[Jeff R]

I am a bit confused about the connection of the F-915 outer seat rib, which attaches to the F-904 and F-705 bulkheads.

The instructions say ?position the top of the rib flange so the distance between the outside of the web and the outer edge of the seat skin is 0.032?. This means a thin strip of flange will be visible past the edge of the seat skin when viewed from the top.?

My confusion stems from the following. At the aft end of the rib, with the rib clecoed (and bolted) to the F-705, and with the seat skin clecoed in place, the skin overhangs that aft part by a good 0.040?. Now, I know that the rib is to be formed to make the curve as it mates to the F-904, but here at the aft end, you can?t bend the rib sideways, so you can?t get the skin to recess inwards by the required 0.032?. Further forward you can, but not at the aft part.

I would think that maybe you could simply trim the skin back, but since the rib is curved, where do you stop trimming as you proceed forward?

I don?t know if I have described things well, but any insights would be appreciated

 

[cnpeters]

Jeff,
I recently finished this area and had the same issue. I was able to guide and drill the 915 rib along the curve of the seat skin at the required .032" offset, but then the last 3 inches or so aft start going under the seat skin so that there is a small overhang by the end. I didn't worry about it - I will decide when I see the side skins on and before the seat skins get riveted if there is an issue. It would be easy to grind the overhang back then.
Carl

 

[mike109g6]

seat rib

I am a bit confused about the connection of the F-915 outer seat rib, which attaches to the F-904 and F-705 bulkheads.

The instructions say ?position the top of the rib flange so the distance between the outside of the web and the outer edge of the seat skin is 0.032?. This means a thin strip of flange will be visible past the edge of the seat skin when viewed from the top.?

My confusion stems from the following. At the aft end of the rib, with the rib clecoed (and bolted) to the F-705, and with the seat skin clecoed in place, the skin overhangs that aft part by a good 0.040?. Now, I know that the rib is to be formed to make the curve as it mates to the F-904, but here at the aft end, you can?t bend the rib sideways, so you can?t get the skin to recess inwards by the required 0.032?. Further forward you can, but not at the aft part.

I would think that maybe you could simply trim the skin back, but since the rib is curved, where do you stop trimming as you proceed forward?

I don?t know if I have described things well, but any insights would be appreciated

Jeff,
Look at the entire process. The side skins will be riveted to the outboard seat ribs. You Cannot have the seat floor rubbing against the side skins once riveted to the rib. Adjust accordingly. Are your side skins on? Much easier to do if the side skins are on. The real issue is that the outboard seat rib web is riveted to the side skin. The floor is simply attached to the rib flange. The distance of over/under hang is not what is important. The cabin curve is determined by the bottom skin and the bends in your longerons, not the outboard seat ribs. Hope that this helped.
Mike H 9A/8A