More pitot planning

Well, not a ton done today or over the past week, though I did get to do some flying today (and also eat out for about the second time since March). I was able to spend a little more time looking at pitot tube position planning.

Last time we “talked,” so to speak, I was strongly considering mounting the pitot tube out by the wingtip. I did ask for opinions on VAF, and while nobody told me my idea was completely stupid, there was a somewhat general consensus of “but why?” I was approaching the question more from a “why not?” perspective, so I didn’t find this convincing.

However, the one obstacle to my planned location was figuring out how to tie the mount into the rib. The base of the mount rivets to the skin and spar, but it also requires bracing to the rib, to resist what I assume is a torsional load on the mount base, caused by drag on the pitot tube way out in the wind. Dynon provides a small piece of angle aluminum for this, but this presumes that the mount is stalled adjacent to the non-flanged side of a rib. My planned location was on the flange side, which would require me to get creative with this reinforcement.

But then I hit on a simple solution – still keep the mount at the second-most-outboard rib, but on the inboard side – then I could reinforce it as per normal. The only concern would be whether I could bend the pitot lines in such a way as to feed them through the tube and then through the immediately-adjacent lightening hole. Figuring this out required a practical exercise, and my initial plan had been to just go ahead and bend the pitot lines and experiment in real-time, shall we say.

But here’s the problem with that: those lines can be bent only once. So what if I bent them and eventually found my chosen location was no good? And then what if that bend was problematic for any alternatives? Clearly committing to the bend was not smart. I needed some sort of analog with which to test.

I spent some time poking around. Maybe some leftover fuel vent line? Huh, apparently I didn’t have any leftover. I have plenty of extra fuel line, but that’s twice the diameter of the pitot lines, and I’ll probably need more of it for fuel-system stuff down the road. Then the perfect thing occurred to me: the pile of Romex wire on a random shelf. The entire bundle is just about the same size as the pair of pitot/AoA lines. So I chopped off a piece the same length as the lines, and went to work.

The good news was that it was easy to figure out a bend that allowed for threading the lines through the mount, into the rib lightening hole, and out towards the wing tip. The bad news was that the lines only reached about halfway through the bay between those ribs. This would give me a new problem of needing to put some sort of support piece in the middle of the bay to support the ends of the lines, but the only thing to attach to would be the spar. Drilling a couple holes in it might not be the end of the world, but maybe still not a great idea.

That was pretty much the end of the wingtip idea. At this point much of the potential access benefits weren’t going to materialize, and there’d be significant mental energy in making this setup work at all.

This left two basic choices: either just outboard or just inboard of the aileron bellcrank bay. As mentioned before, the outboard location poses the possibility of interference with tie downs, but it’s also more difficult to access through an inspection cover, and also makes the bellcrank bay more crowded. So after lots more clamping the mount in various places and futzing with that poor abused piece of Romex, I settled on one bay inboard of the bellcrank.

So hey, let’s see some pictures. First, here’s that Romex, bent as appropriate to go through the mount. That 90° bend has to be pretty gradual to make it through the fairly-long mount:

And here’s a look at what the intended mount location looks like with he fake-bent tubes in place. On the other side of that rib from the mount is an inspection cover, so there will be good access here. The tubes can make a nice 90° bend through the lightening hole, and a piece of angle can be mounted to the rib to support both the tubes and the wiring from the controller. The controller will likely be mounted on the inboard side of that same rib, again easily accessible through the cover.

Overall, I think this will be just as accessible as my wingtip location, and significantly less complicated to implement. The nylon lines into the fuselage will be shorter, and can just run along the spar instead of through the conduit as I’d originally envisioned, which will make the conduit less crowded. And since this is all inboard of the bellcrank, I don’t have to worry about routing around that.

Although, as I type this, it occurs to be that the aileron push tube from the fuselage will go through that same hole I’m considering here…creating a potential interference. So I guess tomorrow I need to temporarily connect the tube to the bellcrank and get an idea where it’ll sit in here. That might be a dealbreaker, we’ll see. Maybe I’ll end up outboard of the bellcrank bay after all.

Welcome to the world of systems planning. Everything seems to affect everything.

