Conduit comedy

Apologies for the amusing alliteration in the title…but it’s an appropriate summary of my feelings today, and maybe a small lesson in just following the plans, so to speak.

Recall that I went shopping for conduit sometime last week, so I could add a short run from the wingtip to the pitot tube location. Now, this isn’t uncharted territory, since Van’s provided solid instructions for running this ribbed conduit through the wings, and even sells the conduit themselves. But they also only sell 25’ of it at minimum, and I needed maybe ten total, for the wing run plus some runs int hen fuselage. So I ordered what I thought was the right size from Amazon, but it was too large – I’d clearly mixed up the inside vs outside diameter dimension. But now I knew the thickness of the conduit, so I couldn’t go wrong. I ordered the right size, and now surely I’d be in business, right?

Well, I picked the package up from the post office (along with another package…more on that in a bit), and came home ready to finally Do Something®. Except…this time the conduit is too small. And there’s no intermediate size for sale on Amazon. Now, this isn’t an immediate deal-breaker – since I’ll be making my own holes in the wing ribs for that run, I can use whatever size I want. But some tinkering revealed that the 1/2” stuff I got in today is too small for even my short wing conduit run, since it needs to accommodate terminals alongside two pitot lines.

So yeah…here we are, a week or so after the odyssey started, and I have a couple lengths of conduit that I can’t really use, and I’m about to just order the stuff from Van’s anyway. If only I’d done that in the first place…

But hey, let’s talk some more positive stuff. As I mentioned, I had another package – this was from Don Pansier of Delta Pop Aviation, containing the antennas I ordered late last week. It’s fun getting stuff like this, starts to really feel like I’m turning this aluminum hulk into a functional aircraft:

 There was one unexpected aspect of this order, though. When I placed the order, I went with two com antennas, one 1090MHz transponder antenna, and one 978MHz/UAT antenna. The former is for, well, the transponder, and the latter is for the ADS-B receiver. So I was a little surprised when I opened the box and saw that both the blade antennas appeared to be identical. This, by the way, is the reason they’re still in their bubble wrap bags in the photo above – I thought maybe I’d gotten shipped the wrong things. I wrote Don a quick email to ask about this, and he responded (at 8 PM) to explain that the antennas were identical, and would perform equally well, and included performance documentation. I’ve heard stories of Don’s great customer service, and he didn’t disappoint.

Finally, after the conduit shenanigans, I did want to get something constructive done tonight, trivial as it might be…so I went with getting the autopilot roll servo mount kit installed. This is pretty simple – you just replace the lower bellcrank pivot bracket with the supplied piece, and add a support arm off the upper pivot bracket. To get that support arm properly positioned, I put the servo I have on hand in place temporarily, and went ahead and assembled the linkage from the servo to the bellcrank just for good measure:

Once again…moving from spare parts too systems. Fun stuff to play with, even briefly. But that’s it for tonight…I think now I need to do some research into antenna positioning, then I can see about getting those mount holes located and drilled. I figure the main thing will be making sure the com antenna locations are moved aft a bit so they can’t interfere with the aileron push tubes, and I’ll want to space the blade antennas a bit off of adjacent structure to allow for good access as well.

And maybe I’ll finally get the right conduit I need this week…here’s hoping if I order tonight it’ll be here Friday…

Posted in Wings | Hours Logged: 1

Fuselage teardown

Welp, this was one of those days where you kind of step backwards in order to move forward, or something similarly zen. I did get the conduit ordered from Amazon, and it did go out for delivery today, but via USPS, and they held it at the office, which means I won’t have it in my hands until Monday at the earliest. I may actually wait until Tuesday, as I also have my antennas coming – I ordered those from Delta Pop Aviation Thursday evening, and they’re already on their way.

So with that in mind, I decided it was time to bite the bullet and get serious about the fuselage. Which meant removing most of the assorted stuff I’d put in there over the past several months. The tail feathers came off and went back into storage, the roll bar and panel came out, all my cardboard avionics mockups got put away, the control column and elevator pushrods got put by the wayside…and now it’s back to just looking like a canoe:

I also vacuumed out everything, which basically means I sucked up a whole ton of dead june bugs. Then I got the fuselage back into the rotisserie, and rolled on its side so I could look at the belly. Since the antennas are coming, I figure I’ll go ahead and get their mounting holes done once I have the templates in hand.

But first, I had to figure out where to put the antennas. There are four that I need to find homes for on the belly: two com radio antennas, and two blade antennas, one for the transponder and one for the ADS-B receiver. There are assorted placement requirements that kind of dictate where these will go. Specifically, the ADS-B receiver antenna needs to be at least 2’ from the transponder antenna, and the transponder antenna wants to be at least 3’ from any com antenna.

