It all hinges on.... hinges.

It's hard to say which of the flight controls is the most critical, but a strong contender in any debate on the topic would have quite a crowd lined up in support of the ailerons. While the RV-12 doesn't officially have ailerons, the hybrid aileron/flap surfaces (known as flaperons) that it does have would carry the same weight of argument. As with any of the movable surfaces, the flaperons would be useless if they were unable to perform the critical function of, well, moving. To that end, at some point I was going to have to construct the hinge braces that will provide the pivot point for that movement. That point was today.

With surprisingly mild temperatures in the low 40's accompanied by low-ish clouds and generally unattractive flying weather, I thought it would be a good day to spend some time in the hangar. We have a cataclysmic forecast for tonight, too, so that was added impetus to get some work done in relative comfort.

First step: make sure we all agree on which holes should be countersunk. This looked to be another double flush operation since the countersinking was done on both sides of the parts.

The "ham in the sandwich" is a thick piece of aluminum that supports the bearing that will be the hinge point. It's a tight fit, so Van's suggests using a 7/16" socket on one side and a 9/16" socket on the other to force the bearing into the hole.

Once it's in there, it ain't coming back out.

I've seen people have a lot of problems building up these sandwiched hinge braces. They get unsightly gaps between the side pieces after they squeeze the rivets in. The plans suggest finding a way to hold the ends together while riveting. I just stuck the ends back into the vise.

They also mis-use the word "random" again in their effort to instruct the builder to spread out the order in which the rivets are squeezed. Between that and the vise, it all turned out just fine.

The hinge braces get set aside while the rear stub spars get prepared to host them. A pair of doublers that I've taken to calling "the tuning forks" are retrieved from the parts shelf.

3.2 miles of the obnoxious blue plastic is stripped from the spars.

Starting at the easy end, a flange strip is clecoed in at the wing tip.

The a hinge brace is clecoed in at the end of the spars.

I was getting pretty cold, having over-estimated the ambient temperature that I would find at the hangar and failing to dress suitably. Rather than proceed with the riveting required to finish up the page (and section 14, for that matter) while distracted by being cold, I decided I'd call it a day.

What are the odds?

It was one of those days. Yes, one of those days. Every now and then I have a day where it feels like I'm walking through a poorly dubbed Japanese movie. It's as if the movement of the lips doesn't match the audio track. Well, metaphorically anyway. Nothing seems to go quite right, and it's hard to get in the concentrative mode that I need to be in to do my technical work. I usually keep some simplistic office work in the bullpen for days like these, but I can't afford to lose the momentum I have on my latest big project so I just had to muddle on through. There will inevitably come a day a few months from now when a user has reported a problem and I come across some of the work I did today. I refer to those as "what was I thinking???" moments.

I did manage to do one thing right, though. I've spent the last few evenings working on the family Christmas letter, an annual duty that I somehow picked up a decade ago and now hate with a livid streak of red-tinged passion. It's a multi-day struggle to try to fit interesting news from the last year into a single page without it sounding like a laundry list of brags. If I don't get it just right, it runs the risk of being a postal version of that most irritating of bumper stickers: "My Child is an Honor Student," to which I always append the implied between-the-lines message "and Yours Isn't." People reportedly like the letters, but I don't find them very fulfilling to write. It's almost a preview of the even more dreaded tax season where I again have to dryly report arcane details in a rote manner. And in the same way, fighting against it is futile. It's a duty, and I do it. There really aren't that many demands on my domestic time, if I were to be truthful, but I still reserve the right to grouse about it.

After a few evenings of dabbling at the annual missive, it was finally done and only needed printing. Unfortunately my printer at home has been slacking off when it comes to the left two inches of the page, and a new toner cartridge had not fixed the problem. I carried the special paper to work this morning in order to print the letters on an old hand-me-down printer I have in my office. With that done, the only thing that could go wrong would be to leave the stack of letters at work. I carefully placed them in a folder by my jacket so I wouldn't forget them. And there they still sat after I came back up from the parking lot to get them, having realized at the last second before leaving for home that I hadn't brought them with me.

