Step 6.1 Fuel tank stiffeners part 2

It seems somewhat ironic that the first step in making a leakless fuel tank is drilling hundreds of holes in it.  The necessary second step is to fill those holes with rivets and Pro Seal.  Pro Seal is a 2 part epoxy based sealant especially formulated to be sticky, gooey, messy, difficult, and uncompromisingly unpleasant.  It is also impervious to gasoline which makes it ideal for sealing up the aluminum fuel tanks.  

The process of sealing the tank is fairly straight forward:  Put Pro Seal in between every surface to be joined.  This means coating the dimple for every rivet, the skin and ribs and rear baffle where they meet, and every fitting entering tank.  

In the photo below I have already cleaned the skins and stiffeners a Scotch Brite pad and then with MEK.  Then I placed a dab of Pro Seal in each dimple on the outside of the tank skin along the row of stiffeners. I set the rivets in place and tape over them, holding them temporarily.  The skin can now be flipped over to coat the skin and stiffener with a thin coat of Pro Seal.  Then the stiffeners are set down over the line of rivets protruding through the skin.  At this point, the row is ready to be back riveted.

After the rivets are set, the formed head also known as the shop head, is coated with a dab of Pro Seal to discourage fuel from using that rivet as a pathway out of the tank.  The last step is to inspect each rivet and edge fillet with a magnifying glass.  It doesn't have to be pretty, just fuel tight.  

Not wanting to appear stingy with the whole Pro Seal experience, I allowed Carol to help out.  Here she applies the black death to the shop heads around the fuel filler fitting.

Here are some little trap doors that are fabricated to prevent fuel from running out of the inboard bay and away from the pickup tube.  The doors cover the lowest hole in the rib separating the 1st and 2nd bays.  In the photo below the hinge pins are not yet cut, but you get the idea.

In the next post I begin the fuel tank assembly using the Rick Galati fay sealing method.  Stay tuned to get the exciting details on this one.