Sink, Counter-Sink

The idea of starting a new section of the fuselage seemed like it would bring with it some kind of change. New parts, new and exciting stuff to do. Well, not so much. The first steps of Section 22 are countersinking holes and riveting nutplates into place. And not just a little countersinking, either. Lot's and lot's of countersinking!

And that was just fine with me. I only had a brief amount of time available to work on the plane tonight and countersinking a passel of holes was just the right size job. It started out kind of tricky - step 1 offered the not so rare opportunity to easily dimple the wrong side of the part. The dimpling was only two holes, just enough to support one single, lonely nutplate on the lower firewall. I took a great deal of time making sure that I got the dimples on the correct side of the firewall. Once I had it figured out, I was taking no chances on forgetting.

Step 2 was much easier, at first. Both the "sloped upper flanges of the tunnel ribs" and the "nutplate attach holes in the fwd fuse skin" were easy to find. It was the last part of step two that caused me so much trouble. Here, read it for yourself:

The sentence in question (or, more aptly, the sentence that caused the question) says, "Machine countersink the upper most hole in the F-1288 Cooler Stiffener." Well and good, that, but not nearly enough. You see, the hole in that part is being countersunk so that the part will sit flush against the firewall when it is riveted in place. The holes in the firewall underneath the part are already dimpled with Van's now-you-see-it-now-you-don't dimpling machine. They only pull it out on rare occasions; pedestrian tasks such as dimpling are nearly always left to yours truly. Anyway, the problem is that they did not dimple only one hole under the Cooler Stiffener. They dimpled, as even the most casual inspection will show, no less than seven holes under the Cooler Stiffener. Countersinking just one of the seven seemed like it simply would not be sufficient to allow the Stiffener to snug down flush against the firewall. It's always possible that Van's has posted a revision to a page, but a check of their web site showed nothing newer than Revision 2, the very version I was looking at.

This, in a word, was a dilemma.

I looked ahead to see if the countersinking was addressed later. It was not. In fact, in just a few more steps the stiffener gets riveted into place.

Usually the best thing to do when faced with a situation like this is to not do anything you weren't told to do. In this case, though, I can't believe that those holes weren't intended to be countersunk. I went ahead and did them.

The rest of the countersinking was easy.

Step 4 wants the Engine Mount Brackets to be clecoed into place and match drilled. I went ahead and clecoed them in, but the match drilling will have to wait. Thursday is my tiredest day of the week and I had reached my limit.

One of those days

Some days I have the Midas touch. Some days I don't. And some days, well, I suppose the opposite of Midas would be the merde touch. It's French - Google it. Today wasn't quite that bad. I think I'm going to go with the petit merde touch.

It started early. I arrived at the paying job at my normal 0615 and settled in at my desk after a brief stint brewing the coffee and yelling at the newspaper. I had left a job nearly done yesterday afternoon and put the finishing touches on it this morning. It's a clever piece of code that goes into the database and retrieves an entire hierarchy of data. In other (equally opaque) words, it retrieves a top, root object, then retrieves the children of that object. As it retrieves each child, it also retrieves their children. If you were to draw out the relationships, it would look like an org chart or family tree. The benefit of getting everything all at once is that I can get at the entire family, if you will, after just one operation against the database. Efficiencies are gained by doing so.

Well, efficiencies are gained by doing so if (and only if) it actually works.  It didn't. Instead of returning my happy family of data, the program crashed with a stack overflow. What that means in a nutshell is that my computer ran out of memory. With the kind of memory computers have these days, though, that would have had to have been one very, very large family. No, it meant that something was horribly wrong in my code.

It came down to a problem with cousins, to drag the familial analogy along even further. After quite a bit of hair pulling and desk pounding, I realized what was happening. When I was creating one of the children, I had it also create its own children. As long as I was doing that, I thought I'd be clever and have it create a somewhat unrelated relative that I thought might come in handy later. You know, as a kidney donor or something. I'll call that new relative a nephew - it's nicer than "parts bank."

The problem was that the nephew was never intended to be included in the family, so as part of his creation he had to find out who his uncle was to maintain at least some semblance of association. So, when the uncle created him, he in turn tried to create an uncle for himself. That uncle tried to create another nephew, who also tried to create an uncle, who tried to create a nephew.....  On and on and on, until there's no memory left to hold it all. Stack overflow, scream of frustration, pound the desk. You know it's bad when coffee is the calming influence on your morning.

