Fuselage

Ugh, I really need to get on top of my work ethic. Two weekends ago I was out of town, that’s a valid excuse. The weekend after that? Yeah, there was stuff to do around the house, but I didn’t make time to work on the plane. Though I think the real issue is me never working on weeknights – really, I think those were as much of a contribution to forward progress as longer weekend work sessions. Maybe tonight will be the start of weeknight work sessions again, guess we’ll see.

So all I had left to do tonight was to drill those last two inboard bracket holes, followed by the four holes for the inboard wear plates. I ordered four 5/16” bits, just to make sure I’d have spares if I had problems with bits breaking again. So of course, this time I drilled both of the holes without breaking a single bit. Guess I’m probably set on 5/16” bits for quite some time…

That just left the 1/4” wear plate holes. What makes these fun is that they’re match drilled using existing holes in the inboard gear weldments – that means they’re drilled from inside the cabin, aka drilling upward since the fuselage is currently inverted. I’d previously kinda considered flipping the fuselage to drill these, but that would require me to remove the gear legs, reinstall the inboard brackets, and then flip the fuselage to drill. That seemed like unnecessary work to me, so I drilled from below instead.

This was where my judgment kinda went south. Once I was lying under the fuselage, I realized it was difficult to tell if I had the drill square to the weldment. The first idea I had was to start each of the four holes, then remove everything and finish the 1/4” holes on the drill press where I could ensure they were square. But then I got worried about the potential for the holes to wander a bit, so I decided to just finish the holes from below.

Here’s the problem with doing this – it’s best to drill each hole in one shot, because heating the steel at the tip of the bit and then letting it cool can result in a local heat treating effect, hardening the steel and making further drilling challenging. Once I started drilling the holes completely, I got through the first one OK, but on the second one, I hadn’t made much progress at all when I stopped getting chips out of the hole. A look at the tip of the drill bit showed that it looked to have dulled. Well, that’s what the spare is for – I switched that one in, and finished the second hole, but got the same result with the third, a bit of progress followed by a complete stall.

Another part of the problem here was that since I was drilling from below, there was only so much pressure I could put on the drill – eventually I’d just lift the front of the fuselage off the sawhorses, which seemed like not the greatest idea. What if it moved laterally when I did that, and missed the edge of the sawhorse when I put it back down? That’d be bad news all around.

So I decided to go with my original plan for that second wear plate. Using the drill press would give me more control over the hole, and maybe I could make it through with my one remaining 1/4” bit. So I pulled the gear legs, took the wear plate over to the drill press, and sure enough, got the holes drilled with little drama. (It probably helped that it was a lot easier to lube the drill bit this way)

That just left the moment of truth – would the holes line up? Good news – they did. After that, I set about cleaning up – there were loads of metal shavings all over the fuselage and the floor around it, oily parts from the Boelube I’d been using, and holes to deburr to boot.

So now it looks like I get to skip back to fitting the forward bottom skins…tomorrow, I guess.

OK, so not a ton of progress tonight, but hey…I actually did some more weeknight work. I know good and well that these short weeknight work sessions are at least as important as longer weekend ones, so I’m happy with myself.

Anyway, tonight I did some final-drilling and dimpling of the left and right forward bottom skins, then clecoed both of them along with the aft forward bottom skin in place. Then I sat down and carefully read through the next few pages in the construction manual, mainly because I found it weird that I was supposed to match-drill everything I’d just clecoed except the holes in common with the floor ribs. Turns out those holes are final-drilled after disassembly, probably because of the minimal clearance between the bottom skin and the forward floor. I imagine it’d be really easy to accidentally damage the floor match-drilling.

So yeah, next time I’ll actually do the match-drilling, then rip everything apart and go on a deburring and dimpling rampage. I might even take some pictures!

Did some more work on the forward bottom skins tonight. (still trying to work on that weeknight work ethic…) I match-drilled all relevant holes between the skins and the gear crossmembers and intercostal ribs. Next I removed the skins and final-drilled all #30 holes, along with opening up a few holes for structural screw around the landing gear weldments. Finally, I deburred all the holes I’d just final drilled, and formed the edge of the main bottom skin where it will overlap the mid bottom skins.

Next up, I get to do some countersinking and dimpling, plus I still need to finish the edges of a couple skins. Then it’ll be time for some riveting!

