Fuselage - Center Section

2005-08-27 - Preparing the center Fuselage. (3.5 Hrs).

Today, I match-drilled all of the holes in the center section, and fit the F-623 corner ribs. I, also, discovered what I did wrong when I originally cleco'd the F-776 bottom skins to the center section ribs and bulkheads. Pay attention, this could save you some anguish. There was a lot of swearing and a little blood today.

Here, I have the center section upside down, so I can match-drill the skins. Originally, I cleco'd everything together from the topside, because I like working on things right side up. Unfortunately, the holes really need to be drilled from the bottom side. The problem is that it is easy to insert clecos from the topside, but very hard to remove them. Also, with the center section upside down, it is even harder to move the clecos after the first set of holes have been drilled.

So, what is the "proper" way to do this? That's right, cleco the skins on with the center section upside down, preferably with it sitting on a couple of saw horses.

After match-drilling the skins, you still need to match-drill the ribs to the bulkheads. Here, I have removed the forward F-704 bulkhead so I could match-drill the ribs to the aft F-704 bulkhead. This is where I think I hurt my back. The center section is not that heavy, but it is bulky, and easy to lift wrong. Instead of lifting from the center, I grabbed it from one side, and lifted it from the floor back onto the table. I felt that little twinge in my back at the time. A few hours later, I really felt it. This lasted for about three days. So, be careful.
I started removing the aft F-704 bulkhead, and figured-out that I still needed to match-drill the top holes. So, back together, match-drill, back apart.
Don't forget to mark the rib flanges that need to be trimmed for the snap bushings.
Here's the proper way to match-drill the baggage ribs to the skins. Cleco from the bottom.
The plans show the front edge of the F-623 corner rib flanges cut at an angle, and not attached to F-705. However, there is a hole there, and F-623 is obviously bent to fit, so I match-drilled the rib to the bulkhead and did not trim the edge back.
This is why you need to flute the front part of the F-623 corner ribs. Notice the rib is bowed up relative to the F-776 skins and F-705 bulkhead.
Aligning the F-623 corner ribs to the edge of the F-776 bottom skins, so they can be drilled.
Turn everything upside down again, and match-drill the F-623 corner ribs to the bottom skins.