November 15, 2019

Closing up the fuel tank

This weekend I made it my goal to close up the left fuel tank. After one last inspection of the tank’s inside for debris, a final cleaning of all the mating surfaces, and staging all the rivets, screws, brackets, and tools, I mixed up a 66g batch of sealant and got to work. It’s a lot of work to complete within the 2 hour working time of the sealant.

Bead of sealant applied to all of the surfaces that mate with the back cover

I ran into one problem that I didn’t quite anticpate – the last U-shape bracket that attaches the tank to the main spar is too tight to get a rivet tool into – so I have a mix of rivets facing opposite directions. But one in particular, just above the 90° fitting for the vent, had no clearance on either side to get in a rivet puller. I have no idea how you’re supposed to be able to set a rivet in this location! Some quick thinking led me to a solution to use an M4 screw with nyloc nut in place of the 4.0mm rivet.

A nyloc nut and M4x10mm screw instead of a rivet

After setting all the rivets for the brackets, it’s a race against time to temporarily mount the tank to the wing to set the rivets that secure the back wall of the tank. Of course, I had some trouble getting the tank lined up correctly to the wing, but once I did, the rivets went in pretty easily.

Finally – a complete leading edge!
Looking inside to the fuel level sender cover

Now the tank must sit like this for 3 days for the sealant to cure, then I get to take the tank off again and perform a leak test.

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