Fuselage

After picking up those important items yesterday, I can move forward on the center fuselage. So today I spent most of my time attending to details surrounding the installation of the steps, the little brackets that I made to hold the corner ribs in place, and a good start on the crotch strap brackets.

Here you can see the scallops in the flanges of the F-623 corner rib, and the hole in the baggage rib that allow the tubing to pass through. The picture above can be confusing because of reflections if you don't look carefully.

This shows how the tubing for the step fits in place and passes through one of the baggage ribs. There will be a block bolted to the inner rib that will hold the end of the tubing in place. As it turned out, the hole that I cut to exactly 1-1/2" diameter was a tiny bit small. I enlarged it just enough with my scotchbrite wheel to allow the tubing to go through it. So how did I figure all this out?

I scratched my head for a bit trying to figure out exactly where to make the scallops in the F-623 ribs, and how deep to make them. I finally resorted to clecoing the forward side skin in place to figure it out. There's a tiny pilot hole already punched in the skin that will be enlarged later for the tube to pass through, and it can be used to locate exactly where the step tube passes through the side of the fuselage.

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Here's the pilot hole. I decided not to drill this hole out to 1-1/2" right now. Instead, I drilled the pilot hole to #40, and used my 12" #40 drill bit to help me locate and mark the F-623 ribs for cutting the scallops. Above, the drill bit sticking through the hole into the airplane.

Inside, the bit is long enough to pass through the 1-1/2" hole already drilled in the baggage rib. Centering this bit in the hole shows exactly where the scallops need to be made in the flanges of the corner rib. I used a sharpie to make a small mark on each flange. Then I removed the rib and began cutting away a curved part of the flange. A couple of iterations later, I had it deep enough.

More details. I taped the end of the drill bit in place temporarily once I had it roughly centered in the large hole. In this picture, the side skin is barely a line visible in the photo.

I used my small ruler to make sure I had the drill bit centered in the hole, and then measured the lower half to make sure the scallops are deep enough to not hit the tube.

Looks good!

UPDATE: October 10, 2009 All of this fussing and time spent on these little details was a colossal waste of time! When you are actually installing the steps, they don't fit very well after all and you end up enlarging these holes in order to make things fit right. So just cut the scallops in the F-623 as indicated, drill the hole through the baggage rib to 1-5/8" and move on. You'll probably end up enlarging this hole anyway later on.

Moving on, I did some work on the little straps that hold these corner ribs in place. The plans aren't real clear on this. Thankfully, I learned from other builder sites online. First, I finally realized that the forward ends of these corner ribs are not supposed to lap up onto the flange of the F-705 bulkhead. I had been wondering why we are supposed to make these straps. Now it makes sense. In order for the rib to lay flat on the skin underneath, it can't lap up onto the flange of the bulkhead. I don't know why these ribs are too long, but they need to be trimmed on both ends.

Here's the rib after I trimmed the end of it to lay flat on the skin underneath. Now it makes sense why we have these attach straps to hold it in place and strengthen it. I had to cut a bit out of the side of the attach strap to make room for the rivet tail. It was too wide at that point. I'm wondering if I may make this over and make it even wider, to encompass the rivets on both the right and the left sides. I don't know. Maybe that's overkill.

UPDATE (March 1, 2009): I decided to go ahead and re-make these straps. I figured, why not? More strength here is better than less, right? I put a picture on the March 1st page.

One thing I did do was to leave the side flange of the rib in place. Why not? It won't inhibit the rib from lying flat on the skin, and can only help strengthen this part of the assembly even more.

Speaking of attach straps... the ones on the other end have been bothering me. There's not enough edge distance for a proper rivet here. So I decided to remake them. There's room, after all, between this strap and the edge of the skin. So I traced this on a new piece and cut it out.

Much better! Below is the one I made for the other side, with the next rib in place to make sure there's no interference.

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