Posted in Wings | Hours Logged: 1.5

Pitot planning

Well, today was one of those days spent almost entirely on chin-scratching. It didn’t start off that way, but that’s just because there was some more cleanup work to be done. I didn’t get around to vacuuming up all the mud dauber debris yesterday, so I did that this morning, then worked on removing some of the highly annoying artillery fungus reside on the inboard spar ends. From my research, this stuff isn’t corrosive, but at least I can remove the highly visible stuff.

From there, it was time to consider what to work on first, and after rolling this around for a bit, I decided to look at the pitot mount in the left wing. This started with a bunch of VAF reading. The factory-recommended location for the pitot is in the same bay as the aileron bell crank, but that’s also assuming you’re doing the basic pitot tube – literally just a piece of tubing that sticks out of the bottom of the wing. Installing a more complex pitot, especially a heated AoA tube like mine, is quite a bit more complex. Instead of just one line, I have two, not to mention the wiring for the pitot heat controller.

Plenty of people have adopted other locations, generally moving to an adjacent bay, either inboard or outboard. Which direction is kind of hotly debated; some thing going inboard might get too close to the prop wash, others think moving outboard makes it likely for tie downs on the ramp to interfere with the tube. There’s the additional consideration that moving the mount puts the pitot further away from any of the access covers, potentially making maintenance more annoying.

Now, all that stuff I’ve read before, but I ran across a different idea entirely today – that of putting the tube way out near the wingtip. At least one person has done this and reports no issues, and others seem to think that it should be a fine location. It’s worth noting that this is where the pitot is located on some Grumman light aircraft. I really like this idea, for a couple reasons. First, it makes maintenance access super easy. Instead of working through a small access cover, one could just remove the wingtip and have good access through the rib lightening holes. Second, there’s no concern about routing wires and tubing in the vicinity of critical control systems (the aforementioned aileron bellcrank bay).

I haven’t decided for sure to go with this, but I did spend a whole lot of time looking at the pitot mount clamped in various locations in the spar. Assuming I do go with the far outboard location, I think I’ll end up positioning the mount beside the next-to-last outboard rib, like this:

The pitot tube itself, which fits into that mount, includes two soft aluminum lines, which will connect to the nylon lines that will route the pitot and AoA signals into the cabin. There must be a minimum amount of the aluminum lines left; since this is a heated pitot, there’s the concern of that heat damaging the nylon lines. My loose plan, in this case, would be to bend those lines toward the wingtip, and install a piece of angle in the rib lightening hole near the spar. Here, adel clamps would provide security and strain relief for both the line and electrical connectors. The pitot heat controller could simply be mounted on the outboard side of that outboard rib.

Will I do this? Yeah, still not sure. I need to check in on VAF, where I posed this question and I’m sure I’ll hear some reasons why this is a horrible idea. It remains to be seen if anyone has a convincing argument. Normally “follow the plans” is pretty good on its own merits, as a way to avoid additional work, but since fitting the pitot tube is essentially a from-scratch operation in any case, there’s no additional work associated with picking this different location.

So we’ll see. If I do settle on this spot, I’ll probably go ahead and bend the aluminum lines on the tube so I can get a more practical (ie less imaginary) look at packaging, and work more towards nailing that down.

Posted in Wings | Hours Logged: 3

Dusting off the wings (literally)

OK…after a fairly drawn-out, but largely successful hangar cleanup effort, it’s time to get back to practical work on this thing. I haven’t been totally lapsing the past few months – there’s been a fair amount of time nailing down electrical design, trying to figure out how to handle financing for the FWF stuff, and so on – but work done while staring at a laptop isn’t going to get this thing flying.

The fuselage is about as done as it’s going to be for a while. There’s still the forward bottom skins to finish riveting, but that has to wait until the tail comes off, and I’m not ready for that quite yet. That leaves two overall efforts to work on: first, beginning to lay out systems-type stuff, and second, getting the wings closed up. I’m going to focus on the latter for the time being.

With that in mind, the wings come out from against the wall where they’ve been sitting for, oh, 3.5 years, and out into the nice open space created by cleanup work, and then I got started on a different cleanup effort. You see, these wings were, well, filthy. There was a general accumulation of Sport Flyers dus, plenty of spider webst, plus the requisite mud dauber nests – and not just the normal nests stuck to things, but a weird collection of mud on the sing that was closest to the wall. As best I can tell, this came from mud daubers building up in the window above, but occasionally clumsily dropping their mouthfuls of mud. Or something like that.