After a frustrating drive home, I was proud of my having accomplished the annual duty as I handed the stack of nicely printed letters over to my overseer. Within seconds she found a typo at the end of the second paragraph. Perfect. A fitting end to a frustrating day that had raised my irritation level to a few degrees over the boiling point already.

Despite that, I debated on whether or not I should go out to the hangar to see if I could make a little progress on the airplane. I hadn't been for a few days and the weather was close enough to tolerable at 30F and lots of sun, but it doesn't always work out so well when I try to work on the plane when my brain isn't fully engaged. I remembered that the next steps were fairly easy assembly jobs, so I thought I'd go on out and see how it went.

The parts were easy to find on the parts shelf and were small enough that the brittle blue plastic came off without putting up much of a battle.

These are the brackets that will support the flaperon hinges. Most of the holes have to remain open for later attachment to the wing. I clecoed a barrier of clecos across the line separating the okay-to-rivet area from the don't-rivet-here-unless-you-want-to-get-really-mad area.

The remaining eight holes on each assembly were to get AN470AD4-4 solid rivets squeezed into them, but not in any kind of specified order. No, they had to go in using a random order, presumably to spread the loads around to prevent warping the brackets with uneven stresses. The thing is, "random" is not really the word they wanted here. They really meant something along the lines of "a varied pattern." The problem is that people don't really understand the concept of randomness. Allow me to share an anecdote that demonstrates this misunderstanding.

Years ago when I worked at Compuserve, the people that were drawn to software development were of an almost universal Spock-like nature. We loved logic. We understood logic, and we understood concepts like randomness. In short, we were all geeks. One night we were over at a friend's house when his wife sent the friend's brother out to buy lottery tickets. He returned with tickets with number selections like '5, 10, 15, 20, 25, 20' and '1, 2, 3, 4, 5, 6'. The wife was livid!! She shouted at him, "You wasted my money! What are the odds of those numbers coming up???"

That was absolutely the wrong thing to say in front of a room full of computer geeks. She didn't understand the outburst of raucous laughter until someone explained to her that the odds of those numbers coming up was exactly the same as the odds of any other numbers coming up. In a truly random selection, there is no difference at all between a series of incrementing integers and a sporadic selection of numbers.

So, here's my point. I could have lined those rivets up in a straight line because that ordering would be every bit as random as any other.

I didn't, though.

I even got into the spirit of the thing and made an attempt at actual randomness.

See what I mean about having gone through the day slightly off kilter? My ear warmer thingy is on upside-down.

The assemblies seem to have come out of it okay. They now get set aside until section 16.

Oddly enough, I was feeling a lot better by that time. It was getting dark, though, and I was getting pretty cold. The sun was setting and a couple of Fahrenheits had slipped away when I wasn't looking. I knew it was getting cold when small wisps of steam would puff up when I squeezed a rivet quickly. I was surprised by that, by the way. The first few times I thought that I must be imagining it, but I watched closely a couple of times and sure enough, when I'd squeeze the rivet quickly it would heat up enough to throw off a little puff of smoke. I don't understand how that's happening - it's not like there's any moisture in a rivet to be released as steam - but I'm sure I saw it. Very odd.

How do you know it's cold? Horizontal icicles, that's how!

Well, the other way is to look at a thermometer. 28 degrees. Hmmmm. Maybe an early start for the hangar wouldn't be the greatest idea. Perhaps a little shopping first....

The benefits of getting an early start on shopping are obvious, but there was one negative issue: Lowes didn't have the 3/8" x 16 tap that I needed. In fact, they continued to reinforce my low opinion of them by having no taps at all. I knew Harbor Freight wouldn't have one, and given that the one I had already worn out came from there in the first place, well, I wouldn't have wanted it anyway. That left Sears. On the plus side, I was pretty sure Sears would have one. On the minus side, they don't open until noon. I know!! Noon!!! I can't for the life of me see how they stay in business.