The com antennas should optimally be separated by 6’, but that’s simply impossible on an RV-8. Most small aircraft handle this by putting one on the belly and one up top, but there’s nowhere up top to do this. So the accepted thing for about every RV-8 I’ve seen is to put the com antennas just behind the main spar carry through, each one as far outboard as possible.

That means the other two get to go further back, and this is a segue into another consideration for placement: I want to be able to access these antennas relatively easily from inside the aircraft. That is, I don’t want them to live under any panel that’s riveted in place. The com antennas satisfy this, since they’ll be under the removable forward seat floor/footwell area. Further back, I have the rear seat floors and the forward baggage floor to consider; both of these will be riveted in.

This leaves two usable regions: the first is basically under and ahead of the rear seat, around where the rear stick is located. The other is aft of the baggage floor. Given the separation requirements, the most sensible thing seems to be to put one antenna in each region, and since the most confining requirement is the separation between the transponder and com antennas, that pretty much says that the transponder is going in the aft location.

So with all that in mind, I made rough marks on the belly as to the location of each antenna. These will of course need to be refined before I can actually drill holes; I need to figure out how far outboard the com antennas can go, make sure they won’t interfere with the aileron push tubes, and similarly check for interference for the blade antennas. But this setup gives me a little over two feet between the two com antennas, a little under two feet between the com antennas and the ADS-B, a good 3.5’ between the ADS-B and transponder, and over five feet between the coms and the transponder.

Works for me.

 

So that’s it for today. I still need to put away a lot of the stuff I removed today, and then maybe I should review the riveting instructions for the forward bottom skin – that’s been deferred for way too long.

Posted in Fuselage | Hours Logged: 3.5

Just organizing stuff

Not putting any hours on this since I don’t consider it active aircraft work, but over the past few weeks I’ve been accumulating a lot of small stuff – connectors and associated stuff to go with my electrical junk, and then today a pile of cushion clamps and snap bushings from Aircraft Spruce. Most of this stuff has been sitting out on tables since it came in.

So I went to Harbor Freight a couple days ago and once again increased my inventory of storage boxes, then just started unpacking and storing stuff tonight. Now, among other things, I have a case full of connectors and terminals and a whole bunch of D-sub backshells:

Some less-great news: the conduit I ordered from Amazon, which was intended to be used to route the pitot controller wiring extension, is way bigger than I anticipated. I guess I was thinking that the conduit diameter specified was the OD, when in fact it’s the ID. So this stuff is kinda huge. And so now I need to order some more. Maybe if I get the order in tonight it’ll come Saturday, it’s like that pitot extension thing is my white-whale task or something.

On the other hand, I also got my AP roll servo mount kit, so I can get that installed on the right wing. I am really thinking the next big thing to do is get the tail feathers back off the fuselage. I think I keep putting it off because it looks so much more like an airplane with them on there…

Posted in Workspace

Finishing the aileron trim system

Since I’m in a seemingly perpetual state of waiting for things for my primary work on the wings, I’m sort of reduced to finding smaller punch-list type items to work on. The aileron trim system has kind of been hanging over my head for a while. Some of the preliminary work was done a while ago; when I was working on the seat ribs, I got the necessary brackets riveted in place. But I got hung up on one part of the system, which is fabricating the pushrod.

Making this piece involves working with a length of aluminum tubing; drilling three 1/8” holes in one plane, then adding a slot 90° to that plane on one end to allow it to mate with the clevis on the trim motor. I made an attempt at this previously, but it didn’t go so well. I did a poor job of keeping all the holes in one plane, and eventually kind of put the thing aside in disgust. Well, tonight was the time to revisit this.

I don’t know if I’m just better at fabricating now or what, but I had no real trouble getting this done tonight. Don’t get me wrong, it was tedious at times, but not terrible. I drilled the three holes first, then went to work on the slot, which I started with a 1/8” hole, then started the slot with a couple band saw cuts, before spending a whole lot of time slowly widening it with a tiny file.

The resulting holes aren’t 100% perfectly in line, but they don’t really need to be. Overall, it looks pretty good, I think:

I’d intended to get the whole system temporarily installed in the fuselage for illustration purposes, but I only got as far as installing the servo and pushrod. One thing to notice here is that the two holes not used for connecting the pushrod to the servo now have cotter pins installed in them. This trim system works by spring bias; on each side of the control column, a spring will run from the cotter pin on that side to the small bracket seen on the column here. Actuating the servo just changes the balance point of the system.

