Pitch trim wire routing

Well, so far there’s been no ship notification for the replacement canopy rail parts I ordered on Monday, which may very well mean that I won’t have those on hand before we head off for our road trip. Meanwhile, I found some time in between trip prep to do a little more work, this time on the pitch trim servo wire routing.

First step was to get the horizontal stab back in place. This was way more fun than it should have been; having that turtledeck skin in place makes attaching the stab way more interesting. Despite my best attempts, I couldn’t figure any way to reach inside and put any of the attach bolts in place from inside. I guess this is just going to require the services of someone really small – it’s going to require going even further into the tail than I went while riveting. I made do for now by just dropping the bolts in place from above to at least sort of hold the stab in place while I worked. One thing I want to figure out is whether or not it’d be sensible to go ahead and final-attach the stab, though it’s not a critical decision at all.

Next up was working the actual wire routing. I decided to add another adel clamp on one of the stab attach bolts to guide the wire up and over the rear stab spar. From there it’ll be attached to the elevator control horn tube, which will of course move with the elevator itself. I added a small snap bushing to the inboard elevator rib for the wire to go inside and connect to the actual trim servo:

Actual connection to the servo will be done by way of bare D-sub pins (ie not inserted into a connector). By using these, and staggering the wire lengths, the result is a nice and compact connection that’s also watertight (the whole thing will be covered by heat shrink). I’d fully intended to get these terminations done tonight, but after a lot of thinking and visiting schematics and thinking about how the trim works, I’ve decided to wait until I can actually test the trim system.

The reason for this is that since I’m staggering the wire lengths, it won’t be easy to switch the two trim wires if I get the polarity wrong, and after all that reading mentioned above, I don’t feel super confident in my ability to reason out which wire goes where. There’s no real reason not to wait until more stuff is wired up to do this, either; it just cost me a little bit of satisfaction tonight.

Posted in Electrical, Fuselage | Hours Logged: 1.5

Canopy rails, misc systems stuff

I picked up this morning with work on the center canopy rail I started on a few days ago. I got all the rivet and screw holes laid out along the rail cap piece, which is what’s used as a guide for all the drilling. As mentioned before, it took me a bit to figure out the plans here, but the gist is that there are eight screw holes a specified distance apart, and between each pair of screw holes are five rivet holes, which make the spacer and cap into a single T-shaped piece.

So I started out by marking the screw hole locations and drilling them initially to #40. That let me cleco the rivet fane between each pair of holes and center punch the rivet holes in between. With that done, I clamped the spacer onto the cap and drilled the screw holes up to #30. This was where the first thing went wrong for the day; since it takes a bit to get the drill through that thick spacer piece, I wasn’t really good at anticipating when the drill would break through, and once I had a few holes in the wood block I was backing the work with…well, on one hole the bit broke through and barely even slowed down, and so I ended up making a nice little circular scratch with the drill chuck:

This was bothersome to me, since this is going to be a very visible part of the airplane that also likely won’t be painted…so there are limited options for getting rid of this ugliness. Now, this hole will eventually be countersunk for a #6 screw, but the screw head is still smaller than the scratch, so that wouldn’t help. I came up with the idea of maybe upsizing to a #8 screw, and to test if that would actually cover the scratch, I intentionally marred a piece of scrap and then worked on countersinking it, and found that I could cover the scratch if I was liberal with the countersink, putting the screw head just below flush.

So with that in mind, I kept going, moving on to drilling the rivet holes in the assembly. Everything seemed to be going well until I separated the parts for deburring and eventual countersinking, and found that the other side of those rivet holes were…let’s say inconsistent. Apparently my attempts to hold the drill bit square to the rail cap failed pretty miserably, and I drilled the holes in various states of crookedness. Still, the visible part looked OK, so I thought maybe the slightly off holes might be OK…until I tried countersinking them, at which point it was obvious they were crooked enough to cause problems with the countersink cage.

At that point, I decided it was settled that these parts were officially junk. Fortunately, the replacement cost isn’t bad at all – under $20 for the parts from Van’s – but I’m sure the shipping will be a bit interesting since both pieces are about 4’ long. Oh well, that’s the way things go.

