Boy, it’s hot outside. Kind of hard to maintain motivation to get stuff done, but about the best I can do is just ensure that something is happening, even if it’s not much of something.

I started out the morning taking care of my final antenna location. Research indicated that going just aft of the bellcrank bulkhead was a fine place, so that’s what I chose for my transponder antenna. Just tabbed up another doubler and got it drilled in the proper location and orientation. So that concludes my antenna prep work for now, though I guess I could go ahead and dimple the doublers and the skin for eventual riveting.

OK, so what next? Well, I guess I can revisit the static system. I’ve done a decent amount of thinking on this the past few days; basically, what I need back here is to connect the two ports with tubing, and provide a T-junction for the line that will lead to the actual avionics. There are prepunched holes on the adjacent bulkhead for just this purpose, but…how to secure the tubing?

The official plans method is to just use zip ties, but that seemed inelegant to me. Adel clamps seemed a better option, but that would also require opening those holes up and installing nutplates. Which wouldn’t be the end of the world, but…well, something about that bothered me too. Eventually I hit one of my “stop overthinking this and just do something” points, and decided to just go with the zip tie method.

So here it is. On the left side of the fuselage (right in the photo), the T-junction is placed very close to the static port, the idea being that this will keep it more or less secured. I also cut a short piece of tubing to insert into the open end of the junction and capped it; this is to prevent the possibility of our ever-industrious mud dauber population from plugging it up.

OK…now what next? The thoughts occurred to me to maybe get my conduit runs done back here. What that meant for today was another period of staring at things and scratching my head. One topic was how to handle the conduit run into the tail. I spent some time looking at what other people have done, and it seems common to run a conduit down at the bottom of the tail, roughly on-center. But there aren’t any holes in the bulkheads for that, and it seems weird to make a whole new set of holes when there are preexisting ones, albeit not quite laid out where I want them.

Eventually, I decided that I’m not going to do conduit back here after all. My rationale with conduit is to provide routing through areas that are inaccessible, such as under the seat and baggage floors. And while the tail will be difficult to access, it won’t require removing permanent fasteners. And I’d still have to crawl into the tailcone even to access the forward end of my planned conuduit run. Finally, that planned run would result in a curved path, which would remove some of the convenience of trying to easily run new wires.

So yeah, I’m just going to install snap bushings in some of the existing holes, add a couple adel clamps where needed to support long runs, and if I ever need to add wires back here, I’ll just be crawling an extra foot or two into the tailcone to get it done.

There’s also the question of doing the runs under the seat floors. Here, I have some prepunched holes, though oddly not a matched set. The rear spar carry through has a 3/4” hole on either side, but the next bulkhead back only has one on the left side. So I’m going to want to add a hole there too, but that’ll be challenging. Put simply, there’s no way to get in here with my unibit – no room for a regular drill, and no way to chuck the unibit in my angle drill. I think what I’ll end up doing is buying a knockout punch set to get this done. Another thing that has to wait for stuff.

The other question is how to terminate those conduit runs. They need to go further both forward and aft of those two bulkheads if the ends of the conduit will be accessible. Neither termination spot is at a bulkhead, though, so I think I’ll end up making some small termination pieces that will rivet to adjoining structure. This might be one of the things I work on fairly soon.

Eventually, I got tired of all this head-scratching and needed to do something tangible again. So I took a look at the aft end of the fuselage, where there are four unfilled rivet holes on each sides. These are where the stock external rudder stops would have been attached, but since I went with the internal stop, I now needed to get these holes filled. The two aft pairs aren’t much trouble – they’re on the portion of the skin aft of the last bulkhead, and so can be easily dimpled for a flush rivet. The forward pairs, though, are in assembly with the forward flange on that aft bulkhead. I could maybe dimple those with my pop-rivet dies, but I find them barely adequate for a single sheet of material; two sheets of relatively heavy gauge seems maybe a bridge too far.

I the end, I elected to lightly countersink all the holes and install NAS1097 rivets. Since these have an undersize head compared to a regular flush rivet, I can countersink the skin without enlarging the hole. So now those are done.

