Wings

Started out today by doing some rib deburring.  Josie got about halfway through the main right wing ribs last weekend – just touching up the little nooks and crannies – and we’d left the stack sitting on the workbench.  I was planning on getting rolling on spar countersinking, which would require the bench, so I decided to just sit down and finish that stack up so I could get them back on the shelf for storage.  Man, if I thought the tedious repetitive stuff was done when I got the last rib straightened, I was wrong. (for the record, I thought no such thing, and I only mention it here for the purposes of rhetoric)  Just sitting there with a couple of needle files, filing, checking, filing, checking, filing… whew.

That done, I brought over the first wing spar and clamped it down on the bench.  Like other parts, the holes for the nutplates are undersize, so I started by reaming the rivet holes out to #40.  That was easy, but then I wasn’t sure about what size the screw holes needed to be.  I got out a #27 bit and drilled a test hole in some scrap, but found that wasn’t big enough.  On the other hand, the #21 bit looked too big.  I sure didn’t want to go hacking up this beautiful spar.  Then it occurred to me that I might not even need to drill those holes to final size anyway.  The procedure specified in the instructions is to rivet the nutplates in place, then use a #30 countersink for the screw hole; that bit will center nicely inside the threads of the nutplate.  Using this method, in turn, means that it’s not necessary to get the hole to final size for the countersink bit to center, since I’m not actually using a #8 screw countersink.

Of course, the screw still has to go through there, but it’s possible that by the time the countersink is deep enough to accept the tank skin, it’ll be deep enough that the hole is large enough anyway.  It was time to put together a test rig.  First problem: there’s no raw material in this kit that’s the same thickness as the main spar channel. But it turned out that the piece of angle aluminum I bought for aligning the trim tab was the perfect thickness…nice!  So I sawed off a section and proceeded to rivet a nutplate in place.  Then I got a piece of scrap sheet the same thickness as the tank skin and drilled and dimpled it for a #8 screw.  This is necessary to get the countersink right, since it accepts the dimpled tank skin, not the actual screw.  With a bit of trial-and-error, I had the countersink right, and wouldn’t you know…it was deep enough that the hole was bigger than the screw.  So after about an hour or so of work, I’d convinced myself that I didn’t actually need to find the right drill size for the #8 screw.

Here’s my little test setup.  Still need to get the countersink a little deeper; the skin piece isn’t sitting flush…

(I did, however, note that the screw holes in the tank skin are undersize…so I’m going to have to figure this out/get the right bit before too much longer…)

Finally, I went to work with the #40 countersink, working on the nutplate rivet holes.  I got through about half of those on the bottom of the spar before dinner arrived in the form of pizza delivery, which seemed like a good time to stop for the evening.  Tomorrow I should be able to get into a good rhythm, knock out the rest of the rivet countersinks, and then start riveting nutplates on.  Even though I went through those complex testing machinations, I think I’ll start by riveting a single nutplate and then countersinking, just to make sure that there’s not a hole size issue in the real thing.  Worst case, I have to drill out a single nutplate…no big deal.

Some of tonight’s countersunk rivet holes:

At this rate, it won’t be long before I’m riveting the skeletons together and hanging them on the yet-to-be-constructed wing stand!

Wow, that actually went pretty fast.  After all that rib-straightening drudgery, it’s nice to be able to go out in the garage and really feel a sense of accomplishment in a fairly short period of time.  It helped that I basically had all my tools set up and ready to roll after my test piece from last night; I had one countersink cage set up with a #40 bit, adjusted for the flush rivets, and the other set up with a #30 bit, adjusted for the screws.  That let me basically just rock & roll through tonight’s work without a lot of the time-consuming trial-and-error setup stuff.  Very nice.

Anyway, last night I got about half of the rivet countersinks done on the bottom spar flange before knocking off for the evening.  Tonight, I went out and finished that flange, then flipped the spar around and did the rivet holes on the other side.  As I mentioned/planned last night, I then riveted a single nutplate in place and did a single test countersink for the screw, then put my tank skin substitute piece in place.  Perfect fit!

I got into assembly-line mode from there.  Basically, my procedure went like this:

• Insert a cleco into one rivet hole for each nutplate
• Lay a nutplate on top of the spar flange by each hole
• Use the previously inserted cleco to cleco each nutplate in place, aligning the other hole
• Drop a rivet into the second hole for each nutplate
• Go back down the line, pressing the rivet down while unclamping and reclamping each cleco.  This was my way of ensuring that the nutplate was well-placed.
• Squeeze the previously placed rivets
• Remove the clecos and replace with rivets
• Squeeze the other rivets
• Lay the spar down (for better stability) and countersink the screw holes

In this way, I riveted all 60 nutplates and did all the screw countersinking in under an hour.  Very nice.

