What does the photo below have to do with sealing the fuel tank???  This is my new Ductless, split type heat pump (air conditioner) AND IT IS FINALLY UP AND RUNNING !!!!!!  It is friggin' awesome !!!!  The last couple of days have been in the upper 80's with dew points in the upper 60's to lower 70's.  More or less miserable for working in the garage.  With the heat pump, I set the temperature on its remote to 70 degrees and within a couple of hours, I was actually cold in the garage.

Let the summer building season BEGIN !!!!!  (In Comfort, I Might Add)

Okay, I have my air conditioner running in the garage, lets get back to building this plane!!!!

I bought some heavyweight painters paper (?) at Home Depot a while back so I decided to use this to cover the benchtop while working with this gooey tank sealant.  I made a cutout around my back rivet plate so that I could find it.

To mix the tank sealant, I used some plastic cups I had laying around the garage.   (Do not use these to mix AKZO Epoxy Primer.  The hardener disintegrates/melts this type of cup)

I cut the cup down so that I just had about the lower 1/3 of the cup.  For working with the stiffeners, I found that if I mix 20 grams of sealant with 2 grams of hardener (10:1 ratio) that I had about the right amount of tank sealant.  You only have about an hour of working time with the sealant and for me, the tank sealant process was fairly slow.  By the time I got to the bottom of the 22 grams of tank sealant, it was already getting hard to work with.

To keep the tank sealant off of the areas where the ribs go, I used yellow vinyl electrical tape (Scotch 35).  This worked great !!!  It comes up easily, leaves no tape adhesive residue and it doesn't "splinter" like masking tape has done for me in the past.

My basic process for sealing the stiffeners went like this:

• Clean and etch surfaces to be sealed with a scotchbrite pad and Alumiprep.
• Rinsed surfaces and went over area with MEK.
• Soaked rivets in MEK.
• Staged a TON of RAGS!!!
• Smeared a light coating of tank sealant over skin of fuel tank where stiffener will sit.
• Flipped skin up and inserted rivets and secured with rivet tape.
• Placed stiffener into position and made sure the rivets were not "cocked".
• Back riveted stiffeners into place verifying shop head dimensions as I went.  (YES, I still check most of the rivets I set.  It is just the habit I got myself into early on.)
• Frosted up the edges of the tank stiffener to skin surface area.  I used a narrow spatula (equivalent to a small popsicle stick) to make a nice, relatively smooth fillet on all four sides of the stiffener.  (I didn't skimp with the tank sealant.)
• Totally encapsulated the rivet shop head in tank sealant.  (This is above and beyond, but I want to ensure NO LEAKS.)
• Cleaned up the surrounding area and removed excess tank sealant with MEK.
• Flipped the skin over, removed the rivet tape and cleaned up the factory head and tank skin surfaces.

Just a sampling of two completed stiffeners.  It is really hard to get in and clean up the stiffener between the rivet holes as you can see on the left.  I tried cleaning a couple of these up, but ended up making it look worse.  Did I mention this is like taffy that has been on the dash of your car on 100 degree sunny day?  It is stringy, gooey stuff.

I went through a ton of rags, rivet tape, latex gloves, and I polished off my first pint of MEK.

Just a snapshot after I was done with sealing the stiffeners and had everything more or less cleaned up.  Everything looked really good.  It was just time consuming for me.  I definitely will not be setting any speed records on the tank.  It took me a good 8 hrs to just rivet the stiffeners on and seal them.