So yeah…it’s been hot. Hot enough that I haven’t been working, in case the long dry spell wasn’t already self-evident. I did actually construct what I intended to be an air-conditioned cubicle around the fuselage a couple months ago – basically just a PVC pipe frame with plastic sheeting draped over it – and I even tried it out once or twice, but still, yeah, nothing got done.

Fortunately, this weekend it’s finally not-hot enough (notice I did not say “cool”) for me to be OK spending time in the hangar, and as a bonus I didn’t have a weekend full of stuff to distract me. And I’ve already been getting back into the building mindset the last few days, so yeah, I finally did stuff again.

Unfortunately, I got off to a rocky start. First order of business was to debar the edges of the left and right bottom skins, which I did on the bench grinder. For straight pieces, this is easy – just run the edge along one of the grooves I’ve worn in the Scotchbrite wheel. For curvy stuff (like these skins), I tend to run the edge laterally across the wheel, working each side of the edge in turn. Well, I guess it’s been so long since I did this that I forgot that doing this with the skin angled *towards* the direction the wheel is spinning is Bad. So yeah, I barely got anything done on Skin #1 when the wheel caught it and put a beautiful little bulge in the edge of my nice skin. Cue lots of grumpiness.

Once I got pas the usual initial THIS PART IS RUINED NOW freakout, I decided to see if I could take the bulge out a bit. A little bit of work with a mallet, and I made it, well, better, but not perfect by a long shot. But the skin still fit OK in place on the plane, albeit with a bit of oil-canning between rivets, but a bit more work on the edge made that better. There’s no structural problem here, just a mild cosmetic one, and it won’t be in a super obvious place, so I decided to build on.

I finished my deburring (much more carefully, you bet), dimpled a bunch of rivet holes, and the skins were all ready to go. Next up, the forward gear crossmember needed some attention – this is the part I had to replace a while back because I prematurely riveted it to the floor and munged up the old one removing it. Both crossmembers needed to be countersunk for the  skin rivet holes, and once that was done, I scuffed, cleaned, and primed the new forward crossmember.

In between all that, I cleaned off all the stuff I’d had sitting on top of the inverted fuselage (following the any-flat-surface-becomes-a-table theorem) so I could put it back on the rotisserie setup and flip it over again. I wanted to get a look at the brake lines in the gear towers – I’m planning on remaking those so they come out of the floor ahead of the gear leg mounts, instead of behind, which will simplify plumbing the short lines from the bulkhead fittings to the gear legs.

My original line of thinking had been to address the brake lines prior to starting to rivet on the bottom skins, but after a second look, I don’t think having them in place will complicate the brake line issue at all – at least not compared to working inside the gear towers themselves. So I’m going to hold off on remaking those, until I get to the point of actually mounting the gear legs. I figure I’ll be able to make a better decision about redoing the lines at that point. (this is provided that I mount the legs prior to putting on the forward top skin, which will definitely make doing the brake lines harder…but hey, I can still punt for now)

Anyway, that was the sum total of work for the day. From here, I get to start riveting these skins in place, which should be interesting given the kinda limited access between the bottom skins and the floor. Still, the procedure in the construction manual sounds like it’ll make it not too bad – in any case, it doesn’t look any more obnoxious than shooting the rivets in the flaps. Shooting rivets will probably have to wait till next weekend though – I get home from work kinda late, and by the time I’ve had dinner, I’m thinking it’ll be at an hour where banging rivets will not endear me to my neighbors (especially the ones with a newborn). I’m sure I can find something else to do – assuming, of course, I can successfully get my weekday work sessions going again.

Hey, maybe I’ll even take some pictures next time!

Took some time after dinner tonight to go take a look at the fuse again. Even though I wasn’t going to rivet tonight, I decided to kind of do a dry run of the riveting procedure for these skins. My reasoning here is that the riveting procedure here is pretty specific – there are some tight spaces, and things have to be done in a certain order before other tasks close them off entirely. So I went through and clecoed the main bottom skin on as specified, then followed with the forward crossmember and one of the forward side bottom skins.

