I spent President’s Day in the shop this week and made a lot of progress fitting the vertical stabilizer skin to the skeleton. It went together fairly easily despite a warning in the instructions that you might have to play with the rib/spar alignment to get it to come together. The nose ribs were the hardest to get right. The radiusing helped a bit and then just a tiny straightening of the rib flanges finished the job.
The matched hole job is astounding. Everything fit together very nicely. As I added each cleco, everything pulled together. I found that giving each one a tiny wiggle as I worked through the line, ensured that I had a tight and aligned fit against the ribs. The nose ribs’ front hole is not prepunched, so you have to drill it through yourself. I had to use a couple cleco side clamps to pull the rib flange close to the skin to get an accurate hole. After a bit of finagling, I got the whole thing clamped together.
You can also see the score lines where I used a soldering iron (rounded off tip!) to melt through the plastic along the rivet lines. This leaves most of the protective coat in place to keep from marring the skin. I’m going to paint, not polish so a few scratches won’t be a problem, but better to keep it as shiny as possible.
The next step was pretty easy. I just had to match drill all the holes on both sides. This meant removing a cleco, drilling the hole, and replacing the cleco. Lucky for me, I’m a little bit ambidextrous, so I was able to pull the cleco with my left hand whilst running the air drill with my right. It went pretty fast. I had a drill stop on the bit to make sure I didn’t push the hole through the other side!
The new air compressor worked well, but it was so cold in the garage (15-20 F) that I had to use a heat gun to preheat the compressor block to make sure the oil wasn’t too viscous. With 11 gallons of air @125PSI, it was able to do most of the holes (drill was running at 40 PSI). I had to recycle the compressor once to top it off at the very end.
Then the instructions ask you to do the most depressing thing. Take it all apart!
You need to remove the burrs and chips that inevitably get made as you drill. I also need to smooth the edges (to remove areas where cracks can start), prime, and dimple for the flush rivet heads.
I didn’t get a full day in on the next Saturday. I went flying instead (a bit gusty, but good to get up again — the weather has been awful for flying), had a nice lunch with the wife (important to keep her happy), and helped a friend pack and move. Despite all that, I did manage to get a couple hours in the shop.
The first point of order was to unclamp and prep the skin. I started pulling clecos out and pulling of the plastic. I had to deburr the holes. I’ve ordered an adaptor so I can run a deburring bit in an electric screwdriver, but it didn’t arrive yet, so I’m hand deburring for now. You move the tool from hole to hole, slide the guide pin in and give it a gentle turn. The interwebs are full of stories of people pulling too much metal off. You just need to pull the slightest amount to remove the rough edge. Here’s a picture of me tipping the tool into one of the 100+ holes (both sides!) that need deburring in the skin.
I’m priming, so the entire inside coating has to come off. Some of the ink from the coating comes off on the skin, but when I prep it for priming, it will come right off. I’ve done this one as a selfie since the common wisdom indicates that the build log should show that I built it myself rather than contracting out the fun.
The skin is awkwardly large, so it is hard to final polish the edges. I tried using the scotchbrite wheel on the bench grinder, but it was too difficult. I was sure to mangle the skin. In the end, I used my smooth file (and the bastard file for a couple of rough spots) and a piece of scotchbrite pad to polish it out. In the end, the edge has a bit of a “wavy” feel, but at least it is continuous and differentiable rather than piecewise smooth (math joke).
I was tempted to prime the skin, but I ran out of time. I always make my mistakes in the last 10 minutes of a session, so I opted to wait. I did, at least, get a chance to check out my paint warming system. The primer does not go on well when it and the metal are below freezing. I bought a cheap hot water bottle and heated some water in the microwave to make a little hohlraum (physics joke) for warming the rattle can and my rivets. I suspect at least part of my squeezing problem lay in trying to drive them at 10 degrees F.
Next up: Priming and dimpling the skin. Deburring, smoothing, and priming the ribs/spars. Countersinking the spars. Then riveting it all together!