A Matter of Trust...

... or, I suppose one could say, "A Line of Credit."

I was hoping to receive the extra fuel line that I had ordered from Van's last week so I could keep up my momentum on the fuel system this weekend. I still had some fuel line to work with, but most of the short runs are done. That leaves the big run from the fuel pump up to the fuel valve to do, and the amount of tube remaining after my first abortive attempt was too short. I had also ordered replacement screws and nuts to finish those pesky six screws that have given me so much trouble. Those needed to be done so I could install the plastic channel blocks that hold the fuel lines and brake lines. As you may remember, I had received a phone call from Aircraft Spruce to tell me that the Visa card that I used to pay for the tube bender had been declined due to suspicious activity. I had heard nothing from Van's, so I assumed all was well that order.

Not so much. My package arrived in time to allow me to continue work this weekend, but it contained a note.

I was thinking about how trusting those folks must be to go ahead and send the order without knowing that I'd eventually pay for it, but then it struck me that if I didn't pay, they were going to be very unlikely to send me a finish kit, or an avionics kit, or an engine kit.... yeah, I think they're pretty sure that they will get paid!  Still, it was an act of good customer service to just go ahead and send it so that I wouldn't have to wait all of those extra days to get the accounting straightened out.

As I was reviewing the steps for fabricating the 40.5" tube that makes the long haul from the fuel pump up to the fuel valve, I got to thinking that I ought to learn how to use the fancy tube bender with all of the intricate and arcane mathematical machinations detailed in the instructions that came with the it. First I measured and marked the 'L' length.

That line is used to match up with one of the plethora of markings on the tool. If all works out as it should, you are left with exactly the right length of tube before the bend.

You have to be careful while doing this. While it looks like the Sharpie(tm) mark on the tube is correctly aligned with the 'L' mark, it actually isn't. If you look closely at the spot that I pointed out in the picture, you will see that the 'O' line on the top part of the bender is not aligned with the 'O' on the lower part. That means that I didn't have the top part of the bender snugged down and aligned tightly enough on the tube. I reseated the tube in the tool until the O's lined up, then made the bend.

Taa-daaa!

A perfect match! The math (well, there was no real math, to be honest.) worked!

So now the bad news: the tube bender that I have cannot make another 90 degree bend as close to the one that I had just made as the one depicted in the drawing. I snugged the tool up as tight as I could get it to the existing bend and hoped for the best. While it didn't match the drawing exactly, in the end it turned out to be close enough.

This is another of those tubes that needs to be pushed through bushings and bulkheads before the second flare is made, besides which I was anxious to see if my too-far-apart 90 degree bends were going to be a problem, so I guess I was in a hurry to get it into the plane. Due to its length, I had to feed it in through the lightening holes in the aft bulkhead. It took a little bending and scraping to get the unflared end up to the first bushing, where the bushing in question refused to allow through passage. The tube wouldn't fit through the bushing! It looked like either the bushing was too small, the slight angle of the tube trying to go through it was causing it to bind, or both. I ended up pulling the whole enchilada back out of there to see if I could figure out what was wrong.

After a bit of trying this and that, what I finally ended up doing was cutting off a few inches of extra tubing (which I could afford to do now that I have way more than I need - it's either feast or famine around here) and sliding it in and out of the bushings to loosen them up a little. Once I had them loosened up, I was able to wriggle and bend and coerce the tube back in through the aft bulkhead, through both of the bushings, and up to the fuel valve. Success!

But wait! What about the channel blocks that the tube is supposed to fit down into. For that matter, what about those pesky screws and nuts needed to hold the channel blocks in place? Drat. Out came the tube again.

You may remember that those screws weren't put in place because the nuts were way too tight and I stripped the screws out trying to get them threaded in. The replacement screws and nuts had arrived in the same package as the fuel tube, so I was ready to try again. I have been thinking about the proposed solution of running a 8-32 tap through them to loosen them up, and I ended up not being too keen on the idea. My fear was that it would loosen them too much - they're lock nuts for a reason. Well, with the new nuts it turned out that I wouldn't have to. For some reason, the screws went into the new nuts exactly like one would expect them to. That naturally left me wondering just what was wrong with the nuts that came with the kit, but I decided to let the teeth of that particular gift horse go unexamined. I was just happy to have it finally done.

