9.4.1 Fuel Cap Installation

Since they leave it up to us to figure out where to install the fuel filler port and cap, I decided I needed to, first of all, mark the locations of the baffles as best I could, and secondly, drill a test hole just to make sure! I marked various reference points on the side of the fuselage then used those points to locate the baffles and bulkheads. I then deduced a good location for the fuel filler port and drilled a test hole.

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Trying to figure out the location for the fuel filler necks.

Once I was convinced that my location worked, I flipped the upper strake piece upside down and started drilling out the various sized holes required for installing the fuel filler neck. I used the procedure in the manual, but sized the final cut through the top of the strake a bit smaller. The manual calls for a 2 7/8” hole saw but I used a 2 3/4” saw because I wanted as tight a fit as possible for the flange of the fuel filler neck to the upper strake fiberglass. I’m glad I downsized it because it almost fit perfectly using that 2 3/4” saw. I only had to carefully sand around the hole a bit to get a perfect fit.

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I flipped the strake top over so that I could easily check the fit of the fuel filler neck.

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The hole for the fuel filler neck is ready for installation of the actual device.

Although not required, the manual recommends adding a ground wire to the filler neck. Naturally, on metal airplanes, the fuel filler neck is automatically grounded to the skin, but we can’t do that on composite airplanes. This is a #14 ground wire that is long enough to reach back into the fuselage. It eventually gets connected to the engine mount or engine ground system. To prevent this from ever loosening up, the entire nut and lug is embedded in epoxy. I used a flat head screw on the other side to keep the filler neck sitting flat on the fiberglass.

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Attaching the ground wire to the fuel filler neck.

The neck is now in place and surrounded by EZ-poxy and Micro. You can see how I’ve embedded the grounding connection in there to keep it in place.

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The fuel filler neck needs to be permanently bonded to the upper strake along with the ground wire. We don't want that wire to ever come off!

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I applied a 2 BID layup over the EZ-poxy + Micro to help lock the filler neck into place. Peel ply was also placed over the layup to help soak up the extra epoxy.

Once all of the epoxy cured, I did a test fitting of the fuel cap. It seems to be working perfectly!

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And here's the finished product with the filler cap in place.

Here’s the other end of the green ground wire. Now that the strakes are closed up I was able to run the wire inside of the fuselage. I used a small plastic clamp to hold the wire in place. It eventually gets attached to the main system ground. I added some electrical tape around the wire to increase the diameter so that the clamp could actually clamp it and to protect the wire.

Fuselage - Fuel Tank Ground Wire

That green wire is the ground wire coming from the fuel tank filler port. There's one from each tank.

Next comes the scary part - installing the upper strake pieces. You only get one chance to get it right! See Section 9.4.3 for details!

ui© John Trautschold 2018