Anyway, I pulled the flaps and gave them a good hosing down (due to the aforementioned weird mud collection), gave the ailerons a wipe down as well, and pulled the bottom skins to get a look inside. I was actually surprised there weren’t more mud dauber nests inside the wing.

I couldn’t quite get to every part of the wings without taking them out of the cradle, which I didn’t do today. Maybe tomorrow. The main thing I have to do now is look back and figure out what order to do things in. There are several things left: a service bulletin fix on the aileron brackets, installing the pitot mount and controller, installing the conduit and pulling wiring for the landing and nav lights, actually installing the landing lights, mounting the wing tips (and, in turn, the nav/strobe light units), and riveting the bottom skins in place.

Which reminds me, I’ll need to order some wire supplies before I can pull wiring in the wings, and it’d be nice to have a general idea of how much and what wire I need for all the electrical work so I can order it all at once, so I guess I need to be thinking about at least loosely planning the wire routing in the fuselage as well…such is the fun of this part of the build, it starts to seem like everything is interconnected in some way.

In other news, I’ve been slowly accumulating some secondhand/discount stuff the past few months. I’ve got a Dynon intercom, a network splitter cable (needed for the dual ADAHRS I’m planning), and just a week or two ago, I got myself a pair of harnesses for about half the cost of a new set, and I can hardly tell they’re used. And fortuitously, VAF put together a group buy on PC5000X prop governors, which I got in on…hopefully that’ll save me a few hundred on the governor, I’ll find out the final price when the buy closes out in a week or so.

Such is the update for today…now I just have to keep that work habit going, which can be challenging this time of year. Houston summers just aren’t a lot of fun.

Posted in Wings | Hours Logged: 2.5

Rudder system rigging

Basically what the title says. Tonight I got the rudder pedals rigged up.

Last time, I quit for the night after realizing I needed the rear pedal hardware in place before messing around with the pedals. Here’s a look at what the attach between the aft rudder cables and the short ones attached to the pedals looks like. I put the bolts in here last time just so they’d have somewhere to live:

So I went poking around trying to figure out where I put the rear rudder pedal kit. That’s building in a nutshell, you can spend an amazing amount of time wandering around the shop looking confused. Anyway, once I got the kit and the proper hardware, I got the idler arms installed, and then the cables reattached. Basically, the only difference here is that the connection between the two cables also is in common with the top of an idler arm. The rear pedals are a couple plunger-type pieces that push on the tops of these idler arms.

Here’s the new/correct rigging up here:

With that done, the final step was to attach the forward ends of the cables to their anchor points on the firewall. The basic way the rudder cables function is that the cables pass through S-shaped passages on each pedal. When a pedal pivots, it “wraps” the cable with that S-shaped passage, thus pulling on that cable (or relaxing, depending on direction of movement. At the same time, if the pedals don’t pivot, they can slide forward or back (for adjustment) without pulling the cables. Kind of ingenious, really.

Anyway, at this point the resting position of the pedals are adjusted by moving around washers on the forward cable anchors. The shanks of these pieces are way longer than the holes they go through, and by changing the distribution fo washers between the forward and aft sides of the firewall, the resting position of a pedal can be changed. So the procedure is to clamp the rudder in a neutral position, and mess with the washers until the pedals are vertical. I ended up setting them up with a slight rearward angle, as otherwise they get really close to the firewall at full deflection. I can always tweak this down the road, of course.

With that done, I had a functional rudder system. Which I of course tested by climbing in and actuating the pedals. Which was cool, but I also noticed a sort of chafing noise, which concerned me. I got Josie to come out and look around while I work the pedals, but there seemed to be no single source of the chafing. Some research on VAF seems to indicate that it’s not unusual for the cables to make contact with the snap bushings that line bulkhead passthroughs, but I’m still unsure about the sound. Time to go make a post and ask.

The other thing I noticed while sitting i the cockpit is that the rudder pedal assembly isn’t as secure as I’d like. The forward-aft slide bar is bolted securely in place, but the nylon blocks at the left and right sides, which I thought were supposed to rest on the floor, don’t. Thus the pedal assembly can rock left and right a bit around the slide bar. There’s another thing to ask about…maybe I’ll need to add some spacers down there. On the other hand, if it fits tight against the floor, seems like that would make adjusting the pedals challenging, so I’m kind of unsure here.