With the screw posts in place to hold the channel blocks, I installed the blocks and pushed the fuel line through the maze again. You'd think it would get easier with repetition, but it didn't.

Yay! Progress!

Short-lived, though. Next step? Cut the end off the tube to make it the correct length (not needed, oddly enough) and pull it back out far enough to flare the end. And don't forget to put on a sleeve and nut!!!

The tube didn't have to come all of the way out (in fact, you would not want to pull it back out through the bushings since you wouldn't be able to get it back through them once it was flared) but it did have to be bent quite a bit to get it up where the flaring tool could reach it.

That was a treat for my knuckles!

Once flared, I screwed both fittings onto their respective ends.

I was going to do the last line that runs from the tank down to the pump, but it turns out that I'm missing the two sleeves build that line. That's what I get for not doing an inventory on the bags. It's only a couple of bucks worth of parts, but it's going to take a few days for them to get here. I'm also missing the nipple that goes in the gascolator, so I had to order one of those too.

A fuelish mistake

You might as well get used to awful puns around the word "fuel"and other fuel system terms for two reasons: it looks like we're going to be here for awhile, and because I think they're a gas! Hopefully I'll get it out of my system before I make a fuel of myself.

What? Too late? I've already gone around the bend? I just don't have a flare for this kind of thing? The words just don't flow right? I need to filter my.... okay, I'm done. Tanks for bearing with me while I got that out of my system.

The few days of delay while waiting for the tube bender to arrive courtesy of the emergency Visa card were well spent enjoying the gorgeous weather we're having. Sure, there was mowing to be done, but there was also some pleasant evening flying in the RV-6. I was even introduced to 12 year old Scotch by the guy that hangars his Cherokee across from my hangar. He said it has a "bold, oak texture." Yeah, so does a good rocking chair. I suppose it's an acquired taste, but I thought it tasted a lot like mouthwash with the cool minty flavoring removed. Still, if I'm ever to be a man-about-town in the William Powell sense, I will have to learn to like it. 

Ironically, once I had the tube bender in hand, the first step of building a segment of fuel line was to unbend the tube. Van's, quite understandably, didn't want to have to ship an eleven foot long box just to enclose the aluminum tube, so they coiled it up. Being aluminum, it uncoils pretty easily.

Of course, being aluminum it also springs back a bit when you stop rolling it along the flat surface you're using to uncoil it against. Trying to get it truly flat required a little hand bending, which resulted in an almost flat, kind of wavy tube. The fuel won't care about that, though.

The particular segment that I started with (after practicing on a much shorter segment, just in case) will run between the fuel shut-off valve and the little electronic fuel flow measuring gizmo. The plans give a specific length of tube to start with, so the first step after flattening out a length of tube is to measure the length and cut the tube. The tube cutter is a low cost Harbor Freight variant that works just fine. It's a simple thing to do, as you can see if you watch the video that I linked to in the Video Tutorial sidebar.

The next step is of critical importance, most of the time. The tube is useless without any means of threading it onto a fitting somewhere, so a "sleeve" and "nut" need to be slid onto the tube. The flare that we're going to make next will do two things: it will hold the sleeve and nut onto the tube, and it will preclude the sliding on of same if you forgot to do it first. On the first side of a straight tube, it's okay to forget because the other side is not yet flared and there are no bends in the tube to stop the sleeve fro sliding along, but it's a very good habit to make sure you always get the sleeve and nut in place before making the flare. And, as it turns out, it's a good idea to make sure they stay on the tube and don't slide off the other end, fall to the floor, and roll under the tool bench.

Yes, really, I have personal experience on this, so trust me.

The flaring tool is a wickedly expensive (well, it's about $90 if you can't find anyone to borrow one from, although even that should cost you at least a nice breakfast or lunch to show your appreciation, or even a twelve year old Scotch if you've acquired the taste for that kind of thing) and complex looking affair, but again, if you watch the video I so thoughtfully provided you will see that it really isn't all that difficult. Actually, it's somewhat fun once you've acquired the taste. Like machine countersinking, it's a fun tool to operate and it results in a professional looking piece of metal.

