Fuselage

Well, tonight is a shining example of what I’m going to call “cascading dependencies.” My initial plan tonight was to start by just finishing the few remaining steps in the current construction manual section, then go back to the incomplete pages from earlier and see where I needed to pick up there. Literally the two remaining steps in this section were to rivet some nutplates to the quadrant cover and then install the quadrant in place.

But here’s where it gets fun. Way back when I was working on the quadrant, I’d decided to go with a fixed-pitch prop, and all my work had revolved around that, from working out the linkage to the rear throttle to fabricating a custom throttle cover plate. Since then, I’ve decided I want a constant speed prop after all, so I knew at some point I’d have to revisit all those things, and tonight was that night.

So I swapped the throttle quadrants out on their mount, then looked at modifying my custom cover plate. Except I discovered a crack in that plate emanating from a screw hole. Sort of randomly I decided to go dig up the factory cover plate (whose opening is too large for the smaller two-lever quadrant), and whaddya know, the opening is the perfect size for the three-lever quadrant. Nice easy solution to that issue.

The next fun was/will be reworking the linkage to the rear throttle. Since the three-lever quadrant is obviously wider, it places the forward throttle lever bit further outboard (I haven’t measured it exactly, but I think it’s something like 1/8”). That, in turn, means that the holes I carefully cut through the center section bulkheads and other parts need to be expanded outboard. I got as far as temporarily mounting both throttle quadrants and routing the linkage, just to begin evaluating where and how I’ll need to trim.

The good news is that I don’t think I’ll need to remove that much material, and also there’s plenty of room to expand the passthrough holes as well. The bad news is that it’s going to be harder to work with these holes than last time – when I did this before, the side skins weren’t on and I had great access. Now I’ll have to be leaning into the fuselage the whole time, though that’s made easier by the fuselage rotisserie setup. But I’m definitely remembering how much time I spent on trial-and-error the first time around with this. The work isn’t that bad, but having to repeatedly install and remove the quadrants and linked is a bit of a pain.

So next time I’ll pick up with this bit of fun. I should be able to get this done in one solid work session, and then I can finally rivet those nutplates and get a little closer to hanging the empennage.

Oh, and that raises another point – this is probably a good time for me to decide whether or not I’m going to preemptively do the SB 14-01-31 reinforcement work. Technically the service bulletin doesn’t require the reinforcement be done until/unless cracks are observed in the spar, and I have to say the work doesn’t look like a lot of fun to do. On the other hand, it’s not going to be any more fun ten years into the airplane’s lifetime either. And to be honest, at this point if I massively ruin something, I’d probably just build a new horizontal stab. It wouldn’t be the end of the world.

Basically it’s just a matter of deciding whether I want to bet that I’ll never actually develop the cracking. It’s been a while since I read up on the SB info, but I seem to recall it was more common on some of the older RV-7 kits that didn’t have precut relief notched in this area. I dunno, I’ve just gotta go do some reading again.

Well, my intent for tonight was to put in some more time on the throttle quadrant situation, but that didn’t really happen. After the last work session, I went back and read through the whole odyssey from the first time I did the throttle quad stuff. One thing I’d forgotten was that normally, the linkage between the front and rear throttles uses clevises at either end, but I’d gone with rod-end bearings in order to move the linkage outboard a bit and get some breathing room on the holes.

This is a useful thought because where the new front throttle lever sits is really close to being in alignment with the linkage going through all three holes. So my thinking after doing all that reading was that maybe I could use a clevis up front and minimize the tweaking of the passthrough holes. First thing tonight was to figure out where I’d put the clevises (which I confirmed that I had ordered by checking my Aircraft Spruce order history). Then it was on to taking a second look at the setup. I did confirm that the linkage is pretty well-aligned with the lever, but that’s as far as I got.

One major difference between the rod-end bearings and the clevises is that the former have male threaded ends, and the latter female. So I can’t attach the clevis directly to the linkage, I need something like a piece of threaded rod to tie them together. And it seems I have nothing of the sort lying around the shop, so I had no way to move forward with trying out the new linkage. Guess I’ll be making a Home Depot run in the near future…

I’m not even logging any hours for this, since all this took me about ten minutes in the shop.