Overall, I’m feeling good about riveting this stuff – again, there are some tight spaces, but nothing that I can’t get into with one of my thin tungsten bucking bars. There are definitely a lot more rivets here than you might guess from just reading the construction manual, though. I’m thinking I might do well to get all this stuff riveted over the course of this upcoming weekend…

Oh, and I finally took another picture – here’s the main bottom skin and one of the forward side bottom ones clecoed in place:

With the dry run done, I moved on to reconstructing the cooling ramp. I actually put this bit together some time ago, but discovered that I’d fouled up trimming the skin – yay, time for new parts. I ordered those prior to the move out here, and now it was time to get to work on them. Apparently I already trimmed the skin (correctly) previously, so tonight I just clecoed the stiffeners in place, match-drilled, and deburred the holes.

And it turns out it’s a good thing I did this – the rear stiffener for the cooling ramp needs to be match-drilled and riveted to the forward gear crossmember – before it gets riveted in place (part of the planned weekend work). So yeah, I guess I’ll be continuing to work on the cooling ramp this week…

So yeah, that’s it for tonight.

So yeah, not a ton done this weekend. Originally I’d hoped to get some riveting done, but I’m waiting on an order from Aircraft Spruce with a new tube of Fire Barrier sealant, which I’ll need when I rivet more of these skins that attach to the firewall (I had a tube, but the “use-by” date on it is about 18 months ago…). Though that still wouldn’t have stopped me from riveting the main bottom skin – but this weekend we got in one last hurrah from the Houston summer, which made me a little demotivated to work outside. But it finally cooled off late this afternoon and I got to work.

As the title implies, today I just worked on redoing the cooling ramp, as well as the forward gear crossmember that I had to replace. Last time I did all the match drilling for the ramp pieces and deburred the holes, so today I cleaned up the edges on the ramps and stiffener pieces, then got them all dimpled. Next I back riveted the single stiffener to the middle of the ramp, and riveted the other one to the crossmember (it won’t get riveted to the ramp until final assembly later on.

I also had six nut plates to rivet to the forward crossmember, for attaching the gear leg cover plates. This part blame inadvertently frustrating – I checked the plans for the required nut plates: K1000-06. I dutifully went to my hardware tray, grabbed the bag of those…hmm, this feels light. The bag container precisely five nut plates. AAAARGH. Fortunately, after digging through other trays, I found some more of these, in the hardware bags for the Ductworks landing light mounts. So now I’ve added those nut plates to my running shopping list, so I can get them the next time I accrue enough stuff to merit making an order. (or else I’ll forget and be frustrated again sometime down the road when I go to install the landing lights…)

Anyway, with all that done, I did a test fit of the cooling ramp in place under the fuse:

Looks good, but one of the trimmed areas is a little close to the floor for my preference:

But that was easily remedied with a little vixen file action. Much better:

This whole area will have Fire Barrier sealant applied, and I’ll probably put a thick bead of it in the area where that skin edge gets close to the floor as well, just to help preclude any possible rubbing.

Next, just for fun, I clecoed all the other bottom skins in place to take a look at the full setup:

So I guess now the question is: what to work on this week? As before, I’m not sure that riveting late in the evening is going to make me popular. I suppose I could go ahead and roll the fuselage over and start on the interior stuff. And there are also those brake lines that I want to remake at some point. So I guess, come to think of it, it shouldn’t be hard to come up with some stuff to do…

Yup, back at it again. Today it was time to fire up the rivet gun for the first time in, well, probably a year, and get some stuff permanently attached.   Actually, there was a bit of trepidation involved – as I mentioned, I haven’t shot rivets in some time, and the very first batch of rivets I needed to shoot today were a bit on the challenging side.

You see, access in general is a problem while riveting these skins, and so there’s a very specific assembly order that has to be followed. Basically, the rivets you set in step 4 close off access to the rivets from step 3, which close of those from step 2, and so on. Step 1 is the most fun, because you start by riveting the bottom skin to the floor ribs. The aft portion of the forward floor slopes down and eventually joins with the aft end of the bottom skin, so this particular area is kinda wedge-shaped, with the “roomiest” area having maybe an inch and a half between the skins. And that’s where you have to hold a bucking bar to get these rivets done. And you have to bend part of the skin out of the way to even get your arm in there.