Viola, as they play in France. What? Oh. Sorry. Voilà, as they say in France.

Now, the fun and scary part. The bends. "Bends," a word that strikes fear into the hearts of novice airplane builders and seasoned scuba divers alike. The novice builder gets an assist from the fine folks at Van's, though. They have provided full scale drawings to work from.

And at long last, the tube bender is in the game!

I just bent the tube until it matched the picture. I suspect that this is one of those things that you could over-think if you read the instructions that came with the bender. There are measurements to make and index marks all over the bender to use for various types and degrees of bends, but I just figured matching the drawing would get me in the neighborhood. 

And it did. 

To do the bend in the opposite direction, I just flipped the tube over. I made sure that it was going to bend in the same plane by visually ensuring that the already bent portion was perpendicular to the horizontal plane of the tool. Sound complicated? It's not; it's purely intuitive.

This tube passes through one of the plastic bushings in a bulkhead, so the flare at the other end will have to be done with the tube already in the plane. Otherwise, the flare would make it impossible to pass the tube through the bushing. Even without the flare, it takes a little maneuvering to get it through the bushing. Good thing that big hole behind the valve was there!

I wanted to get the tube threaded onto the valve before checking the other end for fit. Finger tight is good enough as long as the flared part of the tube is hard against the matching part of the fitting.

For the next picture, I was going to suggest that we indulge in a little game of "what's wrong with this picture," but it wouldn't be fair. The obvious answer would be "the tube is too short," but that's the photographer's fault. Once the tube was attached to the valve, if anything it appeared that the tube was actually too long. It appeared that way because it was too long, but that wasn't the real problem. The real problem was that the fittings didn't line up at all and the fuel flow transducer itself was sitting on only half of the little shelf provided for it. That was happening because the little shelf was installed the wrong way around. Its rivets had to be drilled out and it then had to be reinstalled the right way around.

With the transducer properly orientated the alignment was much better, albeit still not perfect. Tube is bendable for a reason, though. It would just take a simple S-bend to fix that. Alas, the tube would have to be removed from the plane to do that. You can see that the tube is too long:

With the tube shortened and the S-bend made, it all aligns much better.

The S-bend required was not shown in the plans, so I had to ad lib a little. I needed the tube to go a half inch higher and a half inch to the left. Again, I'm sure that there are ways to do all of that mathematically but it was just as easy to eyeball it. I also had to shorten the tube a little bit. I just put the tube up against the fitting, determined where the flare should be, added a titch to that because some of the length of the tube will be lost in the flaring, and cut the tube. Easy!  More difficult was to again resist the urge to flare the other end of the tube before getting it back into the plane, but my unassailable self-discipline was up to the challenge.

Flaring the tube in the plane? A royal pain. Not a lot of room to work. On the plus side, that sleeve and nut ain't gonna be hitting the floor again!

All said and done, the whole operation took about an hour.

Just flailing around for a few days

Right up until I decided that it would be easier to skip over Section 23 and jump ahead to some of the later sections that require easy access to the bottom of the fuselage, I was quite comfortable in following the enforced linear path of "do this, then do this, when you're done with those, do this." Now that I have options, I seem to have lost my sense of steadfast direction. I could work on the rudder pedals, or I could work on the fuel system, or I could starting painting some of the interior parts, or... well, I just can't seem to decide.

Any decision being better than no decision, I had started down the path of doing the fuel system. That was going fine until I tried to bend the first length of tube. As it turns out, there is a difference between the cheapy tube bender from AutoZone and the more sophisticated tools available from airplane shops. The first bend was to be 90 degrees. And it was! Unfortunately, it was a 90 degree bend with a crimp in the tube for the last 30 degrees. The tube bender didn't have any facility for keeping the tube down in the support channel (I don't know, what do you call it?) and the tube lifted out as I was bending the final 30 degrees. Crimpsville, just like that.  Bummer.

Having ruined an entire four or five inches of precious tubing (which in my prescience I have already ordered more of) I decided that it would be more expedient to buy a proper tool rather than throw more tube into the maw of the crappy bender.  I immediately placed an order with Aircraft Spruce, hoping that the tool would arrive quickly in order to maintain what little momentum I had developed on the fuel system work.