Before ordering, it seemed prudent to look at the other two rails, just in case I fouled those up too. At least then I could combine the shipping cost for the parts. These are the two rails that sit on either side of the canopy, and they’re made of some C-channel type extrusions. Interestingly, the back end of each channel is precut at an angle to match the bulkhead behind the rear seats, but the rails still need to be trimmed at the front end. Marking these was a little interesting since they’re not a nice square cross-section, but trimming them wasn’t a big deal.

The more interesting part is that the forward end of the rails overlaps with the roll bar base, so the bottom forward corner of each rail needs to be relieved so it can sit flush elsewhere. This just required some careful rough cutting with the band saw and dremel cutting dock, followed by fine-tuning everything with files. In the end, I got a nice tight fit with the base:

Unfortunately, that’s all I can do with the canopy right now. Next steps would be to install the center rail on the fuselage and clamp these side rails into place, then start working on fitting the canopy frame, but…yup, no center rail for me. So I ended up crawling back inside the fuselage to reassemble some stuff I removed for riveting clearance. First up was reattaching the wire bundle in the aft most bay; I had to remove the the zip ties holding to the pad mounts to have clearance for bucking rivets. Was definitely a lot of fun getting my arms back in there; well actually, I could only get one arm in for aft pad. Turns out starting a zip tie one-handed is an interesting challenge.

Next was permanently installing the ADAHRS mount. This is attached to the longerons with blind rivets, because there’s simply no way to get a rivet gun back in here. I guess screws would have been an option as well, but I don’t really intend for the entire mount to ever be removed, except in the case of a major systems overhaul way down the road. A side note here: the little “pop” you get when the stem breaks on a blind rivet is a whole lot louder when it happens inside an aluminum cone.

But hey, with the network/OAT connectors…reconnected…along with the static line, these are pretty mush ready to go. Only thing remaining will be routing the pitot and AOA lines back here at some point. Original plan here was to run them uninterrupted from the wingtip, though I’m kind of considering putting in disconnects inside the fuselage at the wing root, simply so I can go ahead and get the lines routed back here. I’m pretty on the fence about that.

Oh yeah, look, a photo:

Finally, for one more random systems thing, I took care of some routing for the elevator trim cable. This will come up through the aft deck lightening/access hole; I went with the same anti-chafe setup I’ve done elsewhere, just taking some of my surplus static line, splitting it, and slipping it over the edge of the hole. Then I added an adel clamp to hold the wire in place where it passes through the hole:

Now I just have to figure out what to work on while I wait for parts. Kind of thinking I may go ahead and mount the empennage again, this time for what might be the last time – though I should be careful making pronouncements like that. With the empennage in place I could go ahead and finalize the wire routing and disconnects for the elevator trim servo. I could work on the tail light wiring as well, though that would require getting my hands dirty with the fiberglass rudder fairing.

The other complicating factor is that we’re two weeks out from heading out on a three-week road trip. I’d been hoping to make some good progress on the canopy before then, but it seems unlikely that’s going to happen – I imagine the last week pre-trip isn’t going to be super productive on the airplane. Hopefully I can at least get the replacement rail parts in, and get the center rail in place for future fitting. If I can get the canopy trimming done by the end of October or so, it should still be decently warm during the days, keeping potential cracking as a smaller concern.

Posted in Canopy, Electrical, Fuselage | Hours Logged: 3.5

Turtledeck riveting complete

Another fairly short session. Nothing much to really report, we just went at it one more time with me compressed in the tail, and got the rest of the riveting knocked out. Now I’ve got a nice smooth tailcone:

So this should clear me to get going on canopy stuff. Tomorrow I should be able to pick up on getting the rear slide rail riveted together, and maybe fitted to the fuselage as well.

Posted in Fuselage | Hours Logged: 1

More turtledeck riveting

Well, we didn’t have a ton of time to put into the airplane tonight, but we still made some progress, which is always preferable to none at all. We finished riveting all the bulkhead rivets, and got through the remaining longeron rivets in the aft most bay. This should represent the most unpleasant of this work, so hopefully the rest will be a relative cakewalk.