I stopped at this point because getting those springs hooked up was not proving to be easy. I’m wondering if it’s permissible to trim the spring ends a bit to facilitate installation; right now both ends form a sort of full circle, so they have to be pried apart to hook onto anything. I dunno, and I don’t see any reason to figure it out right now. I’ll probably be flying initially without the springs in place, so as not to mask any rigging issues like a heavy wing.

But hey, here are things in the fuselage:

Now what next? You know, I think it might be time to pull the tail feathers off again. I still need to flip the fuselage back over and get the forward bottom skins riveted. That might also be a good time to pick locations for my antennas and get those mount holes drilled, even if I don’t permanently install the antennas yet. I guess that makes another thing I’ll need to go and order…

Posted in Fuselage | Hours Logged: 2

Mostly more staring

Once again, it’s been one of those days when all the effort seems to be mental, and very little happens from a physical standpoint.

One note from yesterday: after doing some reading, I decided against my idea of temporarily mounting the left wing so I could locate the conduit penetration. Sounds like that would be at least a three-person job, and I’m not sure the benefits would justify the effort and risk – besides, I don’t think there’s real reason to do it right now anyway.

To start the day, I decided to evaluate my idea of going back to running the pitot lines through the conduit, and I did this in the most practical manner possible – by cramming examples of the wires I’d need into the tube, along with the pitot lines. Here I’ve got two 12AWG wires (power/ground for the pitot), one 22AWG (pitot heat status), two 18AWG (landing/taxi light power), and the big shielded wire for the nav/strobe light units. It all fits quite nicely, so I declare this idea to be feasible. This at least settles one packaging concern.

Next, I moved on to looking at the pitot controller. I still can’t finalize the wiring run to the pitot location until I get some supplies, but I figured I could at least work on the connectors a bit. One problem here that had to be solved was with the two 26AWG white wires that go from the controller to the tube. These twisted pairs end in Molex micro-fit connectors, and a couple weeks ago, while trying to clumsily de-pin one of them, I pulled the wire out of the contact. I ordered a proper removal tool from SteinAir, only to find that apparently I need two of them to de-pin, since each pin has two tabs, and the tool only has one prong.

I’d already ordered the necessary parts a while back, including extras, so I just decided that I didn’t need to de-pin after all. I just cut off the old connector, crimped on two new pins, and installed them in a new connector. Done. Also good practice for when I build the intermediate harness later on.

Also, while I was in a crimp experimentation mood, I decided to give my D-sub crimper a try. I cut off a small length of 22AWG and grabbed pins, sockets, and a connector for good measure, all from my last SteinAir order. Crimping the pin was super easy, as was inserting it into the connector with the insertion tool I got from Amazon. Extracting it was a different story – turns out buying this tool from Amazon was a poor choice. The extraction end is malformed and unusable. So now I have a test pin inserted into a connector and I can’t remove it. Fun.

This pretty well transitions into what I spent the rest of the day doing, and that was compiling yet another round of orders. I knew I wanted a actual non-crappy D-sub pin tool from Stein. I also wanted to order the conduit from Amazon that I was looking at last night. Oh, and I wanted some cushion clamps to use for routing the wires at the wingtip, once I had all the materials to actually mount the pitot controller.

And of course, since I was ordering stuff, I wanted to maximize the utility, so there was lots of looking forward to other wiring stuff and adding items. In the process, I sort of firmed up my plans for components under the seat pans – mainly terminal strips for interconnects to wing wiring stuff, but also rough location ideas for the Flyleds controller boards for the nav lights and the landing light wig-wag function.

Now I just need to go actually complete these orders. The real question is, how many days will it be before I realize I need even more things? Also, how much of the cost of building this plane will have gone directly to UPS and FedEx? I don’t want to know…

Posted in Electrical, Wings | Hours Logged: 1.5

Staring at things

I’ll tell you, the more time goes by, the more I really come to understand the whole “90% done, 90% to go” maxim among builders. In my mind, I have a whole roadmap of things to be done, mostly revolving around getting the wiring done. Yet every time I go to try and move forward on that, it seems like there are myriad little hangups preventing forward progress.

As of today, I’ve received all the wiring stuff I ordered. A whole lotta wire in various gauges and colors, an absolute boatload of D-sub components from SteinAir, plus the relay and diode I’ll need for tying the busses together. The general goal of this was to be ready to permanently install the conduit runs in the wings and get all the wiring pulled, and specifically the first thing I wanted to address was getting the pitot heat controller installed with its extended wiring harness.

