Whew…so after a weekend of distractions (and ok, also laziness), I got back to work tonight. The next tasks seemed pretty simple, really. Compared to the left cover, where I had to tinker with the fuel selector mount and locate/cut/drill the appropriate holes for that, I figured I was home free. After all, with the right cover I just had to match-drill the two holes in the auxiliary longeron.

And actually, yeah, that part was easy. Then it was just a matter of drilling the holes for the four nutplates for these four screws. And that is where things got interesting. You see, the one downside to working in this area it that it’s right up against the skin. And the skin is curved in such a way to further limit working space.

Drilling the nut plate mount holes wasn’t bad; in fact, it was pretty quick work with the angle drill. But then came the real fun – countersinking those rivet holes for the flush rivets. For four of the eight rivet holes, I was able to use the countersink cage OK, again by making use of the angle drill attachment (man am I glad I bought that chuck adapter for stuff like this). The other four holes…well, on three of them I got partial countersinks, and the fourth was too close to the skin to get the cage on it.

So I got to finish those three countersinks and make the fourth one entirely by hand. I do have an adapter so I can use the threaded countersink/deburring bits in a normal chuck drill, and I thought maybe I could use that to run the countersink bit in the angle drill attachment, but the shank of the adapter was too big for the chuck adapter. (though it occurs to me as I write this that I might have been able to thread the countersink bit directly into the angle drill attachment. Hooray hindsight!)

So instead my strategy was to hold the bit + adapter in place with one hand and turn the shank (which has a hex profile) with a 1/4” wrench, 1/6 of a turn at a time. I would describe this process as “painstaking.” Just tons of trial-and-error and slow going all rolled into one. I’m pretty sure I spent 15-20 minutes just making that one countersink.

But this was just the beginning. The new problem was how in the world to shoot or squeeze these rivets in these tight quarters. There was absolutely no way I was going to get in there with the rivet squeezer, and it seemed equally impossible to get a rivet gun on these things. Maybe if there’s such thing as an offset flush set for the thing, but if there is such a thing, it’s not in my toolbox.

So I decided to just use blind rivets here. The total material thickness here is actually a bit more than the max grip length for these rivets, so this would be unacceptable for actual structural use. But for securing nutplates, the only purpose of the rivets is to keep the nutplate in place – the screw actually takes all the load. And this is just a cosmetic cover anyway, not any kind of structural piece. Thus I rationalize my departure from best practices in this particular instance.

And that’s it for tonight. Looks like things should be a bit simpler from this point forward – next up will be fitting the front seat ramps, and probably working some more with the rear seat rudder pedal setup, which I did some prep work for before getting the fuselage canoe together, in addition to some more work on the right console and throttle quadrant assemblies. After that, I can get back to working on the rear seat floors.

So tonight’s update includes a fun bit of black comedy. Last time out, I’d discovered that I couldn’t use one of the screw locations for the left-hand mid cabin cover because there was already a screw for the fuel selector mount there. I’d also mostly decided to just fab up a new cover so I could relocate that screw hole and not have a random empty hole in the cover.

Well, after thinking it over, I decided to do just that. So tonight, I cut off a section of my junk leading edge skin, traced the outline of the cover, cut the new cover piece out, got all the edges to match up really nicely, cleaned it all up on the bench grinder, and sat back to admire my workmanship. It was actually way easier than I might have expected. All I had to do now was transfer the screw holes from the old cabin cover to the new one.

It was literally the moment I finished drilling the second hole that I cursed, um, kinda loudly. Because the hole I’d just faithfully transferred from the old cover was the one I needed to relocate. Basically, by drilling that hole I eliminated the entire reason for jabbing up a new cover.

I could have made yet another cover, but I decided that maybe the thing to do was to just use the existing cover after all, and deal with the empty hole. It’s not going to be especially visible. And then it occurred to me that there was a much easier solution I could have done from the start: just fill that empty hole with epoxy. The cover’s going to get painted anyway. That at least made me feel a little better.

So with that, I got to prepping the cover, just cleaning up the edges and doing a couple test-fits. Next I marked the location of the new screw hole and drilled it in the cover. Then I screwed the cover in place with a couple of the preexisting holes that already had nutplates, and drilled the two holes in the longerons for the outboard screws. Next, while everything was still held in place, I got under the cover with a sharpie and traced out the cutout and three screw holes for the fuel selector. Off with the cover, drill the three screw holes, and cut out the big center hole. Nothing fancy here, just working with the unibit to get started and finishing the hole with the dremel.