Getting back into that bay was definitely a challenge; even fitting my upper body through the next bulkhead up required some careful positioning, and once I was in there, I couldn’t really move my arms around a lot..though I did still manage to get yet another fun selfie:

On the other hand, the back of the fuselage is looking nice and smooth now. Just got that one line of holes on either side left to do:

Posted in Fuselage | Hours Logged: 1

Some turtledeck riveting, center canopy rail prep

Today didn’t go quite as I’d planned, but we still ended up OK. I’d been figuring on getting started riveting early, while it was still relatively cool outside, but in short I underestimated the work I needed to do before we were ready to actually do the riveting.

Before I did anything else, I decided to climb into the fuselage (without the turtledeck skin in place) to get an idea just how unpleasant it would be going back in the tail. The main thing I discovered out of this was that the gap left after making the platforms yesterday just wasn’t going to work – that hole was right where I needed to support myself while really far back in the tail. So the first order of business was making one more small platform section – but it was raining until about 8:00 or so, and I didn’t really want to sling a bunch of MDF dust in the hangar, so that had to wait a bit.

There was also a bit more prep work to do. I got out the rear seat shoulder harness anchors – which get riveted along with this skin – and figured I’d better double-check the bolt hole for the belts. Good thing too, it was a bit undersize and needed to be final-drilled and deburred. That would have been no fun working inside. I also went ahead and slipped the attach bolts in place, figuring they’d be harder to install after riveting the anchors.

Finally, I had to actually get the skin in place and clecoed, along with the harness anchors, and also drill that one botched hole up to #30. By this time I was already getting a good sweat on, so after talking to Josie we decided to put off riveting until the evening when it cooled off again. I did go ahead and work on some riveting that I could do solo – more importantly, it didn’t have me lying in the tail baking. That took care of the forward- and aft-most bulkheads, along with the rivets in common with the longerons about half the length of both bays – all told, maybe about a quarter of all the rivets.

I did stop at some point here just to get a photo of the cave I was going to be dwelling in later that day:

Not wanting to waste a holiday, I moved on to starting canopy work. The first portion of canopy fitting is just fitting the slider frame, and the first part of that is working with the rails that the canopy slides on. There’s one rail on each side of the cabin, plus a third atop the tail cone that the back end of the canopy slides on, and that third rail was the first thing to work on.

The rail comes in two pieces; first, there’s a narrow piece of thick stock, which has already been bent at one end to the required contour. This bent end drops into a receptacle just behind the back seat, and the canopy will drop into that receptacle when closed. However, the tip of the piece needs to be trimmed to a bit to sit properly inside that receptacle, so I got to spend some time carefully filing a taper on it:

The other piece of the rail is a wider strip of Alclad, which sits atop the thick stock piece. In assembly, this creates a sort of T-section rail, along which a block will actually slide. The strip needs to be bent to match the contour of the other piece, an operation that took quite a bit of trial-and-error. As can be seen here, it also comes oversize, and needs to be trimmed to final length now that I’ve got the contour matched up:

Next up will be laying out a bunch of rivet and screw holes on that strip; the rivets will join the two pieces into one units, while the screws will attach it to the actual fuselage.

That got us through to later in the day, when it was finally time to rivet. This went pretty well, and while it wasn’t enjoyable, it also wasn’t as miserable as I anticipated. Of course, we only worked on the forward bulkhead, so I haven’t yet had to slide back where it’s really tight. Makes for a decent selfie though:

Fortunately, the fan I rigged up alongside the fuselage worked pretty well for making it more tolerable back there. The real problem was that while lying back there, I was staring at a concave reflective surface. Remember those funhouse mirrors who you were a kid? This was kind of like an extreme version of that setup, made even worse by my eyes seemingly not wanting to quite focus on the reflection. The effect was pretty trippy, and an attempt to get a photo just doesn’t really capture it, but still looks amusing:

So that takes care of one night – we just got the rivets around the canopy receptacle, plus the forward bulkhead and the harness anchors. It doesn’t seem like a lot, but it also takes care of the more complex pieces (this session required four different rivet sizes, plus adjusting the gun pressure several times). I think the next session should go a lot more smoothly; we might not finish (unless we do a really long session) but I don’t think it’ll require more than two more…and then it really becomes canopy time…

Posted in Fuselage | Hours Logged: 4

Prep for turtledeck riveting

First up this morning, before heading over for the usual Sunday morning coffee across the runway, I got Josie’s help with dimpling the rest of the turtledeck skin. There weren’t a ton of holes to take care of here, and we were doing quite well until one, where I had her reposition a bit and then didn’t double-check I was still aligned with the dimple die. Fortunately I was only slightly off, so instead of making the traditional figure-eight double hole, I just slightly elongated it. For the moment, I just hammered it flat again; for one thing, I wasn’t 100% sure how I’d approach the fix, and for another, the elongated hole meant that trying to redimple it again immediately would be tough, since it was hard to tell which end was the “right” one. Something to let my mind work on in the background.