Fortunately, in what’s kind of a recurring theme with this build, the amount of time I spent trying to carefully plan the best way to do this, agonizing over technique, and worrying about possibly screwing up, stood in contrast to how easy it really was to shoot these rivets. The forward most few, I was able to just hold my thin tungsten bar on my fingertips, while for the few further back, I cut a wedge of wood matching the angle of the rib and used that to hold the bucking bar in place. I did avail myself of the option of using blind rivets for the two aft most rivets on each side, though – I have no problems taking the slightly easier path there.

Here’s my high-tech way of holding the side of the skin out of the way for bucking access:

And a couple looks at my wood-wedge bucking setup. This actually works pretty nicely – pushing aft on the wedge (to the right in the photo), exerts upward force on the bar and allows it to move as the shop head forms:

Next, the sides of the skin are tucked into place between the mid side skins and lower longhorns, and clecoed on place along the aft edge (shared with the floor, center section, and mid bottom skins) and along the aft landing gear crossmember. At this point, the skin can be riveted to the gear crossmember – outboard rivets can be accessed with a squeezer, while the inboard ones require more fingertip bucking, reaching under the center part of the skin.

Then comes another fun part – the forward gear crossmember is clecoed to the forward edge of the skin, but nowhere else. This entire assembly gets curled upwards to provide access for bucking these rivets. Once again, some scrap wood worked well as an extra pair of hands:

Finally, the forward crossmember can be clecoed to the forward floor, and the few rivets to the intercostal ribs (between the two crossmembers) can be easily squeezed.

At this point, I’d pretty much reached the limit of what I could rivet solo. The rivets along the aft edge of the bottom skin need to be shot, as well as the rivets between the forward gear crossmember and the floor, but these definitively require a second person. The rivets along the lower longeron I can probably shoot myself, but that’ll be another time. Maybe I’ll try and bail out of work a little early one day this week and Josie and I can do some riveting before it gets too late. Once the forward gear crossmember is riveted, I can proceed with attaching the other two forward bottom skins, along with the cooling ramp – which will wrap up work on this part of the fuse. Then it’s interior time…

Welp, it’s been a long time…again. It’s been a fun few months of back injuries and such, which culminated in back surgery last week. The good news is that I’m feeling a lot better after said surgery. The better news is that I’ve been working from home this week while I recover, which affords me the opportunity to get out and work on the plane a lot earlier in the day. An opportunity which I, of course, squandered until today.

Technically, I never finished the bottom skin riveting, but while I’m feeling better, I’m still not up for the bending/crawling/etc that would be required for finishing that up, so I decided to skip ahead to the next stage, which is working on the interior – seat floors and such. I started tonight by working on the footwells for the rear seat. Each footwell is made up of three parts: an flat angled piece that makes up the “bottom” of the well and two web pieces that make up the side.

The first job is some trimming of those bottom pieces; the corners need to be cut off so they can properly nest inside the web pieces. This seemed simple at first, but given the location of the trims, ended up requiring a fair amount of trial and error and fine-tuning with a file. Here’s a look at a trimmed (left) vs untrimmed (right) corner:

A close-up of the trimmer corner with the web cloches in place:

And a general look at the assembly clecoed together:

After I finished doing all the trimming, I went ahead and demurred all the pieces, then clecoed together the right footwell assembly and put it in place just for a look at the thing in context. Obviously there will be actual floors in place here too eventually:

So that was it for tonight. Next on the docket is a lot more fitting of interior parts; a look ahead in the manual shows that I’m gonna be playing with all the rear seat floors, the baggage compartment pieces, the flap actuator weldment, and much more. Maybe if I get some good momentum going I can have some pieces ready for priming and painting this weekend; we’ll see how that goes.

Got out to work fairly early again today. First order of business today was removing the plastic from all three seat floor panels and getting the edges demurred all nice. Then there followed a bit of a circus – the next step called for cleaning up a couple of spacers that go between floor panels and support angles. I searched high and low for those things. I reached every nook and cranny where airplane parts might plausibly be, in addition to a few implausible spots.

Finally, in desperation, I went to look in the fuselage to measure how long the pieces ought to be, thinking that would help me find them. And that’s when I realized they were already riveted in place to the appropriate support angles, along with the nutplates that’ll be used for attaching the footwells and other stuff. And then I finally remembered – by the plans, these nut plates are riveted through the angles, spacers, and the floor panels. I elected to not rivet the nut plates through the floors, figuring that if I ever have to pull these panels, it’ll be a lot easier if I don’t have to drill out these solid rivets (all the other attachments for these panels are blind rivets).