Once I get the tank attach nutplates on the other spar, I’ll need to go back and prime all those countersinks, since the bare aluminum is now exposed.  That should work out nicely; I can easily get the other spar done this week, and have Saturday to prime the flanges.

In other news, I talked to Daniel Schoning this weekend, and it just so happens that he’s wrapping up his wings and will be done with his wing stands any day now, which he’s offered to give to me.  The only issue is that he had his stands bolted to his garage floor; between not owning this house and wanting to be able to move the wings around to keep the garage functional, that’s not going to work for me.  But he suggested just mounting them on a rolling cart of some kind.  I think it’s a good plan, and it’ll save me some fabrication.  His only condition was that I donate them to another RV builder when I was done.  I can handle that.

Wow…between things becoming crazy at work, and getting some kind of stomach bug, it really has been 2.5 weeks since I touched this project.  Even today, I slept in pretty late in an attempt to recover from a long and stressful week at work, and then spent some time fixing up a side project of mine.  I did resolve to do something out in the garage today though…so I went out and got to work on the right leading edge ribs.

Deburring these things is tedious.  I’d already taken care of all the big edges previously with the bench grinder and die grinder, but all the little nooks and crannies need attention.  The leading edge/tank ribs in particular have lots of these, especially on the nose of the rib.  Oh, and the instructions say to pay special attention to this area to make fitting the skins easier.

I ended up figuring out a pretty decent method, using a couple of mini files and one normal one.  I’d use a mini flat file to hit up the small straight areas, then use a rat tail file to work the corners and such.  That still left the nose area a little rougher than I liked, so I ended up using a normal file to really work the nose area down and get it smooth.

I’m probably going overboard with this stuff, but better to do it right the first time.  Plus I just feel better about my work this way.

Wow, it’s really been two months since I did any appreciable work on the RV.  It started with some craziness at work…we had a big pressing project, which worked out to some long hours and a fair amount of stress.  But even that really calmed down for the most part about a month ago, but I think I was still having some residual stress issues.  I tried to go out in the garage and deburr some of the right tank ribs one Saturday, but it just seemed like horrific drudgery that I didn’t want to have anything to do with, so it didn’t take me long to find an excuse to go back inside.

I guess you could say that I was really in need of a vacation.  Luckily, there’s Oshkosh!  This was the second year for Josie and I; we drove up last year, and I pretty quickly concluded that the next trip should be flown instead, so that’s what we did.  We rented my favorite Archer from Skybound Aviation and headed up for a full eight or so days camping up in the North 40.  I think it was just what I needed; I came back with a clearer head and a much better attitude towards life in general.

So anyway, today I went out in the garage and went to work on those tank ribs again.  This time, there was none of that feeling of drudgery.  Well, it’s still tedious work, but I didn’t have the same feeling of complete detachment the whole time.  Today, I got all those right tank ribs deburred…that completes all the right wing ribs. (now I just get to repeat this exercise again…)

After that, I did one of what I’m going to start calling Sanity Assemblies.  These are temporary assemblies of parts that serve no purpose other than to let me look at and touch something that looks like a real airplane part.  For today, I used the leading edge cradle that Daniel Schoning gave to me and clecoed the right tank together.

That’s all for today.  I still need to countersink the second main spar and get those countersunk holes primed…maybe that can happen next weekend.  Plus there’s the left wing ribs to deburr as well…

Today seemed like a “getting back in the swing of things” kind of day. Which makes sense when you consider how long it’s been since I’ve done regular work. Anyway, I decided today’s project would be to pollute the newly-cleaned garage with lots of aluminum shavings by getting to work countersinking the left spar. I got all the tank attach nutplates done on the bottom of the spar; still have to do the top. That should go by faster than today; today I was trying to take my time and be careful and so forth.

I still have to finish deburring all the left wing ribs as well. Pretty soon I’ll have to start thinking about cleaning and priming all those ribs…

Finally back out in the garage again today. I’m glad I got my portable air conditioner set up out there, because the Houston summer is starting to kick in…

For my first trick, I wanted to work out some good means of storage for the wing skins. Back in Georgia, I just drove some finishing nails into the wall and hung the skins by the rivet holes. It worked, but not particularly well. God forbid I needed to get the wing skin in the back of the stack…I’d end up messing up a couple nails along the way, and the whole thing was a huge operation.