The night wasn’t a total waste, though…I came back inside and spent some more time mucking around with panel design. I like this overall layout with the EFIS screens and other stuff in the main panel. Right now I’m playing with switches on the far left (lighting switched will be on the right console, not shown here), not sure I want to put too many there. This isn’t even representative of all the switches I’ll actually have – for that I need to think some more about what my electrical system is going to look like. I’m kind of thinking of grouping the switches a little more intelligently, maybe putting some up at the top of the main panel, such as things I won’t be using regularly in flight (engine start stuff, emergency bus, etc).

The idea for the Infinity stick grip diagram on the right side I shamelessly stole from another builder on VAF. I think it’s a great idea and a great way to clearly document what all the stuff on the stick will do.

Some more playing with the throttle linkage tonight. Last time I was thinking that replacing the rod end bearing on the forward end of the linkage with a clevis might solve my alignment issues without needing any bulkhead passthrough hole tweaking. Well, I got to thinking about that even more and decided that what would really be nice would be being able to use a clevis on both ends. It’d be way easier to hook up than the rod ends, and in fact the clevises were my original plan when I first played with this stuff.

So tonight I wanted to do some trial fitting with the clevises to see if it looked like my idea would work out. But first there was the issue of needing some threaded rod to connect the clevises to the linkage (both have female threads). Well, I stopped by the hardware store, and they didn’t have any 10-32 threaded rod. So instead I just bought some 10-32 stainless bolts and cut the heads off them. These might or might not end up being the final pieces here, but they at least let me get things mocked up.

One problem with this is that the clevises are significantly longer than the rod ends, so even with them threaded down as far as they’d go, the linkage is way too long. But it was just short enough that I could get it lined up with the forward throttle full forward and the rear one full aft. All I really cared about was seeing how the linkage lined up with the holes horizontally. And it turned out pretty nicely – on the forward end, the linkage sits almost dead center in the center section bulkhead holes. This makes me happy because I’d rather not remove any more material there. The other passthrough point is on one of the bulkheads on the rear side skin – here, as I kind of expected, the linkage rubs the inboard side of the hole, so it’ll need to be widened a bit. But there’s plenty of room to widen it. Another option might be to simply move the rear throttle outboard a bit – I think I can do this fairly easily, the only question is whether the hole cut in the rear armrest will still work or not. I’ll have to poke at that another night.

To finish out tonight I trimmed some material off the linkage tube and then got the cut end tapped for the threaded rod. That’s as far as I got tonight though, next time will be even more test fitting.

In other news, I’ve been continuing to work on systems stuff on my morning and evening bus rides. Right now I’m trying to really nail down the general architecture, which has meant lots and lots of reading, including the VP-X install manual, Dynon Skyview literature, and so on. So far I’ve got a rough idea of the electrical backbone in place, the main thing I’m trying to think through is failure scenarios. There’s a whole wide range of stuff that’s covered by “redundancy,” so I have to parse a lot before I can make a decision about what’s right for me.

But I have been having fun drawing rudimentary schematics in draw.io.

Title mostly sums up tonight, the tweaks all around to accommodate the new three-lever throttle quadrant are now done. I ended up managing to do it without having to do any major rework on the bulkhead passthrough holes at all, which was nice.

Last time out I’d verified that using clevises on both ends of the linkage would work, but would require some work on the passthrough hole in the bulkhead near the rear throttle. I’d also come up with the idea of maybe moving the rear throttle outboard a bit, and it was that idea that I tried out tonight.

Back when I decided to use rod ends on the linkage, I had to modify the quadrants a bit – since the rod ends put the linkage further outboard, I had to add spacers to move the outboard framework out to provide adequate clearance. But If I’m using clevises, I don’t need that space any more, and I can repurpose those spacers to move the quadrant itself outboard in the frame. I just had to disassemble the works and move the spacers from the outboard side of the quadrant to the inboard side. Then came the moment of truth – would the rear quadrant still line up OK with the hole in the armrest? Well, mostly. If I look straight down and kind of squint, I can make out a bit of a gap at the inboard edge, but it’ll never be noticeable outside of that.

