F-6111 aft skin reinforcing rib - 5 hours

 Fitting these F-6111 aft skin ribs is a bit of a head scratcher. The instructions are not helpful. Doing some research on them the general consensus is to start at the bottom and work your way up. Trimming only to match the angle in the longeron and where the rib meets the bulkhead.

Firstly I carefully drew a centerline down the ribs. The interesting thing is that the rib flange varies in width along the length so I was careful to account for this. Starting at the bottom where the rib meets the longeron, I found that the angle is 42deg. (A piece of paper was used behind the skin and a pen dot through the holes....connect the dots and the angle is found).  I transferred this to the ribs and cut accordingly. 

Next I trimmed the angle at the bottom of the rib, fit it to the skin/longeron, aligned the centerline with the first few holes and drilled the bottom hole.

One by one I started working my way up. Aligning, then drilling one hole and cleco at a time.

At this point the bottom of the rib begins to rub against the longeron. So I will need to think about trimming this down.

As I work my way up, I now need to start trimming the top of the rib to match the angle with the bulkhead. Very much a guess and test situation here. I trimmed a little bit.

Kept drilling and clecoing, one by one.

As I got closer to the top, I trimmed a bit more as needed, and then I began to see where I need to account for the flutting in the bulkhead in two spots.This ends up being a compromise of sorta flattening the 2 flutes, and creating 2 shallow flutes in the F-6111 rib (Too much fluting in the ribs cause the centerline to deflect too much) 

By the end, I am really happy with the fit and I did a little trimming at the bottom of the rib for the longeron. I'm still not satisfied with it and I'll get this trimmed better later.