in a lot of 3.3mm hole "cleaning", the need to force the clecoing and riveting process, and problems with oil-canning.

After upsizing, all edges were deburred, and mating surfaces fully cleaned.