I doubt if that made much sense, so suffice it to say, it was all quite frustrating.

Once I figured out what the problem was, it was easy to fix. I neutered the uncle. Serves him right.

Unsurprisingly, my work on the airplane tonight ended in frustration. Not the screaming, desk pounding kind. More of an "Oh well, it's just been that kind of day. It will look fine tomorrow."

It was to be a light night. All I had left to do in the seemingly interminable Section 21 was to rivet on the very last bulkhead. It took four nutplates and 16 rivets, plus a detour into the second of the two autopilot brackets, but it was pretty easy.

Being as this is pretty close to the end of this section, I kind of took an audit of completeness, as it were, basically just trying to see if I had missed anything. Here's a bit of a mystery:

It's passingly odd that there are no bushings in those holes. I went back through the plans and could find no steps instructing that bushings be installed there, so there it is. A mystery.

The second to last step is the installation of a bracket that will support the fuel flow sensor for the Dynon D-180. This sensor will measure the flow of fuel (hence the diabolically clever name) through the fuel lines, allowing the Dynon to display the rate at which it is being burned by the engine. Useful, that.

The bracket goes down in the tunnel between the seats.

It's kind of hard to get at down there, which is unfortunate since it has to be match drilled to the belly skin. The long #30 bit is required.

Once drilled, the bracket had to be removed for the installation of (what else?) two nutplates. That done, I clecoed it back into place and prepared to rivet it in. Looking down into the tunnel and thinking about how hard it was going to get to get the rivet puller down there was a little depressing. Frankly, it was a battle that I did not want to fight. Suddenly it dawned on me that not only would I not need to fight that battle, it would have been foolish to do so. Who wants the wart looking pulled end of a blind rivet hanging out of their belly skin?? No one, that's who! Not even when it's airplane skin we're talking about and not their own skin! 

The right thing to do would be to install the rivets up through the belly skin. There's no easier time to choose do the right thing than those rare occasions when the right thing is also the easy thing.

Well, if not easy, at least easier.

So, last step. Looks easy: install six panhead screws up through the belly skin to act as attachment posts for some device to come later. Six screws, six metal locknuts. Nothing to it, right?

You know what they say are the three most important aspects of real estate are, right? Location, location, and location. These screws are not in good locations. Not.At.All.

After futilely struggling with the first one for twenty minutes, a thought struck me: this is the easiest one.

I uttered a sharp, non-petit "Merde!" and called it quits for the night.

Chapter three. Again.

While it has not (and hopefully will not) reached the level of mundanity, I do have to say that some of this work is hitting the upper boundary of "routine." Cleco-dimple-rivet.  Cleco-dimple-rivet. Cleco-dimple-rivet. Repeat until, well, you just don't want to do it anymore. It's not that it's boring per se, it's more that there are certain things that have become very commonplace. It's sort of like re-reading chapter three after finishing chapter ten of a novel. The again after chapter twelve. And fifteen. It starts to feel repetitive. But even at its worst, it still feels like progress and offers the sense of satisfaction inherent in using your hands to mold a complex object out of tiny little parts. So there is that.

With that enthralling lead-in, I'm sure you're right on the edge of your seats with anticipation and can hardly wait to see what I got done tonight. You're right to be excited: I riveted in two new floor boards. And they had nutplates! Be calm by beating heart!

As is often the case, the beginning of all of this was the replacement of some stuff that had been put in position, removed, and needed to be put back again. In this case it was the re-primed step braces that needed to be clecoed back onto the step ribs and riveted in.

I started out by riveting from the rib through the bracket but soon learned that this caused issues in the lower outside corner when the rivet puller wouldn't fit in. I shifted to putting the rivets through the brackets and into the ribs and it all went much better.

The bulkhead gets riveted on next. Looking at the plans, I could see that I'd have to be careful about what got riveted when. It would be easy to get carried away with riveting the bulkhead not only onto the end flanges of the step ribs but through the step support brackets as well. That would be a mistake because the little aluminum brackets that host the nutplates would then have no open rivet holes available to them. 

There are also a couple of holes that get a CS4-4 flush blind rivet rather than the normal LP4-3. I went ahead and did those first so that I wouldn't forget.

