Things that go Huh? in the night

It sometimes surprises me to find myself suddenly awake in the middle of the night wondering about some trifle or another. It's not so much the broad range of topics that can cross my mind while ostensibly sound asleep, rather it's how critically important even the most trifling thing can seem at the time. A couple of nights ago, I woke up in a near panic because I could not remember having run a string similar to the one that will eventually be used (I'm betting) to pull the stabilator control cables back through the aft bulkhead that would be used to pull the rudder cables. I eventually calmed myself sufficiently to get back to sleep by reminding myself that the tail cone is not yet sealed up. Still, it seemed odd that such a string hadn't been placed at the same time as the stab string. Could I have missed that step somehow in spite of the diligence that I apply to the practice of checking off every step as it's completed?

It wouldn't be until the next evening that I could get out to the hangar to see what was going on. It turned out to be quite simple: there is a step or two required before running the rudder cable string. There are a couple of small brackets whose sole purpose in life is to provide support for a couple of plastic bushings that will ostensibly help guide and protect the rudder cables. In fact, it is the installation of these little brackets that had me out driving in snowy weather on Tuesday night in order to pick up a borrowed 12" #30 drill bit. The directions have us cleco the brackets in place, then match drill a couple of holes using the extended length drill bit. In what turned out to be misplaced faith in the professed need for said drill bit, I braved the slippery roads in order to acquire it before starting the installation of the brackets.

On the plus side, separating the brackets from the now-expected Van's combo-pack allowed me the opportunity to try out my new tool:



Hot knife, it is my pleasure to introduce you to butter! The band saw makes a fast, clean cut that is orders of magnitude better than I have ever been able to accomplish with the tin snips or the hacksaw, and the icing on the cake is the additional excitement that arises from the risk, albeit small, that I could also remove one or more of my lifetime allotment of fingers.

It took a little bit of trial and error along with repeated trips back to the plan book to study the drawings to figure out the correct orientation and placement of the brackets, but as is often the case, it was patently obvious where they belonged once I managed to get them clecoed in:



Finally ready to use the drill bit that I risked life, limb, and automotive sheet metal to attain, I found that I didn't really need it after all. The little Craftsman drill fit in there just fine with my regular sized #30 bit:





Go figure. Someone at Van's apparently owns stock in Acme Extended Length Drill Bit Manufacturing, Inc. Me? I must have missed out on that IPO.

The drilling was the easy part; the spacing of these two rivets was, in a word, bitchy. One of them had to be drilled out and replaced as it rose out of the hole while I was pulling it, which was a first. Blind rivets are usually pretty much fool proof. Of course, when one aspires to be the best fool possible as I do, anything is attainable!

As I retrieved the plastic bushings from the little brown paper bag, I had a horrible flashback to the last bushing I had installed. That would be the 7/16" bushing that was somehow supposed to fit into a 6/16" hole, for those of you that may have missed that little ordeal. It was with great relief that I easily snapped these bushings into the provided orifice. I'm not sure what I would have done had they not fit, but I'm pretty sure it would have involved harsh language and a monumental tantrum.



I'm printing this picture and setting the print on my nightstand tonight, just in case:



Those were the last steps required before a large riveting job on the skins. The timing was perfect as soon-to-be RV-12 builders Don and Kyle were scheduled to arrive for a shop visit just a few hours later. Just let it be said that I have made good use of my high school literary studies, having often leveraged the lesson of Tom Sawyer's clever means of getting other kids to whitewash the fence that his Aunt Polly had instructed him to paint. As it turns out, the only thing easier than blind riveting is having someone else blind rivet for you!

And this is the beauty of the RV-12 in a nutshell. With a "normal" RV, potential builders worry themselves into a froth over not knowing how to drive rivets and wondering if they are even capable of being taught. They make pilgrimages to Oshkosh to attend riveting workshops. They spend hours practicing on scrap metal. The end up drilling out dozens of mis-driven rivets. They sink hundreds of dollars into tools. With blind rivets, if the EAA were to offer a seminar it would take longer to get everyone settled and go through the mandatory don't-blame-us safety briefing than it would to teach the actual operation.

