Month: July 2020

This weekend I finished riveting the top right side skin. This seemed to take a long time, mostly because I ended up removing and redoing several rivets. The angle and awkwardness of access made for a hard time setting these rivets. All of them had a tendency to bend over, making for a bad rivet head. After much experimenting, and a tip from another builder, I found that pre-squeezing the rivets just a small amount made a big difference. The rivets tend to bend within the first 2-3 hits from the rivet gun. Keeping it straight for those first few hits all but ensured a good looking shop head. By pre-squeezing the rivets with the pneumatic rivet squeezer, I was able to keep the rivet straight for that initial compression. This really only worked in some of the rivet holes where I was replacing a rivet and the hole was slightly enlarged (but not enough to up-size the rivet). It also took a lot of practice to get a properly squeezed rivet; straight and not too fat to fit in the hole.

On the last rivet, my bucking bar slipped off the rivet head, and I managed to make a small mess of the bulkhead flange. Luckily it’s just a small dent and not a crack. Annoying way to finish the otherwise good session.

Last week my drill block parts arrived, so today I made the block. I cut about 3 inches off the foot long section of aluminum bar. Then I spent time squaring up my drill press, which meant fiddling with the table to get it sitting perfectly square. It had been about 2 degrees off level, it turned out. With the table square, I drilled two holes and inserted two of the sleeves that correspond to the holes a I need in the aft bulkhead. The holes came out pretty square, this should be great for helping keep the holes straight.

Finished product. On the other side is a channel for redirecting shavings from the drill.

Tonight I back riveted the right top side skin, just the bottom row. Access was harder than with the other skin, but I had success climbing onto my work bench and crawling inside to rivet. This was a “first”; I climbed inside my plane for the first time! My back rivet plate is about the same thickness as the rubber floor mats from Harbor Freight, so I was able to fully support the skin while crawling inside.

The finished result was great; nice tight skin, no oil-canning and good shop heads all the way down the line.

I clecoed on the left top side skin 2 days ago, and last night I back-riveted the bottom row of rivets. Tonight I set the remaining rivets on the bulkheads. There were a few rivets that clenched over and will need replacing, it’s tricky to get the bucking bar at the right angle because of the curved skin.

Tonight I planned to back rivet the rib, doubler, and j-channel to the top skin. Unfortunately I ran into a couple of problems, and was only able to backrivet the j-channel. The rib has a flange on the bottom edge which makes back riveting this impossible without an offset backrivet set. I don’t ah e one, and don’t feel like buying one for this job. I decided to backrivet the doubler plate rivets that were not passing through the rib, but i noticed in several cases there were some cracks forming around the edges of the dimples. I ended up drilling it out and ordering a new doubler plate. On closer inspection, it looks like I didn’t debur these holes enough. It’s also true that some of the cracks were just the primer clacking, as I had dimples this part after priming it. I set it all aside for now and moved on.

In the mail today was my longer flush rivet set. I made quick work of setting the last few rivets on the aft deck.

The next step after finishing the aft deck is to final drill several holes between the vertical stabilizer and the rear lost bulkhead. These are drilled out to #12 and 1/4 inch, and must be drilled perpendicular to the vertical stab. These are bolt holes, and the heads and nuts need to be square to develop the right clamping force. After some fiddling around, I was able to mount the VS. it was fun to see two parts coming together like this. I did have to drill out one hole on the aft fuse to allow the #30 drill bit to hold the parts in position. Flipping through the builders manual, I couldn’t find a place where this hole is final sized. I drilled it out and then everything fit just fine. I decided not to drill these final bolt holes until I can create a drill block that will help me keep the angles correct. I went ahead and ordered a bar of aluminum, and some brass sleeves.

With my benches on wheels, I was able to move them apart and install some lengths of 2×4. These can support the DRDT-2 between the two benches, creating a more convenient area to dimple larger skins. My Dad first suggested this earlier in the year, and I’ve since seen several build logs where this has been done.

With the dimpled in place between the benches, I went to work dimpling parts. Starting with the top skin and components that mount to if (j-channel, doubler and a rivet), then moving onto the top side skins. It took some moving of benches to get at all the holes, but the second one went faster than the first.

My helper! She loves to come and see what I’m doing and help any way she can.

With the skins all dimpled, I clecoed the left top side skin into position for riveting. I plan to back-rivet as much as I can, and will do some research first to see what others have done before I begin.

With the wiring secured, I started riveted the aft deck. I worked on this over several evenings (6/28 -7/1), doing a few rivets at a time. Mostly this was straight forward, but I did have a couple of frustrations with rivets in tight corners near the aft end, and tucked in close to the protruding bulkhead attach points. I was able to squeeze most of the rivets, but had to use my double-offset rivet set on several. It’s really easy for the double-offset rivet set to jump, and it only takes a tiny skip to cause a smiley face rivet.

I emailed Vans about the rivet length callouts where several different lengths are specified in areas where the same material is being riveted together. The response was to go with the rule of thumb for determining length, plans are guidelines. So I measured the thickness of the material and added 1.5 times the rivet diameter to get the rivet length, then rounded up. A little long is better than a little short, provided the rivet doesn’t cleve over.

I haven’t actually finished this step yet, as I don’t have a long enough flush rivet set to clear the forward bulkhead. I’ve ordered one from Aircraft Spruce and it should hopefully be here by the weekend.

Additional wiring for antennae pass through a snap-bushing on the aft deck.