I figured I'd go to Harbor Freight anyway and pick up a new rivet puller. As you saw yesterday, I'm having trouble with the old one. I don't mind the broken mandrels when they're down in the guts of the airplane, but I will have zero tolerance for them when it comes time to do the wing skins. For $37.99 I figured I'd just get a new rivet puller. Harbor Freight air tools are the hamsters of the tool world - they aren't very expensive and you consider yourself lucky to have one live longer than two years.

I dress down when I'm going to Harbor Freight so as to fit in with the crowd a little better. I'm not a sharp dresser in general, but when I'm going to HF I wear older jeans and ratty old sweatshirts. This is a result of an incident a few years ago at a Lowes. I was buying some kind of construction material and was aghast when the cashier took a look at what I was buying, another look at what I was wearing, and said, "Hmm, we don't get too many of your type in here." I have no idea what that meant, but it has stuck with me.

So there I was in line, holding my $37.99 air riveter and looking just as sad sack as the rest of the clientele. There was a guy at the register buying a pair of scissors and a woman behind him buying a roll of tape. The guy handed the cashier a coupon for 20% off, but it was rejected because it required a purchase greater than $19.99. Useless to him, the coupon was wadded up and stuffed in a pocket, the idea of handing it to the poor looking guy standing there with a $38 purchase apparently never crossing his mind. The woman then used her 10% off coupon to save $.40 on a $4.00 roll of tape. I'd have given her a buck for it and come out ahead. As they left the store together, I realized that they had been trying to double-dip on their coupons by splitting their purchases.

When I got to the cashier and handed over my Visa card, she paused as if she was going to ask a question. I had a moment to hope that she would reach under the counter and grab one of the coupons for me, but it wasn't to be. "Debit or credit?" she asked. I told her that I still remembered a simpler time when all we had to answer was "paper or plastic." Those were the days!

I still couldn't figure out why the first guy wouldn't have offered to give me his 20% off coupon, although when I got home I realized something that might have influenced his decision: I was wearing a Van's Aircraft baseball cap. A dead give away, that!

As I mentioned before, I figured that I had no hope of getting a new tap anywhere but Sears, but there's a Home Depot right across the street from Harbor Freight and I figured that it was still early enough in the day that stopping in to take a look would be pretty low hassle. As I was approaching the tool aisle I walked past a store employee.

"Are you finding everything you need?" he asked.

"I haven't even started looking yet," I replied.

"Well, just give a shout if you need any help."

"Okay, I'll send up a flare if I get lost," I told him.

I think he was amused.

I didn't ask him about the taps because I really believed it was a futile effort. I was wrong. Not only did they have a nice $8.45 tap in just the size I needed, but they also had a robust looking $17 handle to go with it. I almost skipped buying the handle, even though the one that came with the Harbor Freight tap and die kit broke yesterday when I was trying to force it to turn that big tap. I figured I'd better break down and buy a new one, though. As you can see, it's a pretty strong piece of kit.

I actually didn't realize just how much better this handle was than the one I had been using until I noticed that it has a 3/8" socket fitting in the back. I didn't really appreciate that value of that until I was about halfway into the 1" hole that I needed to tap and having increasing difficulty in getting the thing to turn, even with periodic clearings of the hole and liberally applied Boelube. As the resistance mounted, I began to realize that a ratchet wrench would give me far more torque than the spindly little handle.

After that it was a simple job to tap all four holes to their full depth. It seemed odd to be tapping the holes that will be on the top of the wing given that these holes are intended to support tie down hoops. I saw someone ask about that once on the Van's forum and the answer was that someone might want to put hoops in the top of the wings so that the wings could be hung from the ceiling when removed from the airplane. That still makes no sense to me since a wing could be hung just as easily upside down, but who am I to judge.