I had each of the visitors pull a couple of rivets under my supervision and then simply turned them loose with a pair of cleco pliers and the air rivet puller. I went and worked on the RV-6, cleaned up the hangar a little bit, and generally made myself scarce while they riveted the entire tail cone. And the best part is, they acted like I was doing them a favor.



Oh, I am soooo good! I wasn't able to convince them to come back for my broom pushing seminar, though. I guess I have my limits.

All kidding aside, it's nice to have neighbors! Don and Kyle will be building their RV-12 down in the area of Jackson, Ohio. That's just a few minutes from Portsmouth, an airport I visit quite frequently. It'll be nice to stop by now and then to see how things are going for them. If nothing else, I'm pretty sure they have a good grasp of riveting fundamentals. They must have pulled a couple of hundred of them with no problems at all.

But the most gratifying thing of all was that those broken skin edges that I was so worried about after having molested them to within an inch of their lives snugged up nice and tight. No worries here:





Which is not to say that I won't be on the look out for other RV builders surreptitiously casting judgmental glances at the skin edges - I will. But I'm much less worried about it than I thought I'd be.

Here's the cone, just about ready to be sealed up:



Amazingly, it seems to weigh about 10 pounds. If the people that ride with us in these airplanes could ever feel how light and flimsy they are during construction, they'd never get near one! It's incredible how much strength they have once they're assembled.

LimaFox Cleco Delivery Service

There were just a few more things to do to finish up the installation of the static ports. Once those were done, two of the last three tail cone skins could be clecoed into place. Which, as it turns out, presented a problem.

As I drove over to the hangar, I couldn't help wondering how painful it was going to be to spend a couple of hours out there working. The concern came from the helpful electronic thermometer in the car that quite blithely informed me that we were enjoying 8, count 'em, 8 degrees of fresh Fahrenheit. In golf that's called a snowman. In everything else that's called, well, it's just called really cold if you want to maintain a family atmosphere in your writing.

All that really remained to be done with the static ports was to finish routing the various hoses and seal the ports with RTV. The former problem I had had with the RTV (which was not having any) had been resolved, but there was a new problem: the R in RTV stands for 'Room', and the T stands for 'Temperature.' And there's the problem: I'm sure Siberian Huskies might consider 8 degrees to be a suitable room temperature, but most of the people that I know insist on defining it as at least 60 degrees more than that. Still, it's bound to get warm at least once between today and the day it actually matters if the RTV has set up, so no worries. On we go.

With the RTV in place, it was just a matter of trimming the 1/8" inside diameter hose to length and plugging the longer part coming from the right static port into a little plastic T fitting, using some of the remaining hose to run a much shorter length from the left static port to the same T fitting, and attaching the 1/4" outside diameter hose that will run its way up to the instrument panel to the third port in the T.



A command decision was required. The instructions that came with the package of static system parts showed one method for attaching the hoses to the T:



The instructions that came with the RV-12 showed a slightly different method:



It was an easy decision; I went with the RV-12 variant. It's not a critical decision anyway. The RV-12 is apparently shaped a little differently than the other RVs and having the 1/4" OD tube coming straight off of the bottom of the T just fits better.

The part of the T that takes the 1/4" OD tube has to first have a 1/4" length of the clear 1/8" Inside Diameter hose applied to it:



That little piece of tube acts as a kind of seal, I think. Apparently the inside diameter of the 1/4" OD tube is too big for the fitting; the small length of clear tube acts as a type of adapter. Easy enough for me to understand, but the 1/4" OD tube was having none of it. It adamantly refused to fit over the clear tube. Fortunately the Cone of Comfort was able to do double duty as the Cone of Coercion. I heated the end of the 1/4" OD tube in front of the heater and was then able to slide it right over the clear tube and onto the T fitting:



