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…

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.

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.

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.

So I spent most of the day working outside, yard work and so forth. But after it got dark and I had some dinner, it was time to get out and do some plane work. I started off working on the console, as mentioned last time. It turned out there wasn’t a ton to be done with this thing. Really, there are just two screw holes at the aft end that need matching holes drilled in the center bulkhead cap it mates to. So it was just a matter of attaching the console with a few screws, drilling those two holes in assembly, and then removing the bulkhead cap and installing nutplates in those two holes.

After the, next up was making the cable anchor that will go inside the throttle quadrant. This piece gets fabricated from raw aluminum angle, and while it’s not hugely complex, it does take some work. Here’s the raw angle sitting beside the depiction on the plans page:

First up was trimming the angle down to rough size. Next I laid out the triangular section, drawing the main cut line. The fun part was figuring out how to draw in the 3/8” radius at the corner. I started to look around for round things that would hopefully have the proper radius, and then it occurred to me that I had just the things for a job like this – my socket set. Easy enough to find a socket with the proper outside diameter, which I used to trace the radius:

Then there was a lot of bandsawing, filing, shaping and smoothing on the bench grinder, and so forth. Oh, and I also had to drill the three 1/2” holes for the anchors themselves. Again, not too bad, just being careful about the locations and stuff. The only fun part is that I don’t have a good quality 1/2” drill bit, just the one in my cheap generic drill bit set. So I ended up drilling the holes with the largest nice bit I had (7/16”) and then opening them to final size with my unibit. And since the angle is thicker than each band on the unibit, I had to do this from both sides. And then I got to working smoothing the inside of those holes, which were just a bit too small for my dremel sanding drums to go into.

Finally, there was just the matter of drilling the four holes where this will attach to the quadrant mount. Here’s the anchor clecoed in place to that mount after the holes were done:

That just left a bit more to be done. Interestingly, these holes won’t be used to rivet the anchor to the the mount; it attaches with screws. But it doesn’t use nutplates either; instead, the holes in the anchor get tapped for 8-32 screws, and then the matching holes in the mount are opened to #19 for the screws.

And then it was time to go inside, feed the dogs, and relax for a while. I still need to do some deburring and cleanup work on the throttle quadrant mount, but before I do that I have to remove the actual quadrant, which is there from when I did the rear throttle sometime far in the past.

So tonight was mostly spent getting those nutplates riveted to the seat ramp components. Took a bit of creativity to get some of the rivets done in some tight corners. These parts should be pretty well done now, though I’ll want to shoot some primer and paint on them, hopefully I can get that done this weekend.

Next up will be the right-side console; I went ahead and pulled the plastic off that piece tonight and deburred all the edges.

Yup, that’s it.

Not a ton of stuff tonight. I started working on prepping the front seat ramp parts. Nothing unusual here – final-drilling some nutplate rivet holes, trimming some extra material, and deburring all the holes and edges. Deburring here was more fun since there were lots of little nooks and crannies. Long straight edges are a cinch on the bench grinder, these little guys require some creative work with assorted needle files.

I was going to get the nutplates riveted in, but I can’t seem to find my little bin of NAS rivets, which is especially frustrating seeing as how I just cleaned and organized all this stuff within the past two weeks. Wait…I think now I remember where they are, sec…

[INTERMISSION]

…yup, found them. So I’m set for some nutplate riveting next time. Then I think these parts just need primer and/or paint if needed. I’ll have to decide what really does need paint – I think only the ribs for the ramp will be visible, with the rest covered by the seat cushion, so there shouldn’t be much to do here.

No photos this time. Feel free to use your imagination to envision me hunched over small parts, squinting and wielding a needle file.