It wasn't to be.

Aircraft Spruce called the next day to tell me that my Visa had been declined. Now I don't want to brag, but overdrawing my Visa account simply doesn't happen. Something else was amiss. I called Spruce and verified that I had entered the numbers and expiration date correctly. We verified my billing address. All of that was correct. On to the bonus questions*:

"Where were you born?"

In a hospital.

"No, what city?"

Oh. Cincinnati, Ohio.

"Is your blood type B-positive?"

Yes.

"Were you married on May 23, 1992?"

Hold on, let me check my notes since I always get this one wrong.... yes I was.

"Well, it would appear that you're well and truly screwed. What do you want to do?"

Nothing, really. I'd have to say that I'm pretty happy in the marriage.

"No, I meant about the order."

Oh.

* It should be obvious, but just in case it's not, the bonus question portion of the above is purely fictional. Well, not the part about being flat out of luck with the Visa - it actually was declined.


I went ahead and cancelled the order since  I didn't happen to be carrying my spare Visa card. I then had the CFO contact the kind folks at Visa to see what was going on. The answer? "We stopped approving new charges after a suspicious charge was made on your card."

Really? Suspicious? It was a $1.00 charge at iTunes. In case you're not familiar, let me tell you a little something about iTunes. It is a website that sells songs to be downloaded onto iPods. The cost of the songs? Well, $1.00. So is it truly suspicious to see a purchase of $1.00 from a web site where 99% of the product for sale is priced at $1.00?  As it turns out, yes. It's counterintuitive to me, but Visa says that there is often a "test" charge on a stolen card to see if it works, and charges like they saw at iTunes are very typical ways of testing. Who knew? It seems to me the best test charge would be to actually go out and buy something expensive right away rather than tip off the Visa Police with a measly $1.00 song, but I guess that would come with more risk because you'd be at a physical location where you could be caught. But then again, doesn't the $1.00 test charge carry the same risk, albeit with the addition of a high degree of false confidence? "Yeah, man, I don't know how they caught me. The test charge went fine!"

So now I'm waiting for a tube bender. In the interim I was able to complete the inventory of the wing kit. There was just one little piece missing, and a call to Van's quickly got a replacement on its way to my front porch. They're always pleasant to deal with on these kinds of calls. I always expect an inquisition asking whether I had carefully checked within the folds of the mountain of paper the parts come wrapped in, but they never do. The apologize for the inconvenience, verify my address (and thankfully have no questions about my credit card), and send the part on its way.

I guess I'll start on the rudder pedals now.

But first, a question from the mail bag that I think warrants an answer:

Did you try filling the tube up with fine sand to prevent crimping? Works fantastic for regular copper plumbing pipes.

This is an interesting question because I came across this same suggestion when I was researching tube bending issues. The problem is that I am loath to introduce any more foreign materials than absolutely necessary to the fuel lines. It only takes one grain of sand or other tiny obstruction to block a carburetor jet. It's inevitable that a little aluminum will get in the tubes from the cutting and burnishing, and every effort will be made to clean out the tubes before they are installed on the plane, but I just cringe at the idea of getting a grain of sand in there that steadfastly resists my cleaning efforts but eventually acquiesces to the pernicious demands of flowing gasoline, only to lodge itself in a very inconvenient location further downstream.

That said, if the fancy tube bender also includes more than a modicum of FAIL with its more sophisticated feature set, I will have to look into other means of bending the tubes. I don't think that's going to happen, but if it does I will have to try a more old-fashioned method. What I would try next is tube bending springs. Just like sand, they're dirt cheap (heh! I really crack me up!) and have the benefit of working external to the tubing.

Just Fueling Around

As with many things, it all has to start with a trip to Lowe's. In this case, it was step one that called for a small amount of pipe thread seal. "Small amount" indicates some arbitrary value greater than zero, and zero is precisely what I had on hand.

It was to be used when installing AN fittings in a couple of the fuel system's mechanical devices. First up was the fuel pump. Nothing fancy about this - I suspect they have them at Walmart.