Before securing the clear tube with tie wraps, I performed the critical blow test. That entails blowing in one end of the 1/4" OD tube and listening at each static port to ensure that air is making it all of the way through the system. The blow test is not in the plans; I invented it myself, even if only for the caption contest that's in it:



Here it is, all installed and sealed up (eventually, weather depending):





That completed all of the steps that are better accomplished with the tail cone only partially skinned, so I was able to then install the next two skins. I'm sure glad that I ignored the suggestion of 38" tall sawhorses! It was hard enough with the stubby little sawponies I'm using:



I mentioned a problem with clecoing. Here it is:



I'm all out of clecos! Lucky for me, Wingman (and RV-10 builder) Ted was flying out to Indianapolis from his home base in Portsmouth, OH and offered to sidetrack a few miles to drop off 150 more clecos for me to use. And thus was born the LimaFox Cleco Delivery Service, delivering clecos to the needy on a moment's notice:



They were put to good use:





I would have kept working, but the next step called for a couple of pieces that I hadn't prepared yet. So, it was back to the shop to cut apart a couple of little brackets using my new and improved method of cutting apart small brackets:



The band saw makes a much cleaner cut than tin snips or a hacksaw. I wish I had picked one up sooner! You don't have to have a band saw to build an RV-12, but I think it's going to be a welcome addition to the shop.

What you do have to have is a 12" long #30 drill bit. I only have a 12" long #40 drill bit. I'm going to have to borrow the bit I need, and I'm at a stop until I do.

It was pretty cold anyway, even with the heater blowing. It can wait a couple of days.

Strings and things

It's been almost a full week since I last did any work on the RV-12. It's been a week of fighting the elements (both Honda and natural) to and from work, only to head right back out into the winter weather to follow the snow blower around clearing the driveway. It's not that we've had a lot of snow as measured by inches on the ground as much as it is that we've had some form of frozen precipitation or another each and every day. Between that and returning to the sturm und drang of the paying job after a two week holiday vacation, there hasn't been a lot of time or enthusiasm for a trip out to the Schmetterling remote production facility.

Even today got off to a slow start, mostly due to the need for a refill of the fuel canister that provides the energy required to generate the Cone of Comfort. That necessitated a trip to Lowes, and no trip to Lowes is complete without the frustration of trying to take care of other to-do list items. Today's extra tasking was to replace a broken set of window blinds in Co-pilot Egg's room. The frustration arose when the machine used to cut the blinds to the correct width turned out to be broken. A blessing in disguise, that, for when I returned home empty handed I found that I had been prepared to irrevocably and without hope of return purchase blinds in the color of Walnut. That would never have done as the blinds to be replaced were in Oak. This is the big city, though, and what the local Lowes does not have can always be found by making a drive to a different Lowes. Well, "always" isn't really the word I'm looking for; "sometimes" or "rarely" seem to be more appropriate. It seems that all Lowes stores have replaced their stock of Oak hued blinds with Walnut.

I am now faced with the two most dreaded words in home improvement: Special and Order.

They did have propane, though, and that ain't nothing. Not when it's 20 degrees (aka "Minnesota heat wave") out.

Having spent almost a thousand words on the weather already, it's somewhat redundant to provide the picture that would have rendered the need for them moot, but here it is anyway:



Fortunately, that area is well out of the Cone of Comfort. Or, as suggested last week, the new Cone of Mild Discomfort that I'm using to save fuel. Even at the lowest setting on the heater, it's not bad at all:



There will come a day in July when that looks pretty appealing!