There are a couple of holes on each side that don't get riveted. I marked those with no-no clecos. I threw caution to the wind in order to put an adrenalin-inducing risk into the game by not covering the no-no rivets with duct tape. Truth is, I'm getting low on tape.

The corners get riveted next.

Finally, the floors get riveted in.

And there it is!

What? I promised you nutplates? Oh, yeah. These were a real treat. See those lightening holes in the ribs down in the gap between the two floor boards? You have to reach through them with a nutplate to install on the corner of each floor board. I don't know if you can get a sense of scale from these pictures, but even with my tiny arms (arms so spindly that an anorexic super model would find them too frail) I couldn't get more than two fingers through. I had to hold the nutplate between my index finger and my driving finger while trying to get the nutplate pressed up against the bottom of a floor board, then try to slide it into position hoping hoping hoping that I would drop it. Dropping one would cause a real dilemma: try to find a way to get it out of there without drilling out all of the rivets holding the floor board in place, or just live with the rattle.

I managed to get both installed without putting myself in the position of having to make that decision.

See? This wasn't boring after all!

An RV-12 ride!

It probably seems odd that I would jump into building an RV-12 without ever having so much as sat in one, but it's not as uncommon as you might think. It happens all the time, starting with Orville and Wilbur, if you think about it. That doesn't mean it's a comfortable thing, mind you. You might think that the worst case scenario is that I spend years building the plane and then find out that I don't particularly like the way it flies, but if you think about it for a second you will realize that there's an even worse thing that could happen: my first flight in the airplane would also be my first flight in that kind of airplane. Learning on the fly, so to speak. So not only would I be wondering if the plane would actually fly, I'd also be worried about whether the pilot could actually pilot it.

That issue was partially resolved today. I've been helping a fellow RV-12 builder with the configuration chores for all of the electronic gadgetry in his plane. Today I hoofed it over to Lancaster (KLHQ) to set up the part of the Dynon display that indicates the trim position. I drove over rather than taking the RV since the weather forecast was typical Ohio weekend: thunderstorms with the chance of more thunderstorms. Better to drive, I figured. That said, the weather had not yet finished its slide into the forecast crud, so there was a small window of opportunity for my first ride in an RV-12. The fuel tank was going to need to be removed later in the day, so burning off a gallon or two was deemed preferable to draining it out. To be honest, I didn't need much arm twisting to talk me into it.

While Mr. Rush was preflighting, I was busy taking pictures of areas of interest. "Areas of interest" to a builder is defined as the parts of the airplane currently under construction. In my case, that is the bottom chunk of the fuselage, in specificity the steps used to climb up onto the wing to enable ingress into the cockpit.

You can, of course, read all about that over on the Schmetterling blog.

The RV-12 is a few inches wider than the RV-6, so the seating was quite comfortable. The Rotax was a little reluctant to start but finally got its wind up with the application of the choke knob. New stuff already - my Lycoming doesn't have a choke knob. Once the engine was running (very, very smoothly!) the avionics master is turned on and the light show begins.

As we taxied out for takeoff, I made some adjustments to the avionics. Having just gone through this with my Garmin 396 last year, I was able to find the menu page on the 496 to shut off the highly irritating XM radio commercial that plays through the headsets. I also found the page to increase the brightness on the 496's screen - it was set low enough to be nearly invisible.

At the end of the runway, I saw one of the really cool differences between the old mechanical gauges of my RV-6 and the modern computerized stuff in the 12. Consider this picture:

The oil temperature is at 100 degrees, still twenty degrees below the 120 required by Rotax for exceeding 2,300 RPM on the engine. The engine RPM is shown in the upper right corner of the display - it was 2,240 RPM at the time. Notice that the RPM needle is in a very small green arc region, with yellow and red at higher RPMs. Now look at this picture:

The oil has warmed to 128 degrees and the colored arc around the tach has changed accordingly. The green arc has expanded to the full operating range of the engine. Let's see a mechanical tach do that!

The takeoff was brisk, quite possibly even more sprightly than the -6. We climbed out at 80 knots, showing about 800 feet per minute climb on the Dynon (once I was showed where to look for it, that is). The view over the nose was something that I expected to be better than the taildragger RV-6 on the ground, but I was still impressed with the forward visibility in the climb, too.

