Fuselage

So last time out I was worrying a bit about how to buck the skin rivets alongside the horizontal stab attach bars. That actually wasn’t the first time I’d worried about that, I’d seen that those were going to be a problem a few days ago. But after thinking it over, I ended up working out a fairly creative solution. I have a gasket scraper which was thin enough to fit in the tight spot, but didn’t have a sharp edge like a chisel (which could cause damage if it contacted the wrong thing). I then used carpet tape to attach my mini tungsten bucking bar to the flat of the scraper, and added some duct tape to hold it all together (and also because no ghetto tool is complete without some duct tape). The end result was, in effect, an ad hoc footed bucking bar:

I was a little worried about how it was going to work out, and I considered trying it on a test rivet, but ultimately I just went for it. And it turned out that it was ridiculously easy to use, and worked great. Those eight rivets I’d been worrying about were all done in about 15 minutes.

Next, I set about shooting all the rivets at the junction of the aft side skins and the aft bottom skin. These were pretty straightforward; the main issue was they required lots of bending over (like many of the rivets I’ve been doing lately) and weren’t visible from above. So it was a mildly tedious process of shooting a few rivets, bending way into the fuselage to check the shop heads, and so on. Plus there were just a lot of these rivets to shoot. But I got all of them done today, with the exception of the ones way back by the tail spring mount. Space is tight in there, and I’m going to save those for a time when I’m not tired.

I also riveted the rear lap belt mount points to the aft side skins, and finally shot some rivets through the mid side skins and into the outboard seat ribs. At this point, I’ve done just about all of the rivets that I think I can manage solo. There are the aforementioned rivets in the tail, and I also want to try the rivets at the bottoms of the mid side skins, though I think those may prove to be too annoying to do solo.

I was originally planning on inverting the fuselage as soon as I finished the solo riveting, but after looking ahead in the instructions, fuselage riveting is followed by flipping the fuselage over again, doing a few minor riveting tasks, and then inverting it once again for installation of the bottom forward skin and the main landing gear. That seems kind of repetitive, so my plan is to do the admin stuff and then just invert the thing once both for riveting and the gear and stuff. We’ll see how that works out…

In the meantime, here’s the fuselage sporting far fewer clecos than it’s had for a while:

Quite a varied day out in the shop. The main goal for today was to reach the point of flipping the fuselage over. The only spots left where I thought I could so solo skin riveting were on the aft side skins between the two aft most bulkheads, the mid side skins just behind the wing spar passthrough, and the lower edge of the mid side skins where they rivet in assembly with the outboard seat ribs.

The rivets at the spar passthrough were a lot of fun. There are two rows of rivets here; the forward row only goes through the skin and the center section reinforcement plate. These are “inside” the center section, so bucking them required reaching into the passthrough to hold a bucking bar in there. It wasn’t too challenging, but still not much fun. It was impossible to avoid smashing my fingers against the center section bar while riveting in some spots, and doing this on both sides meant that both hands got smashed equally. The other row of rivets, which additionally goes through the center section bulkhead flanges, was comparatively simple.

I tried shooting the rivets at the lower edge of the mid side skins, but quickly decided they should be a two-person job. The bottom skins stick out a bit where they’ll mate with the wing, and so shooting these requires my looong rivet set. This, in turn, makes it rather awkward to shoot and buck while reaching way down inside the cabin. I shot one rivet like this and it was barely acceptable. I figured the quality was likely to get worse if I kept trying, so I gave up on those.

The aft side skin rivets were a bit tedious as well. There’s not a lot of room at all in that aft most bay, especially when shooting the rivets close to the bulkheads…but I got it done.

Any further skin riveting would have required flipping the fuselage – but as I mentioned before, there were other tasks to do with it right side up, which I decided to take care of first. First up was riveting the aft deck in place, which was easier than I expected:

Next I riveted the aft armrest bulkheads to the gussets that attach them to the rear spar carry through assembly. Then it was time to rivet a couple of floor angles to gussets on the forward armrest bulkheads – and here was where the day started to get interesting. I clecoed the angles in place, then noticed that they had nutplate attach holes, but no nutplates attached. I looked back through the manual and saw no reference to riveting the nutplates. I figured it would be far easier to rivet the nut plates with the angles out of the plane, but I wanted to make sure it was OK, so I went in for some research. Turns out there’s a spacer that goes on top of the angles, but under the floor, and it needs to be riveted in assembly with the nutplates. The problem there was that I’d already countersunk the angles for nutplates. That’s not a good thing if another piece of alumni will go on top and leave a void there…well, time to add something else to my shopping list.

