Drilling the J-stiffeners and the ribs^2.5h

Today I drilled the F-786A top J-stiffeners to the aft skins, then drilled the F-6111 ribs to the front aft top skin.

First, the J-stiffeners. I did not want to get inside the fuselage to hold the stiffeners to the skin, so I reached as much as I could from the front and the back, aligned the centerline, then drilled. It worked out okay in the end. The right stiffener is drilled a bit off the centerline in one section, but since my line was closer to the vertex of the bend, it still has enough edge distance.

I am always nervous drilling through the material where I have a flange behind it (especially, given that these flanges already have very short edge distances for some reason), so I place a scrap shim to stop the drill bit. All the holes aligned well with no issues.

Then I drilled the F-6111 reinforcing ribs. I used the process described on VAF. First, trim the bottom side so it sits against the longeron (I trimmed the outside flange at an angle). Then, draw the centerline on the rib and start drilling it from the bottom. The top need to be trimmed as well to fit against the bulkhead. In the end, it was mostly the angle on the outer flange (acute angle) and a bit from the tip. So, the rib doesn't require shortening even though the instructions say to shorten it. I only did a very little bit of fluting, mostly to accommodate the flutes on the F-706 bulkhead.

I turned out okay, but the very top hole (the one shared with the bulkhead) is a bit too close to the vertex of the angle. I dimpled it to see how it looks, and there is enough space (the dimple doesn't get to the bend), so it should be fine. The fit, however, is iffy, as there are multiple layers of aluminum plus the flutes on the bulkhead.

Finally, I drilled the holes in the F-709 bulkhead (the rear one). There are three nutplates on each side that need to be installed into the bulkhead (but you won't know about it until you get to the fairings, it's on the DWG 44). The issue, however, is that due to the fluting on the F-709, the nutplates don't fit. I am thinking of getting some of the small Click-Bond nutplates (CB6014), to see if they would fit between the flutes.