But hey…rudders!

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Posted in Empennage, Fuselage | Hours Logged: 1

Rudder cable stuff

OK, so this wasn’t exactly the most victorious of work sessions. I’d hoped to get the rudder cables rigged up and the pedals set up properly, but I didn’t make it that far.

You see, before connecting the rudder cables tot he rudder, I needed to secure the little plastic tubes that protect the cables where they exit the sides of the fuselage. Seemed pretty simple – it’s just an adel clamp on each tube, screwed to the fuselage side. Except the manipulation required to get those things in place was made rather difficult due to lack of access to that area. The attach point is behind the first mostly-solid bulkhead, the one that has the horizontal stab attached to its top. It has two holes, the smaller of which might be able to accommodate a toddler’s arm, and the larger of which has the elevator push tube passing through it.

I got a little more working room in that larger holes by moving the elevators to full up – this displaces the tubs upward a bit – but even then I could barely get my wrist through there. Long story short, it took pretty much a solid 45 minutes to get those things in there.

This was followed by another 10 minutes trying to find the bolts needed to attach the cables to the rudder horn. I was about ready to knock it off then, but decided I might as well push through and attach the cables to the pedals, then anchor the cables to the firewall. Then I remembered that I need to have the idler arms for my rear-seat pedals in place for all this to work, so I decided to jut call it a night. Maybe next time.

Posted in Empennage | Hours Logged: 1

Rudder stop adjustment

Tonight I picked up where I left off last night, with working out a method to measure rudder travel. As alluded to previously, I ended up creating an angle reference on the floor and using that, plus a plumb bob at the trailing edge of the rudder, to get things worked out.

I’d been sporadically giving this thought throughout the day, so by the time I finished dinner I had a pretty good idea how I’d proceed. The basic idea was to draw a centerline aligned with the fuselage, mark the rudder pivot point on that centerline, and then use good old trigonometry to lay out the necessary angle reference lines, which I could then compare to the plumb bob position.

This meant I needed to to some drawing on the floor, which in turn meant I needed a surface I could draw one. I also needed to be able to secure it in place, since if my reference thing moved, it’d kind of munge up the whole works. Paper seemed the material of choice, but I needed to cover an area roughly 2’x3’. I guess I could have taped together a bunch of printer paper, but that seemed annoying. After poking around the hangar a bit, I found the perfect thing. A while back when Josie and I were doing a fair bit of shooting together, I bought an enormous roll of full-size paper silhouette targets, and we’ve come nowhere near using the entire roll. One of those, turned facedown, was the perfect canvas.I folded the sheet in half to help me initially position the paper at or near the centerline – it’d be annoying if I taped the paper down and then it was way off-center and I couldn’t draw all my angle references.

Th initial centerline was laid out using the tailspring as the reference. The one complication here was that there was no good way to hang a plumb bob right on the center of the spring – so I ended up hanging it off each side at the forward and aft end, resulting in two pairs of marks. Finding the halfway point between each pair gave me my centerline reference. I meant to take a photo of this procedure, but by the time I remembered that, I’d already removed the bobs. Oh well.

Next, I needed to locate the rudder pivot point, which would be the vertex of all the angle lines I’d be drawing. To do this, I just removed the bottom hinge bolt, ran the plumb bob string through it, and got my mark made. This time I actually remembered to get a photo (note that I also had to remove the tailspring since it would have been right in the way here):

Now it was time to resort to math. The specs for rudder travel are between 30 and 35°, and for whatever reason I decided to draw a 25° line as well. The basic idea here was to identify, for each angle, a right triangle with measurements that were close enough to normal fractions to be measured pretty accurately with jut a yardstick. That was just kind of trial-and-error: get the tangent value on my phone calculator, and multiply it by successive whole numbers until the result (the other leg of the right triangle) was relatively tidy.

Next I laid out the centerline/“long-side” measurements along the centerline, and used a square to draw perpendicular reference lines at each point. Then I could use the yardstick at each point to measure the short sides of the triangles and mark those points. Finally, I used the yardstick to draw lines from the vertex under the hinge point to each of those points.

