LH Fuel Tank Fitment – Success!

I took a bunch of photos and texted them to Jean d’Assonville. After several days of phone tag – one or the other of us were busy – we connected for a brief chat. That’s all it took.

It turns out that I was in pretty good shape after all. My hell was all in my head. Having quite a few rivets that were hand-fitted at various places around the fuel tank flanges is a good sign. The thing that really set me free was to hear that it is acceptable to dress stubborn rivet holes with a chucking reamer or drill. The same thing is true for Z-bracket holes on the spar. You have to do what you have to do. I just needed to hear the guidance. I’ve learned from experience – it doesn’t usually pay to be impetuous.

A shim is necessary under the top of the Z-bracket at the root of the tank. The other Z-brackets fit well enough. Other builders have needed to shim several brackets. Mine were flat on the spar. Another good thing.

Over a period of several days I evaluated fitment and planned my procedure. Then, I carefully fit the tank in place, one last time, as I’ve done twenty times or more by now.

I made a little shim from material I had on hand. A washer would have worked too, but I thought aluminum against aluminum might be better than against steel. Slightly more surface area is probably not such a bad thing either.

I fitted as many rivets as I could – by hand. The remaining 4,0 mm holes around the flanges were match-reamed with a #20, straight-flute chucking-reamer and deburred. Clecos and additional rivets were hand-fitted.

A mix of AN3-4A and 3A bolts, with washers, were threaded through the spar web and into the anchor nuts on the Z-brackets. (I began with the 4A length for 2 outer brackets, but then worried that the length might turn out to be slightly long.) At the root Z-bracket, two AN3-13A bolts, with washers and nuts and with the shim in place – were finger-tightened.

Finally – today, I mixed up a tiny bit of Flamemaster CS-3204 B-2, as recommended by Sling Aircraft to deter galvanic corrosion between the aluminum and the stainless steel rivets that are called out for use at the wing root – top and bottom.

Dipping the SS rivets in the sealant – one-by-one, I placed them and then pulled them with my trusty Milwaukee M12 lithium battery-powered tool. Rivet pulling continued with for the balance of 4,0mm aluminum rivets. Lastly, the 3,2 x 8mm rivets around the leading edge at RIB-105 were pulled. The Z-bracket bolts were all torqued. The 4A and 3A lengths are both fine. It’s all good. The fuel tank is mounted!