Fuel Tanks

Day 1 of building the fuel tanks! We have some mixed emotions about this section-- we're kind of excited for it but also scared to screw them up. It seems most builders struggle at least a little with leaks, and while we accept the challenge we hope we don't have to struggle too much. Also, Proseal sucks, plain and simple. It's smelly, it gets on EVERYTHING, and it's impossible to remove from something once it cures. Sarah loves it for some reason. I'll be sure to put her on Proseal duty :-)

Before we get to the Proseal, we have a lot of prep work to do. Most of this is old hat by now, except for maybe some plumbing which we'll be getting to later this week. We laid out the left and right tank parts on two different tables, and we each got to work on our subassemblies:

The L and R tank assemblies, ready for step 1!

I swear, we actually do real work in this garage. Sometimes.

See?

The first few steps involve fluting the ribs followed by some simple cutting/fabrication of 14 stiffeners, 7 attach "zees", and one J-channel (per tank). After a few hours at the bandsaw and belt sander, we had a pile of parts ready to assemble.

L tank assembly, clecoed together and ready for final drilling

Both tank assemblies

Things went together fairly smoothly so far. Before getting too much further, we had to start on one of the mods we're making. (We are making two modifications to the tanks worth noting: (1) Installing different, larger fuel caps; and (2) Installing a fuel return line.)

A word on the fuel caps: Substituting the standard UD-3 fuel caps that come with the Van's kits is a common practice, however typically folks opt for a set of locking caps that are of a similar size. After receiving the UD-3 caps with our wing kit, it is obvious why people want to use something else... these caps are awful! I can't even fit my finger under the lip to pull the tab up to twist it to get it open! I think uncorking a bottle of wine by hand would be easier... aaargh. To this day, the caps have never been successfully opened, even after a number of attempts from both Sarah and I. They have been put back in the box, and will end up either on ebay or on our blooper shelf (yes, we have a blooper shelf).

Anyway, I digress. We went off the beaten path a bit and chose the ACS-10600 fuel caps for both cosmetic and practical purposes. They twist off like most conventional aircraft, and the opening is a larger, more "normal" size to be able to put a nozzle in AND see the fuel rising as you fill. It's the simple things in life, right? The problem with this method is, the tank skins are already pre-punched for the smaller stock fuel cap, and there are some clearance issues with tank ribs, stiffeners, and rear baffle... all of which are nearby. It took a bit of careful planning and creating a template out of scrap aluminum to trial different mounting configurations, but we eventually ended up with this:

The ACS-10600 cap clecoed into the L tank skin. The cap "sort of" reuses two of the forward-most (at about 5 and 7 o'clock in this picture) holes intended for the original cap. I say "sort of" because the holes had to be elongated slightly to fit the pattern of the new caps. By first drilling them out to #40, we could get everything into position properly, and then by enlarging to #30 the holes are now perfect (We'll use six #4 flush rivets instead of ten #3 rivets to hold the caps in). Three other holes will need to be filled in, as they are not used here (at about 4, 6, and 8 o'clock). It took quite a while to figure out exactly where to mount this cap, and how to enlarge the hole!

View from inside the tank. Some trimming of the cap flange was necessary to clear the outboard rib and rear baffle. It was a lot of work, but I think it's worth it!

Otherwise, aside from some match-drilling, that's about it for today! More titillating tank trials & tribulations... tomorrow!