Right Tank Update   November 27th, 2007

Chugging along. I am in the process of fitting the capacitive senders, modifying the end rib, etc…

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Fuel Cap   November 18th, 2007

The last step before starting work on the right fuel tank is the fuel cap. The cap flange has a slight bend in it to conform to the shape of the leading edge. It took a while to get it to line up. Once I had a good match, I used some C-clamps to hold it in place while I drilled the holes.

Then, on the bottom side, I made a little bracket that will hold the vent tube when it is finally fitted in.

And that’s it for now….I’ll start work on the right tank, which will hopefully be just a boring repeat of the left tank. So, no pictures for a while.

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Modifying the Tank End Rib   November 18th, 2007

The end rib of the tank (the rib closest to the fuselage) needs some holes for the vent and fuel lines, as well as the BNC connector and the reinforcement plate where the inspection plate attaches.

I started by drilling the vent line and BNC holes. Note that the vent line is a 7/16″ hole, which I drilled to 9/16″. I wasn’t ready to get a new rib and start over, so I made a washer out of 0.032″ aluminum that will sit between the rib and the fitting, on the outside of the tank. I emailed Van’s about it, and they said it’s OK as long as I seal it well enough so it doesn’t leak.

After dealing with this screwup, I lined up and drilled the holes for the reinforcement plate. I found that the best way to do this was to place the reinforcement plate on the outside web of the rib, making sure the rib hole and the reinforcement plate hole match up. I then drew the outline of the reinforcement plate with a marker, and placed the access plate in the same spot. This guarantees when I drill the access plate to the rib, it will be centered in the hole.

After drilling the screw holes, I clecoed in the reinforcement plate and drilled the platenut holes.

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Capacitive Fuel Sensors   November 15th, 2007

Rather than use a float sensor (This is an aircraft, not a toilet!), I decided to use capacitive sensors. Seriously, I figured a system with no moving parts has less chance of breaking.

The system is fairly simple. Just two plates get bolted to the tank ribs. These two plates form one side of the capacitor. The other side is the tank ribs and tank skin.

The first step is to take the plates and match drill holes in two of the ribs. Once these holes are in both the plate and the ribs, we attach nutplates to the capacitive plates, facing OUT from the rib.

The plate is mounted with a screw, a bunch of plastic washers, and a piece of 1/4″ plastic hose, to insulate the screw from the aluminum rib. Pretty clever. Here are the plates mounted on the two ribs.

And here are two more pictures showing the detail. Note that I had to cut out the corners of one of the ribs to make sure it didn’t get too close to the stiffeners.

When I’m ready to assemble the tank, a wire will go from one plate to the other, and then to the center pin of a BNC connector attached to the outer rib. The shell of the BNC simply attaches to the aluminum rib.
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Tank Drain   November 13th, 2007

This is the fitting that allows your to drain water from the tank. The fitting actually goes on the outside of the tank (the other side from where I have it). It’s just easier to drill it from the top and then just flip it. Note the two blue marks to make sure I can line it up later.

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Tank Access Plate   November 9th, 2007

After a long break due to some work travel, I’m back in business. The fuel tank rib at the end of the tank has an access plate, where the fuel pickup is located. The hole for this plate has to be drilled out. The hardest part of this was just finding the center of the hole. Once I lined things up in the drill press, it was just a matter of holding on, clenching my teeth, and letting the fly-cutter do its thing.

The result is a nice clean hole…

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