Oh, I also spent some time thinking about wiring for the landing/taxi lights. A challenge to be dealt with here is that the terminals for the landing projectors are on the front side of the unit, but the terminals for the taxi light are on then back. I’d like to run these as a four-conductor bundle out to a Molex plug at the wingtip, but haven’t been sure how to do this while still making the light unit removable. I need some way to route the wires from the front two terminals to the back of the unit that doesn’t prevent removal. After a bunch of poking around, I have a plan now, involving snap bushings and some slight modification of the mounts. It’s probably better shown than explained, so that’s all I’ll provide for now. Also, it’ll be a while probably before I get that done – I need some smaller snap bushings than I have, and I’m not going to pay $8 worth of Aircraft Spruce shipping fees to get a pair of ten-cent bushings on-hand. They’ll get to wait until my next parts order.

Well…time to bite the bullet and drill some holes in my nice fuselage. I knew it was going to happen, but it still felt kind of wrong…

First up were the two comm antennas, and I started by preparing the doublers. I ordered four pieces of .040” sheet to use for these a while ago, and since then I’ve been thinking about how to form them. There seem to be lots of approaches to these doublers, ranging from people who just add a flat piece of sheet inside and call it done all the way to people who make joggles in the doubler so it can be riveted in assembly with nearby structure. Technically, the latter is best practice, but really kind of overkill for our (relatively) slow aircraft.

Anyway, my initial plan had been to make my doublers with flanges on all four sides, to maximize stiffness. But there’s one issue with that, and that’s dealing with skin curvature. Immediately behind the main spar where the comm antennas were going, the skin is flat laterally, but longitudinally it has a slight curve to it. Having a flange in line with that curve would make it tougher to get the doubler to conform properly. And realistically, both these locations are close to solid structure, so I eventually decided forward and aft flanges only would be fine. (this, by the way, is how Van’s supplies prefab doublers for RV-14 kits)

I also had to settled on the precise location for the comm antenna. Things were a bit tight here; first, there’s the location of the aileron pushrods just behind the spar, and then just behind those are the passenger footwells, which project down below the floor. So I needed to make sure I located the antenna center behind the pushrod region, but ahead of the low point of the footwells. I ended up making a cardboard template, which I used to trace the footwell profile on the outboard seat rib, and that let me lay out the fore-aft location.

Finally, there was the issue of drilling the three antenna mount holes correctly. The layout is pretty simple – three holes in a line, the center one 9/16” to accommodate the antenna connector, and the other two 3/16” to accommodate the mount studs. Spacing between the holes is 7/8”. I was a little concerned about marking and drilling all these holes freehand, so I decided to make a drill template instead.

The template just has three #40 holes, which I use to make pilot holes in the actual thing to be drilled, and then I can open those up to the proper size:

Next, I wanted to try the template our on a piece of scrap, to make sure it was correct before I put holes in something I couldn’t easily replace. Works like a charm:

Then there was just a lot of drilling, positioning, clecoing, unclecoing, etc. In addition to the three antenna mount holes each doubler has a row of rivet hole around the perimeter, with which it will be permanently attached to the skin. But eventually I got it all done, and had my comm antenna locations done:

After that, I moved on to relating this process for the ADS-B antenna, just ahead of the rear spar carry through. I still have the transponder antenna, furthest aft, to deal with…for that, I want to do a bit of research first. My original plan was to put it basically adjacent to where the elevator bellcrank lives, but now I’m thinking that puts it below the avionics shelf, which may make routing the coax cable a little interesting. So I’m thinking of putting it just behind the bellcrank instead, but the potential issue there is that the skin isn’t nearly as well-supported there.

Additionally, the curvature issue I discussed before is reverse here – it’s straight longitudinally, but curved laterally. So optimally, I’d put the flanges on the sides – and that might actually be best here, since that’s the dimension in which the skin can flex the most. I still kind of think I’d want a lateral flange at the aft end, though, since it’s far away from a bulkhead and the skin’s pretty floppy.

So once again, it’s time to go look at what other people have done. Hopefully tomorrow I can get this last doubler done, and then…well, I guess I’ll set them aside, since I’ll need a helper to get them riveted. Probably wait until the same time I finally finish the forward bottom skin riveting for that.