The mount for the fuel pump was installed in Section 21. While the fuel system is presented as Section 28, I think it ought to be Section 24, coming right after the addition of the nose chin and lower firewall. I chose to do it this way so that I wouldn't have to work around and over the side skins, but it would also have been a little easier to install the pump if it had been done the same time as the mount. I would have bolted the pump to the mount, then riveted the mount to the belly skin. That would have saved me a couple of lacerations caused by rubbing my hands against the edge of the tunnel while reaching down in with a wrench. Another thing that would have helped that would have been to buy the nut drivers I went to Harbor Freight to get. I'm not sure how I managed to forget to do that.

There it is, ready to be the first station on the fuel's journey to the engine.

Aircraft fuel systems always have a valve for stopping the flow of fuel to the engine. The next piece of hardware was this type of on/off valve. In most airplanes, this valve would also act as the selector between two or more fuel tanks. This is the case because most airplanes carry their fuel in the wings. The valve selects which wing tank is to be used, in addition to providing the normal on/off selection. In the RV-12, there is only one fuel tank located back in the baggage area. Having only one tank simplifies the fuel system and also makes it much easier to have removable wings. Not only is fuel heavy, which would make the wings much harder to remove, store, and reinstall, but the added complexity in building a fuel system that could be easily connected and disconnected would be prohibitive.

With that in mind, behold the simplicity of the RV-12 fuel shutoff valve.

The first step is to remove the red plastic sleeve on the handle of the valve and drill a #30 hole in the handle.

The red knob comes with its own instructions, but they are confusingly written. They say to start by drilling a #16 hole and then drill the hole wider to #11. I'm not sure what the #11 hole would be intended for. Drilling it that large would make it much larger than the screw provided to hold the knob on the handle. I drilled the #16 and called it quits.

A couple more AN fittings get screwed in. I used a couple of wrenches to get them in nice and tight. It was blind luck (or good design) that they tightened up right when they were oriented correctly.

With both fittings in, a little box is built around the valve to hold it. 

If you look under the two clecos, you will see a little plate slid under the side wall of the box. That's the way that it fit in the easiest. But...

Darn. The drawing has it on the other side. It would have to be moved. On the correct side, though, the fit was much tighter and it was harder to get the rivet holes completely aligned. Now I've been known to grab a drill and use it to remind some holes just what it means to wear the #30 on this team, but I was reluctant to do that in this case. It took some pushing and prodding, but I finally got it assembled.

The actual installation in the plane was a piece of cake.

A piece of cake which, it would appear, has a cherry on top!

Six little screws

I'm still buggered by those six little screws that have been taunting me since the last page of Section 21. It looked so easy! Just put six screws up through the belly skin and attach them in place with six little lock nuts - how hard could it be?

The first sign of difficulty came when I couldn't reach both the screw head and the nut on the other side of the skin at the same time. That's when I knew I was going to need help. That should have been easy too, but I soon learned that the help available to me within the family was not up to the task. The nuts are pretty tight on the screws and try as she might, young Co-pilot Egg simply couldn't hold the socket wrench tight enough. I enlisted outside help, but it was quickly determined that part of the problem was the insufficiency of my tools., The socket I had was too shallow to allow the inch long screw to be fully threaded onto the nut. The suggested alternative was to go to Harbor Freight on a procurement mission for nut drivers. No problem, that, since I also needed a tube cutter for the pending fuel line work.

Harbor Freight did have nut driver sets, but none of the sets contained the required size. The nuts in question are a relatively exotic 7/32" and the Harbor Freight nut drivers skipped from 3/16" (6/32" for those of you that need a translation) to 1/4" (8/32") with no intermediate stop at 7/32". While the sizing of all Harbor Freight tools is somewhat approximate, I didn't think I could count on a convenient 1/32" spread, so it was off to Sears, Home of Precisely Sized Yet Onerously Expensive Tools. It wasn't all that bad, as it turned out. $3.79 for a deep well 7/32" socket. I wouldn't want to buy a 64 piece set at those prices, but it was okay for a one-off.

