Finally got some skin riveting done! But first some good news – I flew again with Joy in the Citabria this morning and after the flight, she flipped to the back of my logbook and endorsed me as a competent tailwheel pilot. I’ll still be flying with her though – she requires 15 hours dual before I can solo her plane. So I’m thinking that in addition to doing the usual pattern work, I’ll ask about some spin training and maybe even aerobatics. Anything’s better than just buzzing endlessly in circles around the airport…

Anyway, back at home, I again decided to take advantage of the nice weather, so instead of jumping right into skin riveting, I went ahead and cleaned, scuffed, and primed all those aileron stiffeners:

Then we went to work on the skin rivets. We started off using the back rivet set, and I was able to set acceptable rivets, but only just so. Even the ones I set had the shop heads smearing a little off-center, despite me attempts to be really careful. We also had one rivet sitting pretty proud on the skin side; I dunno of Josie let off the big bucking bar for a second or what. In any case, I decided to ditch the whole back riveting thing. I felt that while it worked OK, it wasn’t conducive to getting consistently good results; if the best I could do while being careful was to end up with rivets where I said, “I guess that’s OK,” that doesn’t bode well for the rivets I’ll shoot after a couple hours of work.

So we switched to just using the usual mushroom set. I shot from the skin side while Josie bucked on the other side. It didn’t take long to get into a pretty good rhythm, though we had to take frequent breaks for her sake. She had a harder job than me contorting her arm to hold the bucking bar, especially inboard with the closely-spaced wing walk ribs. But we didn’t have any bad rivets that needed to be drilled out, which is a much better record than we had with the back riveting.

We got all the rivets on the left inboard skin done, and about half on the outboard skin, before deciding to call it a night:

I think we should have no trouble getting the rest of these things set tomorrow. Hopefully if we get an early start I’ll have time to go get the materials for the wing cart and at least do the work that requires daylight. The fun part about the wing cart is that I’m going to reuse the lumber from the wing stand bases – which means I’ll have to take the wings off the stands and set them aside somewhere while I build the cart. We’ll see how that works out…

Tonight I clecoed all the aileron stiffeners in place on their skins and match drilled:

Then I deburred the holes and dimpled the stiffeners:

I wasn’t quite ready to quit, so I found a small stupid job to take up a little more time. There are four aileron spar reinforcement plates to be made. There are four .040” alclad pieces already cut to size, they just need the corners rounded and the edges cleaned up:

A little work on the bench grinder and they’re looking good:

Tomorrow I think we really will get some riveting done. I’ll probably also make a Home Depot run this weekend to get materials for the wing cradle and also to make a bending brake for the ailerons and flaps. I built one before for the tail control surfaces, but apparently I left it in Atlanta. No big deal, it’s just some 2×6 lumber and door hinges.

So yeah, still no more riveting activity. Josie has been under the weather the last couple days, and as much as I’d like to go shoot some rivets, it’s not worth pushing her to help when she’s tired and/or not feeling well. No rivets is better than bad rivets. So I took last night off and then started tonight with some general housekeeping – first tidying up the area and then working up a materials list for the wing cart. Then I jumped ahead to working on the ailerons.

Task #1 is making a bunch of stiffeners, 32 to be exact. The good news here vs doing this for the elevators is that all the stiffeners are the same, instead of having various lengths. But like all the other stiffeners, they come in long angle pieces that have to be cut down to size and trimmed:

I started out using the bandsaw to make the taper cuts at the ends, but I was about halfway through when a loud thud erupted from inside the thing. Seems the blade broke – maybe I shouldn’t set it so tight. But no worries, I had a spare blade to swap in! Except it turns out I bought the wrong length blade. So I finished up the taper cuts using snips.

I almost quit for the night at that point – it was getting towards 11 – but I decided to go ahead and fire up the bench grinder to clean up the edges. I’d figured on maybe doing some of the work and then stopping, but of course I just ended up doing all the deburring, which took over an hour. But now I’ve got a nice set of stiffeners, ready to be match-drilled to the skins:

Well, we tried riveting the skins, but it didn’t go so well. More on that in a moment. I had a head start by myself – Josie had to work a little late again – so I decided to assemble the aileron hinge brackets that I primed yesterday. But first I wanted to practice some double flush riveting, since I have yet to use that technique at all. I’d done some research ahead of time, mainly wanting to learn how to properly size rivets for this technique. Not too surprisingly, the length spec is a bit shorter to allow for the countersink to be filled.