Eh, not much tonight. I just decided to get that last bulkhead riveted in place. Which only constitutes 24 rivets, but they’re kind of interesting to access with a squeezer (or anything else), so yeah, it really took an hour to get them done.

That’s all.

Super short today. I got myself some epoxy, and then this evening I bonded the static port inserts into place. I thought about starting on my antenna doublers, but decided to just make it a short night.

Static ports from inside:

And outside; here you can see how these ports protrude from the skin a bit, mimicking the profile of the Van’s pop rivet:

That’s it. Tomorrow I suppose I’ll work on the doublers, or else the plumbing to link these two ports together. That’s assuming I don’t feel I need to do some more hurricane prep, depending on what our friend in the Gulf does tomorrow…

Just a bunch of bulkhead work today. I’m kind of wishing I’d gotten a head start on this one of the previous two nights, but oh well. Originally I was thinking I’d be able to get these all riveted in place in the next work session, but I forgot one crucial step: the forward most bulkhead needs to be primed and painted before it can go in, since it will be visible in the interior. And before that can happen, some subassembly needs to be done.

I started off today picking up with deburring all the stuff I’d match-drilled previously, then moved on to the various dimpling and countersinking operations. Basically, I prepped every part except for the actual skin, which I’ll handle when it’s time for it to go on the airplane. There’s plenty of holes to mess with here, so this did take some time.

Next up was some assembly. The harness fairleads and canopy rail receptacle got riveted in place. The former was straightforward, as was the latter…kind of. An issue here are the three lower rivet holes, whose shop heads sit inside an acute angle. There’d definitely be no squeezing those with the tight clearance, and even bucking them with my skinny tungsten bar would have been a challenge. So I decided to use blind rivets on these instead. But then I was bothered by the idea of having some the rivets here be solid and the others blind (since the heads will be visible), and so I ended up just using blind rivets for all nine holes. Oh, and I had to drill out and replace two of them, because they didn’t quite go in perfectly flush.

It was late in the day by this point (I spent the middle of the day going out for pre-hurricane supplies), so priming today was out of the question. But hey, while I couldn’t rivet that one bulkhead, the other three could go. So I took those over to the fuselage and got them riveted. I was a little concerned about this, since some of the rivets joining the upper and lower bulkheads sit kind of tight against the skin and/or longerons, but I got them all squeezed with no trouble. Oddly enough, the most problematic ones were on the aft most bulkhead, which rivets to the aft deck. The two outboard riveted there are super close to the longerons, and I tried about three different ways before I ended up shooting them with a long straight set.

So now I’m all – well, mostly, I guess – bulkheaded up:

Hopefully tomorrow the rain holds off and I can get the last bulkhead primed and painted. It’ll still be a bit before I can rivet it after that – I’ve found previous that this granite-texture paint can take some time to really harden, so I’ll want to let that part sit for probably a week before I abuse it by doing some riveting. Kind of thinking I might go ahead and install the static ports and the first part of the plumbing while I’m in a bulkhead-ey mood. Maybe finally get back to the wing wiring stuff too, now that I have my conduit.

Boy, it’s been a while since I did a good old-fashioned cleco-match drill-uncleco work session. Kind of nice to do something so mindless, actually…

With the prep work on the harness anchors complete, tonight was just match-drilling the aft top skin to the bulkheads and other components. First, though, I had to knock a few years’ worth of collected dust and spiderwebs off the skin. If I’d followed the construction manual to the T, I’d have gone ahead and removed the blue vinyl and deburred the skin edges, but I figure I’ll leave the vinyl on until I’m about ready to put the skin on for good. For now, I just want to get to the point of riveting the upper bulkheads in place.

Anyway, with the skin cleaned off a bit, on it went. Getting it clecoed was a little interesting, particularly aligning the two center bulkheads, where I can’t just take one hand and move it into alignment. A straight pick was useful for inserting into one nearly-aligned hole, and then maneuvering the bulkhead so an adjacent cleco could go in. Then it was just a bunch of match-drilling.

Look ma, a turtledeck!