I will more than likely use the holes to hold my jack supports far more often than I will use them for tie down hoops. I went ahead and tested them for that particular usage.

'Tis a fine lookin' hole:

That was the end of the work on the main spars for awhile, so they needed to be moved back into their storage location over by the sailboat.

With the workbench clear I went about getting the new rivet puller ready for use. The instructions that come with it say that it requires hydraulic fluid to be added and provides directions for doing so. I disassembled the thing to add fluid but there was already plenty in it. That's a good thing since I don't really have any hydraulic fluid.

The new riveter is a little smaller than the old one, which will be nice. The new one is on the right:

Say what you will about Harbor Freight, but I'm pretty impressed that the new riveter came with a complete rebuild kit. That's like a hamster coming complete with replacement lungs, heart, kidneys, and the tools required to transplant all of them. Of course, you have to know how to do surgery on hamsters and air riveters to make use of all that stuff.

I don't.

Back to work on actual airplane stuff. The main spars get set aside and the "stub" spars get pulled out. These are the spars that will support the tabs that fit into the side of the fuselage. The tabs have to be riveted onto the spars. A couple of rows of rivet holes get held open because wing ribs will eventually be riveted into them. I marked those with X's.  I also marked the holes that required a special type of countersinking. 'CS 100 BS' is my code for 'Counter Sink 100 degrees, Both Sides'. It seems odd to countersink both sides of a hole; normally only one side needs to be countersunk for the rivet head to fit down into. In this case, we will be installing "double flush" rivets.

"Double flush" is not a specific type of rivet. Rather, it is an installation technique. By countersinking the other side of the hole, the squeezed part of the rivet (the "shop head") will expand into the countersunk area and be flush with the tab. The fit of the tab into the fuselage gap is pretty tight, so the rivets need to be flush on both sides.

All of the holes in the flanges of the spar stubs get countersunk too, although these require the 120 degree bit. I'm not sure what will eventually fit into these countersunk holes, but I think it will be some kind of dimpled skin. The directions warn against using a dimple to determine the correct countersink depth and suggest using a 1/4" hole drilled into a piece of scrap metal instead.

Here is the 1/4" template held up against one of the countersunk holes:

Here's the first row of holes. There were four rows in total that needed to be done. I was getting pretty cold by the time I got all four done. I had the hangar door up so I'd have plenty of light for working, but doing so meant that I couldn't fire up the Cone of Comfort. I've been listening to the Compact Disc version of James Herriot's All Creatures Great and Small on my lengthy commutes to and from the paying job for the last couple of weeks and working out in the cold hangar reminded me of some of his stories of winter work in the northern English farm land. He thought he had it tough, but I couldn't help thinking that at least half of his farm calls involved at least getting his arm up into something warm. I'm betting you get over the "Ewwww" factor pretty quickly once it gets cold enough outside. I know I would have been willing to give it a try after three hours in the hangar!

I had no such luck. All I had was a pair of thin gloves that are starting to wear through.

When it came to squeezing in the AN426AD3-3 double flush rivets, I didn't even have the gloves. The rivets were so tiny that I had to strip off the gloves and go with bare hands just to be able to get a grip on them. Now don't get me wrong, I love that Cleveland rivet squeezer - it's a far better tool than I would ever have bought for myself - but it was freezing cold!

It did a great job on getting the shop head of those rivets flush, though!!

I was able to put the gloves back on to squeeze in the larger AN470AD4-4 rivets. As I was doing so, though, I was kind of bummed that there were no blind rivets to do. I would like to have tried out my new air riveter.

I'd had enough of the cold by the time I was done with those rivets. The nice bright sun that had been melting the snow off of the hangar roof had been replaced by a gloomy layer of low clouds. It had gotten even colder as a result. The melting snow had refrozen on its way down the slope of the open hangar doors.

Some had leaked into the man door and frozen on the inside.

Like I said at the beginning: you know it's pretty cold when the icicles are horizontal!