I went out to the garage with pretty low expectations tonight. I figured I’d aim to shoot all the main wing rib rivets that I could manage by myself, and then just kind of wing it from there. Well, there were exactly three ribs I could do solo, so that took all of about…maybe 30 minutes. Josie is busy working overtime for a big work project, so I couldn’t recruit her to come out and help rivet.

One of my main short-term goals is to get this right wing skeleton finished so I can clear it off the workbench; right now workspace is hard to come by. Between Josie’s unavailability and needing to wait for that replacement rib (which should be here Monday), it seemed that being productive this weekend was going to be tough. So I decided to abandon riveting on the right wing skeleton for the time being, and we moved it over to the wing stand. That freed me up to do some more work on the left tank.

First order of business was to drill the attach screw holes on the outboard edge of the tank. These screws will go into nutplates that will be on the W-423 joint plate. This was pretty straightforward, but before drilling, I double-checked everything to ensure that the tank was in the proper place. It’s been a couple weeks since I last set it up there, and it’d be really annoying to misdrill holes because I didn’t verify alignment and such.

Here’s a picture of a #19 hole for one of the screws. Exciting, huh?

From here, I’d figured I’d pull the tank off and start looking at all the various internal parts. But then it occurred to me – I already had the thing clecoed together, and it was going to need to be match-drilled at some point…might as well take care of that now. First I pulled the tank off the spar, set it in the cradle, and match-drilled the baffle-to-rib holes. For the skin-to-rib holes, I put it back in place on the spar; the cradle limits access to some of those holes.

With that done, I marked the ribs and pulled the whole tank apart again:

I was on a roll, so I figured I’d go ahead and get all the match-drilling done. The only things left were the stiffeners for the bottom of the tank, which I cut and prepped a few days ago. So i got those out, clecoed them in place, and match-drilled them too.

The only prepunched holes that still need attention now are the attach screw holes along the aft edge of the skin. These just need to be drilled out to final size. However, I seem to recall reading something about problems with these holes cracking when dimpled. I think there was a specific approach to prevent those cracks, so I’m going to research that before I do anything.

I suppose tomorrow I’ll really get into the nuts and bolts of the tank’s innards.

Well, we had quite a day out here. We decided to run down to the beach with dogs and make a half-day or so out of it. Unfortunately, things got interesting on the way home – the car overheated. Seems I have a bit of a cooling system leak somewhere. I managed to make it home without any more overheating, but at the cost of driving with the heater running full blast. In the Houston summer heat. Actually, it wasn’t that bad on the highway, except for my feet getting thoroughly cooked. I now know that this car’s heater is tremendously effective.

Anyway, by the time we got home, I was tired again and I took a nap. Then it was finally out to the garage, where I got to work on the T-405 tank attach angles. I’m glad I decided not to try to do these last night; they weren’t terribly difficult, but there was a lot of time-consuming “how should I do this…” along the way. If I’d put some time pressure on myself to finish it last night, I might well have messed something up.

First, the chunk of angle gets cut to the rough length of the attach piece:

One side gets a symmetrical round profile, while the other is shaped to fit inside the nose of the inboard tank rib. I used one of the reinforcement plates as a pattern for this. Here’s the cut line I made on the first angle:

Roughly cut to size in the bandsaw. I did a fair amount of vixen file work to fine-tune the shape, but I can’t remember if this photo is before or after I did that:

Then it’s over to the bench grinder to remove all those nasty tooling marks and make all the corners nice and smooth:

The second angle went a lot quicker, mainly because I could just use the first one as a pattern instead of having to carefully lay out cut lines. Here’s the pair:

These will eventually get drilled to the tank ribs, but that will wait until I can get the right wing caught up with the left. Weather tomorrow looks good, so provided my local Napa has a good stock of 7220 primer, I can finally get those right wing ribs primed and then work on riveting that skeleton together.

I also took some time tonight and read through the instructions for the capacitive fuel sender kit. I can see that these tanks are going to take some time; there are lots of little details that have to be attended to. Fuel senders, access holes, vent lines, caps, drains…fun times!

So I had a good little mini-vacation this past weekend. I even got in a little flying while I was in Raleigh, doing an Arrow checkout up there. I’d hoped to be able to take my niece up for a flight, but unfortunately the weather on Monday and Tuesday wasn’t agreeable. While I was gone, my shipment from Van’s came in, in a nice wooden crate, which Josie got to manhandle into the house by herself (sorry babe). Wednesday night, I moved the crate into the garage, opened it, put everything away, and then tore the crate down. Hooray, more scrap wood! Then I took the rest of that night and last night off.

Tonight I decided to make all the tank stiffeners. These will be attached to the bottom skin between the ribs to provide, well, stiffness. After all, each of these tanks will hold 21 gallons of fuel, which weighs 126 pounds! The stiffeners come prepunched, but they’re also attached together into long strips that have to be cut to size using notches for reference. I finally learned my lesson here after making stiffeners for the tail: I removed the blue film before I cut the stiffeners to size. Much easier to remove the film from four long pieces than from 48 short pieces.

After a lot of work with the snips and a sore right hand, I had a pile of scrap pieces and a larger pile of very rough-edged stiffeners:

Then it was time to spin up the bench grinder to clean up the edges. I gave that grinder a workout tonight – I probably ran it for about 40 minutes straight. When I was done, I had a bunch of nice smooth stiffeners:

I was about 90 minutes into the evening at this point, but I didn’t quite feel like quitting, so I decided to look at fabricating the T-405 inboard tank attach angles. These get fabricated from raw angle and attach to the nose of the inboard rib on each tank. There’s also a reinforcement plate that goes on the inside nose of the inboard and outboard ribs on each tank. Since the attach angles are made to fit the contour of the nose rib, it seemed like a good idea to clean up the reinforcement plates first to use as a guide/pattern. So I broke them out, removed the film, and fired up the bench grinder yet again to take the corners and tooling marks off. Very nice:

From here, I found the piece of raw angle that the T-405s are fabricated from. I briefly considered getting started on them, but it was getting late by this point, and I was a little worried about cutting corners if I decided to try and make them tonight. So I went inside instead; I’ll probably do the attach angles tomorrow. Actually, now that I look at the weather, tomorrow looks clear. If I can restock on primer tomorrow morning, I should take advantage of the good weather and get the right wing ribs primed. Maybe I can get the right wing skeleton riveted this weekend too. Right now the right main spar is living on the workbench because I don’t have a good place to store it. It’d be nice to have that whole workbench back…

So when we left off yesterday, I’d victoriously dropped the fuel tank onto the spar, only to find that the joint plate was too wide. As such, the first order of business today was to fix that. First off, I measured the gap with the tank slid as far outboard as possible; this way I could tell what the minimum amount of material to remove would be. Turned out to be a hair over 1/8”. After removing the tank and measuring the exposed joint plate, it turned out that I needed to remove enough material to leave 11/16” of an inch showing. Which is – surprise! – exactly what the instructions said in the first place. Though, in my defense, the wording was something like “there should be 11/16” instead of “make sure there is exactly 11/6”.

Whatever. So I went ahead and marked a cut line all the way around the plate:

I’d spent a bit of time mulling over the best way to make this cut, and I eventually settled on just using the snips. The downside of the snips is that they leave a rough surface that needs a fair amount of cleanup, but about the only other method I could think of was to use a Dremel cutoff wheel, which is just annoying and imprecise. So I pulled the plate off and went to town with the snips.

it was a long and tedious process; the plate, after all, is something like four feet long, and with it being curved, that just adds to the fun. By the time I finished the cut, my hand felt on the verge of cramping. Now I had a nasty rough edge, so I broke out the vixen file and went to work. This, too, proved to be difficult, as there wasn’t much of a good way to clamp the curved plate, so I ended up just holding it in one had while I filed. If this sounds iffy, good call. In the course of the filing, I learned that a vixen file will remove skin just as effectively as it will remove aluminum.

Finally, I had the thing cleaned up, and I finished it off in the bench grinder for a nice edge. All told the cutting, filing, and general cleanup took me almost an hour.

So I put the plate back in place, put the tank back on, and all was well. Now the tank sits nice and tight against the leading edge:

With that done, it was time to drill the tank attach brackets. With the tank slid over in place, I put a couple of ratchet straps around the wing to hold the tank nice and snug:

The inboard bracket is drilled first, because, well, it’s the only one visible. These holes are kind of nerve-racking to drill, what with the spar right under them. I used a drill stop for all these holes, and I checked the thing about every five holes to make sure it wasn’t coming loose. Soon, the inboard bracket was drilled:

Next, the leading edge assembly comes off to reveal the outboard bracket, which can then be drilled:

And finally, the clecos between the tank skin and the baffle and outboard ribs are removed, allowing the interior brackets to be drilled in place:

Since I don’t really have anywhere to store the leading edge and tank assemblies, I just put them back on the spar for now. Then, I decided it was high time I got to working on the right wing, so I clecoed the right skeleton together and got it all match drilled. About this time, dinner showed up, so I decided to call it a night.

I’ll be out of town next weekend, so I guess the next opportunity to get the right ribs primed will be two weeks away. I suppose I’ll get them deburred this week so they’ll be ready to go when I get some good priming weather. In the meantime, I can work on some of the common tank pieces – there are a number of things to fab up, like stiffeners, mount plates, fuel lines, level sensors…yeah, no shortage of things to do.

Technically, I did a little work last night, but not enough to merit writing an entry. All I did was go out and finish stapling the carpet onto my C-frame table thingy, which took maybe half an hour. I also placed a nice-size order with Van’s on Friday: replacements for my damaged skins, replacement tank brackets (plus a few extra for good measure), tank sealant, and a few other sundries.

Today, I set out to redeem my bracket mangling from out last outing. First up was to drill the inboard bracket (for the third time). This time I got the center hole where it was supposed to be, squared the bracket to the spar, and drilled the other two holes. Nothing to it when you actually use a good sharp drill bit:

Next up I drilled the center bolt hole in the other six brackets for this wing. To help to this in a consistent fashion, I only measured the first bracket before drilling, and then I set up a little arrangement on the drill press table so I could quickly drill the other five brackets:

I’m leaving this in place for when I get the replacement brackets next week; at that time, I’ll go ahead and drill the six outboard brackets for the right wing as well. Might as well go ahead and get them done, even if that skeleton isn’t together yet.

From there, I went down the spar, bolting each bracket in place and drilling it using the spar holes as a guide. The work went fairly quickly, although it left a large amount of metal shavings in my previously spotless wings:

Oh well, that’s what the shop vac is for. Next, the outboard brackets get drilled for nutplates. There are nice little jigs out there for drilling nutplate mounting holes, and I hear they’re nice, but honestly, I didn’t find it to be too tedious at all to just use the nutplates as my patterns. I picked out three nutplates to be sacrificial, since I’d be bolting/unbolting them many times. This let me set up each bracket and drill all its holes in quick succession:

Next I gave all the brackets a good deburring, both the holes and edges (the edges were pretty rough). Then I countersunk the opposite face for the flush rivets, since this side will sit against the spar. Finally, it was out to the back yard for a good cleaning and priming. I masked off the bracket face that will attach to the tank baffle; this will get a coat of sealant, so the primer would be counterproductive to getting a good seal there.

Here are all the primed brackets in place, ready to be bolted on for tank fitting:

Now it was time to cleco the tank assembly together. This was a real chore; the leading edge is tough to get together, but the tank skin and ribs are made of thicker material, and it takes a fair amount of force to get some of this stuff into alignment. Oh, and I ran out of silver clecos while doing this, and had to kind of ration the things to get everything together. Guess it’s time to order some more.

But finally, it was all together and it was time to set it on the spar and see how everything fit. And it’s hard not to cackle when you see this sitting in your garage:

Except there was one problem. Back when I was doing the leading edge joint plate, I found that I had more plate sticking out than expected, and I was worried about it interfering with the tank rib, so I moved it outboard a bit before drilling. The good news is that my concerns were well-founded. The bad news is that I still have an interference problem. This is as far outboard as the tank will go before the rib makes contact with the joint plate:

So I’m going to have to trim that joint plate now, which will be a bit of a pain. Since the plate is bent, I can’t just run it through the band saw. I guess I’ll probably have to remove it, draw a guide line, and trim the thing with my snips.

I’m kind of glad I’ve held off on the right wing skeleton. On the one hand, if I was doing these tasks on both wings simultaneously, I could probably go a little faster by combining tasks. But on the other hand, I’d be making mistakes like this twice. Now, when I do the right wing joint plate, I’ll know better than to fudge the specs.

First order of business today was simple: drilling the skin hole for the tiedown attach to full size. I actually skipped a step a while back that’s relevant here; the plans tell you to draw a couple of lines on the bottom skin that intersect at the center of the tiedown attach bracket. Then, when you set the leading edge in place, you’re supposed to use those lines to determine if the prepunched hole in the leading edge is located correctly. Well, I forgot about those lines until I’d already pulled the bottom skins off. Whoops.
But it’s actually pretty easy to check the location of that hoe otherwise. First off, there’s a gap between the skin and the attach, so you can see in there a bit; it appeared that things were aligned OK. To double-check this even more, I found an Allen wrench that fit in the skin hole, inserted it, and angled it until it hit the edge if the hole in the attach bracket. In this way, I could look at the angle and pretty effectively determine if things were OK, and they were. Si I busted out the Unibit and drilled the hole up to 3/8”. I don’t have the tiedown eyes, but I screwed in a carriage bolt to check the fit, and it looks great:

Then it was on to the tanks. Now, somehow I got the idea in my mind that tonight I’d be setting the temporarily assembled tank on the spar and looking at a whole wing-shaped object. That was…a bit optimistic. There’s a good bit of work that has to be done on the tank attach angles first. I dove in headfirst with the inboard angle. This one is different from all the others in that the bolts go in from the forward side and screw into nutplates riveted to the spar, wheres the other angles have nutplates riveted to them, and the bolts go in from the back side. I started with the inboard one because this is where I riveted those nutplates ahead of schedule, and I wanted to go ahead and find out if that was a mistake.
First, I laid out the spot for the center bolt (of three) and drilled it to full size on the drill press. Then I bolted the angle in place and squared it against the spar bars. Since I’d be using the nutplates as a guide, I’d have to drill the other two holes undersize at first and then enlarge them in the drill press. The first problem was picking the right bit. #30 was kind of small, and didn’t fit the nutplate very well; not good for precision. #19 was too big. So I busted out my cheap drill bit set (MISTAKE) and went with a 5/32” bit. I wrapped it in a layer of blue tape to hopefully avoid messing up the nutplate with the bit.
Somehow it never occurred to me that I’d be drilling these holes from between the wing walk ribs, a rather narrow space. I had to hold the drill really awkwardly, but I got it in place and drilled the first hole. Then I removed the angle from the spar, drilled that hole to full size, and bolted the angle back on with those two holes. Repeat for hole #3, and…immediately I could see that the holes weren’t straight. The angle had apparently moved while I was drilling hole #2, probably because that crappy drill bit was taking forever and I put some extra pressure on it.
Drilling through the nutplates wasn’t the direct cause of this, but it was clear to me that my from-the-hip solution wasn’t helping matters any, so I went ahead and drilled out all three nutplates. I grabbed a fresh attach angle, intending to try the inboard one again, but this time I misdrilled the first hole, such that I couldn’t even get a socket on the bolt to put it in place. ARGH
I was pretty disgusted with myself, so I abandoned the tank stuff for the evening and decided to work on something else: building a table for the C-frame. I got away without this while doing the tail, but it was kind of a pain. I feel this will be a necessity for dimpling the big wing skins. I picked up and cut the lumber over the weekend, and it’s just been sitting around waiting to be assembled.
Here’s the assembled frame. I built it such that the C-frame can be placed in any one of three spots, for extra flexibility:

I started adding the carpet on top, but it was getting late and I was getting tired, so I quit after just putting one of the three panels on:

I guess tomorrow I’ll try the tank attach angles again, or I might just take the evening off and try to think through this problem a little better. I’ve got to place an order with Van’s soon anyway; I think I’ll just go ahead and order a bunch of extra attach angles. I doubt they’re expensive at all.