I took over the flying once we got away from inconveniently close objects and any other obstructions that I might fly into. I found the handling of the RV-12 to be very similar to the RV-6. It is nicely balanced in pitch and roll, meaning (to me, anyway) not that the forces in each axis are identical but rather that they go together as well as macaroni & cheese. The roll forces are light and the wing is willing and responsive, much like in the -6. This is often confused with "twitchy," but that's not an apt description. It's more accurately described as "turning by thought." You think about turning, your hand makes a small gesture of agreement, and the plane turns. This is wonderful in the roll axis (for VFR flying, and with an autopilot available to lend a hand while you nap or use the potty bag) but not at all desirable in pitch. When it comes to pitch, I want the plane to be a little more reluctant about changes. I don't want it to feel stiff, but I do want it to feel stable. That's the way the -6 is, and to my immense pleasure, that's the way the -12 is.

The RV-6, as with most (if not all) of the RVs, is tremendously easy to see out of. The -12 is even better. The aft location of the wing clears a lot of view downward. It's going to be fantastic for a photography platform.

I removed my headset for a few moments to see how loud the Rotax is. I've heard it described as quite noisy, and I suppose it is if you're used to heavier, store bought planes. I didn't think it was any louder than the RV-6. That's not to say that it isn't loud; it is. It's just that I'm used to it.

This being an Ohio weekend, the current weather had exceeded its five minute sell by date and was starting to look a little nasty. The few gallons that needed burned off were gone, so it was back to the airport.

Trust me, I have an RV grin on the inside!

Back in the pattern, the plane slowed down nicely. Since we were close to very hard and immovable things again, Mr. Rush was back on the stick. I begged a few seconds to see what the controls felt like at the slower speeds in the pattern and found that the forces hadn't changed much. That's a good thing, I figure. It didn't feel mushy. Mushy controls at landing speeds are what convince pilots that they are going too slow. This is how airplanes like Mooneys end up getting a bad reputation for landing "hot" and being "floaters."

I didn't make the landing, but it looked easy enough. For all I know, Mr. Rush's 3,300 hours have resulted in a "greaser every time" capability, but what I know for sure is that the landing he made for me in the -12 was a real keeper. Hopefully that had more to do with the airplane than it did with some form of super human ability and I too can finally make landings that don't have their own designated Seismic scale once I get my RV-12 done. 

Having had the dance, it was time to pay the piper and get busy on the Dynon work. As I get more comfortable with the menus and navigation on the Dynon, the easier it gets. It didn't take long at all to get the trim indicator working. Once you learn your way around the menus, it gets quite easy. You find the thing you want to configure and the Dynon provides step by step instructions. Very cool!

I'm glad we did the flying early; it wasn't long at all before the weekend weather arrived. These guys waited too long.

Sealing the steps

The aerodynamic shape of the steps in the portion that sticks out into the airstream is nice, but carrying that shape all the way up into the fuselage would make the bolting of the steps onto the supporting bulkhead require a much longer bolt. As a result, the streamlining stops just before the part of the step that goes through the fuselage skin, leaving an opening at the top. Van's asks that this hole be sealed using fuel tank sealant. That is the extent of their advice on the topic. Left unanswered are the questions regarding whether the entire void should be filled or just enough sealant put in to form a sort of lid, how one goes about keeping the sealant in place if one chooses the "lid" option, or how much sealant would be required to completely fill the void.

The choices are 1 quart (way too much), 1 ounce (probably enough for the "lid"), and 3.5 ounces. I went with the 3.5 ounce option - once you're paying shipping, it's better to err on the side of buying too much than not enough. Besides which, the 3.5 ounce size comes in a nice dispenser while the other two options come in cans. The 3.5 option also has a downside: since you mix it in the dispenser, you have to use all of it at once. It turns out that there is another problem with the 3.5 ounce option: the instructions are real head scratchers.

Here's what it all looks like right out of the bag:

Here are the directions provided:

Between all the dashers, rams, and vexation, I didn't know if I was learning how to load a cannon or if I was reading a Christmas story. "On Dasher, on Vexation...." Doesn't it go something like that? As I figured out how the thing worked, I grabbed a Sharpie and labelled the pieces:

Follow along as I go through the steps and translate into English.

Step 1: "Pull dasher rod towards the neck of the cartridge so that the mixing head is located at the nozzle end of the cartridge." Translation: pull the white knob out as far as it will go.