And yet…after thinking about how to run the wiring from the controller to the pitot location, I’ve decided the smart thing to do would be to put in a short run of split loom conduit from the wingtip to the pitot bay. If I were to ever need to replace that wiring, this would vastly simplify the process. It also provides better wiring protection, and finally, enables me to satisfy a concern I had about the wiring service loop.

I’ll need enough slack in the wiring to allow the pitot to be removed from the mount until I get to the preinstalled disconnects. But with no good access to the pitot bay, the best I can hope for is just cramming the wire in there and having it floating around unsecured. It’d probably be OK, but the thought bothers me. With the conduit, though, I can keep the service loop normally at the wing tip, where I can secure it carefully. If I need to remove the pitot, I can just feed the extra wire into the conduit, providing the slack needed at the mount.

The downside is that, well, I need some conduit before I can move forward on that. The good news is that I can get that from Amazon and have it here early next week with free shipping. But it’s still a wait…

That brings us to the next hangup of the day. This started with me thinking about the holes I’ll need to cut in the fuselage sides to allow the main wiring conduit to protrude inside, but that moved into a different question related to the pitot tube. I’ve been planning on running the nylon pitot/AOA lines though snap bushings in the ribs alongside the main spar. But then I have to figure out how to get them into the fuselage. I can’t just make penetrations right in line with the line locations, because on the fuselage that’s where the spar center section structure lives. There’s an existing hole nearby, but that’s where the aileron push tubes pass through…routing lines through there seems unwise. So if I stick with location, I’ll have to route the lines in the tight space between the wing root and fuselage aft to some sort of passthrough.

The more I think about this, the more I end up back at my original plan, which was to route the lines through the wiring conduit. Then it can enter the fuselage at the same place as the wiring, thus simplifying everything quite a bit. Additionally, the lines can exit the conduit at the wingtip, and go through the same flex conduit as the controller wiring, and have the same service-loop securing setup as the wires. That has a nice tidiness to it.

The question just remains: how well will everything fit? Well, at least I now have the materials needed to make that evaluation. Something for tomorrow’s to-do list, I guess.

So that brings us to the one bit of tangible work for the day, though there’s an amusing twist at the end. This returns us to the question of making the fuselage penetration for the main conduit. A while back I came up with the idea of making a template that I could use to locate those holes, and tonight I decided to put that into practice.

Basically, the idea was to locate the conduit relative to the bottom of the aft side of the spar. This wasn’t too hard, just required some careful work with a try square, ruler, and other fun stuff. I then transferred my measurements to a piece of scrap 1×4, and drilled a #30 pilot hole. I figured I’d eventually use this to drill a pilot hole in the fuselage, which I’d then enlarge with a unibit.

With the pilot hole drilled, I did a visual test against the conduit bracket on the inboard rib, and it seemed to line up well, so I added the last piece: another scrap 1×4 piece screwed 90° to the other one. The idea is that this piece is slid into the center section and held against its aft side, providing the reference needed to locate the hole.

Here’s the finished piece, sitting by itself and then held in place on the fuselage:

 

Now, for the amusing twist: I’m not sure I’m going to use this after all. After attaching the 90° piece, I did another sort of test-fit against the end of the wing spar, and then it seemed the hole wasn’t lined up well at all. Granted, this is probably because I had to hold the piece much further from the conduit bracket, but that just made me think that there’s a lot of slop in this setup, and so my overall trust in it is pretty low.

I’m thinking that just figuring out a measuring scheme I can transfer to the fuselage is smarter. Maybe first measure the distance from the bottom of a wing rib to the bracket center, ensuring I’m square against the rib when I do it. Then I can make on the rib where the line intersecting the bracket hits the rib, and measure the straight-line distance from that to the intersection of the rib and the spar. That should be easily transferable to the fuselage, and seems more reliable than my template idea, which kind of feels like the old telephone game where intermediate reps end up garbling the original message.

I’m also thinking now about just seeing if Josie can help me…well…very temporarily install a wing on the fuselage. This would have a couple benefits: I could then run the conduit through the wing in question and directly trace its outline on the fuselage, and have a lot more confidence in the hole location. I could also measure the clearance between the inboard rib and the fuselage at that location, which would help me trim the conduit to final length, and thus eliminate a source of trial-and-error when the time comes to more permanently fit the wing.