Then it was time for the real test fit…can I actually install the selector? Answer: yes!

With that done, I removed the cover again, went over to the workbench, and set about filling the unused screw hole. I deburred the hole more than I usually would, in order to create a chamfer on both sides – that should help the bit of epoxy I put in there hold. Then I mixed up the epoxy, set the cover over a piece of wax paper, filled the hole, scraped off thee extra, put another layer of wax paper on top, and capped it off with a piece of lumber and two buckets of clecos. Tomorrow I should have a nice plug…I hope, at least. We’ll find out how well my idea worked then.

Aaaand here we have yet another instance of “seemingly simple things gone wrong.”

Tonight I had low ambitions; I figured I’d get the selector mount riveted together, temporarily mount it in the fuse, and fit the left mid-cabin cover and get the holes needed for the selector at least marked and maybe even cut/drilled. Doing the riveting wasn’t difficult, as one might expect, though it was a bit more tedious than I expected. (it takes some experimentation to figure out how to hold oddly-shaped parts steady for squeezing rivets)

The fun came when I screwed the selector mount into place. Here it is in all its glory (I clecoed the face plate on just so it’d look a little more like something):

Now for the mid-cabin cover. Now, here’s the thing with these covers: They basically cover the trapezoidal area seen in the photo above, and mount with screws around the perimeter. The screw holes and nutplates are prepunched on the braces and the spar center section, but the auxiliary longeron (bottom in the photo above) needs to have to screw holes drilled. The cover itself has these holes prepunched, so you just temporarily attach the cover and use it as a guide to drill those holes.

Except for one problem: it turns out that the forward part of my selector mount sits almost exactly where one of those holes has to be drilled:

So long story short, I can’t use that hole location. Not really a huge deal though, I can just make a new hole in the cover an inch or two forward. But then if I use this prefab cover piece, there will always be that empty screw hole that probably only I will know is there. The good news is that I have material on hand to make a new cover; the covers are the same thickness as the leading edge skins, and I still have by damaged skin sitting around. I figure I’ll just cut a new cover for the left-hand side out of that. Shouldn’t be too hard, the shape of the cover isn’t especially complicated.

But that’ll be a job for another night. And who knows, by then maybe I will have decided that an extra open hole isn’t that bad after all. We shall see…

Not a ton of activity tonight, just trying to be doing something basically.

I cleaned and primed the parts for the fuel selector mount; well, the angles and spacers at least (no need to prime the alclad mount plate piece). I did the ghetto cleaning; that is, rather than scrubbing with degreaser, I just scuffed the pieces and gave them a good wipe down with acetone. I honestly considered not even priming these parts – they’re not going to be exposed to the weather or anything – but in the end the directive to prime everything that’s not alclad was irresistible.

Then I switched gears to the flap bearing blocks. Now that I had the blocks trimmed and drilled correctly, I fit the flap weldment into the blocks and put the whole assembly into the fuselage. The two rear bolt holes for the blocks are predrilled and already have nutplates installed, so I put bolts in those holes to hold the blocks in place. Then I drilled through the other holes to make the forward bolt holes through the floors and mount angles underneath. Later on I’ll get to drill for nutplates in this semi-confined space and rivet them. Should be fun.

Getting this done was made easy by my new tool I got from Cleaveland. I’ve had my angle drill attachment for ages, but one issue with it is that it only accepts threaded drill bits, which is kinda limiting. In this particular case, using anything but the angle drill would have been tough, and the threaded bits were nowhere near long enough to go through the bearing block and then into the actual stuff that needed drilling. But it turns out you can buy a normal drill chick that threads into the attachment, allowing you to use normal drill bits in the thing. Very handy.

Here’s a look at that assembly – also visible in the background is the flap weldment (the white powder-coated tube):

Next up, I’ll rivet the fuel selector assembly, get that finally fitted into the fuselage, and then finally pick up with fitting the mid-cabin covers.

Welp, not the most productive weekend, but hey, I still did stuff.

All my various ordered came in, so I got the bandsaw up and running again. That allowed me to trim the corners off the flap bearing blocks, and since I also got the #10 drill bit, I was able to drill the bolt holes out to the correct size. I kinda stuck the flap linkage and blocks into the fuselage in place, but didn’t do any actual fitting – I wanted too focus on the fuel selector stuff.