Next, while it was still cool and I had a second set of hands, I reinstalled the transponder and ADS-B antennas, using caulk on the outside to seal them and the permanent locknuts on the inside. Then it was time for coffee, plus working on the museum’s Helio Courier. (almost got the annual done so we can fly her!)

Back at work this afternoon, I had my plan for fixing that elongated hole. First up was going to be correcting the dimple; from there, I could evaluate what other action was needed. To fix the dimple, I minimally clecoed the skin in place on the fuselage; this way, I could use the matching hole in the upper bulkhead to properly locate the dimple. The plan was to use the pop-rivet dimple die in the assembly hole, even though I knew it wouldn’t make a full dimple. Then I could remove the skin and use the shallow dimple to properly locate the final thing. Not only did this work out quite well, but the final hole was only slightly elongated by the time I was done. What I’ll do when I reinstall the skin for riveting is drill the hole up to #30 and use a NAS1097 rivet here; that should give me a nice quality result overall.

Finally, I needed some work platforms to go in the tail. The lower skin is pretty flimsy, and there are also the bulkheads sticking up – basically, there’s no way to safely lay back in the tail without some kind of provisions. Some folks stuff foam between the bulkheads, but the plans include dimensions for fabricating plywood back boards to go in the bays and rest on the longerons, which should be much better for load bearing than the skins or bulkheads.

Originally I’d considered borrowing the boards from my neighbor – he bought an -8 project and it came with the boards already made – but after looking at my setup and thinking it through I decided to make my own, for a couple reasons. For one, this won’t be the last time I need to crawl back in the tail, so these are probably things I should just have on hand. Second, because of the way I have the wiring routed with the rear avionics shelf, the plan-specified boards would need some modifications anyway.

I further modified the plans a bit – while they called for a single large board in each bay, I chose to make two boards for the aft bay. The main reason was that this worked well with the scrap MDF I had lying around, but I think this will also make it easier to get the boards and and out if I need them down the road for maintenance. For the forward bay, I made what was intended to be the forward half board, but it ended up fitting further back than I expected. I’m going to initially try things with just these three boards, and see if the gap bothers me – if so, I can always cut one more narrow board to go in the space where the avionics shelf normally is.

We’re going to take advantage of the holiday tomorrow and see if we can make some good progress on riveting. I’m not sure if we’ll get through it all before it gets obnoxiously hot in the hangar, but we’ll try. The plan is for me to be the lucky soul wriggling back into the cave and bucking while Josie does the shooting from outside. I’m hoping I can get a fan rigged up somehow to blow air through the tail while I’m in there, otherwise it’s going to be pretty miserable. Well, I’m pretty sure it’ll be miserable no matter what, but at least a fan would reduce the misery a bit.

Posted in Fuselage | Hours Logged: 1.5

Tail cleanup and prep

Today was just getting stuff ready for the tail riveting, roughly along three lines: removing stuff from the tail area and cleaning, working on the turtledeck skin, and making sure there’s nothing else I want to get done before turning the tail into a cave. The first part was pretty self-explanatory: I removed the avionics shelf and ADAHRS mount, then gave everything a good once over with the shop vac.

For the skin, I removed the vinyl film, cleaned up all the edges, and deburred the holes. Unfortunately I then realized while reviewing the construction manual that I’d never final-drilled the holes that will be common with the aft side skins and the longeron – these were to be done with the skin off the fuselage, since the corresponding holes on the fuse are already drilled and dimpled. So I did the match drilling and then redid what amounted to about 2/3 of the hole deburring I’d just done. Finally, I applied a slight bend not he lower edge to help it sit flush against the aft side skins, and dimpled all the holes I could reach with a squeezer. The rest will have to wait until Josie can give me a hand tomorrow morning.