Will I do it? I dunno, we’ll see if I still feel positive about the idea after a good night’s sleep. Though first I guess I’ll be finishing up my Amazon order…

Posted in Electrical, Wings | Hours Logged: 2.5

Landing light mounts

So today’s task was to work out the landing light mounting. Way back when, I bought the Duckworks leading edge landing-light kit, and at that time I’d intended to use some sorta-nonstandard Whelen lights, and so the kit I ordered came with blank mounting plates – rather than, say, having an existing cutout for a PAR36 bulb.

In the intervening years, Flyleds became a thing, and I went with their combo light, which we’ve seen before. One of the nice things about this combo light is that it fits in a PAR36-sized cutout (though the unit is a lot deeper than a PAR36 would be), so it’d work great with that Duckworks mount…if only I had it. And in fact. I did consider just ordering two new mount plates, but in the end it seemed stupid to not at least try to cut the mounts I had.

And really, the task is pretty simple. Vertical positioning of the light is a no-brainer – just put it on centerline. The horizontal position is more interesting, though – the mount spans the entire bay in the leading edge, but the cutout is small, so the light obviously needs to be aligned with the cutout. So I spent some time with a ruler, reaching inside the bay, to measure the distance from each rib to the corresponding side of the cutout, and the width of the cutout itself. Armed with this information, I marked off the rough size of the light on the plate – a 4” square (technically it’s round but the square works fine for this). Then I installed the mount in the wing and verified the lineup. Actually, I did this twice, because the first time I measured a bit wrong and put the mark an inch off. Which is, of course, why we start with just marker…

This photo (and a few subsequent ones like it) is a bit awkward – the wings are still in the cart, leading edge down, so I’m basically shooting up from the floor to get this angle. Yeah, I did a decent amount of squirming on the floor today:

With the position verified, it was time to make the cutouts. I actually decided to make these about 4.25” instead of 4”, to provide a little more clearance for some of the components. This ended up being unnecessary, for reasons we’ll cover later, but oh well. My fancy hole-cutter tool, which hadn’t been used in some time, made short work of this:

Next I did some more positioning lines, which allowed me to position a light unit in each mount, and use the prepunched mount holes in the lights as a drill template for the mounts. This gave me my mounting screw locations, and allowed me to cleco the lights into the mounts for the first time:

Now, that photo – in particular, the way the lights are located behind the mounts – belies a whole ton of head-scratching. At issue was the question of how exactly these lights would be installed (and potentially removed for maintenance at a later time). Put simply, there seems to be no way for the lights, as delivered, to be inserted into the bay of the leading edge. There are two possible avenues here – in through the leading edge cutout, or through the lightening hole in the outboard rib.

It does seem to be possible to get the unit in through the leading edge cutout, but only with the taxi light projector removed. That would mean installing that thing inside the wing, a somewhat fiddly operation thanks to the long screws and springs involved (that is, the mechanism for aiming the light). I did not like this idea at all, so I decided that I’d plan on going in through the rib. The catch here is that the installation process for these will entail first installing the mount, then installing the light. That, in turn, means that if I’m putting the light in through the rib, it has to go behind the mount.

Still, there was the problem that the light wouldn’t fit through the rib hole either. The useful news here is that while the combo light circuit board is rectangular, the actual circuit traces are confined to a 4” circle. The rest of the board is fair game for trimming to fit a particular application, and that’s exactly what I did.

My original plan was to mark a circle just a bit larger than the mount cutouts, and use that to trim the boards, retaining two “ears” where the screw holes were located. This plan lasted about as long as it took for me to try and figure out how to trace the cut line with a marker. That was challenging enough, but making the cut would be not much fun either. So I decided to start small, and simply mark 45° cut lines starting at my potential mounting “ear” locations. I figured worst case, if those cuts weren’t good enough, it’d be material I’d be removing anyway for the circular cut idea.

Removing the corners still didn’t quite allow the light to pass through the rib, but by simply trimming a bit off the top and bottom of the boards, I was in business. It still takes some careful maneuvering to get the light through, but it’s doable. The resulting trimmed light unit has a sort of elongated octagonal shape:

This just left the question of attaching the lights to the mounts. Normally, if you were installing the lights from the front, you’d install nutplates on the back of the mounts, to receive the mounting screws. That wouldn’t work in this case, so there were two options: either install the nutplates on the front of the mounts, so the mount screws were installed from inside the wing, or install the nutplates on the light itself, so the screws would go in from the front. The latter seemed like a better option: first, I wouldn’t have unsightly nutplates visible in my landing light cutout, and second, trying to line up the screwed working through the lightening hole sounded like no fun.