With the environment as comfortable as it can realistically be, I picked up where I left off last week. The first step was an easy one. If all of the steps were this easy, it would actually be true that absolutely anyone can build an airplane. All I had to do was run a length of string back through a couple of holes in the aft bulkhead:





I'm just guessing here, but I'd bet that this string will eventually be used to pull the horizontal stabilator control cables from the control stick back to the rear of the plane, where they will be attached to the stab control horns. On the topic of "Things that Would be Greatly Annoying," I would say that "having that string fall out before I'm ready to use it" is somewhere near the top. Van's agrees, and they suggest that we tape the ends of the strings down to avoid that potential irritation:



That was too easy, wasn't it? Well, it must have been, because the very next step is one of those clever little traps Van's throws in now and then to see if you're paying attention. It sounds easy enough: do the same thing you just did string, but now do it with the WH-P30 wires. These are the wires that will carry electrical current back to the electric trim motor. It sounds easy, but it actually gets added to the ever-growing list of things that end up being harder than they sound.

What could be hard about it? Well, note that the ends of the wires are not identical; one end has little brass pins, the other has partially stripped wires:



Note too that the drawing does not tell you which end goes to the front or which end goes to the rear. Either one of those details provided individually would have been adequate; the process of elimination works particularly well in binary decision situations. I sometimes wonder if Van's does things like this to teach you to read ahead in the plans. It's not like there hasn't been a revision to this page that would have provided a golden opportunity to disambiguate this step; a revision was released just a few months ago. The only difference between the original page and the revised page is the addition of an 's' to improve an uncomfortable grammatical situation and the replacement of a specific part number on a snap bushing with the less maintenance prone text "snap bushing." Seriously, I'm not making that up. Those changes were worthy of a revision, while telling the builder which way to run the wire was not. It's a very strange decision making process they're using, at least from where I'm sitting.

All of that said, the answer is only a few pages into the future.

In section 11, the ends of the wires coming through the aft bulkhead get crimped with connectors and thence crimped onto the wires coming from the trim motor:





Using the best-case process of elimination described above, I was able to intuit that the brass pins go towards the front of the airplane. All that remained was to actually do it, and that didn't present any difficulties. The wire gets pulled through the snap bushing, then it rides along inside the comfortable trough created by the J stiffeners. Wires are never left to their own devices in an airplane, though. They must always be constrained in some way to avoid having them interfere with other moving parts and to ensure that they don't rub against any edges that might cause them to be cut. Which is why I found this so perplexing:



Once the slack is taken up on that wire, it is virtually guaranteed to chafe against the edge of that J stiffener. If you consider where the wire is and how utterly inaccessible it is going to be when the airplane is done, it certainly makes you wonder why it would be positioned where it is. I'm going to poke around on some other builder blogs and see what others have done to protect the chastity of the wire, but for now I positioned it such that the part number tag bears the brunt of whatever chafing may occur in the future:



To do that I had to leave just a little more than the 6" extending from the back of the aft bulkhead that the plans call for - I hope I don't find out some time next year that my wires are an inch too short to reach the trim switch in the panel!

As I said before, wires have to be restrained somehow, and in the case of this wire that job is performed by tie wraps. In case you aren't familiar with tie wraps, here's what one looks like:



Tie wraps are very convenient and easy to use, but it is important to note that they are a one-time use item. They tighten in a ratcheting manner, which is to say once you tighten one, you can't loosen it. What that means is that if you are going to tighten it, you had better be sure that everything that you want it to hold for you is already in it. That's okay here in the back of the plane, but there is a bold font warning to leave them loose once you get forward of the furtherest forward fuselage frame. There will be other things that need to be installed before the tie wraps are tightened.

Installing the tie wraps was a simple matter of feeding the nose of the strap through a hole conveniently pre-drilled in the J stiffener, making sure that the trim motor wire was captured in the loop formed as the nose of the tie wrap was fed into its ratcheting mechanism, tightening the tie wrap, and cutting off the excess tie wrap with a pair of side cutters:









Just like the string before it, the remaining length of wire gets secured to the front edge of what Van's refers to as "the existing airframe."



