This barely even merits an entry here – I’m not even putting down any hours logged – but tonight I put a balloon on the right tank and pressurized it. Hopefully it’ll hold air and my leak testing can stop there. Last time the leak down test didn’t work, which turned out to be due to air leaking out of the base of the balloon. I only found this out when I pressurized it again and covered it with soapy water to look for bubbles.

Unfortunately, the soapy water test requires daylight, something that’s in short supply now that the time has changed. It’s dark by the time I get home from work these days, so the soap test would probably have to happen on a weekend…but I’m about to be gone the next two weekends. So I decided to give the leak down test a try again. This time I rolled up an extra balloon around the vent line fitting to act as a gasket, and put two zip ties around the balloon to hold it in place.

I’m hoping that’ll seal well enough for me to not have to do the soap test. If not, I might go so far as to go into work early one day this week just so I can make it home before dark and do the soap test. I’m feeling a pretty strong compulsion to have the leak testing done before I go out of town for some reason.

Here’s a fuel tank with a balloon attached. Exciting, huh?

Well, that does it…unless I find some leaks in this tank in a week or so, I am done dealing with tank sealant for the foreseeable future. And boy, does it ever give me pleasure to write that sentence.

Anyway, not really a lot to write about today. Mostly it was a replay of closing out the left tank a couple weeks ago. The major differences were me putting the sealant for the baffle on right the first time, and avoiding that whole annoying process of taking the baffle back off and doing it all over again. There was also the flop tube to deal with – I’d safety-wired it to the inboard anti-hangup guide to keep it from flopping around, so I had to be sure and remove that before closing the tank. I also was a little worried about the flop tube weight getting stuck in some excess sealant after I put on the baffle, so I made sure to give the tank a shake after I was done so I could hear it moving around in there.

I also was a little too task-oriented to take a lot of pictures today. Again, just go look at the photos of the left tank if you feel cheated.

Here’s the finished right tank on the spar:

And I got another pic of the workbench. This thing looks like it’s been through the apocalypse or something. I guess it’s thoroughly broken in now…

So yeah, not much done these last few days. We had a Halloween party on Friday, and most of the preceding evenings were spent getting ready for that. Yesterday, in turn was spent recovering from said party. I had originally intended to close up the right tank today, but some events from the past few days made me change my mind.

Something like last Wednesday, I did have time to run out to the garage, install the leak test kit on the left tank, and pressurize the thing. I figured I’d let it sit for a day or two and see if it held air. Sadly, when I went out to check the next night, the balloon on the vent line fitting had deflated. That was a bit of an ego hit, thinking about the possible need to open this thing right back up to fix some leaks. But it occurred to me that the air might be leaking out around the balloon too.

So today I took the tank out in the driveway, pressurized it again, and started spraying soapy water all over the thing to look for air leaks. Lo and behold, the only place where I got some bubbling action was…around the base of the ballon. I made sure to thoroughly wet down the baffle seals, since those were the most likely leak source…no bubbles!

Of course, by the time I did this, it was too late in the day to start closing the right tank, so I guess that’ll wait until next weekend. But hey, the end is in sight!

In other news, I also scheduled my first tailwheel lesson for next Saturday down at Texas Taildraggers. I popped down to AXH this past Saturday to meet Joy and verify that I could, in fact, fit into a Citabria. It’s tight, but it’ll work – the main problem is being able to get full back stick with my gut in the way. Sounds like we’ll probably end up removing the setback cushion and replacing it with something thinner just to ensure I get full control authority. I really should get on losing some of this weight…

Yup, today was the day, time to close up a tank. I’d kind of hoped to close up both today, but as is par for the course with these things, it took far longer than I expected. I think maybe it’s impossible to accurately estimate the time needed for this stuff, like the sealant somehow bends space-time or something.

