Section 18 - Fuel Tank (finished left tank; started right tank)

Finished the left tank yesterday, after riveting the baffle and installing the fuel finger strainer and plug (with permatex #2 thread sealant) - it needs to cure for several more days prior to leak testing under <1psi pressure. Also, I made substantial progress over the weekend on the right tank. Since the steps are the same as the left tank, most of the posts on the right tank will be shorter.

Here we go again!  7 RIGHT tank ribs, straightened and ready for fluting:

Section 18 - Fuel Tank (j-stiffener; inboard aft rib; vent line; fuel level sender; proseal baffle & z-brackets)

Finished sealing the fuel tank this week!  First, I riveted the j-channel and attach bracket to skin, and then Prosealed (5th cartridge) the inboard aft rib, bulkhead union fitting and nut, and encapsulated shop heads of rivets in j-channel and attach bracket.  Then I fabricated left fuel level sender (most of time was to bend wire - first one broke, used wire from right sender; had to order another sender [$29] since Van's nor vendor sells just the wire). Finally, I torqued the bulkhead union nut (55-60in-lb) with a crowfoot wrench attachment for a torque wrench, and then Prosealed (6th cartridge) the fuel level sender (checked continuity after sealing), and prosealed & clecoed the baffle and z-brackets to tank, as well as wet-installed pop-rivets in the baffle/z-brackets. Images are a bit out of order:

 Encapsulated shop heads on j-stiffener:

Section 18 - Fuel Tank (riveted ribs, prosealed j-stiffener and attach bracket, encapsulated shop heads, prepped baffle)

I'm slowly progressing through the left fuel tank, trying to take my time and be methodical so that I don't screw up something vital. This week, the primary tasks were to rivet the 7 ribs, proseal the j-stiffener and attach bracket, encapsulate shop heads of the internal ribs, put a belt-and-suspenders fillet seal on the inside of the outer ribs, prep the inboard aft rib, and prep the baffle.

I moved the left wing assembly to the wing cradle, to be able to utilize the 4'x8' table for construction.  It helped to lay the fuel tank on the table (bottom down) to insert the j-channel; when gobbed with proseal, it's a PITA to feed through the holes in the ribs.

Section 18 - Fuel Tank (riveting stiffeners, et al.; next two Prosealing sessions)

Slowly, but surely, the left tank is coming together ... and the gooey Proseal is getting a little easier to manipulate. During these sessions, I first back-riveted the stiffeners and fuel filler flange to the skin, riveted the drain plug, and riveted various fuel and vent ports on the inboard aft rib. The second Proseal session included encapsulating rivet shop heads, while the third Proseal session involved sealing 7 ribs to the skin.  The latter took a lot of planning and testing to ensure that the ribs would hang without smearing Proseal all over the skin.  Details of that process are provided, below.

Riveted and Proseal-encapsulated the vents/ports on the inboard aft rib:

Section 18 - Fuel Tank (final prep; first Proseal session)

A few last-minute prep chores were completed prior to the dreaded first Proseal session.  These tasks consisted of countersinking the fuel cap flange, fabricating the attach bracket assembly, scuffing the hell out of all mating surfaces with scotchbrite pads (that took hours), and cleaning with Acetone and a final wipe or two with MEK. I then Prosealed using the fay-seal-and-forget method, as recommended by Rick on VAF:  fully cleco the mating surfaces that have Proseal slathered on them, try to work a fillet seal around the edges, and let it cure overnight or over a couple/few days. At that point, I'll wet-install the rivets (swirl Proseal in the dimple, stick rivet in hole, and bang n' buck).  Even using a Semco sealant gun with pre-filled cartridges from Aircraft Spruce, the process was messy.  But mess favors the prepared mind ... and workspace.  Have a plan, lots of wipes, double glove, and don't turn up the pressure too high on the sealant gun (40psi on mine works well ... 90psi is like a noodle-maker), and it is manageable. Thanks, Ken B., for recommending the Semco gun and pre-filled cartridges - I can't imagine doing it any other way!

Countersunk the fuel cap flange: