Dave’s RV-7A Building Log

The left fuel tank is leak free!!! The water level dropped the first day, but the temperature was lower. I pumped up the tank a bit more, marked it again, and watched it for another day. It held rock steady. Loctite 290 is a great solution for a leaky rivet.

I spent some time cutting and sanding down the extra ProSeal I had put on the baffle-to-skin rivets. This build-up was interfering with the inboard part of the wing spar reinforcements and preventing the tank skin from laying flat.

Set up the manometer on the left fuel tank to see if the leaky rivet is still leaking. The level went down a bit during the night, but that’s probably because it’s cooling off. I sprayed some soapy water on the problem rivet, and there were no bubbles. We’ll see how it’s doing tomorrow

Set up the left tank to finally fix the one minor leak in the rivet just forward of the fuel filler. Van’s suggested to use some wicking Locktite 290 with a slight vacuum in the tank. I hooked up a tube to the fuel pickup and sucked the air out. I applied a little Locktite to the bad rivet and let it sit. You can just make out a tiny bit of green in the (fuzzy) picture. I’m not sure how long it takes for the Locktite to dry, but I’ll test it in a few days.

The right fuel tank is leak free. The level bounced up and down 3-4″ with the change in temperature of 70 to 77 degrees, but stayed right in the range of the warmest and coolest mark I made on the first day. Yeehoo!!

With the one problem rivet duct taped, the left tank is holding air. That’s good news. The water level in the manometer was down this morning, but went up past last night’s level once it warmed up today.

I set up the right tank for an overnight test. Fingers are crossed.

Time to test the fuel tanks. Since the plastic tube is still hooked up to the left tank, I decided to test that one first. This tank had the one leaky rivet near the fuel filler that I tried to fix. I set up the tank, and sure enough the level started going down very gradually. I used the soap bubbles to find out that it was leaking around the fuel cap and unfortunately around that same darn rivet. Bummer. The worst thing about that leaky rivet is that I can’t make sure the rest of the tank has no leaks. But then an idea hit me. I put some duct tape over the problem rivet, put more fuel lube around the fuel cap, and pumped it up again. We’ll see if everything except that stupid rivet is holding air.

Last big ProSeal session on the tanks putting on the right rear baffle and access cover. The rear baffle is such a monster session–lots of rivets. It took about an hour to set up. Even though everything was set out and ready to go, I still had to MEK the rivets, get out the tools, and clean all of the surfaces one last time. There was about two hours of riveting with Julie helping for one hour and then an hour and a half of clean up. I took an hour longer to do this baffle than the other baffle. I guess I was just being extra careful.

I started out by thinning a little bit of ProSeal with some MEK and applying it to the troublesome leaking rivet on the left tank. I used lung power to create a small vaccuum in the tank. I could see the skin between the ribs pucker in. It looked like there was one spot that pulled in the ProSeal. Hopefully that stops the leak.

This time around, I spread a thin layer of ProSeal on the baffle flange and put a bead ON the rivet holes of the skin. I also paid close attention to the corners, making sure the ProSeal was on all 3 surfaces, and squeezed out nicely when I put the baffle in place. Looking in through the access cover, the corners looked great. Just to be sure, I stuck the gun in the corner from the outside and shot a little more in there.

In all of my careful ProSeal application, I forgot to dab ProSeal on the last few spots of the capactive sender wire. I could reach the inboard most bay through the access hole, but the next bay over isn’t secure. I decided it wasn’t a big deal and moved on.

The blind rivets were fairly uneventful, except that a few mandrels didn’t break right at the rivet head. I had to use a vise grip wrench to bend them back and forth. Otherwise, I couldn’t get the squeezer on the skin rivet next to the blind rivet. I blame the cheap rivet puller that I have.

On the skin to baffle rivets, Julie helped place rivets while I moved clecos and did the squeezing. There are a ton of rivets there, but we chugged through them. I squeezed the outboard Z bracket rivets and Julie helped rivet and buck the inboard bracket. I had just enough ProSeal left to put on the access cover with some hex cap stainless screws.

Lots of clean up ensued. The ProSeal was getting pretty set, so it took quite a while to clean up the tank.

Fingers are super crossed that the left tank is now sealed and that this tank turns out well. Even if there are some leaks, I’m happy to have these puppies done. I set the tank leading edge up to cure. This should help the ProSeal ooze down into the seam versus out of the seam.

Julie is so cool. She said the next time, we’re doing QuickBuild. First, she recognizes that I’ll probably build another plane some day, and she’s already bought into the QuickBuild. I certainly wouldn’t mind having someone else do the nasty tanks and the monotonous wings next time.

While the left wing was out of the stand, I removed the fuel tank for further testing to see if my touch-up of ProSeal on the rivet by the fuel filler fixed things. Unfortunately, it didn’t. I’ll have to try the trick of sucking thinned ProSeal around the rivet.

Prepped for the final ProSeal session. It’s amazing how I think I’m ready to ProSeal, and then an hour or so later I’m actually ready. I installed the inboard capacitive plate (a PITA) and screwed down the vent line fitting. I scuffed up the mating surfaces on the rear baffle, cleaned out the tank real well, and MEKed down all of the mating surfaces.

Here’s the tank from inboard to outboard:

And a shot of the inboard and outboard ends and a close up of the tank attach angle:

So after all of the prep work I decided there really wasn’t time to do the baffle. Bummer.

Hopefully did the second to last ProSeal session on the tanks. I put in the two end ribs and with Julie’s help, the tank attach angle. I also sealed around the connectors on the inboard capacitive plate, touched up some rib rivet heads that weren’t quite covered, and sealed the vent fitting and coax connector to the inboard rib. For some reason, this session seemed especially messy.