Anyway, knowing that a lot of things would be going together, I spent a fair amount of time prepping the work area and getting everything I needed ready to go. To start with, I taped some wax paper over the spar bars on the left wing. This was so that, once the tank was closed, I could immediately set it in place on the spar to be doubly sure that no squeezed-out sealant would give me fitment problems down the road:

Next I put the tank assembly, baffle, and attach bracket on the work bench, and gave all the mating surfaces a good cleaning:

And with that, it was time to mix up some sealant. Lots of sealant, as a matter of fact, because there were lots of mating surfaces to deal with. The essence of the procedure here is to lay a bead of sealant along the rivet line for the skin-baffle joint; when the baffle is dropped into place, it will push the bead ahead and make a nice seal. The mating surfaces of the ribs also get a coat of sealant, plus some sizable blobs at the corners of the tank – apparently these are a very common leak location. Here’s everything all lubed up:

Next, I dropped the gaffe in place. I was surprised how easily it went in…next it gets 100% clecoed to the skin. As I did this, I began to suspect a problem, I was getting almost no sealant squeezing out of the joint as I clecoed, which made me worry about whether I had a good seal – especially coupled with the ease with which the baffle went in, like it didn’t actually do much pushing of sealant. I debated a bit as to whether I wanted to just move forward and hope for the best, but it didn’t take long for me to realize that hope was a pretty bad thing to count on. So I removed all the clecos, pulled the baffle out, mixed up more sealant, and applied a second bead of sealant, further towards the back of the skin. This time, when I dropped the baffle in, I got lots of squeeze-out. (in fact, that whole process of removing and replacing the baffle was pretty hilariously messy)

So with the baffle back in place and clecoed, I went to work on the baffle-rib joints. These get blind rivets, since there’s no access to the inside of the tank, and the rivets get swirled with sealant before insertion to ensure they don’t become a leak path. The attach brackets go on the same way, but here the clearance to the rivet stems was tight, and I ended up grinding a fair amount of material off the nose of one of my pop rivet guns. Nothing like some field-modified tools to help things go together…

Finally, I set the outer baffle-rib joints and attach angles with solid rivets, then finished things off by squeezing all the skin rivets (an operation which left my arms rather tired). This was followed by a rather extensive cleanup session, with most of the time spent cleaning the skin behind the baffles, which will sit on the spar. Again, I don’t want any firmer issues here from sealant build-up.

The baffle, brackets, and such, all finished:

And the completed tank sitting on the wing:

So yeah, this took way longer than I expected, although doing the baffle sealing twice didn’t help much. No way is the right tank going to get closed up on a weeknight this week, so I suppose I’ll leave it for next weekend, because tomorrow we’re going to be out of town for the day. But hey, this tank odyssey is almost at an end!

Not much going on today, but I did get the water leak test done on the tanks. I checked the leftover sealant from Monday last night and it was pretty well cured, so I decided to go ahead and to my leak test tonight. Not really much to this, just put a tank in the cradle, plug the drain and fuel feed fittings, and try to ghetto cap the vent line fitting (the leak test kit doesn’t come with that cap; you’re supposed to use a balloon instead).

I have to admit that it felt a little wrong to just start running water from the hose into these things. All the hours I’ve put into them, the electrical connections and so forth, and here I am just blasting it with water. I know everything in here will eventually be submerged in fuel, but still…

I filled each tank to the highest rivet line, then let the water sit for about ten minutes to give any seepage time to happen. And at no point did I see any water seeping out of anywhere. That was satisfying enough to offset the discomfort at getting these things wet.

Right tank filled with water:

And no seeping:

I was hesitant to do this test for several reasons, but in the end, I’m glad I did. It’s a big confidence booster to see these hold water. This still doesn’t mean that fuel won’t seep through somewhere, but it’s a very good sign.

Anyway, the tanks are now sitting upright on the workbench. I won’t touch them until Saturday; that should be enough time for the water to evaporate, especially in the toasty garage. (we’re still getting highs in the 80s here in Houston).

I also spent a little time tonight looking over the Duckworks landing light kit instructions. Doing the cutouts for those will probably be the first thing I attack once I get to working on the leading edges…which won’t be long!