Well, that only wasted about half an hour of my time. Anyway…from here, I clecoed both of the aft floor panels in place, followed by the baggage compartment floor and shelf. Then I embarked upon a whole lot of match drilling between these various panels and the ribs beneath them. Some of that was kinda fun, since some of the holes were right up against the fuselage walls. I put the ole angle drill to use here quite a bit. On the other hand, having the fuselage turned sideways on the rotisserie makes this a lot easier – instead of leaning over the side, I just sit on my little stool and work right in front of my face.

With all the match drilling done, I next final-drilled the two prepunched holes for the aft control mount. Those two holes were secured with bolts, and then I drilled the two aft holes (which aren’t prepunched). Then that control mount came right back out, and this was about the point I decided to call it a night. Tomorrow I get to move on to working on the flap actuator weldment.

I’ll close with a photo of the interior with the floors and such clecoed in place:

Well, this was an interesting and somewhat frustrating day, for various reasons. We went out for breakfast and then took care of some errands, so I didn’t get started until early afternoon.

Job #1 was to prepare the delrin bearing blocks that the flap actuator weldment pivots in. These blocks have the sockets for the weldment already bored, but they need to bolt holes drilled and some corner trimming to fit around bulkheads in the fuselage. Well, problem #1 is that the bolt holes are supposed to be drilled to #10 instead of #12. Which is odd, because AN3 bolts, which will go in these holes, call for #12 holes. A bit of research revealed that apparently delrin expands a bit when drilled, so you have to use a slightly oversize bit. I went ahead and marked and drilled the holes to #12 on the slim chance that the bolts would fit.

Next I went looking for the AN3-17A bolts called out here. I found the bag that claimed to contain these bolts. I did not, however, find said bolts. Hrm. After a bit of searching and head-scratching, I finally figured it out. Way back when I built the fuselage rotisserie, I drilled 3/16” holes in the engine mount bolt locations for the firewall fixture. And then I attached those with…wait for it…some long AN3 bolts from the parts bin. Looks like that little decision finally caught up with me.

Eh, no problem, I’ll run to the hardware store in town and get some regular 3/16” bolts to replace the AN bolts with. Well, turns out you can’t get good strong bolts in that size, just cheap machine screwed. Some googling indicated that said screws would have about 1/3 the strength of the AN bolts. I wasn’t too comfortable using these to hold the fuselage on the rotisserie, so I decided that I’d just order some more AN3 bolts. I’ve got a bit of a list built up for a Spruce order anyway.

OK, can’t go forward with the flap weldment stuff. But since I’ve got the blocks out I’ll go ahead and trim off the corners. Should be easy, just mark the cuts and make said cuts with a wood blade in the bandsaw. So I did all the marking, went over to the bandsaw, got the table set up all nice, fired it up, and…after about ten seconds (fortunately before I started cutting) the blade came off. ARGH. Turns out the rubber tires on the bandsaw wheels have degraded such that they won’t stay on the wheels any more. I only learned about this after disassembling said saw, doing some tinkering, and a couple more failed attempts to reinstall the blade and run it again. Well, another thing for the order list.

Fine, what can I work on? I started reading through the manual, and ended up starting more work on the footwells and the forward seat floor that will join them. The floor has a couple of stiffeners that need to be clecoed and match drilled, and then that assembly gets temporarily mounted in the fuse to drill a couple of screw holes in a mount angle. Next the footwells themselves get match-drilled, then clecoed where they’ll attach to this floor panel and those holes match-drilled as well.

Hey look, it’s a photo of the floor + footwell assembly:

From here, I followed the usual builder’s script of tearing all of that right back apart again and deburring all the holes. From here, I’ll go ahead and dimple/countersink/etc all this stuff, then prep and prime tomorrow before riveting this stuff together permanently. Then I’ll go ahead and final-paint this assembly since it’ll be effectively complete then. This is technically skipping ahead; by the manual I’d be doing similar stuff to the other two floors, fitting stiffeners and so forth, but I can’t move forward with that until I can get the flap bearing blocks done. At least this way I have something to do while I wait for stuff from Spruce.