Finally, there was the issue of remaining tail tasks. The plans call for drain holes ahead of each tail bulkhead, which I never did, so I finally added those today. I also removed the zip ties I’d used to secure the rudder cables in the tail; the slack is now just hanging out the sides of the fuse (this would have been a poor choice when I was still rolling the fuselage on the rotisserie).

The one remaining item I want to take care if is permanently installing the transponder and ADS-B antennas. Only the former is actually confined in the tail, but I might as well take care of both fo them. For these, I just need to remove the plain nuts I used for the temp install and use lock nuts and star washers, as well as applying caulk to the outside to ensure there’s a good seal at the antenna bases. These will also have to wait until Josie can give me a hand.

At this rate, I might be spending my Labor Day doing some riveting (and probably also copious sweating)…

Posted in Fuselage | Hours Logged: 2

GPS-175 rack fixed

I started out tonight by getting to work on some cleanup. The main purpose was to get my big work table cleaned off so I’d have space to work on the turtledeck skin; along the way I got some stuff out of the fuselage as well and just generally rounded up tools and loose wire that had been lying around since I was neck deep in building harnesses.

Once I got the table cleaned off, I was about to pull down the turtledeck skin…but sort of on a whim, I decided to take a stab at fixing the GPS rack. Fabricating a new pair of angles would be a little tedious, but probably not too bad. First I wanted to confirm my suspicion that the rack was mounted too far back – to do this, I removed the rack from the panel mounts, installed the backshell, and put the GPS unit in, snugged as far as it would go. No big surprise, when I flipped the power on, it powered right up.

So I got to removing the panel and moving it over to the work table, where I then removed both HDX screens and the knob/intercom units. I knew I was going to be making some metal chips and didn’t want to get more into those guys. Drilling out the rivets in the mount angles was no big deal, but once I removed them, I discovered something interesting. I don’t remember doing it offhand, but apparently the first time I dabbed these angles I decided the GPS was sitting too far forward, so when I riveted everything together, I added a thin spacer between each angle and the panel.

It’s not easy to see, but the spacer is visible here, edge-on to the camera, with the rivet stumps still sticking up:

This was potentially a useful discovery – what if simply removing the spacers was enough to get the backshell to engage with the unit? So I went to work finishing the extraction of the old rivets, then clecoed the angles back into the panel and attached the rack. Back over to the fuselage, panel back in the plane, backshell reinstalled, and GPS snugged in, it was time to flip the switch, and…it came on. Before declaring immediate victory, I gave the backshell and rack in general a good wiggle, just in case the engagement wasn’t good enough to be secure in, say, bumpy air. I wasn’t able to get the unit to power off this way – very nice.

So that settled it – no need for fabricating new parts after all. I pulled the panel back out, got the angles riveted back in place, reinstalled all the avionics, and put the panel back into the plane. At long last, it was time for the full-up beauty shot I couldn’t quite get to previously:

So here we are – I’m running out of excuses not to get that turtledeck skin riveted on. Guess I’ll be sweating in that little cave in the not-too-distant future…

Posted in Avionics, Fuselage | Hours Logged: 2

Pitot line routing, done

So as alluded to yesterday, today I basically started from scratch with this routing issue. After a night of thinking I concluded that I definitely didn’t wan to keep using the conduit, based on how difficult things were yesterday. Routing the lines separately using snap bushings will make it difficult-to-impossible to service/remove/replace them without pulling up the seat floors, but surely no worse than the wrestling I did yesterday with the conduit.

With that in mind, I spent a lot more time tonight staring inside the fuselage and trying to decide where to place the passthroughs. There were really two principal questions: First, for the routing between the rear spar carry through and next bulkhead aft, should I go inboard or outboard of the outer seat rib? Going outboard would mean needing to be sure I stayed clear of the flap pushrod, which would in turn probably require some careful securing of the lines in a tight space. Going inboard would make things easier to get to, but would put them closer to the rudder cables. That said, the rudder cables are less of a concern, since they’d be running parallel to the lines and thus would be easy to keep clear to prevent chafing.