On that point, I cut my 1/8” spacer pieces to go between the selector mount plate and the mount angles, got those drilled to match the plate, and then dimpled the plate and countersunk the spacers for flush rivets. I also countersunk the two screw holes I final-drilled in the mid-cabin brace last time out. Oh, and I fitted and drilled the holes for the nutplates in the selector mount angles that will accept the screws I countersunk the mid-cabin brace for.

While working through this stuff, I also got to thinking about how I was going to eventually actually mount the selector. There are three screw holes that go through the selector faceplate and the selector body. The body is already predrilled for nutplates. For some reason I had thought the selector would be screwed to the mount plate, and the large cover plate that covers the space between the aux longeron and mid-cabin braces would only have a hole for the selector shaft to go through. But the selector cover plates has to be on top (since it has the L/R/OFF/ indicators), so I guess the screws will go through all three pieces.

Anyway that left the question of what screws to use here. The holes are 3/16”; AN3 bolts would work here but seem like an odd choice. Maybe pan head AN screws, but I don’t have any of those lying around. I did find some flush head AN screws, maybe those would work. Hm, do I even want non-flush screws here? I assembled the selector and determined there’s room for the selector to move and not interfere with pan head screws, but hey, they might catch my knuckles or something. Eh, I’ll go ahead and use the flush screws.

So I countersunk the face plate for the screws, and riveted the appropriate nutplates to the selector body. Also – keeping in mind last weekend’s experience with “borrowing” hardware and then forgetting about it until way down the road when I needed said hardware – I decided to start a list of “borrowed” hardware. In some cases this isn’t necessary – for example, there are tons of surplus rivets, and probably certain screw sizes, and so forth – but in this case, both the screws and the nutplates are an unusual size that I only have small quantities of, so here I want to note the borrowing I did. Though I’m still not sure how I’ll handle this list – I could add these items to my ongoing shopping list, or I could try and figure out where they’re actually needed. The latter is kinda hard though. I had a slim hope that the electronic plan documents I had would be text-searchable, which would make this super easy, but alas, this was not the case. Oh well.

Anyway, that’s it for this weekend. Next up, now that I have all the selector mount stuff prepped, I want to get them cleaned and primed, and then I can get the selector mount riveted together, at which point I can get back to fitting the cover plates, which was the quick task that started this whole fuel-selector bazaar.

Not a ton to report tonight. As I may have mentioned previously, I’ve done as much as I can do with the seat floors until I get some stuff resupplied this week. So tonight I skipped ahead to the next approachable section, working with other interior stuff. First order of business here is to fit the two covers that go over where the mid-cabin braces tie the spar carry-through and the gear towers. On the left side, this is where the fuel selector will go, so the first order of business is to finalize the fuel selector mounting.

This is a spot where I diverged from the plans, ditching the cheap factory Van’s selector in favor of a nice billet Andair unit. Many months ago, I cut and fitted the two pieces of angle that bridge between the mid-cabin brace and the auxiliary longeron, and thus provide the mount for the selector. However, it turns out I did that a bit naively – not in a way that causes huge problems or anything, just stuff I have to pause and address now before I can proceed.

Basically, the way I have this mount setup now, there will be a 1/16-1/8” gap between the selector mount plate and the cover. The inconsistency is due to the difference in thickness between the longeron and the brace – the angles for the selector simply nest against the bottoms of those pieces, while the cover will sit on top of them. I could probably leave this as-is and let everything get pulled together when the selector is screwed into place, but that’s just a little too ghetto for me.

So after poking around for a bit, I devised a plan to fix this problem:

• On the brace side (thinner than the longeron), fabricate ~0.1” thick spacers to sit between the selector angles and the bottom of the brace. With these in place, the top side of the selector mount angles should be recessed the same amount from the top of both the longeron and the brace.
• Fabricate two ~1/8” thick spacers to sit on top of the angles, between them and the piece of sheet Al to which the selector itself will mount. These spacers will place that piece of sheet very close to level with the tops of the brace and longeron.

Between those two actions, I should solve my misalignment problem here. Now I just have to actually make this stuff. From a quick survey tonight, I think I have material on hand to make these spacers, but I can’t really cut the thick stuff easily until…I get the bandsaw going again. So here we are back to the part where I’m waiting on stuff.

In any case, by this time it was getting late, so I called it a night. I think I’m in good shape at this point to start putting this plan into effect for my next work session.