Out in the garage, I cut up one of the extra fuel access plates I had lying around and used those as a double flush test. My first attempt, I still used a too-long rivet and ended up with quite a bit of a head sticking up:

So I made another hole, countersunk, and tried again with the next shorter rivet size. Much better, though still sticking up a bit:

Realistically, that’s fine for this task; the plans call for normal shop heads, so even though I’m going for the double flush technique, having a bit of a shop head sticking out isn’t a huge deal. And sure enough, the rivets in the brackets came out looking quite nice:

After shooting/squeezing the remaining rivets, I had four finished brackets:

And then it was time for the real fun. After much reading, I’d decided to back rivet the wing skins; my logic was that this only really required a skilled person on one side of the work. Seemed more likely to turn out some nice-looking rivets. Using this technique require the use of a ridiculously long double offset back rivet set:

Oh, and as a random aside, here are the dogs watching from inside the house, wearing their ear muffs. Yeah, we have those:

Unfortunately, as alluded to earlier, the riveting didn’t go so well. Here’s my first attempt, with the rivet already starting to lean over. And that was after I felt like I was beating the thing to death with the gun:

I found a problem almost immediately. See, on the other side of the skin, Josie is holding this big five-pound bucking bar against the flush head. It came with some kind of coating on the faces of the bar, which for some stupid reason I thought was supposed to stay on, but after seeing how the rivet was making a dent in it, I realized I was really wrong. With that soaking up some of the impact from the rivet gun, no wonder things weren’t going well. So I peeled the coating off the bucking bar, drilled out the rivet, and tried again.

Still didn’t go right; despite banging on the rivet way more than I felt should be necessary, it didn’t form a good head and instead just folded over a bit. Ugh.

Clearly I need to do some more research on this technique. Maybe I need to crank up the pressure at the gun some more. I probably should have practiced on some scrap before going to town on the wing; the way thing are going, I might end up with an “oops” NAS1097 rivet in my very first hole.

One thing is for sure, this back riveting technique seems just as fraught with peril as just shooting these things the normal way. Seems pretty awkward to me as well. I might even abandon it entirely if I keep having issues during the next work session…

Yup, I still have yet to do any riveting on the main skins. But I have good reasoning behind it! What I got to thinking about today is that the riveting is an inside job, and doesn’t require nice weather or daylight. Priming, on the other hand, requires both, and it was a really beautiful day. The next task after finishing the main skin riveting is to build and attach the aileron hinge brackets. The way I figure it, if we put in a bunch of time today to rivet he main skins, I’d find myself without a lot to do over the course of this week. So instead I decided to make it my goal to get those bracket pieces primed today.

Each bracket is made of two pieces of really thick alclad, with a bearing trapped in between and angled pieces to allow attachment to the rear spar. As is usually the case with the thick alcad pieces, the edges are pretty rough:

Previously, I’ve just taken pieces like this straight to the bench grinder to smooth the edges, which turned out to be somewhat tedious. This time I took a different approach, clamping the pieces in the vise and using a vixen file to remove the tooling marks on the straight edges. Much faster:

After doing all eight pieces, I ended up with quite a pile of shavings:

From there I went to the grinder to finish the edges and take care of the corners and curved portions, then I clecoed each bracket assembly together for match drilling. The plans call for a combination of universal and flush rivets here, presumably due to potential interference issues with the ailerons. One of the callouts for the flush rivet seemed odd to me – by the plans, the outboard brackets would have the flush head outboard and the protruding shop head inboard. I went in to do some research and there didn’t seem to be a great consensus as to whether this was correct or not. A common recommendation was to countersink both sides of the holes and make a double-flush rivet. As the name implies, to do this you countersink/dimple both sides, and when you rivet, the shop head forms in the countersunk hole instead of sticking out.

The double-flush option seemed like a good one, but I was still loathe to go ahead and commit to countersinking. It was bothering me that I couldn’t really visualize how everything would go together, and eventually I decided to cleco together the left aileron to help get an idea of what everything looked like together. As a side benefit, it’s cool to have this on your workbench:

In any case, I decided to go ahead with the double-flush rivet option, so I went to town countersinking, then cleaned, dried, and primed all the bracket pieces:

I still had a bit of daylight left, so I looked ahead to the day (hopefully next weekend) when the wings will come off the stands. I’ll need to build a cradle/cart for them, the design of which I’ve been mulling over for a couple weeks. I decided to use the remaining daylight to cut two pieces of MDF that will be used for the ends of the cart. Then I spent some time drawing the layout of the end pieces; I can now set these aside and come back to them with a lot of the grunt work done already. I’ll still need to cut out the curved sections where the outboard ends will sit; the inboard ends will rest on the spar protrusions:

One modification I’m making to the Van’s design is to add a “pocket” between the two wings. My main reason for this was so I could store the bottom skins, though it may also be good for storing fuselage skins when they get here, depending on how big they are. I think this will help save some space in the shop.