The result is a little difficult to make out since I just drew it with pencil, but I’ve got my nice reference lines:

This was where the night got interesting. With the reference lines in place, I was able to get an idea of where my travel was to begin with, and it was way off – maybe 15° in either direction. I started filing away at one side of the rudder stop, but it was tedious work in a tight space, and I hardly seemed to be making any progress. It seemed that I was going to have to remove a substantial amount of material.

This was the point where my spider-sense started to go off a bit. Everything I’d read where people talked about installing this stop, they indicated it needed hardly any trimming at all – which was not how I’d describe the work I was about to start doing. Something here didn’t add up, and so I stopped to go do some digging.

What I finally realized was that I hadn’t set the pivots on the rudder up to spec. These are simple rod-end bearings, and they’re screwed into/out of large nutplates on the rudder spar to adjust the distance of the hinge point from the spar. When I messed with these last night, I got them all aligned so the rudder could be physically mounted, but paid no attention to any actual spacing specs. And there are very specific specs laid out in the plans, and I was pretty sure the bottom rod end was threaded in significantly more than it ought to be. This would explain why my starting travel was so small – with the rod end threaded in too far, the rudder spar was closer to the rudder stop than it should be, and thus made contact after very little travel.

The conclusion was inescapable: I needed to remove the rudder again and check those bearings. I might even have to take the thing on and off several times to get the bearings lined back up again. And I was worried something would move and all that work for my angle reference would be wasted. I actually almost quit for the evening, but that also made me worry that an errant dog might tear up my angle reference too. Eventually I decided to press on.

As seems to be the case with most tasks I dread, it was no trouble at all. Once the rudder was off, I checked the bearings – the top one was to spec, the middle was a bit wonky, and sure enough, the bottom one was in too far. But I figured that if I was strategic with my bearing adjustments, I could preserve the alignment of them all and avoid more trial-and-error. The bearings are equidistant apart, so if the upper one wasn’t moving, then all I had to do was make sure that the number of turns I put on the lower bearing was twice what I put on the center one.

Three full turns got the bottom bearing to spec, so I gave the center one 1.5, then went to give hanging it a try again. And it worked – everything lined up on the first try! And now my starting rudder travel was closer to 25° – much better.

From there, it was just a bunch of progressive removal of material from each side of the stop. I chose to stop right at the 30° mark on either side. The other spec that must be met here is the clearance between the rudder and the inboard end of each elevator. I figure more clearance here is good – the idea here is preventing those two surfaces from ever coming in contact. RVs are pretty well-known for not lacing rudder authority, so I don’t see any reason to try and get closer to the max 35° travel spec.

And the rudder stop now makes nice, even contact with the spar at max deflection:

I think my next order of business will be securing the exit sleeves for the rudder cables, temporarily connecting the cables, and setting up the rudder pedals temporarily. Then I’ll be able to sit in the cockpit and make two control surfaces move! I think I could go ahead and get most of the brake system installed in the cockpit, but I’m not sure I want to do that right now. That seems more like a thing to do closer to final assembly.

If I don’t do that, then…well, I’m about as done with fuselage work as I can be right now. I do still have riveting to get done on the lower forward fuselage, so I suppose I’ll have to remove the tailfeathers once I tinker with the rudders so I can flip the canoe over again. Then I’ll have to find something else to do – probably closing out the wings and doing some fiberglass work.

I really need to get on my bank-robbery plan so I can start ordering some expensive stuff. It’s getting to the point where systems work isn’t something I can put off any longer. Which I guess means I need to sit in the cockpit and do some more chair-flying so I can finally decide that I’m happy with the panel layout.

Posted in Empennage | Hours Logged: 2.5

Rudder hanging

Time to get back at it. Tonight I decided to see about getting the rudder hung, preparatory to setting up the proper travel.

First oder of business, dating back to when I fitted the rudder stop a while ago, was relieving the center of the stop to allow for the rod-end hinge point to move freely, since I’m mounting the stop in between the hinge brackets. To get started, I removed the lower rod end from the rudder (and wrapped tape around the shaft to make sure the stop nut didn’t move and I could put it right back in the position I removed it).