So I drilled the lights for the nutplates and got them installed, and then, it was finally time for a full-up test fit. First, the mount went in, then the light, and the result looks pretty good:

From the back side of the bay, we can see that the heat sinks have plenty of room:

So that’s pretty much the end of this bit. The one remaining question is how I’ll handle the wiring for these; this is particular interesting since the wires for the three landing light projects attach on the front of the unit, while the wires for the taxi light attach on the rear. I intend to run all four wires to a single Molex connecter in the wingtip, and I’d like for the wiring pigtail to be removable along with the light unit; so I may have to get creative with that. Worst case, i guess I could just use two two-position connectors instead of a single four-place. In any case, I can’t really do anything with this until the wire comes in.

So now I guess I gotta figure out something else to do that doesn’t involve wire. Maybe I should dig up the aileron trim servo and see about getting that system done; I worked on that years ago, got frustrated, and moved on. Perhaps I’m better skilled now than I was then…

Posted in Electrical, Wings | Hours Logged: 4

Aileron hinge service bulletin

All right – so over this past week, I’ve been kind of getting my focus refined. As I mentioned last time, the whole reason I got started with this systems planning exercise was so I could get a rough estimate of a wire order, and in turn be ready to get the wing wiring runs pulled. That goal has been achieved, and this past week I placed several orders for a bunch of electrical stuff – some crimp terminals for general use, what I hope are all the D-sub connectors and pins I’ll need, some Molex connector supplies (which I intend to use for the wingtip light connections), and last but not least – about three-tenths of a mile of wire. Seriously.

With that done, it’s time to refocus on the original sort of strategic task – getting the wings closed up. One task that kind of holds that up is completion of a service bulletin on the inboard aileron hinges. The service bulletin relates to spar cracks emanating from the rivets that attach the hinge brackets. The fix is to add a rather beefy doubler on the inside of the spar. Getting this done on a flying aircraft has to be a whole lot of fun, though it’s not required unless cracks are found. Since my wings aren’t closed up, and I have good access, I’m doing it as a preventative measure.

To start with, the brackets have to be removed, which means drilling out eight rivets per bracket. Nothing too exciting here, other than being really careful not to damage the spar. Fortunately, with the factory heads on the outside, if anything’s likely to be damaged, it’s the brackets themselves. That’s no fun, but it’s way better than mangling a spar and maybe having to build a new wing.

About halfway through taking the rivet heads off. Sorry, photo turned out a bit blurry:

After removing the heads and punching out a few rivets, and having the bracket come loose:

And here we are, a bracket-free spar:

Next up is fitting the doublers. Each spar has two doubler pieces, both made of heavy alclad angle material. One doubler covers the rivet holes on both sides of the bracket, the other doubles again (triples?) the outboard rivet holes. The result is a sort of U-shaped assembly on the spar, like so:

There is, however, a small catch here. Those doublers are nearly the height of the spar, and as such their ends sit pretty close to the spar. Multiple people on VAF have expressed concerns with being able to set the adjacent skin-to-spar rivets. Not only is there no room to get a bucking bar in here, some folks report there’s not even room to put a blind rivet in these holes.

Fortunately, Van’s has approved removing the corners of these doublers,. This doesn’t compromise the strength, and opens up a good bit more working room. It’s simple to mark and make the cuts necessary.

The doublers as delivered:

And after removing the corners for clearance:

After getting those all smoothed and deburred, it was time for some riveting, and before long, I had installed aileron brackets once again:

This was a really straightforward procedure, honestly moreso than I expected. I’d been dreading doing it a bit, I guess just from the general idea of drilling around my lots-of-time-invested wings, and maybe due to a little PTSD with how the horizontal stab SB went. Nice to get it all knocked out in a single day.

So now what’s next? Well, in the process of all that systems planning, I was thinking about how the wing wiring will enter the fuselage. There’s no holes in the fuselage in that area, other than the ones for the aileron push tubes, and obviously I’m not going to be running wiring through there. What I’d like to do is just have the wing conduit runs extend into the fuselage, with the wires then routed to their connection points under the seat. This, of course, will require adding holes in the fuselage sides, but the real fun has been trying to figure out how to locate them so they match the conduit locations. I can’t just easily hang the wings on there and mark it with a sharpie.

So what I’ve been thinking about doing is making a drill jig, which can locate off the rear of the main spar. I can fab this up using the wing as a guide, then put it on the fuselage using the carry-through as my reference point, and make my holes. it won’t need to be ridiculously precise, as I can make the holes slightly oversize compared to the conduit OD. It’ll still be a little nerve-wracking making that hole, though, especially since it’ll be months before I get to find out if I did it right…

I suppose something else I could be working on is fitting my landing lights to the mounts in the wings. Maybe I can get the nav/strobe lights mounted in the wingtips, too. Neither of these are really blocking closing out the wings, but they’ve gotta be done at some point, and I guess it might as well be now.