Step 2: "Insert the ram rod into the hole of the dasher rod. Push the ram rod until approximately 10% of the material contained in the dasher rod has been expelled into the cartridge." Translation: put the black stick in the hole in the white knob. Push like hell against tremendous resistance until the seal breaks and shoots 90% of the material contained in the dasher rod into the cartridge. Swear a blue streak at the 80% over-expellation of material.

Step 3: Read it yourself. That's too much typing. Translation: if by some remote chance you haven't already expelled 90% of the material contained in the dasher rod into the cartridge, continue to push the black stick in while simultaneously pushing in the white knob. Step 3: (cont.): "DO NOT expel a large quantity of the material in the dasher rod into the top or bottom of the cartridge."  Translation: ha ha ha ha ha ha! Now you gotta problem, Bub!

Step 4: Well, does it really matter what Step 4 says? You're already in a pickle. Just hope for the best and pull white knob back out and push it back in, twisting it clockwise all the while. Repeat 75 times or until you're arms are so tired that you just can't do it anymore.

After a couple of cycles

After approximately 75 cycles

It's pretty easy from here. Just unscrew the white knob (the dasher rod will follow along) and screw in the nozzle. Stuff the whole mess into a caulk dispenser.

Start squeezing it into the step.

So, here's the deal. This stuff stays where you put it (which is a good thing, but it also means it stays where you put it whether you put it someplace you wanted it or not - wear rubber gloves!!) so the seal is going to be somewhere between the "filling the void" method and the "lid" method. It will only go as far down into the step as the nozzle will reach. I filled it to the top, scraped off the excess with a scrap of wood, and put duct tape on it to hold the "lid" in place just in case the sealant actually moves at a pace indiscernible to the eye.

Be careful when setting aside the dispenser - it has some kind of momentum behind it and will continue to ooze.

As I mentioned, I taped the ends with duct tape and put the steps in a vise to keep the sealant from sinking away from the opening, assuming that's even possible.

I had a lot left over.

If I was doing this again, I'd either order the 1 ounce size and just spoon it into the hole to for a "lid" using a popsicle stick or I'd just wait and do it at the same time that I was building the fuel tank or sealing the edges of the firewall. This stuff has a shelf life (and it's not particularly long) so I couldn't just order a quart and leave it waiting around, but someone building at a much faster pace than me could get away with that.

Here are the finished steps:

Stepping through the steps steps

There are more steps to installing these steps than.... ah, I got nuthin'. I just wanted to play with the homonym.

The most notable thing about the angle brackets that I trimmed and primed before is that only one of the two flanges on each has holes drilled in it. This is, as I have learned, a strong indication that there will be match drilling in my near future. That future is today! The brackets get clecoed into place on the back side of the bulkhead:

Then on to the match drilling, which as we all know means "the simultaneous creation of two holes that will not align."

There are nine holes to be drilled on each side of the plane - a column of five and a column of four. The bottom hole of the outside column then gets final drilled to 1/4". Having already been drilled to #30, the hole is easily expanded to 1/4". A bolt is then fed through the lower bolt hole on the step and through the 1/4" hole. The step is then pivoted to a position that makes the actual step part of the bigger step piece horizontal with the ground while still  keeping the upper end of the step piece below the upper edge of the bulkhead. It's easier to understand with this picture:

I clamped it into place in order to hold it still while I drilled another 1/4" hole through the upper bolt hole and through the bulkhead:

Because I hadn't led off with a nice #30 hole, it was a real chore to get the 1/4" hole drilled.

With all of the holes drilled, the steps are in what will eventually be their permanent positions.

The steps aren't actually bolted on yet, but not because they would just be in the way for the remainder of the build (although that is certainly true) but because there are no nutplates behind the bolt holes yet. Everything gets taken apart again at this point, up to and including the bulkhead which was only being held on with clecos. Four aluminum braces with a nutplate each are positioned by installing a bolt through them to hold them in place while they are match drilled. Fortunately I've been double- and triple-checking things lately, so I noticed a problem before committing to an irrevocable drilling operation:

  

All of the bolting and unbolting and moving stuff around was pretty rough on the bulkhead and the braces so I gave everything another coat of primer. Make sure you mark the location of all of the pieces before you remove them - they're match drilled, but things will go much smoother if you put everything back in the same place you found it.

Once the primer is dry, all of that stuff will get riveted onto the fuselage.