Bottom Skins

Another riveting session tonight. I am almost done with this step, which is the top half of the skin. I decided to stop where I am, so I can have my tech councilor come over and review my wiring runs and everything else on the wing before I close it up completely. It was easier than I expected to get these rivets in, and they all set well with no need to replace any of them.

I think the bottom half of the skin may prove tougher to rivet, as I’ll have less ability to flex the skin as I get further towards the bottom.

Given I’m going to wait for my tech visit, I’m going to move on to the next section which is flap installation, then aileron install and actuation.

Tonight I spent time riveting the left bottom skin. I spent 2 hours on it, and set about 50 rivets. I was worried that I’d struggle to get this done working by myself, but so far it hasn’t been too bad. Riveting across the rear spar flange, and down the ribs, I have something to brace the bucking bar against. This makes a big difference because it keeps the bar square in one dimension, and helps to steady the bar. I can’t actually see the bar, and am doing it by feel, but all of my rivets came out nice. It was actually enjoyable just listening to music and banging away. It’s slow going because I have to feel my way on the inside of the skin.

It feels really good to be finally riveting these skins on! I’ve been making slow progress for months, and this feels like the home stretch.

Riveting the bottom outboard skin

Today I torqued up the fuel tank bolts on the right wing, then spent time cleaning out the inside of the wing, removing filings and dust. I added some spiral wrap to protect the wiring where it passes near bolts in the spar, and some addition zip ties to stiffen the wiring runs up some more.

With that done, I filed the edges of the outboard bottom skins where they form a lap joint with the inboard skin. Since the inboard skin is already installed, I just shaped the outboard skin by rounding the edges of the skin. I’m not too worried about it, since it’s on the bottom and will be out of sight.

Once I had the skins done, I clecoed them to the wings and started riveting the left wing first. It’s definitely a stretch to reach up to the rear spar, but so far it has been doable. I anticipate many more riveting sessions in the coming weeks while I finish off both wings.

Tonight I deburred the left wing j-channel, dimpled it, then primed both j-channels. I also torqued up the left wing fuel tank attach bolts and applied torque seal.

I’m curious to know if the j-channel will fit neatly in the gaps in the ribs, of if there will be interference. It’s difficult to tell, but will become obvious as I start riveting the bottom skin on. I was careful to position the channel just right on the most outboard rib, but even a slight movement or bend in the channel could cause a problem.

I deburred the left wing j-channel, then dimpled all of the holes.

Then it was time to torque the fuel tank attach bolts. Vans stress that these bolts must be checked, as they are not necessarily torqued at the factory. I found that all the bolts were inserted, and most were torqued correctly. A couple needed some extra turns, including the one I removed when installing an adel clamp for the pitot and AOA tubing. I also checked the other bolts on the spar and then applied torque seal to each bolt.

With the left wing done, I moved in on to priming the j-channels. These were easy, but the preparation is always so time consuming.

Tonight I cut the second (left wing) long j-channel, clecoed it to the wing skin, and match-drilled the holes.

We were away for the weekend, so I didn’t make any progress over the last few days. Last week I had a call from Rian at Vans asking if I had observed any corrosion in my QB kit. I told him about some I had seen on the wing rib flanges and webs, and that I was planning to sand and repair. This wasn’t symptomatic of the problem Rian was tracking down, but he recommended scotchbrite and prime the affected areas. Tonight I fixed the issue; scotchbrite on all affected areas, then spray-can self-etching primer to seal it up. I papered over all the wiring, bolts, and electronics, then carefully painted the impacted areas. There were several ribs on both wings that needed treating. I also inspected the other areas inside the wings to check for signs of corrosion but couldn’t find anything.

Tonight I finished a little backing plate for the rib repair I made a couple of days ago, and I dimpled the right wing bottom long j-channel stiffener.

Tonight the dryer stopped working, so instead of working on the left wing j-channel, I spent time troubleshooting the dryer. Turned out to be a blown thermo fuse, so I ordered a new one and spent an hour cleaning lint out of the dryer and the vents.

I spent 30 minutes or so on the airplane; I drilled out a rivet that was causing an alignment issue, and pop riveted the last two holes on the gap seals.

The rivet was one of the Quick Build rivets, in the second to last rib from the outboard end of the right wing, where it joins the rib and the wing spar flange. It appears that when setting the rivet, the rib moved out of position slightly, and it was never corrected. The vacant hole above the set rivet was not aligned, and not fixed. The spar flange hole appears to have been countersunk sometime afterwards, and due to the alignment problem, the countersink is elongated slightly. I emailed Vans some pictures and concurred with my plan to drill out the rivet, reset it, and use a doubler as an extra precaution.

I will make up a doubler plate for the inside as my next step, then rivet this when I put the bottom skin on.

Then I set the two cherrymax rivets. I used 4-02 rivets, per the specification. This came out looking nice.

Tonight I finished match drilling the right wing bottom long j-channel stiffener. I used my electric drill, but in hindsight my air drill would have been faster. Will do that on the left wing.

The bottom skins have a length of j-channel running down the middle to stiffen the skins. in a slow build, the plans call for these to be match drilled against the spar early in the build. With quick build, there isn’t a great way to do that, so I have to carefully install the channel, then the skin, and then match drill from the skin. I didn’t realize the j-channel wasn’t match drilled, or I would have done this much earlier before I had dimples the skin. Anyway, I installed the channel and spent time carefully aligning everything and then match drilling the right wing outer bottom skin to the j-channel. I didn’t finish the whole thing, but should get it done tomorrow.

Because I have dimpled already, I had to go much slower. The problem is that dimpling stretches the hole diameter, about two drill sizes larger. So match drilling with a #40 drill bit is too sloppy and inaccurate. To account for this, I used a #38 drill bit to start the hole, really just to put a center point on the channel. Then I switched to a #60 drill bit, and made a tiny pilot hole in the center. Then I stepped up the hole to #40. For each hole, I’m drilling 4 different holes, so it’s slow but the results are good.