Of course, as I type this, it occurs to me that I’ll probably want to pull wiring for the roll servo in the right wing before I close it…which will probably work best if I have the servo on hand…I’ll at least want the bracket in there before I close anything…oh right, I need to pull the pitot lines in the right wing before I close it too.

OK yeah, there’s plenty to do.

Posted in Wings | Hours Logged: 3

General systems planning

I’m only calling this one shop hour, even though I’ve spent a whole lot longer over the past two days with this stuff. This is just me drawing a (somewhat arbitrary) line between being out in the shop doing stuff vs. sitting inside with a laptop researching until my brain turns to jelly. If I logged all the latter time I’d probably be close to 2000 by now…

Anyway, the shop time mostly revolved around continuing to play around with component locations. I’ve ended up adjusting things a bit more, though I don’t have any photos of tweaked layouts this time around. The first big change was to the lower shelf. Even though moving the CPI2 ECU off of it made it less crowded, I still wasn’t really happy, and I eventually decided to relocate the voltage regulators to the baggage bulkhead, which turns the lower shelf into basically just a fuse block shelf.

The nice thing about this is that I can move the block around a bit and make the layout a lot more logical – which I count as a win, as the essential-bus architecture can be a bit weird at first. The new layout will better visually show what’s going on. Another benefit is that I don’t have to make this shelf as wide as possible any more. Instead, I can make it just as narrow as the upper shelf, and not worry about it interfering with the gear towers, and also bring wire bundles up around the ends instead of having to go through the shelf with a snap bushing.

Now, the downside to this change was that I needed to move the Skyview backup batteries off the baggage bulkhead. Packaging these was proving to be a pain, since they were kind of wide and flat…but then I came up with the idea of stacking them and putting them right beside the CPI2 backup battery. They’d be no taller than that battery, and have half the footprint. I figured I could just cut some aluminum tube spacers to go between the top and bottom batteries, but the thought of finding the necessary hardware (ie some long screws) was interesting.

But then I came up with an even better idea – mounting the two batteries vertically. I can pretty easily fabricate a small vertical “wall” of sorts, and then just have one battery on each side of it, and instead of needing long spacers and longer screws, I can just use short screws and nuts. It doesn’t really save a lot in terms of footprint, but it’ll be a lot more elegant.

It’s actually kind of bothersome to me that I can only work this stuff in hypotheticals, using little cardboard mockups and imagination. I’d really like to have this stuff on hand so I can do some real packaging work! But it shouldn’t be that much longer – at this point I’m planning on making big purchases probably around the end of August. I don’t know what kind of lead time I can expect on avionics orders, but hopefully I’ll have a lot of this stuff on hand by mid-September.

In the meantime, I can be focusing back on airframe stuff…like the wings. This whole systems planning odyssey came from me wanting to get materials to wire up the wings, and not wanting to make a bunch of piecemeal wire orders, and thus feeling like I needed to at least rough out systems stuff so I could get an idea of wire materials needed. I think at this point I’ve kind of surpassed that…but it’s so much fun…

This leads to the major effort of the weekend, which was just doing the grinding required to gin up a bill of materials of sorts. I did some rough measuring in the airframe of expected wiring distance between various locations – avionics shelf to panel, shelf to switch console, console to underseat (where wing wiring terminations will happen), back to the rear shelf and to the tail, etc. This was information I could use to rough out wiring distances between various components.

A lot of the wire runs are pretty simple. Network and serial data wires can all be plain old 22AWG white wire. Power wires are a slightly different matter – here you can picture me spending a few hours refreshing my knowledge on wire sizing, and working out the proper gauges for power supplies. And there’s also multi-conductor shielded wires for certain applications. All of this information then got applied to the distance chart I’d made earlier, and the end result being a big list of wire types/gauges and required lengths.

The end result comes out to a total of a little over 1300 feet of wire, of various sizes, types, and colors. I’ll end up ordering more than that – I figure that on average, adding about a 15-20% buffer is a good idea. I’d definitely rather have too much than too little, especially when it comes to the super-common 22AWG white stuff.

