Saturday, July 17, 2010


It's beginning to dawn on me that there is a reason that people buy airplanes already built. It's just for the fuel systems, I think.

Having finished the rudder pedals, it was back to the fuel system. But a little housekeeping would be needed first. It's been awhile since I've straightened up and it was getting hard to find things that I had just set down moments before.

It's a cluttery process, this airplane building. Every tool has its place, but it seldom visits it. After a little rearranging, I was ready to start.

I still don't have the nipple for the gascolator, but I did somehow manage to order the correct sleeves so I could finish the fuel supply line that runs from the fuel tank to the fuel pump. I had already made the first 90 degree bend in that line, but progress came to a screeching halt when I went to get the nut sleeve from the parts bag. As it turns out, even if the sleeves hadn't been missing, I was in for a rude awakening. You see, in my fervor to get the first 90 degree bend up tight to the end of the tube (as shown in the apparently fictional rendition in the plans) I hadn't put the sleeve that I didn't have on the tube. Had I done so, I would have realized that the flaring tool wouldn't work with the short length of tube left after making the bend. With the sleeve pushed back as far as it would go, the end of the tube fell 1/8" short of where it needed to be for the flaring tool to work. BAM! Two feet of aluminum tube tossed aside as ruined.

Fortunately for me (but not so much for the fellas I was going to donate my extra fuel line to - better order some, Kyle) I had a lot left over from the spare length that I had bought. I rolled out another two feet (plus two inches, just in case), put the nut and sleeve on and made the flare, then did the first 90 degree bend. Which, oddly enough, is the exact order written in the directions. Imagine! Still, my tube bender can't get the bend where Van's wants it, but the extra two inches of tube I had to work with would cover the extra distance the tube would have to run. And the best news is that there would still be enough tube left to give at least a couple of feet to Kyle.

For the second 90 degree bend, I did the measuring to find the location of the 'L' line as specified in the instructions that came with the tube bender. That bend went perfectly. Then there is a slight fifteen degree bend that I had to do by eyeballing - the tube bender instructions are notably mute on the topic of bends less than 45 degrees. That left only one more bend: another 90 degree bend that would turn the line up from the plane of the first three bends to attach to the bottom of the fuel tank. I measured an 'L' line, very, VERY carefully made sure that I was bending in the right direction (it's surprisingly easy to go the wrong way), and made the bend. I set the finished line down on the plans and found the the last bend was about 1/2" out of position. Argh! That's way more than can be waved away, besides which using the extra length of tube to get the bend to the wrong location had eaten up enough tube that the vertical part would be too short to reach the tank.

Remember the old adage "measure twice, cut once?" I've amended it for fuel line fabrication: "Measure twice, bend once, start over."

I grabbed the last of my tubing, made the flare with the nut and sleeve installed, made the first 90 degree bend, measured the 'L' line for the second degree bend, and confidently made the second 90 degree bend in the wrong place. Yep. The wrong place. I got something wrong in either marking the 'L' line or getting it positioned in the tube bender and the distance between the first and second 90 degree bends ended up being too far. Desperate, I decided to try to save the tube by making the fifteen degree bend a 30 degree bend, my thinking being that the vertical 90 degree bend only had to be in the right point in space, no matter how convoluted its path in getting there.

That seemed to work. If I could only make the third 90 degree bend in the right place this time, all would be well. I didn't bother with an 'L' line this time, that method having failed me twice already. I eyeballed the last bend and very, VERY carefully ensured that I was bending in the right direction, drove to KFC for a bucket of chicken to sacrifice at the altar of all deities affiliated with tube bending just to increase my chances of getting it right, and made the bend.


Well, you'll have to take my word for it. All of the stuff described above is hidden under the baggage floor.

Flush with victory, I went on to the next step. With the fuel delivery line completed, I now have to build the fuel return lines. It would seem that not all of the fuel that leaves the tank ends up getting burned, or at least not on that particular trip. Some apparently gets returned to the tank. Not as much as leaves the tank, though; these are 1/4" lines, not the 3/8" of the delivery lines.

Step 1: put a fitting through a bulkhead. A bulkhead that is now accessible only through an inspection port in the belly skin. The belly skin that hasn't always been there. It's the belly skin that I put there. I put it there when I was told to. You know what would have been nice? If I had also been told to put this fitting in before putting the belly skin on. It would have taken two minutes. Instead it took hours.

Putting it through the bulkhead wasn't so bad.

Getting a nut and washer tightened onto the other side was. It ended up taking hours and giving me a painful case of conniptions. Whatever those are. I think it's something my grandparents had, back in the day. We get vaccinated for it now, but even modern medicine has its limits.

The first problem that I ran into was that I needed a way to hold the fitting in place while I wrenched on the nut. I tried having Co-pilot Egg hold it, but she couldn't get enough of a grip on it. Also, when she held it flush the corners of the flats on the nut would hit the belly skin and I wouldn't be able to turn it. I was at a loss. It was time for the last resort, which is to search the forums on the Vans Air Force web site to see if anyone else had run into this problem. Someone had. The rest had been smart enough to put the thing on before riveting on the belly skin.


The trick is to hold the fitting in place with a pair of needle-nosed vice grips clamped to the side of the bulkhead. Then you go to Harbor Freight and buy a set of Crow Foot (I think they're Native American technology, going by the name) wrenches.

With the vice-grips holding the fitting, I was able to reach up into the inspection port with the Crow Foot wrench and tighten the nut. It still wasn't easy, but it was manageable.

All I have to do now is see if those clever Crow Foot indians ever came up with a cure for the conniptions.

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