Fuel Tanks - Proseal bottle #6

It was an emotional moment today installing the baffle and closing off the rear of the L fuel tank, effectively entombing all of our hard work on the tanks so far. The last few steps including the vent line, capacitive and float fuel sensors, and wiring seem to have gone excruciatingly slow. The good news is that we're past all that now and ready to close these babies up!

Started today off quadruple-checking all the rivets and sealant bead lines and then blowing out the tank to clear away any dust, metal flakes, etc that might have gotten in there. The proseal from previous rounds has pretty well cured by now, so we had a good read on how it's going so far. It seems to have cured properly and makes a continuous seal that appears to be quite strong and leak-proof... I guess we'll see if that actually ends up being true. One thing that bugged me a little is I found a couple metal shavings stuck in the sealant that I had to wedge out with a fingernail. We've tried like hell to keep shavings out of there but in the end it's just not possible to keep them all away with all the drilling and cutting going on, and a couple must have fallen in. I'm pretty confident they are all gone, but it might be wise to run some extra fuel filtration for the first few hours of operation to make sure everything is out of there.

Last thing was to adjust the L tank float level sensor so that it would have the same Z-bend in it that we ended up with in the R tank. The travel seems much better this way, and the resistance readings are much closer to the desired amounts:

L tank full - 31.7 ohms

L tank empty - 247.1 ohms

After that, it was time to break out our mini-bottle of CS3330-B2 "Access door" sealant to seal up the fuel level sender and the custom fuel tank access panel. I was a bit disappointed that although the unmixed sealant is pink, once it is mixed up it turns almost the same color as regular proseal, with maybe just a dim shade of red.

The access panel (bottom) and fuel level sender (top) sealed and screwed into place.

Then it was time to break out the "real" proseal and final-attach the vent line and fuel tabs to the fuel cap flange. This went pretty well, and we ended up with a configuration like this:

L tank fuel cap flange, tab, and vent

R tank fuel cap flange, tab, and vent

I think the vent is in a near-ideal location and should allow for maximum tank capacity. Although we would have loved to sit and stare at our work, with the proseal clock ticking away it was time to start attaching the rear baffle. We ran a bead of sealant along the top and bottom aft rivet lines on the skins, on the aft rib flanges, and put big globs at each of the four corners as the plans suggested. We also buttered the baffle itself with a thin bead of sealant, and then plopped the piece into place. Using the holes in the skins that had not yet been countersunk, we installed clecoes to secure the baffle into position and got to work installing the pop rivets as well as wet-setting the rivets for the skin-to-baffle seams. It went pretty quickly but seemed kind of messier than usual.

L tank after baffle installation

We pondered doing the right tank, but decided this was enough work for the day. Tomorrow, hopefully we can find time to do the same thing to the R tank!