I had some scrap lumber sitting around from building the workbenches, and after rolling ideas around in my head, I came up with my idea. Basically, it’s just two units with a vertical piece that leans back a bit, plus a bottom lip for the skins to rest on. I put them on the floor a good distance apart and the skins just naturally rest on them. It’s kind of like a two-piece easel, I suppose.

With that out of the way, I finally unwrapped the main spars from their bubble wrap cocoon, still left over from the move. I have one more row of fuel tank attach nutplates to do, but today I decided to instead go with the more unpleasant task – rib deburring. It’s tedious work, but it needs to get done.

So I sat down and managed to deburr all the leading edge and tank ribs for the left wing. The end of debarring is in sight now; all I have left are most of the main ribs for the left wing. Once I finish those, then I’ll be on the road to putting the wing skeletons together, though first I’ll need to figure out what I need to do for wire runs to the wingtips and such, as well as clean and prime those ribs. Still, it’s good to be working again, and also to know that soon I’ll be hitting on of this building phases where, after a long period of not much getting done, suddenly I have assemblies that look like actual airplane parts.

Actually, that title isn’t 100% accurate. Really, this whole time I’ve been talking about all the deburring, I’ve been referring solely to the really tedious part: that is, getting into all the little nooks and crannies in the ribs with a needle file to make things nice and smooth. It’s the kind of work that makes your eyesight wander a bit when you stop, because it’s been a while since you looked at anything more than a foot away from your face.

But hey, it’s done! I went through all the left wing main ribs today went cross-eyed about five times, but got through. The reason I say the title isn’t 100% accurate is that there will still be more deburring; all the rivet holes will need a pass once they’ve been match drilled and dimpled and so forth, along with whatever holes I drill for wing plumbing; pitot lines, electrical conduit for wingtip lights, etc.

That brings me to the other thing I worked on today, trying to plan all the wing plumbing. I could theoretically drill the holes for this stuff after putting the wing together, but it’d be a lot easier to drill the ribs while they’re not attached as opposed to working inside the partially-assembled wings. So I’m working on planning all the stuff I’ll need to run lines for, and then I have to decide where to run the lines, making sure that I don’t interfere with the aileron pushrods or anything (control jamming is A Bad Thing).

So now I’ve got a sort of worksheet going so I can go forth and research. What pitot do I want to use, and should I get a heated one? I know I want an AoA system, but which one? The Dynon system, for example, requires a specific pitot tube, but I’m not sure if I want an EFIS-integrated AoA. AFS makes a good standalone system, but it looks like it’ll require a second pitot tube (I could be wrong, I haven’t fully researched this). Of course I’ll need wire runs to the wingtips for nav lights. Do I want to put landing lights in the leading edges? Aveo Engineering’s ZipTips look really slick, but I hear they’re Expensive with two or three capital Es.

So yeah, lots to think about. In the meantime, after finishing up all that deburring, I clecoed all the main ribs to the left wing spar. The rationalization I made for doing this was to help me visualize wiring runs and such, but mostly it was so I could step back and cackle a little.

Not really so much of a work day today, more research and head-scratching. I spent some time searching around for how other builders had done their wing plumbing, then went out to the garage to try and visualize things a little better. The big concern here is the control system for the ailerons; obviously I can’t have the plumbing interfere with flight controls.

The “standard” Van’s instruction calls for running black ribbed conduit for the electrical stuff, and using grommets through existing tooling holes for the pitot lines. However, this setup has some downsides in my opinion.

• The ribbed conduit will probably be more difficult to route wires through since the interior isn’t smooth.
• Running the pitot lines through grommets would make replacing those lines a potentially unpleasant task; not that these lines wear out frequently or anything, but why complicate things unnecessarily?
• Speaking of unnecessary complications, why have three separate line runs? I don’t see why the pitot lines would need to be separated from the wiring.

Considering all these things, I was leaning towards skipping the conduit and instead running something like 3/4” PVC or PEX through the existing lightening holes. Several builders have done this, and it seems simpler than drilling holes to run conduit through. But this also puts the conduit further into the wing interior, which goes back to the “don’t interfere with flight controls” issue.

To give myself peace of mind, I decided to mock up the aileron control system in the left wing. I already had the main spar sitting on the bench with the ribs clecoed on, so I got out the rear spar and clecoed that in place as well. Next, I loosely put the aileron bell crank in place. This piece converts the side-to-side movement of the main aileron pushrod (which attaches to the control stick in the cockpit) to forward-backward movement of the smaller pushrod that directly actuates the aileron. The smaller pushrod was my main concern, so after putting the bell crank in place, I laid the rod in place using the bell crank and the rear spar passthrough holes as references.

This confirmed what I pretty much knew anyway: The small pushrod sits towards the top of the wing, and leaves plenty of room to run 3/4” tubing through the second lightening hole at its lowest point. I’ll probably go ahead and get the tubing I’m going to use tomorrow or this weekend just to make really really really sure it’s OK.

The only thing I haven’t really accounted for is possibly wanting a second, isolated wiring run. I’m debating whether I’ll want to put in a wingtip VOR antenna at all. I intend to have this plane be IFR certified, and while it doesn’t seem that a VOR antenna is required, it might be prudent to have one as a backup to GPS. That, in turn, raises the question of possible noise from the electrical wiring. I’ll need to keep researching to determine if this will be a problem. For the time being, though, I think the single conduit run will probably be just fine for everything.

Finally, a good productive day. Haven’t had one of these in some time. I started the day off with a trip to Home Depot to pick up my conduit materials. I was sort of hoping for some Class 200 PVC, but I ended up with PEX instead. The Class 200 PVC is very thin-wall, generally used for vertical runs from water heater pressure relief valves. It’s only used vertically since the walls are so thin, and it can’t support much weight. But that also makes it far lighter than normal Schedule 40 PVC, and it would be perfectly suitable for my conduit run. Unfortunately, Home Depot didn’t have any other than some short prefab lengths in the water heater section. I need a 10’ run, and I don’t much feel like going to the trouble of buying several short pieces and joining them together. So I went with 3/4” PEX instead. They even had nice 10’ precut sections, exactly what I need. I also picked up some hangers, which I’ll use to secure the PEX to the ribs with pull rivets.

Back at home, I wanted to do a rough run of the PEX through the assembled skeleton I had just to double-check everything. I even went so far as to mock up both the aileron pushrods with the rod ends and put them in place, so I could see what everything would look like. Here you can see the bellcrank assembly, the small pushrod that runs from the bellcrank to the aileron, and the long pushrod that runs from the bellcrank to the control stick. Below the short pushrod is the PEX pipe, sitting in one of the hangers and temporarily clamped in place.

A closer detail of where the PEX and the pushrod cross paths. There’s a couple inches clearance in here, and the worst case I can envision if the PEX were to come loose of the hangers would be for it to rub against the pushrod. I can’t see any way it could cause a control blockage issue.

On another note related to plumbing, I’ve decided to stick with just this one conduit run. The consensus I’m getting from reading VAF experiences is that I shouldn’t have any issue running coax for the NAV antenna in with everything else. The main source of interference people seem to report is from HID landing lights, and I suspect that by the time I finish this, LEDs will have dropped in price enough that they’ll be the best choice.

Now that I’d satisfied myself with the plumbing, I decided that since I already had the whole skeleton clecoed together on the bench, I might as well go ahead and match-drill the spars to the ribs. I made a somewhat unpleasant discovery in the midst of this though – it seems that the garage outlet circuit isn’t up to powering both the compressor and air conditioner. Which is kind of odd – I’d thought this might be an issue before, so I made a point one night of running both at the same time, and I had no issues. No such luck today though…I’d gotten through a few holes when the compressor kicked on briefly, followed by darkness and a deep silence caused by my music stopping as well. Well, time to go reset the breaker. Fortunately, the garage seems to maintain temperature fairly well for short periods while the A/C is off. I guess I’ll just have to be sure I turn it off before I do a bunch of drilling.

With the ribs match-drilled, I now need to keep track of each rib’s position on the spar. Most likely I could switch them around with no issues, but it’s good practice to be sure. On the tail, I used a simple system of punch marks for this, but here I have far more ribs (14 per side to be precise). I went full nerd on this topic and devised a binary marking system. Doing it this way means that each rib only needs four punch marks; I just number them from inboard to outboard. Hopefully these marks don’t disappear under the primer…

Here’s an example of a mark. This is 0111, which is #14, or the most outboard rib. It’s hard to see, but there’s one “low” punch followed by three “high” punches.

Finally, after taking a break inside for some dinner, I set about finishing the evening by doing my last row of tank attach countersinks. Not really difficult work, though I was cognizant of how long it had been since I did this last. I got back in the groove pretty quickly, but still, I’m way more confident doing stuff like this when I’m in practice. I’d better keep up the work!