Good news, but now how does the linkage fit? Turns out…great! There was a bit of light rubbing at the aft center section bulkhead, but just a little bit of filing took care of that issue.

The aft center section bulkhead is a bit tight but still clear. This is where I can’t expand the hole any more without running into edge distance issues with the rivet holes for the caps:

The rear bulkhead is A-ok, no concerns here:

To finish up the night, I removed the stainless bolt shafts I was using for the clevises to attach to, and then reinstalled them with red Loctite. They won’t be going anywhere.

This mostly wraps up the rabbit hole I went down before riveting some nutplates to the forward quadrant cover and moving on to other things. There’s just one thing I need to decide if I want to deal with, and that’s this gap between the cover and the quadrant itself:

The top of the quadrant sits flush with the top of the mount bracket (bottom foreground), but the cover plate necessarily has a radius to the bend, which results in that fair bit of gap between the two pieces. With the two-lever quadrant, I made my own cover that fit flush, with the three-lever the factory piece fits, and I’m not sure I want to make my own cover again. So I have to decide if I can just let the gap be or not. I’m considering making a filler piece to go in here; I can probably get some thick aluminum material that will fill the gap, cut it to fit around the quadrant, and just rivet it to the over plate. I’ll probably see what the VAF folks have to say about this, I can’t possibly be the first person to deal with this (since I’m using a factory piece and a super common quadrant).

In other news, at the local RV lunch today I got to talking with another builder about the service bulletin modifications to the horizontal stabilizer. This bulletin involves inspecting for cracks at the forward spar of the h-stab, and if they’re found, adding reinforcements to the area. Doing this is fairly invasive, and would mean really messing up the paint on a finished plane, so I’m strongly considering just going ahead and doing the reinforcements now, when there’s no paint to ruin. Not doing it now would basically be gambling that my plane would never have cracking. It seems to me that there’s no better time to do this work than now, so I think I’ll order the SB parts kit from Van’s soon. After all, before too much longer I’ll be mounting that horizontal stab to the fuselage…

Had a little time tonight, so I went out and did some thinking about dealing with that unsightly gap on the forward throttle quadrant. I posted about my problem on VAF but I’ve gotten no responses, so I dunno if the solution is stupid obvious or no one else cared about this gap or what. Regardless, I think I’ve settled on a solution.

The gap between the top of the quadrant and the cover plate is right at 1/8”, so I think I’m just going to fabricate a spacer out of some 1/8” thick aluminum stock. To this end, I’ve got am Aircraft Spruce order working for the necessary raw material. I’m going to attempt to make the spacer in one piece, which should look the best, I think.

And yes, I spent a full hour mulling over this, and disassembling/reassembling various things multiple times.

So, as mentioned last time, I decided to fab up a spacer to fill the unsightly gap between the throttle quadrant and the cover plate. Last time I said I was working a Spruce order, well, I actually ended up ordering the material from…wait for it…Amazon. It was significantly cheaper than Spruce for the same alloy and amount of material. If this had been something structural, I probably wouldn’t have done this, but it’s just cosmetic. I also ordered way more material than I actually needed, enough to make four spacers if I wanted. I figured I might mess one up, after all. Predictably, the first one came out fine.

Anyway, tonight was just a lot of semi-painstaking fitting. I’d been thinking through the procedure of fitting this thing the way I wanted it, so tonight was just putting that into effect (and figuring out all the weird issues I didn’t think before). To start with, I cut one of my two plates in half, which gave me the rough size of raw material I needed for a spacer. I had to trim off one corner to match the angle at the back of the cover plate as well, since this has to nest in there. Then came the first fun bit: the cover plate’s inboard edge has a radius, and I wanted this spacer to nest in there nicely, so I needed to take the square edge of the raw plate and shape it to match that radius.

