Fuselage

We continue creeping ever closer to getting this riveting done. Tonight we finished up all of the really annoying riveting around the aft seat ribs and also shot a handful of rivets at the rear seat lap belt anchor points. At this point I feel like the tough riveting is behind us (for the time being, that is), and it should be downhill from here. Hopefully we can get this wrapped up tomorrow…I’m kind of getting tired of sitting on the garage floor under the fuselage…

It’s done! I got a bit ahead of myself last night be declaring all the annoying riveting to be done. It turned out there were still some challenging spots left, most notably the rivets at the lower aft end of the mid side skins, where they curl underneath to the belly. The radius of the curl is pretty small, which forced me to use a narrow bucking bar on several of the rivets, and I also had the outboard aft seat ribs in the way as well. There were a couple rivets here that we had to drill out and re-shoot – this was entirely due to me having trouble keeping the bucking bar in place due to the cramped quarters.

Once we got those done, though, it was smooth sailing. We shot all the rivets between the mid bottom skins and the aft portion of the center section (the forward line will be riveted later in assembly with the forward bottom skin). Then we shot all the rivets along the lower edge of the forward outboard seat ribs, plus a few assorted rivets I couldn’t quite get to by myself.

That just left ten rivets on each forward side skin, in the area of the gear towers. These were more fun than some of the others and required some fresh contortions. While the cabin and tail area of the fuselage is open at the top, there are two braces across the cabin at the tops of the gear towers, which I had to work around to buck these rivets. All in all it wasn’t especially challenging, just uncomfortable. I can’t imagine, though, how horrible these rivets would have been had I not done the removable gear tower cover modification. At least I had nice big holes through which to hold the bucking bar.

While I was down there, I decided to try and grab a selfie to illustrate my discomfort. Here I’m leaving against the sawhorse that’s supporting the fuselage. There’s just enough room between it and the brace for me to get my upper body in there:

But once these were done, that was it – the end of this riveting odyssey (for the time being, at least). Once I crawled out from under the fuselage and retrieved all my tools that had collected down there, we rolled the fuselage upright again, for the first time in – let’s see – three weeks. Looks much sleeker without a few hundred clecos sticking out:

I also took care of some other tasks during the day today when Josie wanted to go inside and rest for a bit (I have to remember that working the rivet gun is probably a little more physically challenging for her). I finished demurring the replacement seat ribs I got the other day, match-drilled them with the spacers that will sit on top of them, and riveted the nutplates in place. Those angles are now ready to rivet in the near future.

Most notably, I riveted the seatback support plates to the mid side skin bulkheads. I had originally planned on doing these after we’d rolled the fuselage upright again, but after looking at them while sitting under the fuselage, I decided they’d be easier to do this way. These plates were challenging to rivet, since I had to hold the bucking bar inside a cramped space between the plate and skin. At one point, I seriously considered ordering some expensive Cherrymax blind rivets to use here, but eventually I managed to get them all shot.

Next steps will be to rivet the cockpit rails in place (should be a solo job, I think), and then permanently attach the seatback support. Then we’ll roll the fuselage over once again, and it’ll be time to fit the landing gear legs!

Finally, with the fuselage back upright, I can start moving forward through the construction manual again. I’d figured I’d get the cockpit rails riveted – or mostly riveted – tonight, but there ended up being more small things to do than I thought.

First up was finally torquing the two lower bolts which attach the seat ramp angles to the center section. These bolts have been loosely installed for some time; they weren’t tightened because they had to be periodically moved to allow for shooting rivets. The rivets through the center section and the mid bottom skins were the last ones of concern here, so the bolts could finally be torqued. Doing this was kind of fun; holding the bolt involves reaching inside the center section, and there’s not much room in there. I ended up with Josie reaching in from the outside to hold the wrench while I leaned over into the cockpit and tightened the nuts.

Next up was installing the rear seat lap belt brackets. These slide through slots in the bulkhead webs, in between the aft lower longeron and another bracket mounted above, and three AN3 bolts hold the assembly together. The fit here is pretty tight, and I had to do some tapping with a hammer to get the brackets in place, and also to get the bolts through the holes. Getting the nuts started and torqured wasn’t much fun either – at one point I was lying on my back on strategically-placed pieces of lumber in the fuselage.

Here’s a shot of one of the brackets in place. Note the bulkhead to the left, leading to the cabin. The nuts are barely visible under the bracket. Note also how the bracket curls upward away from the fuselage skin. This made it fun to hold the bolts while torquing the nuts:

Next up, I riveted the finished floor support angles in place. This required some creativity with riveting, since the angles are close to the mid side skins, and the seat ribs also restrict access with, say, the squeezer. I was able to squeeze four of the rivets, but had to shoot the other two using an offset rivet set – and holding the gun in a weird backhand way, squeezing the trigger with my thumb.

I started unclecoing the center section bulkhead caps, preparatory to clecoing the cockpit rails into place, but I realized that the left cap needed a little work. Way back when I was working out the rear throttle linkage, I cut holes in the bulkhead web for the pushrod to pass through – well, matching notched were needed in the cap flange. I figured it would be easier to cut and tweak these holes now, without the cockpit rails in the way, so I did that:

A look at the aft notch with the cap clecoed in place (through a mirror, because there’s no way to get a decent direct shot):

Finally, I could cleco the rails in place. It was getting close to quitting time by this point, but I went ahead and squeezed six rivets on each side for good measure:

I’m pretty sure I’ll be able to squeeze most of these rivets, and the ones I can’t squeeze should be easy to shoot. The only exceptions, I think, will be the rivets behind the mounting plates for the seat back support. I may need to recruit help for those…hopefully I won’t have to lie on lumber in the fuselage to buck them. Further along in the planes are instructions for cutting plywood into work platforms for the tail – I might go ahead and make those for times like this. I’m also thinking that it might be time to go buy a cheap Harbor Freight engine stand to make a rotisserie out of – a lot of the work tonight would have been a lot easier if I’d been able to turn the fuselage sideways instead of leaning over. Actually, come to think of it, riveting the cockpit rails would also probably be easier with the fuselage sideways…guess I might be making a stop on the way home from work tomorrow.

Last night, I mentioned thinking about going ahead and building a rotisserie for the fuselage, and I hadn’t changed my mind by the time I left work today – so I stopped by Harbor Freight on the way home and picked up a cheap 1000-pound engine stand. I also went by Home Depot to get some pieces of angle iron and a few bolts and nuts.

The general idea of the rotisserie is to go ahead and drill the engine mount holes out to 3/16” (not their final size) and use these to attach the angle iron in such a way that the firewall can then be attached to the engine stand. The tail can simply be supported by the tailspring, and the fuselage is turned by simply turning the engine stand.

The first issue evident once I got the engine stand assembled was that the upright wasn’t vertical – the digital level actually showed it off by about 3°. In order for the rotisserie to work properly, I want it to be pretty close to dead vertical. So began a long series of tinkering with the thing, trying to figure out ways to straighten it. There’s no kind of adjustability for this, so basically I just started figuring out ways to reassemble it incorrectly that would tweak the angle. But nothing seemed to work right, and eventually I resigned myself to needing to buy some more hardware to make this work.

I’d given up for the night when I had another idea for tweaking the thing – and this time, it worked. The upright is now just .3° off dead vertical, which I figure is close enough for government work. So tomorrow or Friday, I should be able to attach the angle iron pieces to the firewall and get this thing put together. Then I can finish riveting those cockpit rails…

Tonight’s goal was pretty simple: finish the rotisserie. And I did it – slightly more tedious than I expected, but it turned out pretty nice. First on the list was to drill the engine mount holes to 3/16” through the firewall to attach the frame. There are prepunched holes in the firewall for these, but the spacers just behind them have a seam right in the middle of the hole. I wasn’t confident I could drill from the front and keep the bit from wandering. Fortunately, there are also prepunched holes in the weldments inside the cabin, so I drilled from there instead. It was a little more annoying working inside the cabin, but it worked great.

Next up, I cut the two angle iron pieces for the vertical frame pieces, drilled the top and bottom holes in each, and bolted them to the firewall. That was straightforward, but now came the fun part: the horizontal pieces. I wanted to line these up carefully to put the center of rotation in the center of the firewall. Well, not exactly the center per say, but the point equidistant from the “corners” of the firewall. This was to ensure maximum clearance when rotating the fuselage. I’d laid out this center point yesterday, and so today I used that as a reference to position the lower horizontal angle. With that clamped in place, I drilled the holes to attach it to the verticals, then used those holes to lay out the bolt holes to attach the angle to the engine stand mount plate. I used those holes, in turn, as a template to drill the same bolt holes in the upper horizontal.

Finally, I bolted both horizontals to the engine stand plate, then bolted the lower horizontal to the verticals. After leveling everything carefully, I drilled the last two holes to bolt the upper horizontal to the verticals, and added the bolts. Everything got torqued down for good measure, and it was ready to go into the engine stand base:

Looks great, but there’s one problem: the angles are a bit too wide, and the mount plate unit can’t slide far enough into the base to allow me to insert eh locking pin when I’ve rolled the fuselage to the desired position:

I actually started to quit of the night, thinking I’d need to trim the angles somehow, but then it occurred to me that there was a ridiculously simple solution: just drill a new hole in the base for the pin, allowing the plate to sit a bit further out:

To roll the fuselage, I just move the tail sawhorse so the tailspring is sitting on it and acting as a pivot point. That sawhorse already has a v-shaped cutout, so the tailspring naturally remains in one spot (other builders have mentioned needing to make sure the spring doesn’t roll off the sawhorse). Then I can roll the fuse to any position I need:

Now I can get back to riveting those cockpit rails!

Tonight I just worked on the cockpit rails. Well, first, I cleaned up from last night, since I left tools out all over the place after finishing the rotisserie.

About a third of the cockpit rail rivets are accessible with the squeezer; the rest obviously have to be shot with the gun. This is slightly challenging since there’s only a small flat area around the rivets, then there’s a bend that has to be worked around. All in all, though, the riveting was pretty easy, especially with the new ability to rotate the fuselage sideways. I’m pretty sure this would have been a lot less pleasant if I’d had to lean over the rails to rivet.

The only real challenging part was the area where the seatback support plates are already in place. After checking the construction manual, I realized that the original build sequence is to rivet the cockpit rails first, then the plates – so I kind of did this out of order. That would have provided much better access to the rails, but also would have made it a lot harder to rivet the plates. It actually wasn’t that tough riveting under the plates, but I had to get creative to buck them. Somewhat amusingly, I don’t think this is the first time I’ve duct-taped a bucking bar to a stick:

There was also another issue that came up here. On the left side of the cockpit, the longeron sits a bit low, and as a result the mid side skin sticks up just a hair above the cockpit rail. By the time I realized the consequences of this, it was too late – I’d put a nice series of dents in the skin while riveting the rails:

Fortunately, I was able to do a decent job smoothing the area out with the rivet gun, and then I filed down the excess skin a bit. It’s not perfect, but it looks much better now. I believe this area will eventually be covered by the canopy skirt anyway:

Finally, I masked everything off so I could shoot the interior paint on the rails. I’s previous debated whether to paint this like the interior, or maybe have it match the exterior – obviously, I decided on the former.

The rotisserie really came in handy here. The texture paint shoots best on a vertical-ish surface – easy to do with the rotisserie, basically impossible otherwise. The finished product:

This does present an interesting problem for tomorrow – this texture paint takes a while to dry. I usually try to leave it alone for a couple days at least. The next task is mounting the seatback support, which involves working in the same area. More notably, it involves shooting some more flush rivets on the rails, which I didn’t think of before painting – I was mostly thinking it would be easier to mask for paint without the support in place. I’ll probably just skip shooting those rivets for a week or so to let the paint dry, and even then I suspect I’ll have to do some touch-up afterwards. Oh well.