Finished row of nutplates:

Tomorrow I think I’ll make another Home Depot run for some 1/4” plywood. I want to make templates so I can drill the rivet holes for the conduit hangers. I also need to get another pack of five hangers; I forgot to count the ribs before I went this morning, so I guesses at the number of ribs and came out a little low. If I can get those holes drilled, I can make a final debarring pass on the ribs and start thinking about priming them and riveting the skeletons together! Which also means I need to start thinking about building my wing stands…

Well, not so much of a highly productive day today. I gave in to the urge to sleep in and had some other things to do around the house. But I still found time to get all those holes drilled for the conduit mounts.

The first order of business was to create some kind of template so I could locate the mount holes consistently. The main concern I had here was figuring out a way to reliably locate the template relative to the lightening hole. After some thinking, I decided that the hole itself was the best reference. The circumference of the hole has a slight channel pressed into it, presumably for greater rigidity. I decided to make my template a two-part affair; first there would be a piece of 1/4” ply cut to butt up against the edge of the channel, and on top of that would be a piece of 1×4 I had lying around, which would have the actual holes drilled in it.

The first step was to trace the edge of the channel relative to the rib flange. Yes, that’s a piece of a McDonald’s bag. Go ahead, judge me.

Next I cut the paper in that line and transferred the shape into a piece of ply:

Then I cut the curve on the ply in the bandsaw, ensured everything lined up, and glued the ply piece onto the piece of 1×4. I didn’t get any pictures of this.

At this point, I had some dead time while I waited for the wood glue to set, so I decided to review all the instructions for the wing kit. I was particularly interested in seeing when the wing skins would get match drilled and the ribs dimpled. With the empennage, everything pretty much went together at once, so by the time I got around to priming a rib, it was already fully match drilled and dimpled. Not so with the wings; the skeleton goes together and then the skins are match drilled with the skeletons hanging in the stands. Ergo I’mm be match drilling and dimpling ribs that are already primed. Not that this is a problem really; I even did some tests with dimpling primed pieces a while back and the rattle can primer held up just fine.

Mostly, though, I just wanted to kind of get the big picture in my mind. It looks like once the skeletons get hung, the skins are match drilled, and then work shifts to the leading edge section and the tanks. I’m sure the tanks will be quite a bit of work. Only after those go on for good is it time to rivet some wing skins. then it’s time for the ailerons and flaps!

Anyway, fast-forward a couple hours (and maybe a nap…), and the template was dry. I used one of the hangers to locate and drill the two holes:

I ended making a few modifications after this; the 1/4” ply is actually a good bit thicker than the lightening hole channel, and I wanted the top part of the block to fit better. So I shaved off some of the ply in the bandsaw and then went to town with the bench grinder. I struggled a bit trying to figure out a way to hold the template in place while I drilled the holes, and then a solution became obvious: the template sat against the rib flange, which had holes for the wing skin. All I had to do was locate it properly, clamp it in place, and drill 3/32” holes through the flange, and then I could just cleco the template in place for drilling. Very nice.

After checking everything about 20 times, I finally took a deep breath and made some holes. It worked out quite nicely:

I think I’ll probably get some washers to put between the pull rivets and the hanger itself, since it’s somewhat soft plastic. Can’t hurt to distribute the clamping force of the rivets a bit.

After this, I repeated this procedure 27 more times. Which was actually four more than I needed; at the inboard end of the wing, there are four ribs spaced closely together to support the wing walk, where people will be stepping as they get in and out of the plane. There’s no need to put a hanger on each one of these, so I was going to skip the two “inner” wing walk ribs, but I kind of got on a roll with the drilling and drilled all of the ribs.

Anyway, that’s it for today. Next steps will be to do a final deburring of the left wing ribs, then prep and prime them. I’m going to wait on the right wing ribs until I have the left ribs primed and at least clecoed back to the skeleton. The reason for this is that while I like my binary marking system, it has no provision for denoting left/right wing ribs. So I figure I’ll just keep the batches separate for now.

Thing is, cleaning and priming all these ribs is going to be an all-weekend project for sure. I’ll probably just wait until next Saturday to do that. This week after work, I can finch the deburring, but that’ll be trivial. Maybe I’ll work ahead a bit and see about building the aileron pushrods or the bellcrank assemblies or something like that. I feel like I’m getting some momentum going here, so I want to keep rolling on something and not get in the habit of not working on things.