Next, I riveted the forward armrests to the center section bulkheads, then clecoed the bulkhead caps in place. They won’t get riveted yet, but presumably should provide some rigidity while other work is going on. The next item would have been to rivet the seat back support plates in place, but they needed to be primed and painted first. So that left nothing to do but to flip the thing.

To do this, I installed the tailwheel spring to act as a pivot point at the rear, then moved the rear sawhorse so the spring was sitting in it instead of the tail structure. This would let it be a pivot point while I moved the forward end. At the forward end, I just rolled the fuselage on its side, then over complete y so it rested on the longerons. I also moved the forward sawhorse back a bit; this raised the fuselage up a touch and also gave me some extra breathing room in terms of sawhorse width. I’d initially thought I might want to raise the forward sawhorse to provide more working room under the fuselage, but as it is, I can sit on the floor and be at the perfect height to work underneath.

So here’s what the garage looks like now:

Rather than jump right back into riveting, I decided to get out the forward bottom skin and fit it in place. The practical reason here was to see if the two blind rivets I set forward of the spar pass through would interfere with fitting the skin, but mostly I just wanted to see it in place and cackle a bit. Reading forward in the manual, though, I realized I made a mistake a long time ago. When I installed the forward landing gear crossmember here, the manual said not to rivet it. I took this to mean not to rivet it to the skin, and didn’t do that, but I did rivet it to the intercostal ribs. That, it turns out, was a mistake, because that spot also has to be riveted in assembly with the forward bottom side skins.

The really fun part about this is that the factory heads are in a super tight location:

I pretty quickly determined that it would be nearly impossible to get a drill in there to drill these out – and if I messed up the intercostal ribs, things would get worse since I’d have to remove them as well. So I decided instead to grind off the shop heads – this would ruin the crossmember, but that seemed better than the consequences of ruining the ribs. So I got out the die grinder and a cutting bit and went to work (I really need to clean the camera lens):

Yup, there’s another item for the shopping list. Anyway, back to fitting the forward bottom skin! I was able to get in place even with the blind rivets in place, which was nice. Then I decided to cleco the cooling ramp in place as well – but the flanges interfered. I assembled this part over a year ago, and part of the work was trimming the flanges for clearance. Turns out I trimmed the wrong ends of the flange. Another item for the shopping list.

I’m not really sure why they have you put the cooling ramp together so early. The manual even makes a point if how you won’t actually install the thing until much later. If I was just making the thing now, my mistake with the trim would have been obvious, but when I was working off the plans, that wasn’t really the case. Oh well.

I wrapped up the day by crawling under the fuselage and riveting the rear armrests to the rear bulkhead – these rivets where impossible to get to from above, but easy while sitting under the fuselage. The only downside was that it was kinda hot under there. I also took those seat back mount plates outside and primed and painted them. Whenever I get around to flipping the fuselage over again, they’ll be ready to go.

And that’s it for today. Tomorrow Josie should be able to help me work on some of those two-person rivets. The end of fuselage riveting is in sight!

So today ended up being one of those super-lazy Sundays, and even though we’d been talking about getting riveting done, we didn’t actually get to work until pretty late in the evening. The going was kind of slow as well, part of the issue being getting a decent team rhythm going. Two-person riveting can definitely be a challenge in that regard. We only ended up shooting the rivets on two bulkheads in the tail, and of those, four had to be drilled out. That was almost entirely my fault; I was sitting under the fuselage bucking while Josie did the shooting, and I found it surprisingly difficult to get the bucking bar aligned properly. Maybe it had something to do with weird light from my headlamp, reflecting off all the shiny surfaces, I dunno.

Still, progress is progress. even if it’s not a whole lot.

Josie did have a moment to get a photo of me sitting under the fuselage, and our dog acting as a living tool table:

So progress remains slow. This week saw me taking on some new responsibilities at work, which kept me busier than usual, which in turn made me write the evenings off. On top of that, scheduling work sessions becomes a bit more challenging when you need a second person to help out.

Today we got through riveting another bulkhead and both of the baggage ribs. There was some creative contorting on my part to figure out how to securely hold a bucking bar inside those baggage ribs, especially at the aft end where the bellcrank bracket gets in the way. There were also several rivets that had to be drilled out and redone.