It took me a bit to figure out the best tool for this job. At first I tried the file but that seemed too rough. The scotchbrite wheel on the grinder was nice and smooth but removed material super slowly. So i ended up doing most of the rough shaping with a cutting bit on the Dremel, and fine-tuning the shape with the scotchbrite wheel. After lots of trial and error, I ended up with this:

With the rounding of the edges done, the spacer piece could now nest fully into place where it belonged against the cover plate. So I clamped it in place and traced the outline of the cutout in the cover plate:

Then rough-cut it with the bandsaw:

The cutout section in the spacer plate is intentionally a bit smaller than the opening in the cover plate. The plan was to final-shape both piece in assembly, to hopefully get as smooth a combined edge as possible. For now, though, it’s still rough:

Next up, I clamped the spacer in place and laid out and drilled my rivet holes. The spacer will just get flush riveted to the cover plate. Here I’ve already dimpled the cover plate and countersunk the spacer:

A lot of material had to come off the outboard edge; the cover plate sits against an angle piece on the outer skin, so the spacer can’t interfere. Technically this trim was done in the previous photo, but it’s easier to see the extent of it here:

Next the spacer got some edge cleanup, removing burrs and smoothing everything out, then I clecoed it to the cover plate again and went to work final-trimming the edges that needed to be aligned with the cover plate. This was just a bunch of filing and Dremeling and sanding and polishing and smoothing and checking and blah blah blah. In the end it’s not quite perfect, but workable as far as I’m concerned. This photo’s a little blurry, but oh well, Should have used macro mode, I suppose:

As I was doing this, though, I did realize I’d neglected to consider one thing. The top plate of the throttle quadrant is larger than the cutout on the cover plate, so the spacer plate will rest on top of that throttle top plate. This is a problem because of the rivets – if I’d set them without thinking about this, the cover plate wouldn’t be able to sit flush against the throttle due to the shop heads of the rivets. Fortunately, there’s an easy way to handle this – I countersunk the other side of the holes in the spacer plate, and I’ll just set the rivets double-flush. if I need to I can even sand the shop heads down a bit – it wouldn’t be best practice for a structural piece, but here it’ll be no problem.

But before I could rivet, I needed to shoot primer on the spacer. So I got that done, and set the piece aside. I’ll probably see about getting it riveted tomorrow night, and then I can trial-fit everything together and see what it looks like. I think what I’m going to do here as far as paint is make the entire quadrant mount black, rather than using the stone-texture paint like everywhere else. The idea will be that the instrument panel, right console (which will house some switches), and throttle quadrant will all be black and sort of match. It remains to be seen what paint I’ll actually use here, though…that’s a problem for later.

So technically, this work session tool place over two days. I started working on this stuff last night and got about half an hour in before a certain dog decided to eat a large piece of rope and we had to take him to the vet. Fun times…

Anyway, to start with I got the filler piece riveted to the throttle cover plate, now that the primer had had time to cure. The double-flush rivet idea worked pretty well; the shop heads sit just slightly proud of the surface, but not enough to make things look bad.

Next up was making another filler piece to go between the inboard edge of the throttle and the mount. To get things lined up for the pushrod to the rear throttle, I’d used two washers to space the throttle slightly outboard, which works out to 1/8” of spacing. Which just happened to be the thickness of the raw stock I bought for the filler, so I cut another narrow piece to use as this second spacer. Clamped it to the mount, drilled the two bolt holes, nothing to it.

This was followed by just a bunch of test-fitting with various parts of the throttle assembly. I ended up having to trim that filler strip a bit, as it interfered with the cover plate. But eventually it all came together. Now that unsightly gap is gone (though there’s still a slight gap on the outboard edge, but such is life):

And here’s the whole assembly clecoed into place in the fuselage:

I still haven’t put the handles back on the throttle because I’m not quite done with it yet. Adding the spacers to move it outboard means that I need longer bolts to go through the assembly. I had the right bolts on hand for the four mounting bolts (the heads of these are visible in the photo above), but there’s a fifth bolt that acts as the pivot point for the levers, and on its inboard side the friction adjustment lever attaches. I don’t have the right length bolt replace that one, so the friction thing can’t work right just yet.

