Fuselage

Now if I precisely followed the plans in a linear fashion, the next step would be to rivet the aft side panels in the baggage area into place. But wait a minute! The next step after that says "Now is the time to install the steps...". That makes no sense because if you rivet the side panels on first, there's no way you can rivet the steps in because the rivets are underneath the side panels. Duh! So the steps need to be done now. THEN I will rivet the side panels into place. It pays to read ahead and see what's coming and think it through. For some reason, some of these things are out of order in the plans.

The steps present a new set of challenges. I'm disappointed in these welded steps as they come from Vans, because they don't fit very well.

This was heartbreaking. All the very careful measuring, hole cutting, and precision work I did back on January 30th was a complete waste of time. I put the step in place and here's the initial fit. Very poor. The angle on the welded plate is wrong. It looks like a lot of adjusting of some kind needs to be done in order to get this to lie flat against the skin. I stared at it in disgust for quite a while trying to figure out what to do next. I finally decided that since the bead from the weld requires an enlargement of the hole to make room for it, I would start with that and see what it looks like.

I carefully enlarged the hole about 1/8" with my Dremmel tool, and then deburred it and polished it smooth. When I put the step back in, it went in a bit farther and now that it had a bit more "wiggle room" I could see that it improved the fit a little bit. Now I needed to do the same thing with the hole in the baggage rib. The plans with the steps tell you, after all, to enlarge the hole in the baggage rib as necessary to allow movement enough to make it fit.

By enlarging the hole in the side skin more in the direction toward the forward end of the hole, and by trimming the hole in the baggage rib more toward the aft end of the hole, the angle of the tube was able to be moved enough to get the steel plate to lie flat against the side skin. I worked slowly and carefully with this trimming a little at at time. Warning: DON'T trim the side skin hole down any lower! There's a gap left here as is, and you don't need to trim any lower. The enlarging of the hole in the side skin needed to be forward in my case, and slightly upward. I hope that makes sense. You just have to work with this and take your time, doing whatever needs to be done to gain the clearance needed. I could see that when I got enough "wiggle room" I could move it around as needed to get it to lie flat on the side skin. I was hung up on the notion that the holes needed to be just the exact size as the tubing, so as to help support the tubing. Well, that's not the case. What supports the step are all the rivets through the skin and the F-724 vertical bulkhead, and the white block on the other end of the tube inside. So the holes can be enlarged as needed to give clearance all around the tube, without being excessively large, of course. I plan on using some proseal on the steel plate when I finally rivet it to the skin, to seal it from any possible water leakage.

Once the holes are enlarged enough to allow the plate to lie flat, it's time to start drilling the plate to the skin. I took the step out and went to the bench to measure, mark, and pre-drill all the holes except the vertical column of rivets that go through the F-724 bulkhead. (circled in the drawing below)

I'll mark and drill those holes after fitting and drilling the step to the fuselage, so as to make sure I'm drilling through the F-724 bulkhead as shown. Drilling holes through this steel plate takes a while, especially after you're used to drilling through aluminum. I used lots of Boelube and took my time. I drilled the holes to #40 first, then enlarged them to #30.

Next, the edge of the plate has to be aligned parallel to the F-724 bulkhead as shown below. How am I going to do that, since the F-724 is inside the plane?

At first I was contemplating leveling the fuse and using plumb bobs, then I realized all I really need is a reference line.

The vertical line of rivets already in place is centered on the F-724. My reference line can be measured directly off the centers of these rivets. So I measured 1-3/16" over from the centers of the rivets in several places and drew a vertical reference line. This line, being parallel to the rivets, is parallel to the F-724. Above is the right side of the fuselage. Below is the left side (later on, after I had some of the drilling finished) showing the vertical line through the rivets and the reference line I drew to the left of it.

Now, the edge of the plate can be easily lined up next to the reference line to make sure it's parallel. At this point, I was able to make sure the plate was flat against the skin, the tube inside cleared the holes all around, and it was parallel to the reference line. Then I drilled and clecoed the first hole. After double-checking everything, it was easy to finish drilling the rest of the holes, with the exception of the vertical column through the F-724 and the two lower holes on the far left end.

The plate needs to be bent and trimmed first, before I drill these two holes.

After the drilling and clecoing, I figured it's a good time to remove the blue vinyl under the plate. That area will need to be scuffed and primed before riveting.

Next, I marked the plate for where the vertical column of rivets through the F-724 will be drilled. I'll need to take it off to mark it and pre-drill it because I don't want to drill through any rivets underneath, or drill too close to them either.

At this point, I pulled the clecos out and held the plate up to the rivet line in the F-724, to see where I should drill the holes in the plate while avoiding drilling too close to, or through, any of the existing rivets. After marking carefully, it was back to the bench to drill the holes through the plate. In the picture below, I put little X's to show where the rivet holes will be drilled in between existing rivets.

As it turns out, one of the marked holes on the plate was so close to an existing rivet, that it made the most sense to just drill out this rivet, enlarge the hole to #30, and use it. So I didn't drill this particular hole in the plate at this point. I drilled the rest. Then I clecoed the step back in place and drilled the rest of the holes through the skin and F-724 using the holes in the steel plate as a guide. Then I backdrilled this hole through the plate from inside the fuse. I hope that makes sense.

With the vertical line of rivet holes through the F-724 completed, there are only two holes remaining to be drilled through the fuse. So the next step is to cut off and round the corner of the plate where the fuselage curves away from it. This part of the plate also needs to be bent to conform to the curvature of the fuselage. There's no easy way to do any of this. I resorted to a hacksaw with the blade turned sideways as shown above, to make the first cut. Needless to say, this took a while. Then I spent a lot of quality time with a series of files to round the corner off and make it nice and smooth. Finally, I used a crescent wrench and a mallet to bend the steel plate to match the curvature of the fuselage. There were a lot of on-and-offs to check the fit before it was finally as good as I can get it. It's not perfect, but I don't think I can get it to fit any better.

The last two holes were finally drilled and clecoed, and here it is! This is the step on the right side. Below is the left side. Sorry the pictures are blurry.

The step comes off once again for deburring of all the holes, etc. Now it's time to fit and drill the blocks on the inside.

Boy am I glad I have this angle drill. I found this on eBay several years ago for a fraction of the cost of a new one. I've used it from time to time throughout the build. There's no way to do this step job without one of these. There's a bolt that goes longitudinally through the block and the steel tube, and two more that hold the block to the baggage rib (I'm drilling one of them above). I actually climbed up on each step at this point. They bend slightly under your weight, but I knew that would be the case. Overall, they seem rock solid. The next job will be to clean everything up and prime these steps before finally riveting and bolting them in place.

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