I also spent a bunch of time researching tools, and ended up ordering a few more crimping tools, some tools for inserting/removing pins in D-sub and Molex connectors. Still left to do is to work out a starting order for connectors. The easy part will be D-sub connectors, backshells, and pins – this list is pretty well dictated by my equipment, and not long. The one thing to consider is that I want to have service connections on the upper forward shelf, which will probably be D-sub, and I’ll need to plan those out. I also expect to use some Molex connectors in a few select places as well. I don’t expect to get that list 100% right off the bat, but I at least anticipate using them at the wing tips for connecting the pitot heat/lights/etc. Got to think that one through a bit.

One final end result that I’m strongly considering is to redo my electrical schematics kind of from scratch – an idea I do not take lightly, as I’ve invested a ton of time in them already. But the current ones are divided into various sheets mainly from a functional standpoint – one sheet for power distribution, one for all the simple switched stuff, etc. I think what will serve me better as I move towards building up harnesses will be sheets divided by physical location – so the forward upper shelf can be one (or more) sheets, and can depict the service connectors I want to add. These sheets should be a lot simpler to translate into harnesses, and also more useful for troubleshooting down the road. I probably won’t start this immediately, though, since the layouts will depend on final packaging, which I don’t expect to nail down until I have all the avionics on hand.

Anyway, that’s the weekend in a nutshell. Not a lot to show in terms of hands-on stuff, but I feel like I’ve gotten a lot done, and I’m definitely getting excited about systems stuff, despite the challenged involved.

Posted in Avionics, Electrical | Hours Logged: 1.5

Forward systems planning, again

Nothing too crazy tonight, just continuing with last night’s proceedings. I’d intended to start out by making a cardboard cutout for the upper shelf and starting with that. kind of like I did last night, but I decided instead to go straight to whiteboard drawing this time around. It has its detractions – most notably, I can’t use lay stuff down on a flat surface and visualize, I’ve gotta draw – but on the other hand, I didn’t have to start by cutting cardboard, and I could potentially adjust the shelf dimensions depending on what I found by trying to place stuff.

Probably the most notable thing I decided to roll with right off the bat was to try moving the CPI2 ECU from the lower shelf to the upper once. As mentioned last night, I wasn’t a huge fan of how crowded the lower shelf was. This may or may not be a decision that sticks – I’m going to make a VAF post when I’m done writing this to ask some questions about the CPI2 system, specifically opinions on how accessible the ECU should be. One of the nice things about this is that Ross Farnham, the owner of SDS, is very active on the forums and helpful. This is, in fact, one of the things that prompted me to go with the CPI2 ignition.

Anyway, the final thing that became evident tonight was that just the two shelves weren’t going to cut it for all the behind-the-panel stuff. This isn’t a huge deal, as I also have the backside of the baggage bulkhead I can use here, and that’s a pretty common place for -8 builders to put stuff. With this decision made, though, I think I have a pretty solid layout for this area – pending, of course, responses to the CPI2 questions, which might throw all this in disarray. But that’s the way things go.

First up is the revised lower shelf. Here, I just replaced the CPI2 ECU with the voltage regulators for the two alternators. I could probably put these a little closer together and gain some room with the fuse blocks, but that’ll be something to experiment with another time. This is, after all, still in a sort of rough-draft phase:

Next up is the upper shelf layout, which ends up being nice and roomy for everything. This shelf could actually be made wider, but I’ve intentionally drawn it so it’s narrow enough to pass through the space taken up by the main panel – if I ever needed to remove the shelf for maintenance or whatever, I could do it. Here I have the EMS unit on the left, the remote com radio center, and the CPI2 ECU and its backup battery on the right. I’ve also got what should be ample room to accommodate all the connectors here, particularly the large ones on the EMS (including a 37-pin D-sub):

And finally, a really rough look at the stuff on the baggage bulkhead. Here we have the Skyview network hub on the right, with the ARINC-429 interface box beside it. The ARINC-429 box is what will allow the Skyview system to talk to the Garmin GPS-175 certified GPS, and the location here is nice since the back of the GPS-175 tray will be close at hand (basically high and center). On the right side are the two backup batteries for the two Skyview EFIS screens:

I’m pretty sure that covers all the stuff that needs to live back here. I think at this point I probably need to review my electrical schematics and make sure I really have covered everything, and then…well, I guess it’s maybe time to see about fabricating shelves, These will be mostly simpler than the crazy aft shelf, but there will be the additional complication of the hinges for the lower shelf. Also, it’s possible my trashed wing skin may not be workable for these. Hopefully I’m wrong about that, since ordering sheet from Aircraft Spruce will make for some really expensive shipping…

Posted in Avionics, Electrical, Fuselage | Hours Logged: 1