I may go ahead and order that bolt from Spruce, along with some other stuff. One useful tip I saw from a guy on VAF was to keep a running list of more expensive build items that will be needed eventually. Then, if some small part (like an individual bolt) is needed, I can just add the expensive part to the order and get free shipping. Otherwise, it’s just dumb to order a $1 bolt and pay like $5 for shipping. Though for the moment I’ll probably just add the bolt to my running shopping list. While I do want to get the throttle finished up, it’s not really super urgent or anything.

Oh, and I finished up this evening’s work by doing the simple task that sent me on this whole throttle-modification odyssey: I riveted the four nutplates onto the throttle cover plate. At this point I’m done with this section of the construction manual, but I need to go back and look at the stuff I skipped earlier, with the rear floors and stuff. I also still have some riveting on the bottom of the fuselage to do, which will require a second set of hands.

Yes, really. Just one minor detail though. Through all the fitting of the new three-lever quadrant, the one thing still left to do was to replace the pivot bolt with a longer one. Since I added a spacer to tweak the throttle’s lateral location a bit, this made the whole assembly a bit wider. I had the right bolts on hand to replace the four that hold the whole thing together, but not the pivot. The pivot bolt is capped by a little friction lock lever, followed by a nylock nut. With the original bolt, it was impossible to put any tension on the pivot.

So a few weeks ago, I decided to order the horizontal stabilizer SB kit from Van’s, and while I was at it, I threw in the one single AN bolt I needed to fix this up, and tonight was install night. And yes, it did take half an hour (a bit more actually) to replace one single bolt. See, first I had to unbolt the quadrant from its mount plate, and then disassemble the quadrant itself. The pivot bolt is actually held captive to one side of the quadrant by a little metal fitting, which traps the bolt head against the side plate. This fitting is riveted on, so I had to drill out the old rivets and then re-rivet it with the new bolt in place.

The pivot bolt also needs more thread depth than a standard AN bolt, so I had to get out the tap & die set and cut some additional threads. Then everything got assembled one more time. And viola – now I have a quadrant with a functional friction lock!

In other news, I’ve had the build on my mind a lot lately. Been doing a lot of more concrete research and budgeting for the big purchases, particularly the engine. The basic engine choice is either a box-stock Lycoming or a slightly-more-polished Lycoming Thunderbolt, both available directly from Van’s. Then there are a number of aftermarket builders out there. I’m really wanting to be closer to 200hp than the 180 provided by a regular old IO-360. An angle-valve 360 will provide that, but there’s a weight penalty (about 30 pounds) and also a nontrivial financial one.

Another option is a stroked 360; these are sold by both Aero Sport Power in Canada and Titan in Alabama. The result is a 371ci engine, but for some reason Aero Sport calls it a 375, while Titan calls it a 370. Anyway, I put in a quote request to Aero Sport a few weeks ago for an IO-375. It took about a week to get a response, and the quote was…um…high. It made that angle-valve 360 seem like a bargain in comparison, and was pretty disheartening.

Titan, meanwhile, claimed on their site that the -370 “started” at something like $27k. It almost seemed to good to be true, especially compared to the Aero Sport quote, which was over $10k higher than that figure. So last week I shot an email to James Ball, who’s the official POC for Titan. I was impressed when not only did he get back to me (answering my barrage of questions) within about an hour, but he also provided me a best-guess quote that was extremely competitive with the stock Lycoming offerings.

Long story short, I was super happy with Titan, both from a customer-service and value perspective, and I’m pretty well set on buying an engine from them now. If I put a deposit down before the end of August, I’ll get the $500 Oshkosh discount, and James said he might be able to get me free shipping too (not a trivial amount since it has to come freight). I have a bit of legwork to do to get the funds lined up, but I think I’m going to go ahead and order next month.

I’m really trying to firm up a lot of these decisions. Last year after Oshkosh I decided my goal would be to fly the -8 up for my next trip in 2020. I haven’t made very good use of the past year, but I do still want to make that goal. It’s not going to be easy, but getting ahead of stuff like this will help. Obviously, the main requirement is that I get my butt out in the garage and get work done more often.