Continuing to work through the list of "stuff that you had better put in now because it is soon going to be very difficult to get at," the plans refer us to the instructions included in the separate static line kit. More specifically, this separate kit provides the static ports and lines that will feed outside ambient air pressure to the flight instruments. For those of you that have no idea what I just said, I refer you to Wikipedia's description of the Pitot-Static System here. And for those that can't be bothered to follow the link (you know who you are), here's the bare bones gist of it:

Static pressure
The static pressure is obtained through a static port. The static port is most often a flush-mounted hole on the fuselage of an aircraft, and is located where it can access the air flow in a relatively undisturbed area. Some aircraft may have a single static port, while others may have more than one. In situations where an aircraft has more than one static port, there is usually one located on each side of the fuselage. With this positioning, an average pressure can be taken, which allows for more accurate readings in specific flight situations.

The RV-12 has two static ports.

The ports themselves are essentially glorified blind rivets and are, in fact, installed exactly the same way as any other blind rivet:



When I read ahead to this step, I was curious as to why more information wasn't provided in the drawing to provide a specific location for the hole that would need to be drilled for the rivet. Well, the answer to that question turned out to be "because the hole was already drilled for you":



While I said above that the static port rivets were pulled just like any other blind rivet, I wasn't being entirely honest. Yes, the method is the same, but there is a lot more pressure to get them perfectly flush to the skin the first time - two are needed, and only two are provided.



Good news! They went in just fine!



That wasn't the full extent of my lie of omission, though. Normally a blind rivet retains a piece of the mandrel (the "nail" that the rivet puller pulls out to form the shop head of the rivet) after the rivet is installed. That's a good thing - it increases the strength of the rivet. It would be a bad thing with these rivets, though, because it would seal the static port. A sealed static port is really nothing but a decoration on the side of the plane (planes have actually crashed from having static ports blocked), so the remaining mandrel has to be driven out of these particular rivets. Remember that "things that sound like they should be easy but aren't" list?

Yeah, this goes on it.

It's assumed in the instructions that you emerged from your mother's womb knowing how to remove the mandrel from a static port rivet. I wasn't so lucky. I had to figure it out for myself.

My first attempt involved using one of the hundreds of blind rivet nails that I have captured from building the existing airframe by inserting it into the static port and whacking it with my dead fall mallet. That approach had a couple of problems. First, the sharp pointy end of the nail was digging holes in my mallet. Sure, it's a Harbor Freight tool and therefore easily and cheaply replaced, but what kind of attitude is that?? Second, the tail cone skin is thin and whacking it with a mallet seemed like a good way to create a dimple where the static port was supposed to be.



Solving the second problem first, I drilled a hole into a block of wood that the inside part of the static port rivet would fit into and clamped the wood into place on the side of the tail cone. That gave me a little more rigidity in the vicinity of whacking:



The problem of the sharp nail was solved by a tool that is nearly as ubiquitous in problem solving as duct tape: the vise grip. I clamped the vise grips down hard on the nail, then used the mallet to whack the vise grips:



Even with all of that, it takes nerves of steel to pound a mallet against the side of your airplane. Me, I have nerves of highly malleable lead, so it was a very, uh, puckering experience. But finally, success!





The ports are connected with a length of clear rubber hose that resembles the type of hose used in aquariums. Remember that problem with blocked static ports? Well, it doesn't have to be the port itself being blocked to cause a problem; anything blocking the rubber hose would have the same effect. That's why I was very concerned with the kink that got creased into the provided hose as a result of pressure from a metal part being applied to the hose during shipping:



Fortunately the kink is near one of the ends of the hose and it's possible that more hose than is actually needed is provided in the kit. Unfortunately, I won't know that until the hose is installed. The problem here is that the hose gets installed with tie wraps, and as we learned before, tie wraps can only be used once.

What to do, what to do.

Ah!

Here's a nice ball of string! And what is a short piece of string if not basically a cleco for a tie wrap?

Yep, that worked nicely!





It looks at first glance as if there will be plenty of hose to allow the damaged part to just be cut off and thrown away.

The next step is to push the ends of the hose onto the inner nipples of the static ports and seal that in place with clear silicone RTV. I don't have any, though, and for some reason I'm enormously reluctant to go to Lowes to get it.

But I will. It's going to take awhile, though. I have a special order to place.