Aft fuselage and longeron dilemma

Unfortunately, in my enthusiasm and intent to get this section of the build done, I forgot that I was not to rivet the bulkheads in above the J-stiffeners. I re-read that "the top skins must be able to bend away from the upper sections of the bulkheads so the main longerons can be inserted later". Wow......I would have to drill a whole lot of rivets out AGAIN.

As I look at this, I cannot see why the longerons won't simply slide into position from forward to back. I did open the "L" shaped openings on the bulkheads so that they would fit better (they were too small....as I read on the forum.) I see that the slit cut in the longeron to accommodate the 711 will be a problem, but I think that I can make that work. Can I work around this, or am I once again going to have to drill out a bunch of rivets?

I have read ahead on the longeron insertion, but I am not visualizing the problem, although I am afraid that they didn't want me to rivet those skins yet for a reason!

With no rivets above the stiffeners, it's easy. With half of them there (riveted halfway up the bulkheads from the stiffeners toward the top edge) it would be possible but a little more tricky. If you riveted all the way up... Well, you won't know until you try it, right? Maybe you can slip them in there without bending the side skins. I wouldn't worry too much until it's time to install the longerons. If you end up having to drill out some rivets, you drill. Maybe you get lucky.

Jwputnam said:

As I look at this, I cannot see why the longerons won't simply slide into position from forward to back.

Click to expand...

The skin dimples will make it difficult to slide the longeron into place, as they will want to seat into every countersunk longeron hole as it passes by.

Can it be manipulated to save you having to drill out a bunch of rivets? I'd sure try. However you might consider rounding the very aft edge/corner of the longeron where it might scrape against the skin. You don't want a huge longitudinal scratch in the structural skin right at that joint.

When you get to that point, you might find that drilling just a few rivets on each side (we get pretty good at it by this point in the fuselage kit, right?) saves you a lot of swearing and damage potential.

You won't be able to push it past the F-711C bars

Aha......the dimples! I hadn't thought of that. Of course they would slide in easily now, but when match drilled, removed, deburred, countersunk and skins dimpled, the problem becomes clear.

I will probably try just removing a top few rivets , but it occurs to me that the skins COULD be dimpled AFTER the longeron is prepared and installed. I believe that there is enough room.

I thought about the 711 bars. I believe that I will definitely have to relieve the skins there, but they (the longerons) seem to be flexible enough to get them in.

Like I said, I will likely go with removing top three rivets and see how it goes. I do appreciate the advice about avoiding scratching the sides. I will be very mindful of that.

Well, I tried inserting the longeron without removing any of the rivets and it slid in quite easily. I was able to twist it very slightly to make it slide over the F-711. It appears to be lose enough to do it again even with the dimples.