Back at it again tonight. To start with, I took a look at the construction manual and confirmed I was basically done with the throttle quadrant section. The only remaining steps here are to prime and paint the throttle quadrant and cable anchor, but that wasn’t stuff I could do tonight. I do, however, need to think about what I’m going to do about paint for the quadrant. While I’ve been painting all the assorted interior stuff with the granite texture paint, I know I’m going to want the panel, for example, to be a different color. Probably the glareshield, too. And since the quadrant itself is black anodized aluminum, I kind of feel like the surrounding mount should be black as well. And then I’ll probably make the right-side console black also just for some sort of symmetry.

All that is to say that I’ll probably want to pick up some paint to test with soon. The final step in the quadrant section is to mount it in place in the fuselage, which seems like a point at which it ought to be final painted (though it is removable). Just something else to think about…

Anyway, with that section put to bed, I moved back to where I left off with the seat floors. I don’t even remember any more why I stopped in the middle of those and jumped ahead, I guess I should look back and see if I mentioned it at the time. But anyway, the first order of business was installing nutplates on a couple of floor support angles. This was a bit annoying, since said angles are already permanently mounted to the seat ribs. Ergo, I had to work inside the fuselage, and there wasn’t a ton of space.

The fun part was deciding how to put the nutplates in place to serve as drill guides. Normally I’d put them where they’ll be finally, and hold them in place with a screw, but in this case that would have required drilling the rivet holes with an angle drill. The other option was to screw them in place on the top/accessible side of the angle; that made drilling easy, but I had to use a stubby screwdriver at an awkward angle to hold them in place. But it wasn’t too bad:

With the holes drilled, I just had to countersink for flush rivets and rivet the nutplates in place. Done!

Next on the docket was the aft control mount. This is a beefy chunk of aluminum that, well, serves as a mount point for the control column. First order of business here was demurring the thing. That’s always fun on pieces like this made of super-thick material. The tooling marks on the edges are substantial and take a bit to remove. I ended up using a combination of the vixen file, bench grinder, and Dremel with assorted sanding bits to get this done.

Then it was time to pull the seat floors out of the fuselage, where they’ve been clecoed for…some time. Removing them was pretty easy, but that led to more fun. There were several sizable mud dauber nests hidden under them, so I got to spend some time removing them. By the time that was done, it was 10 PM and it seemed like a good time to quit for the evening.

I’m hoping that, before the weekend’s out, I can get those seat floors completed (I think they just need stiffeners cleaned up and riveted) and then primed and painted. We’ll see how that goes…

Bit more progress today. A lot of the day was taken up with the monthly local RV people lunch, along with some other home-project stuff, but I got up early enough this morning to get some work in, and then got some more in after dark.

But yeah, it was just nutplates. First up were the four nutplates where the aft control mount will attach. These weren’t too hard, just had to set up the nutplates, drill the holes, countersink, and set the rivets.

The other two were more fun. Way back, just ahead of the baggage bulkhead, is where the two bearing blocks that support the ends of the flap weldment sit. One of the two holes for each block is prepunched, and that nutplate was riveted, I think, back before the seat angles were even installed. The second hole was drilled using the block as a guide, and now it was time to install those second nutplates. Access here is a lot more fun, since they sit really close to the fuselage side skins.

It was clear from the beginning that this would require the angle drill attachment. Drilling the holes went well, but then they had to be countersunk. There was no room for the countersink cage here, so I just threaded the countersink cutter into the angle drill extension, and sort of eyeballs the countersinks. And I just had to get a photo of this Rube Goldberg arrangement (side note: there’s a lot of mud dauber debris still down there):

Next up was figuring out how to rivet these. The construction manual suggests squeezing them using a pair of flat vise grip pliers. For one thing, that seems super ghetto to me. For another, I don’t have a pair of those. I elected instead to use blind rivets for these nutplates…way easier.

And then it was 11:00 and time to call it a night. Next up will be getting the stiffeners in place on the seat floors.I guess I should see about priming the cable anchor for the throttle quadrant at some point too…probably easier to do that on the weekend when I have plenty of daylight, vs trying to squeeze it in on a weekday evening.