I also put some time into planning for my next big task – mounting the landing gear. Each inboard mount bracket needs to be used as a template to drill a 7/16” hole in the matching wear plate. Last week I ordered some new cobalt bits from Cleaveland for this purpose and boy, were they worth the money. I had no problem at all drilling through the steel wear plates.

The weather looks good for tomorrow, so my main goal for the day is going to be shooting epoxy primer on both gear legs. I probably won’t get to mounting them until late this week or next weekend, but I want to have them ready to go when that time comes.

In the meantime, we’ll just keep riveting. The next session should be fun – the outboard seat rib rivets look like they’ll be really challenging to buck. But once we get through those, it should start to become a lot easier.

My main goal for today was to get the gear legs primed; as I mentioned last night, this would hopefully prevent me from getting hung up this week or next weekend when I was ready to work on the gear. Though at the rate riveting is progressing, who knows…

My first challenge was figuring out how to set up the legs for priming. Lying them on flat plywood seemed subpar, but hanging them was equally interesting since they’re kind of heavy. I ended up with a sort of ghetto solution – I found a piece of scrap lumber that fit between slats in the big gate to the backyard, then supported the other end with my step ladder. Two eye hooks in the wood held up 50# monofilament loops, which could simply be passed through a hole in the gear leg and hung from the hook.

This held the legs up nicely while hardly blocking any area from the primer

Prepping the epoxy primer was more fun. The stuff I’m using is rattle-can 2K epoxy primer from Eastwood. Basically, you push a pin on the bottom of the can, the two parts are allowed to mix, you shake the can for about 3 days or so to ensure proper mixing, and you have epoxy primer without a lot of cleanup. The can also implies this stuff is kind of toxic, so I made sure my respirator was on nice and tight before I started shooting. I shot with the bottoms of the legs up first, let everything dry for about an hour, then flipped the legs so I could shoot the tops up at eye level.

The legs with nice gray primer:

The primer went on pretty nicely, though the finish is surprising rough. I don’t particularly care in this case since this is just for protection, not looks, but if I was shooting topcoat on this stuff, I’d definitely feel the need to sand it smooth first. In my case, I imagine the exposed portions of the legs will get stripped back to bare metal when the plane gets painted anyway.

While I was in the priming mood, I also got the cockpit rails out and primed them:

Once all the rivets get shot on the bottom of the fuse, these will get riveted back on the top side. My intent is to topcoat them with the same interior paint, but I’m not going to do that until they’re riveted in place, because all the flush rivets would undoubtedly mar the topcoat anyway. I’m actually leaning towards waiting indefinitely to topcoat these, simply because I figure they’re likely to get marred at a later time. It’ll be easy to mask around them when I’m ready.

After the priming was done, we had some other stuff to do around the house, but we planned on shooting rivets again after dinner. We reshot a number of rivets in the tail that had been drilled out previously, then started work on the mid bottom skins and the aft bottom skin. Unfortunately, it didn’t shape up to be a good night after this – there wasn’t a great vibe out there and after three bad rivets in a row, I decided we should call it a night. Quitting without a lot done is frustrating, but less so than ruining a bunch of rivets and having to drill them out anyway. Sometimes you have to pick your battles, so to speak.

So when I built out the in-flight adjustable rudder pedal assembly a few weeks back, I made the mistake of cutting the release cable too short. Since there was no urgent need to fix that, I simply put the needed repair parts on my shopping list. Meanwhile, last week I discovered a number of parts I needed to replace, which got my shopping list to a point where it felt worthwhile to pony up for the shipping. My order from Van’s showed up yesterday, so tonight I set about fixing up the rudder pedals.

Basically, I ordered all the parts needed to make a new release assembly; the cable + latch center, six aluminum spacers, and two steel endplates. While I was looking at the old stuff tonight, I noticed that the endplates on the current release assembly were already rusting, so I decided to prime the new endplates before assembling. Through some kind of miracle, the rattle-can epoxy primer I used on the gear legs last weekend was still spraying (despite the claimed pot life of 48 hours), so I used that on the endplates, figuring it was a little more durable than the regular Napa stuff. Besides, the epoxy was expensive, and it’s nice to extract every last bit of it I can.

After letting the primer dry a bit, I riveted together the new assembly and installed it. This time I didn’t trim the release cable at all – it’s a bit long, but I’ll take that over playing chicken with getting the length right again.