And then it all came back apart again… Look ma, no more turtledeck!

Next I get to do a bunch of deburring, plus figuring out what parts of the manual to do now vs. save for later when the skin goes on for good. I suppose the reasonable thing would be to just get deburring and dimpling done on the bulkheads and maybe the other parts that go in assembly. I’m thinking I can probably get these bulkheads riveted in place in my next work session.

Not a lot to look at tonight – I just did the prep/modification work on the rear seat shoulder harness anchors. Last time I mentioned the idea of using shims between the anchors and the skin in lieu of filing a relief for the bulkhead flange, and…I decided not to do that. When considering the shim idea, I had a sort of vague thought that what I was considering might weaken the joint’s shear strength, but I couldn’t quite put it into words. As I figured might happen, someone on VAF set me straight.

Basically, simply adding the shim into the joint would result in it effectively “floating” between the anchor and the skin. Obviously this wouldn’t involve lots of movement, but in a case where the harness was put to the test, the shim could allow for a tiny bit of relative movement between the anchor and skin, thus allowing the rivet to stretch and/or bend a bit, instead of acting in pure shear.

There’s no telling how much this might compromise the joint – it might be tiny for all I know – but in the end, I don’t think it’s worth it to go off-plans here. So today after work, I got to filing. To make things easier, I clamped a 2×4 block in the vise and match-drilled a few holes using an anchor as a guide, which let me cleco the anchor in place while I worked on it. Next, a block of 1×4 scrap wood, clamped in place against the closest flecks, acted as a guide for the filing. All I had to do was keep the side of the file along the block as I worked, to get a fairly straight cut:

After a fair amount of trial and error, the relief was looking good. However, I didn’t want to leave the sharp edge left by the file and block, so I next went to the bench grinder and removed material to make the transition more of a bevel:

And finally, I did some fairly aggressive radiating of the long edges that will sit against the skin. The reasoning here is that these flat pieces will be attaching to a curved skin; I expect the radius should help these more easily fit snugly against the skin:

After this, it was time to go get the grass mowed, followed by dinner. I guess next up I get to cleco the skin in place and do a bunch of match-drilling…

Today I was soundly beaten by the Houston heat. I got some work done in the morning before going across the runway for coffee, but after that I just wasn’t up for dealing with it.

During that single hour, I deburred the canopy receptacle and got it clecoed in place and match-drilled. Then I ended up doing some trimming on the gussets I put in place yesterday. They didn’t fit well against the bend radius of the bulkhead, and the wouldn’t sit flush, so I had to remove some material from the corners.

The next step would be to get the actual skin deburred and put in place, which can maybe be a task for tomorrow. A more pressing thing I’m thinking about is the two shoulder harness anchors. These are riveted to the top skin and the second bulkhead back from the rear seat, and are made out of thick alclad sheet. What’s interesting is that they need to sit flush against the skin, but also need to be relieved for the additional thickness of the bulkhead flanges.

By the plans, you’re supposed to file this area down to fit, but that seems like an unpleasant way to deal with this. First of all, this fitting has to be done with the skin in place, which means working inside the tailcone, which is already not fun. It’d be even less fun with the trial-and-error that comes with fitting work like this.

So I’m entertaining a different option – rather than filing the anchors down to allow for the bulkhead, why not instead make shims out of .032” sheet (same thickness as the bulkhead) to go between the anchors and the top skin? This seems like it’d achieve the same goal of ensuring the anchors sit flush, without the filing and trial-and-error. The only issue I can think of is that the additional material might make the joint a bit less strong in shear, which would be the expected loading if the harness was ever asked to do its job.

I’ve asked this question on the Van’s forums; it’ll be interesting to see what kind of responses I get. There are some good engineering types in there that ought to be able to point out any horrible flaws in this plane.

It also occurs to me that I could possibly do the filing of the anchors (per plans) without the repeated fitting if I use my .032” stock as a guide, which makes it a little less unpleasant. It still puts the onus on me to do some very precise removal of material, though.

Anyway, that’s it for today. It remains to be seen how much I get done this week, as it’s supposed to stay hot about all week. At least I’m still getting small things done from time to time…