Building, testing and operating an experimental aircraft

Finishing the Fuel Tanks

07 Jan 2012

I was finally able to get back into the shop over the New Year’s holiday, so Dad and I broke out the goop and finished the last few major operations on the fuel tanks.

Fuel Tank Complete Fuel Tank Complete

Since we’d gooped and riveted the stiffeners and tank ribs way back in July, and Dad had done the fuel vent tube installation in August, all that remained to do was to seal and rivet the rear tank baffle.

Proseal Application Syringe Proseal Application Syringe

We were anxious to try Dad’s ingenious idea for laying down the bead of sealant along the baffle flange – a handful of modified syringes stuffed to the gills with goop.

Laying Down a Bead of Goop Laying Down a Bead of Goop

Since Dad had enlarged the pointy ends of the plastic syringes slightly, they did a nice job of applying just the right thickness of sealant for the all-important baffle flange.

Finished Bead Finished Bead

We probably gooped these tanks a little more than we really needed to, but -hey- better safe than sorry.

Ready for the Baffle Ready for the Baffle

Here’s the aft end of the tank after gooping, and just prior to lowering on the baffle. As mentioned in Van’s instructions, the baffle acts as a “squeegie” and spreads out the bead of goop, hopefully sealing itself in the process.

Rear Baffle Clecoed Rear Baffle Clecoed

Here’s the tank baffle installed, with the Z-brackets pop-riveted. Be sure to triple-check the orientation of the brackets before firing off those rivets. We thought double-checking would suffice, but sure enough, we installed one of the end brackets backwards and had to drill it out. (Extra credit: see if you can find the backwards Z-bracket!)

Looking Up at the Rear Baffle Looking Up at the Rear Baffle

In this view looking up inside the tank through the inspection/sender cover, you can see amply-gooped joint between the skin and the rear baffle. The squeegie method seems to work!

Looking Up at the Rear Baffle Squeezing Rivets

Lastly we squeezed the row of rivets along the baffle flange and skin. As you can see, the rivet spacing and density is considerably higher here than on your average skin-to-spar joint. Each row took a little over an hour to squeeze.

Dads QC Inspection Dad’s QC Inspection

For some reason, some of the countersunk holes in the tank skin weren’t quite deep enough; here Dad applies the “T-LAR Method” (That Looks About Right) with the deburring tool until the countersinks were satisfactory.

Finishing the Tanks Finishing the Tanks

While I finished the squeezing, Dad got busy assembling and gooping the fuel pickups and inspection covers. We decided to leave those off until the sealant on the tanks is dry and ready for a final inspection. Once everything’s together, we’ll use Van’s tank test kit to verify that our many hours of gooping did, in fact, produce leak-free tanks!

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