While I was working the pedal assembly, I also noticed that the slide bar was rusting where it’s just bare metal. I don’t want to put any kind of heavy grease here, since when I’m flying in jeans or other long pants, they’re sure to make contact with the slide bar and get nasty, but obviously leaving it bare wasn’t going to work at all. Instead, after scrubbing off all the surface rust, I got out my trusty can of CLP from the gun cleaning box and applied a light coat. It works for keeping the guns from rusting without getting them oily, it ought to work just as well here.

Josie has been busy this week, so no more fuselage riveting so far, but hopefully tomorrow night we can get back to it.

Not much to report, we’re just continuing to slowly work our way through the riveting, a bit at a time. Tonight we shot most of the rivets at the joint between the mid bottom skins and the aft bottom skin. These will be some of the last rivets that don’t require interesting contortions, so I guess I’d better try to enjoy them…

So tonight was kind of a turning point, I think. Two-person riveting so far has been an often-frustrating experience; it seemed like Josie was just completely unable to get a handle on using the rivet gun in moderation, resulting in lots of overdriven rivets. After thinking it over, it occurred to me that it was a bit unfair of me to drop her right into riveting with little direct feedback, just me trying to coach through a sheet of aluminum. It’s a lot easier to learn riveting when you’re doing it solo and you can watch the rivet tail deform as you shoot.

So last night, in lieu if riveting the fuselage, I drilled a bunch of holes in some scrap to make a riveting practice kit. While I think that helped it still seemed like Josie was having trouble handling the gun. I was thinking things over before bed last night and realized the obvious problem – I run the rivet gun at a pretty high pressure. This gives me lots of power when I want it, but requires precise trigger control. It works great for me because I’ve literally shot thousands of rivets with the thing. It’s also about the worst setup possible for an inexperienced riveter, where an extra millimeter of trigger pull can go from “that’s good” to “I destroyed the rivet in a quarter second.”

So today, I turned the pressure to the gun way down, to where it was impossible to run the gun at a “destroy everything” level. We shot a few more test rivets in scrap and it seemed promising, so we went back to the fuselage. The results were…great. No overdriven rivets, none requiring drilling out. We didn’t get a huge number done, but I’m OK with that because everything else went so well.

To think, all this time I’ve been frustrated because I thought Josie was being careless, when in fact I was careless and I set her up for failure. Lesson learned.

Josie wasn’t feeling well tonight, so rather than do any riveting, I decided to work on some of the replacement parts I got from Van’s last week. First I separated the floor support angles and final-drilled all the holes. I also dug up the spacers which will sit on top of the angles, separated them, and clecoed them to the angles. I considered match-drilling the spacers to the angles and going ahead and riveting on the nut plates, but I decided it’d be better to do that once the fuselage is upright again, so I can ensure that everything fit together OK.

Next I worked on prepping the replacement forward gear crossmember. I cleaned up the edges, final-drilled the holes, and countersunk the required places. I’ll probably shoot primer on the crossmember Saturday. Finally, I got out the new cooling ramp and trimmed the edges. I didn’t do any match drilling on that though, because I decided it would be more fun to cleo it in place temporarily for fun.

Here’s the cooling ramp by itself under the forward floor:

Then I clecoed the forward bottom skins in place to get the big picture:

Hopefully tomorrow we can pick back up on the riveting!

So not a whole lot of interest to report here, just more and more riveting. Tonight we worked on the rivets at the aft end of the seat rib assembly, and I think these are probably the most tedious ones to deal with here. The understructure here is such that it’s almost impossible for me to even get a good look at the rivets I’m bucking. By itself, this isn’t a huge deal – I’ve shot plenty of rivets and just held the bucking bar by feel, but in most of those cases I had good access to hold the bar in such a way that I could make sure it was square. In this spot, it’s also hard to get my hand on the bar to hold it securely, which makes things a lot more fun.

At this point, we have almost all the rivets on the right side of the fuselage in this spot done. We stopped short of a few, simply because I could not for the life of me figure out how to get any of my bucking bars onto the rivet tail. I guess I’m hoping that maybe I’ll have an epiphany overnight or something. I’ve also considered using blind rivets here, but I don’t think I have any that have the required grip length here. Several spots in the build specify that MK-319BS rivets can be used in place of the 426-3 flush rivets, but they’re always spots where it’s just a single skin and a rib. Here I have two skins and a slightly thicker-then-normal rib, so I’m not sure the MK319-BS rivets would be acceptable.

The good news is that once we get this area done, everything else that’s left will be simple by comparison. Assuming I can figure out a way to buck these last few obnoxious rivets (or use blind rivets in their place), I think we might have a good chance of finishing up the fuselage canoe riveting this weekend.