So this actually covers some short work sessions both from Saturday and today. Saturday turned into an interesting day; I’d found an interested hangar home for sale by its owner a few days before, and we contacted the guy and decided kind of on a white to go check it out that day, since the man was available to show it. And it was pretty cool, and pretty affordable, and so we’re going to try and make a move on it. So that whole thing kind of took up the rest of the weekend in research, discussion, etc. Neither of us have bought a home before, so this is uncharted territory.

But enough about that. All I got done this weekend was to mount the seatback support weldment and get it screwed/bolted/riveted in place. There are a lot of fasteners that attach this thing; I assume that it has a pretty major role in stiffening the fuselage structure around the cabin. On each side there are four #8 structural screws, eight AN3 bolts, and ten rivets. Access to those AN3 bolts is especially fun, since they bolt through the support plates. That means reaching into the narrow space between the plate and the skin and trying go install a tiny nut on a tiny bolt. Here again, the rotisserie proved its worth; by rolling the fuselage 135°, it was much easier to see what I was doing.

I was expecting the rivets to be somewhat unpleasant, but they were actually pretty easy. Torquing the bolts was far more work. So now I have a seatback support:

Bolts through the support plate:

Screws and rivets in the cockpit rail (for some reason the camera thought I was taking a photo of the inside of the plane and focused there):

With that done, I rolled the fuselage inverted again and took it off the rotisserie, back to the sawhorses:

Next up, I get to mount the main gear legs. You know, if we end up getting that hangar, it’ll be convenient that I’m to the point of mounting the gear legs. Moving this thing will be far easier if I can just put it on wheels and roll it around naturally. But I’m getting ahead of myself…

Eight months? Really? I figured it had been maybe six at the most, but 8+? Wow. Kind of reminds me of the last time I moved, when I said something like “it might be a couple months before I work again” and it ended up being six or so… This move has been even more interesting. For one thing, there was more stuff (including that pesky airplane, which got a truck all to itself), and for another, there’s a lot less space inside for storage, so getting stuff put away has been a challenge. (and to be honest, it’s still not really “done”)

But hey, I’ve got a nice roomy hangar to build in now, no more cramped garage!

Anyway, last week I made the first useful move, scooting the fuselage away from the wall where it had been sitting for a while, and flipping it over on the sawhorses. Today I first had some general housework to do (mowing and such), then it was off to Home Depot for some shop materials. Back in Atlanta, I’d built a neat little vertical rack for hanging up plans sheets. It was a useful thing, but unfortunately it became a casualty of the move as the truck filled up with stuff. I never felt like I had enough room in the garage at the old house for such a thing, so I just kept the plans laid out on a workbench. With all the newfound space, I decided it was time to build the second incarnation:

One small improvement from the last version is provision for binder clips at the top and bottom of the sheet. It’s kind of necessary out here, because it’s almost always windy, and we have the hangar doors open most of the time. Pretty sure that without the extra clips, there would be some…incidents.

So with that done, it was time for some real work, and time to finally put these nice Grove gear legs to work. The basic gist of fitting the gear legs goes like this: There are three predrilled holes in each inboard weldment, and that’s it. Only one of those holes is for the gear leg itself, where a 7/16” bolt goes through the leg. That bolt becomes the pivot point for future fitting, which involves carefully aligning the gear legs and eventually drilling the final few holes in the outboard and inboard weldments, at which point the legs better be aligned… (at least there are shims available for the inevitable alignment tweaking)

So first up, I final-drilled the predrilled holes in the inboard weldments, then put the inboard and outboard wear plates in place, followed by the legs themselves and the inboard brackets, all held in place by that single 7/16” bolt. Now, the next task according to the manual is to put the outboard brackets in place and trim the landing gear crossmembers for clearance. For the factory legs, I believe this trimming is pretty minimal, but the Grove brackets are a little bigger. My real issue, though, is that the location of those outboard brackets (and by extension, the extent of the trimming) is indeterminate until the alignment is at least roughly set. Again, maybe this is less of an issue with the factory legs, but for the trimming I’ll need to do, I felt it was best to jump ahead to the alignment.