The second question was what to do once through that second bulkhead – at which point I’d be under the baggage floor. I could either continue straight back, go under the avionics shelf, through the next bulkhead, and then route the line upward, or route above the shelf, along the fuselage side, and go through an existing snap bushing hole up high. This was pretty much a tradeoff of where I wanted to do fancy securing of the lines – in the former case, all the careful routing would happen aft of the bulkhead in open space, whereas with the latter I’d have to be much more precise to make sure the lines didn’t spend their entire lives tubing against the backside of the baggage floor.

Well, actually, there was one more question: Did I want to drill pairs of holes, routing each line through a separate small snap bushing, or larger individual holes with the lines going through together? At first I was going to do two separate holes, but upon further thought I felt that a single larger hole would be preferable, mainly to make potential servicing a bit easier down the line, but also to simplify laying out the hole locations.

So after lots of hemming and hawing, I went with 1) routing inboard under the seat floor, 2) routing straight back under the avionics shelf, and 3) using a single hole in each passthrough. With that decision made, the rest of the work was pretty straightforward.

First up are the forward passthroughs. The lines run alongside the rudder cable here, but are separated both laterally and vertically, and the short span between the two bulkheads means there’s not much chance for the cable to rub the lines. Still, I may go back and add a zip-tie pad on the outboard rib, just to keep the pitot lines secure and separated in here:

In the next bay aft, the situation is similar, except there’s a much longer run between bulkheads, which means more opportunity for the cables to meet the lines. To help prevent this, I added a zip tie pad on the lower skin, to ensure the lines stay laterally away from the cables. Here I’m just holding the lines in place for the photo op:

Finally, after going through the last bulkhead, we get to route upwards and pick up the adel clamp I drilled for yesterday. In order to keep the lines securely clear of the rudder cable, as well as the edge of the longeron, I added a second adel clamp further up the bulkhead. With both clamps in place the lines are held quite securely:

Slightly different angle of the routing:

Finally, I also decided to add some security to the short static line run from the bulkhead aft of the ADAHRS mount. Previously the line was free to move around – probably not a big deal since there were no sharp edges to encounter, but I still wanted to tie it down a bit better. So I added a zip-tie mount to the forward mount angle, where I’ll attach the line once everything gets final-assembled. Also, looks like my phone camera chose poorly with the autofocus, oh well:

So now…well, I guess I’ll pull those two lines right back out and start clearing and cleaning the inside of the tail for getting the turtledeck skin in place. Though I’ve still got to do all the deburring and dimpling on that skin, but that won’t take long at all. Also I need to clean off my big work table for the work on the skin, which will also be handy for the impending canopy work.

Posted in Fuselage | Hours Logged: 1.5

Pitot line routing

Well, I thought this would be a pretty straightforward evening of work. All I needed to do was to pull the pitot and AoA lines back through the conduit and figure out how to route them to the ADAHRS shelf. This seemed so easy that I even considered not doing it prior to riveting on the turtledeck skin – after all, surely I could just figure this out later on. Fortunately reason won out, because this routing was nowhere near as straightforward as I expected.

Basically, the issue revolves round picking a good route where I can secure the lines and ensure they stay clear of moving parts back here. The principal concern is the rudder cable which, over time, would merrily saw right through these lines, but there’s also the elevator bell crank and push tube to worry about, though staying clear of those is a lot easier.

After a lot of hemming and hawing and staring and scratching my head, I thought I’d hit upon a workable solution – pass both lines through the same lightening hole as the transponder antenna cable, secure all three together using the standoff I added for the coax, and then have them arc nicely up to where an adel clamp on the longeron would secure them.

First off, while getting the first line through the conduit was easy, the second was not at all – it really wanted to get bound up in there. Second, once I had the adel clamp positioned and clamped down, the lines didn’t want to fall and stay clear of the bulkhead like I wanted. After fighting with them a bit, I eventually decided it was one of those times to call it a night and revisit another day.

Already, as I sit inside in the air conditioning, I’m rethinking routing the lines through the conduit. I wanted to make the lines easy to service if needed, but given how hard feeding them through was, I don’t think I’m achieving that goal at all. I’d probably be better off to run them outside the conduit, just using some small snap bushings to pass through the rear spar carrythrough and the other couple bulkheads in the way.

So yeah, no photos or anything tonight, but just more things to maybe rethink and redo. Such is life sometimes.

Posted in Fuselage | Hours Logged: 1.5