Rivet pattern

[mongo2]

Does anybody know why the rivet pattern line on the fuselage skin at the longest tail extrusions is slightly curved? If I lay my new extrusions against the existing rivet lines in the skin, they have to be slightly curved to keep the holes on the extrusion centerline. Left side has more of a curve the the right. This is all fwd of the bellcrank bulkhead. From there aft, the extrusions are straight down to the Tailwheel mtg bracket. When look at the originals removed, you can sight down them and see the curvature in the ext. with the rivet line staying on center. I can statically get everything to line up, but before I start drilling and clecoing, I was wondering if and why the factory may have done this.

[GAHorn]

How do you know that was factory work? It may be a repair or an undocumented salvage.
When riveting, it's very common to see a curve when a jig is not used. As each rivet is bucked, it places a slight stress on the part, and subsequent alignment may be affected.

[mongo2]

I am not completely sure it was factory, but I have talked to another 170 owner who did the same repair\rework, and his rivet lines were curved as well, and the markings on the interior of the skin follow all the way fwd.It would have to be intentional, as the rivet holes are in the center of the curved extrusion. Its hard to see from the outside, but if you lay a straight edge down the outside of the skin on that rivet line, you can see it is not straight.

Rick

[Indopilot]

On a Cessna you can some times spot a repair by noticing straight rivet lines. Or skin panel edges that actually line up with the edges of others.