Here again, things get fun. The method described in the manual seems pretty arcane to me, involving plumb bobs hung from the inboard and outboard portions of each leg, and another at the tail on centerline. As best I can tell, the idea is to use the bobs on the gear legs to get both legs in the same plane, and then use the bob at the tail to square that plane to the fuselage centerline. What we’re really going for is to A) have the faces of the gear legs parallel to each other (i.e. zero toe) and B) have the faces parallel to centerline. My issue with the plans method is that A) iit seems like a roundabout method to get the faces parallel to each other and B) it depends on the forward edge of the gear leg being perpendicular to the face, which I don’t trust. Here again, maybe it’s different for the Grove legs than the factory ones, I dunno.

Another builder, Matt Dralle, took a different approach that I think is kind of deviously simple. He used two long pieces of aluminum angle, match-drilled to the axle bolt holes, and bolted to each leg. He then used a sheet of plywood between the angles to get (and keep) the legs parallel to each other, leaving only the task of getting them parallel to the fuselage. I decided to modify this approach a bit, replacing the plywood with two identical-length wood planks, mainly because I don’t have a good vehicle for getting a 4×8 sheet of plywood home.

Drilling the angles was easy enough, as was bolting them in place:

Next up was cutting the planks. I just used a couple 1×4 common boards. I measured the distance between the angles at the gear legs, marked one board, double-checked the marked board against the angles, clamped both boards together (gotta make sure they’re the same length!), and cut them with the chop saw. But somehow, despite my double-checking, the resulting boards were 1/4” too short for the gap between the angles. Harrumph. But at least it was a nice round number like 1/4”. So I just grabbed some 1/4” plywood scraps and made little spacers to nail to the ends of the boards:

Much better! Now to just put them in place at the ends of the angles and see how smart I am! Except…wait…if I put a board on one end and snug the angles up to it, the angles at the other end are too far apart for the other board to even sit in there. Um, what? I looked again and realized the angles were distorted ever so slightly; if I sighted down them from front to back, they were a bit concave (as viewed from outside the fuse). So I applied some brute force to them until they were straight. That should fix the problem! Nope, same thing…hm. It turns out that the act of putting the board at the end of the angles appears to bend the ends out a bit. So I’m not just going to be able to rest the boards in place. I’m thinking that I’ll just end up clamping the boards to the angle ends to keep everything in place, and I’ll just have to add the step of sighting down the length of the angles to check that they’re straight before committing the any drilling.

We’ll see how that goes another day, cause that was where I decided to call it a day. Overall, it wasn’t huge in terms of time invested, but hey, I did something, which is way more than I’ve been doing…

So when we left off last time, I’d marked the gear crossmembers for clearance cuts, but I was concerned about edge distance. A bit of research confirmed what I was already pretty sure was the case – this is pretty normal for the larger Grove gear leg brackets, and violating edge distance here isn’t likely to be an issue. I do still think I might drop an extra rivet between the two here just for a bit more insurance.

So today, I started out by making those cuts in the crossmembers. As per usual for making cuts with corners like this, I started by drilling a hole at the corner, then used the Dremel cutoff wheel to make the other cuts. Then there was a lot of filing, checking, double-checking, filing again, etc etc, until I finally felt OK with the clearance:

Next, the forward bottom skins also had to be trimmed around the brackets. Once again, this just involved a lot of trial and error after making the initial cuts. I think I probably put each skin on four or five times over the course of refining the trim lines. The clearance is still a bit tight in some places (see photo below), but I don’t think I’m going to remove any more material right now, at least not until I really and truly align the gear and drill the holes:

So yeah, that was basically the summary of my work day. Here, just as a bonus, is a photo with the bottom skins clecoed in place:

So I started out today by removing those bottom skins I’d clecoed in place yesterday. Sure, they looked nice and all, but they were in the way for the next steps, which were…um…let me go look at the manual (for the first time in a couple weeks, I might add). Upon consulting the manual, I was a little surprised to discover that there was basically nothing left to do except actually drill the holes for the gear legs. I’m not exactly sure what other intermediate steps I expected, but there weren’t any.