At first I was thinking of making a cardboard template, tracing the rod end’s outline, and then using that against the stop, but then I realized there was a much simpler solution. I used a couple long bolts to put the stop in place on top of the upper bracket, and another long bolt to align the rod end with its pivot point. Then I just used a Sharpie to trace the outline of the rod end:

Then I just went to town on the stop with a sanding drum on the dremel. I was surprised how little material I had to remove. I saw someone else’s build log who’d done the same thing, and they’d marked off a pretty large area to remove. It only took a couple trial-and-error iterations to get the clearance I needed. Kind of hard to tell, but in this photo the rod end is sitting inside the stop’s pocket where it was above in the previous one:

Then I installed the stop in place between the brackets, including the necessary spacer washers (because the stop is thinner than the gap between the brackets). Then it was time to get the rudder hung!

This ended up being a bit more of an operation than I expected. Way back when I first did the empennage, I adjusted the rod ends for proper alignment when mounted to the vertical stab, so I expected to have the rudder just fit nicely, but…wrong. When I installed it the first time, I lined up the upper hinge, then the center one, and…the lower one was nowhere near being aligned with the brackets. Best I can figure is that as built, the stab spar had a bit of a bend in it, which was remedied when I fitted it to the fuse and ensured alignment.

Since I used a taut string to align the brackets, I figured I’d use the same approach to getting the rod ends aligned. But there was also the question…which of the three rod ends should I adjust? Upon inspection, the center one was clearly far further out than the others, so I decided to move it in. I also used the measurement from the spar to the rod end centers as a baseline for alignment.

This ended up requiring a couple of iterations as well to get right. The first attempt after checking with the string, the center rod end was actually too far in, so I got to remove the rudder again, thread it out a bit, and try again. Fortunately, that time everything lined up, and I got the bolts dropped in. So now I’ve got a rudder in place:

Next up will be setting the travel. At the moment, the stops clearly need a fair bit of material removed, there’s way too little travel. Before I can set this properly, though, I’ll have to work out a method for measuring the rudder angle. This was easy to do with the elevators, since a digital level could show angular displacement, but that won’t work for this. I suspect I’ll end up making a sort of manual protractor drawn on the floor, using a plumb bob on the rudder to track the travel. That’s for another night, though…

Posted in Empennage | Hours Logged: 1.5

Panel-ey stuff

OK, so I’m not logging any actual time for this, which is pretty much in keeping with what I’ve been doing all along. I only really log time spent actually out in the shop. Time spent doing random research/reading/design/admin stuff I don’t keep track of (if I did I’d probably be over 2000 hours by now).

Anyway, after continuing to tweak and move stuff around in the panel design, I decided it was time to update the mockups in the plane. I decided I didn’t like the intercom in the right console after all, and put it back up on the panel. So now all my physical switches are either on the right console or at the lower left of the panel.

Basically, the left-side switches are all what I’m considering “immediate action” items – things I’d need to hit immediately in case of an emergency. Fuel pump and starter arm switches would come into play in case of a loss of engine power, autopilot servos might need to be disabled in a hurry if they went bananas for whatever reason.

Right-side switches are all less-urgent things. I might need to move these in response to an issue, but not necessarily urgently. It’s not depicted here, but what I intend to do here are sprinkle in some guards in strategic spots to help group the switches and allow for finding them by feel if necessary.

I didn’t really do any chair-flying with the new setup tonight, just climbed in long enough to get the photo and make a few token airplane noises. From here I think I’ll do some serious chair time, working through checklists and such to see how everything flows. The one concern I have at the moment is that the rearmost switches on the console seem like they might be awkward to reach. I don’t think I can put the switches much closer together, so I may end up moving the ignition switched to the right wing to live beside the CPI2 controller they’re associated with.

Always something more to think about…

Posted in Panel

Rudder stop fitting

The holidays are over! Which normally isn’t something people say in a joyous tone, but in this case it means I can start getting back into the swing of things. I spent most of today working on building some new shelves for the hangar, but set aside some time in the evening to at least touch the airplane a bit.

In the time since my last post, my internal rudder stop piece came in, which gave me the chance to plan for its install. At a glance, it’s pretty simple – the stop piece has two AN3 bolt holes, and it just needs to be positioned on the rudder hinge bracket and matching holes for the bolts need to be drilled there. The catch is that simply using the stop – which is made of nylon – as a drill template could easily result in its holes getting enlarged. The instructions called for just marking and drilling holes, but I don’t really trust the accuracy of that method.

