Tank building
Alright, so where are we… I guess it is time for a progress update. Fuel tank construction is well under way. While I have been building tanks, Tanya has been deburring leading edge skins and ribs. My fuel tanks have one modification of adding a fuel return line to each tank for the Subaru engine. There are a lot of parts that make these tanks very time consuming.
So I began by cutting the large round hole in the inboard rib for the access plate. The fly cutter is always an exciting tool to use. Any margin of safety is fully in the hands of the user. After letting my heart slow down from that process (no parts were launched), I clecoed all the tank ribs in place. Of course, Tanya helped fight the ribs into place. They are very tight and require a lot of pushing and pulling. With the ribs in place, I drilled the end rib nose reinforcement plates and tank attach brackets. I fabricated and drilled a small piece of aluminum sheet to cover up the tooling hole in the outboard rib. Otherwise fuel would come right out of that hole. Imagine that, fuel tanks aren’t supposed to leak.
The majority of the work was in setting up all of the plumbing at the root rib. There are a number of things here that have to be setup: fuel level sender (float), fittings and plumbing for the fuel pickup, fittings and plumbing for the fuel vent, and fittings and plumbing for the fuel return line (Subaru modification). It is worth noting that there is a nearly invisible clear protective plastic on the little round spacers that are used with some of the bulkhead fittings. It was only when I was deburring the spacers that I noticed the plastic. I wonder how many people have assembled tanks with this plastic still on these spacers inside the tank? I imagine that as soon as the fuel hit the plastic, it would turn into a gummy mess. That wouldn’t be good at all.
I used some small diameter brazing rod to mock-up the tubing bends that needed to be done. I could much more easily bend and adjust the thin rod to get things just right before I started bending tubing. The fuel return line is 5/16″ tubing and is a bit difficult to bend, so having a pattern to match helped a lot. These were my first tubing flares with the Rolo-Flare tool. It only took me three tries to get the first one right. You would think that the left and right fuel sender units would be exactly the same except mirrored. Well, they aren’t. They use the exact same internal bracket, so in order for their orientation to be mirrored (to make a left and a right one), the manufacturer has to flip the bracket. This means that the float arm attaches to the front of the sender on one tank and attaches to the back of the sender on the other one. This is all well and good, except that the forward attaching one conflicts with my fuel return line plumbing, hence the reason for the wire art on one of the float arms. I was laughing at myself for the multitude of bends that I had to put into that float arm to get everything to clear and work correctly.
So, the current state of things: All of the fabrication and pre-assembly work on the tanks has been completed. Both tanks have been fully disassembled in preparation for deburring and dimpling. Both outboard leading edges have been deburred and are ready for dimpling and priming. There is a whole lot of dimpling in our near future.