So I went and triple-checked everything, ensuring the tape measures were properly lined up and straight, moving the left until they were equidistant from the tail, and then putting my sheet of plywood in place to check parallel again. Then I verified the positioning of the outboard wear plates (3/16” in from the longeron edge), reverified the gear leg positions, got out the drill and drill bits, checked everything again, etc. It’s always a bit nerve-wracking when committing to something like this – once I drill that first hole, the legs sure better be aligned, because they’re not moving without some major modifications (by which I mean probably rebuilding a lot of stuff).

Following the manual, I started with the 3/8” holes in the outboard brackets. For the drill, I left the air drills in the cabinet and got out my big hammer drill (albeit with the hammer turned off – this ain’t concrete). Copious reading at VAF had taught me that when drilling through these steel weldments, it’s pretty important to use a high-torque drill, and to drill the entire hole without stopping. Stopping means that steel that got heated up by the drilling cools of rapidly and maybe gets some heat treating along the way, making continued drilling unpleasant.

Anyway, the outboard holes went off without a bitch, aside from the aforementioned nerves when committing to that first hole. Next I moved on to the 5/16” holes for the inboard brackets, and this is where things got interesting. I went at the first hole, the drill going through nicely, until abruptly things went wonky and I realized that…the drill bit had broken. Mind you, this was a brand-new bit I bought last year for this specific purpose.

The aftermath:

I was pretty upset at first, because I wasn’t sure if the bit had broken through yet, and if it hadn’t – well, the broken part was below the top of the bracket, so extracting it would be pretty interesting. Fortunately, when I crawled under the fuselage to look, I saw that it had broken through. I also saw that I’d made an error of judgment – I’d thought there was nothing below the hole I was drilling to get in the way, when in fact there’s a sort of flange in the weldment that goes across the path of the bit at an angle. The tip of the bit was resting against this flange, so I concluded that the bit had hit the flange, caught a bit, and been deflected sideways, causing the breakage.

Extracting the rest of the bit was easy enough, but I was worried about the damage I might have done to that flange. Surprisingly enough, though, I saw only a single tiny nick – not what I was expecting at all, but in a good way. Well, that was a bit of a relief…

Fortuitously, when I ordered these bits for the landing gear, I bought two of each. Always good to have a backup on hand, right? I was certainly proving it now. I removed the broken bit, installed the backup bit, and moved on with my day. This time, I anticipated the possibility of hitting the weldment when I broke through. I didn’t have a drill stop for a bit this large, but the side handle on the hammer drill allowed me to position my left hand such that it could stop the handle when I broke through and prevent overtravel.

So again, I started drilling…and I got an almost-exact repeat of the previous attempt. I calculated I was almost through when the second bit broke! This time I knew I hadn’t gone far enough to contact the weldment, and a look under the fuselage confirmed it. So now I was just confused…the only thing I can figure, in retrospect, is that the bit was binding at the moment of break-through, hard enough that the high-torque drill just snapped it. I’m still not sure why this wasn’t an issue with the larger bit – though I imagine the larger diameter would make it a bit stronger.

In any case, the good news was that I got two of the four holes drilled, but the bad news was that I’d now destroyed both of my bits. No more 5/16” holes today. I think this time I’ll order four of the things, so I’ll still hopefully have two left over after I’m done.

I did go ahead and drill the two remaining 1/4” holes on each outboard wear plate – since the bracket holes had been drilled, everything was set in place and there wasn’t any reason not to drill the holes. There are also two holes in each inboard wear plate, but they have to be drilled from inside the fuselage, through prepunched holes in the weldments. Not sure yet if I’m going to drill those from below, with the fuselage inverted, or figure some way to drill them after the fuselage is upright again. I’ll have to think that one through a bit.

Anyway, here’s a look at the fully-drilled mounts for the right gear leg:

I’m not sure if I’ll be doing any more work until next Monday now. This coming weekend I’ll be at the MotoGP race in Austin, and most of this week will be waiting for new drill bits, followed by getting all my gear together to camp trackside. But I took the following Monday off, so I ought to be able to make that into a nice work day, I think…