So I came up with an alternate plan: to fab up a drill bushing that would fit tightly in the bolt hole. This way, I could drill a smaller pilot hole using the stop as a template, then enlarge the holes to #12. I couple days ago, I took the stop with me to work, and stopped at Ace on the way home and went to scavenging. I was hoping for a small aluminum or steel spacer piece, but they didn’t have any small enough – the smallest were 1/4” OD, and I needed 3/16”. The tubing section, though, bore fruit, and I ended up buying a 12” piece of 3/16” OD stainless tubing.

Tonight, I took that piece of tubing and cut off exactly half an inch of it, then slowly ground down the bushing until it just slipped between the upper and lower hinge brackets. The stop can either be installed on top of the upper hinge, or between both hinges. I elected for the latter; it should be a bit sturdier, and it also positions the stop a bit closer to the control horns. I care about this because one of the criticisms of this piece is that if the pilot pushes hard on the pedals at the stops, it induces the spar to twist a bit. This is a problem that can be mostly solved by pilot skill, but mitigating it by reducing the distance between the two points of force application seems like a good belt & suspenders approach.

Anyway, with the bushing cut to length, I reamed it out to #30 (it was pretty close already), and then it was time to get going. Basically, the procedure was to clamp the stop on top of the upper bracket, drill one #30 pilot hole, then clamp the stop between the brackets and drill through the bushing and make the matching pilot hole in the lower bracket, Then the stop came out, those two holes were drilled out to #12, and then the stop was clamped on the upper bracket again, this time with a long bolt through the drilled hole to ensure position. Then the procedure was repeated with the other hole.

Here’s the stop clamped in place, ready to drill the first pilot hole. The bushing is visible on the left:

Then clamped on top again, with a bolt through the first hole:

And finally, positioned between the brackets, with both bolts in place:

I still need to figure out the proper washer stickup to put on the bolts between the brackets. The stop isn’t thick enough to fill the gap, hence the need for the washers. I have a pretty good idea, but to get it absolutely right, I’ll need to clamp a 1/2” spacer in the bracket hole for the rod end. I think I’ll probably have to relieve the stop itself for clearance around the rod end, since I chose to put it between the brackets. Hopefully I have a spare rod end around, otherwise I’ll have to remove the one from the rudder (not a huge deal really, but it means I potentially lose my careful length adjustment).

In other news, the past two weeks haven’t been wasted. I used the ample downtime away from home to put a lot of time into refining my electrical system plan and panel layout. I think I’m pretty close to a panel layout that I’m happy with, after soliciting and integrating some feedback from folks on VAF. I need to mock up my latest design in the plane and do some chair-flying to verify that I like the folks, but from just looking at it and thinking through procedures, I think it’s pretty solid.

Here’s the current working layout (click for a full-size image). This depicts both the panel itself and the right-side console, since the latter will be housing some things that I don’t think need to be in the prime main panel space:

Panel rev2 2 copy

About the only thing I’m not 100% on here is having the intercom on the right console. The faceplate fits fine, but the unit itself would stick out past the bottom of the console, unless I build a custom one (which I don’t really want to do). I’m not sure if I’m OK with that idea or not. I played with an alternative this morning a bit, and found that I can fit the intercom on the far right below the SDS CPI2 electronic ignition controller. Gotta think on that one a bit more.

Other than that, there are some small items that are still missing, but nothing major. I’m hoping to nail this down in the next month and maybe even (gasp) order some avionics…

Posted in Empennage | Hours Logged: 1.5

Rudder control stuff

After an overnight stay in Houston for the FlightAware holiday party, we got back home early this afternoon, and I found a few hours to get a spot of work done. I decided to go ahead and attack stringing the rudder cables, even though I won’t have a rudder to connect them to until my rudder stop comes off backorder and ships (hopefully this week).

Stringing the cables is a fairly straightforward procedure; you feed them in from the rear and just slowly move them forwards. There are two sections of protective plastic tubing around the cables; a short section at the rear avoids chafing where the cables pass through the aft side skins, and a longer section further forward protects where the cables run in close proximity to the rear-seat footwells.

The cables end up passing through essentially every bulkhead from rear to front, and as the cable is threaded through each passthrough, a snap bushing is slid over the cable end and popped into place. Things get interesting, though, when you make it up to the seat floor area. This is where we need to rig that long plastic tube in the footwell area. Here, the cable passthrough is a small detachable piece on each side, which is attached to a seat floor angle with a screw. I’d already riveted the nutplates here, so it was time to do the snap bushing rigging.

We want the plastic tube to be fixed in place, so it gets secured to the snap bushing and the cable guide at its aft end. This is just a matter of cutting a small hole in the tubing, forward of the snap bushing, and threading a zip tie through that hole and the end of the tubing, to secure it to the support.

Here’s the support threaded into place:

And here it is with the zip tie installed. Note that I chose bright orange for really no reason whatsoever:

With that done, I returned to the rudder pedal assembly that I was working on last Friday. I’d mostly reassembled this, save for reattaching the brake pedals, so I got those back in place. I still haven’t installed the cotter pins on these pivot pieces – I thought about doing that today, but decided there’s still no reason to finalize the assembly yet. Then I got the pedals installed on the forward floor.

This was a bit interesting, and where my delaying of riveting the forward bottom skins caught up with me a bit. The pedals attach to two nutplates through the firewall on the forward end, and two nutplates through the floor at the aft end. Well, those aft nutplates aren’t there yet, since they’re riveted as part of the forward lower skin procedure. For now, I just put two bolts through to locate the pedals there, though it occurs to me I can cleco two nutplates in place, and will need to do so to actually test this stuff out. That’ll be another day, though.

From there, I wasn’t quite sure what to do, so I decided it was time to mock up the cockpit a bit more and start evaluating my panel/control layout. Of particular concern was the location I’d chosen for the SDS CPI2 electronic ignition system’s controller. In my mockup, it fits fine on the left panel wing, but in the cockpit, there’s a canopy rail that seemed like it might make access interesting. Also, the forward top skin/glareshield figured in here too, so I dragged that out and clecoed it into place. I also stuck in the throttle quadrant for maximum realism.

It’s really looking airplane-y now:

And then I hopped in and spent a fair amount of time just sort of chair-flying:

And lest anyone thing this was just a chance for me to sit in there and make airplane noises, I was attempting to really evaluate how the cockpit flow would work out, and I’m actually considering making some changes. For one thing, the paper cutouts I have now aren’t quite right. The displays are older Skyview Touch units, whereas I’ll be using newer HDX units. They’re essentially identical in size, though, so this doesn’t really affect the mockup hugely. More notable is that the TSO’d GPS I have is a GTN650; I think I made these before Garmin announced the much more budget-friendly GPS175 earlier this year. The GPS175 has a bit less screen height that the 650, so what I have here is a bit off.

The big remaining question is how I want to lay out my various switches. I’ve already decided that lighting and other similar stuff will go down on the right-side console, and common in-flight switches (that won’t be on the stick grip) I intend to put on the left wing panel, just above the throttle – but that still leaves me with a handful of switches to manage the electrical system. Most of these I’ll only be touching at startup/shutdown, but some will also be emergency-procedure items, ie handling in-flight electrical failures. So there’s the question of location there – I don’t want them in an annoying place no matter what, but I’m not sure how close at hand they need to be. And really, after sitting in here, the panel is so small that I’m not even sure I need to be careful about location – nothing on the panel is going to be hard to reach.

Anyway, I’m leaning towards something like this:

Panel rev2

Its not quite as OCD symmetrical as previous designs, but I don’t think it looks horribly unbalanced or anything, and I like how it moves some of the controls. Shifting the displays right a bit means that the left display (PFD) is a little closer to centerline. I may even run that screen normally split between the flight controls and engine instruments, and have the left one be all map all the time. This also moves the com radio down closer to where my hands will be, and the power distribution switches all end up where they’re easily reachable by my “free” left hand.

One thing that may be smarter would be to swap the intercom and autopilot panels. I like having the intercom panel by the radio, since they’re sort of associated, but the intercom isn’t something I’ll be messing with frequently. The AP panel, though, is way more likely to be used in-flight. Of course, functions for both the AP panel and radio will also be able to be accessed through the touch screens.

Anyway, I could go on about this all night, but I should probably sleep at some point. So I’ll just stop here…

Posted in Fuselage | Hours Logged: 2