With the nut now held firmly in place with the Craftsman Unaffordium socket wielded expertly by a manly helper, there was only one other possible point of failure: the screw head itself. Which is, naturally, where the next healthy application of FAIL came from. The fit of the screws through the nuts is so tight that the screwdriver finds it easier to just eat away at the screw head than to torque the screw into the nut. We managed to get two of the six installed, had to use the Dremel to cut two partially installed but completely ruined screws out of their holes, and ruined the remaining two screws in abortive attempts. I now have replacement screws and nuts on order from Van's, along with a preemptive order for more fuel line because I'm pretty certain how well that job is going to go too.

In the meantime, I placed a request for helpful hints on the Vans Air Force web forum. To date the best reply is "tap the nuts with an 8-32 tap first to loosen them up," followed closely by "use Loctite to keep them fixed in place if you do."

That sounds like a workable plan.

Finishing the chinny-chin-chin

With just two more pages to go in Section 22, today was the final stretch for the lower front fuselage, or what I have taken to calling "the chin."

 It started out easily enough with the installation of the mount that will hold the fuel flow transducer. That little gadget will measure the amount of gas running through the line and pass that measurement along to the Dynon display. It was simply a matter of installing a pair of nutplates (although I had to counter-sink some holes in the mount despite there being no mention of doing so in the manual) onto the mount, clecoing the mount to the inside belly skin, final drilling the #30 holes for the rivets, and riveting it in.

This is the transducer set in place just to see what it will look like.

At long last, the chin was finally ready to be riveted to the rest of the fuselage. I wanted to have it positioned so that I could get clecos in to hold it in place, so I flipped the rest of the fuselage over. Not only was that somewhat tricky to do alone, it also turned out to be a mistake. No matter how I wriggled and jiggled the chin, I could not get it to mesh with the front of the fuselage.

If turning the big Chunk O' Fuselage over alone was a pain (it was!), turning it back over again would be even worse because I'd have to be very careful to align it with the sawhorses so as to avoid having them place untoward torque on the protruding clecos, thus running the risk of bending the skin. I had to ask co-pilot Egg for assistance. With her help I was able to get it turned over and see what the problem was.

It seems that parts of the chin skin that has to overlap the fuselage skin have notches to allow the flanges to mesh, while other parts do not. The only way I could get the non-notched parts to mesh was to force the fuse skin to slide under the flange of the chin. All of the pushing and prodding had scratched up the skins a little bit, and as this is the bottom of the plane and thus likely to be exposed to relatively wet and dirty conditions now and then, I cleaned up the skins and applied a coat of primer to each.

Here's what it looks like in the area where there's no notch:

Here's an area with a notch:

With the chin finally tentatively held into place with a few clecos, Egg helped me get it flipped back over again for riveting. That accomplished, I release her from servitude.

While I had been having problems getting the chin to fit on the rest of the fuselage, I checked with some other RV-12 blogs to see what the problem was. To no avail, as it turns out, as no one else seems to have had a problem with it. I did see one of those helpful suggestions that I run across now and then that suggested installing a couple of parts from Section 23 before getting too far along with the riveting of the chin. Just as I started the riveting of the chin to the fuselage, I realized that I hadn't installed those parts yet. Doing so now would require either calling Egg back downstairs to help flip the fuselage over again or crawling around on the floor to do the riveting. 

I chose the floor.

With that done, it was just a lot of routine riveting. I thought about hauling the whole thing up to the hangar so I could use the air riveter, but I'd only have to being it right back when done. I just did them all with the manual puller.

The reason I would have had to bring the whole back to the shop rather than just leave it out in the hangar is that I'm going to skip ahead to Section 28. Section 23, which would normally come next, is where the side skins get attached. If I do that now, Section 28, which is the installation of the fuel lines, will be much harder because I'll have to lean down into the fuselage to reach all of the places in the bottom of the fuselage where fuel fittings and lines are to be installed. Better to just do all of that while the access to the areas that stuff has to be installed is much easier, I figure. And better to do it in the temperature controlled basement than in the hot, muggy hangar.

I've got all of the fuel system parts, fittings, and materials laid out and ready to go.

I still have to get those pesky system blocks screwed into place, though, Living in a house full of women, I haven't got anybody that can hold the wrench tight enough or turn the screwdriver while I hold the wrench. My only options at this point are to call for external help or adopt a little boy and wait fifteen years until he's old enough to help.

Tough choice, that.