Left tank progress

Progress on the left tank has been pretty good and working with the tank sealant isn't nearly as bad as I had thought it would be. The stuff certainly makes a mess of everything but if your careful and watch what your doing it's manageable. I bought a quart of acetone and a bag of rags to use for clean up. The rags will be plenty for both tanks, but I should have bought a gallon of acetone. The recommended solvent for clean up is MEK but that stuff seems really awful for you, and is hard to find in CA. The acetone has worked very well as long as you don't let the stuff fully set prior to cleaning.

   

Left tank rib installation with sealant bead

We tried to get 2 ribs done each work session, and the long stiffener done with the tank filler and drain flanges. The inboard most rib and forward attach bracket were done Saturday prior to leaving for the holiday weekend. All the contact surfaces were scuffed up and cleaned well prior to starting, with a final cleaning of the surfaces planned for that day right before beginning. Our process was to mix up the sealant, place three good beads of sealant material on the skin, and then 100% cleco the rib into place. Sealant would squeeze out of the sides and the rivet holes and this sealant would be used to create a continuous fillet of sealant around the edges of the rib. In a few cases the squeezed sealant was not enough to create a fillet large enough for my satisfaction so I added some and spread it out.

Left tank prior to placing inboard end rib

 

Once we were satisfied with the fillet we riveted the ribs into place. Rivets were also cleaned in acetone before use. We would remove a single cleco, place a small dab of sealant on the hole, and then place the rivet. This process left a small ring of sealant around each rivet. There are a few rivets that stand just a bit proud because of the sealant, but I would prefer that to having a leaky tank cause paint blisters later. Finally we spread sealant on the shop head side of the rivets to ensure coverage there as well.

Outboard tank bay with fuel tank filler flange

We put a lot of excess sealant on the long stiffener since we were a little worried that sliding it in from the side would squeegee all the sealant from the inboard end. Turns out this fear was unfounded and we ended up with crazy fillets and plenty of excess to cover the shop heads as well. One rivet on the filler flange will have to be drilled out and replaced. I forgot to install the vent line clip on the aft side as called out in the plans. I thought about just drilling a new hole aft of the flange and using a rivet specifically for the clip, but decided that it would look funky.

The vent line will have to be installed prior to dropping the back baffle and completing the left tank. I ordered up the required tool to create the flare in the tubing, so this will probably get done this weekend. Then it will be time to cross our fingers and pressure test the tank. In the meantime I'm getting all of the parts for the right tank ready. All in all I don't think that doing the tanks is too bad of a project, certainly not as bad as countersinking the spar flange. That said, I will be glad to get them done.