Dave’s RV-7A Building Log

Finally worked up the nerve to test the left fuel tank again. I hooked up the manometer with fairly high hopes. It lost 1/2″ after an hour. Not good, but maybe the temp just went down. It lost another 1/2″ after that and then another. Not good.

I pulled the tank outside, put a ballon on one of the fittings and pumped it up. I sprayed soapy water all over the tank and couldn’t find anything. On the third time around the tank, I finally noticed a few small bubbles on one of the fuel filler flange rivets. (You can just see it in the second picture below.) It’s the one that is holding the fuel vent clip. I had trouble with that rivet when I installed it. I didn’t tip the tank on the back rivet plate to account for the bend in the flange and the head ended up proud of the surface. I had to drill it out and redo it. Well, I must not have had enough ProSeal in that one the second time around.

Rather than mix up a whole batch of ProSeal for one rivet, I’m going to fix it when I work on the next tank. Hopefully I can just reach through the fuel filler hole and dab some ProSeal on the inside of the rivet.

Anyway, I’m moving on. I’m quite certain that the baffle is no longer a problem. Woo hoo!

I put the fuel tank on the wing. Things were not lining up well. I had gunked up the ProSeal on the baffle flange a bit thick. I cut that down a bit. Still not fitting. Then I remembered someone on the list saying they had a similar problem that they solved by jacking up the middle of the wing a bit more. So I pumped the jack once–better. Twice–perfect fit. Eventhough I used a line across the spar to make sure it was lined up, I guess there was still a millimeter or two of sag.

A side note on fuel tank testing. I left the ballon on the tank just for fun. After several hours, there was no noticeable decrease in size, eventhough I know I have a small leak. I’d suggest using the manometer method instead of relying solely on a balloon for testing the tanks.

Primed all of the aileron bracket parts, the pitot mounting parts, and the corners of the left wing skins that I sanded down. I also touched up one of the left wing ribs that needed a bit more primer.

I put the left top inboard skin onto the wing for hopefully the last time. I think it’s finally ready for riveting.

Deburred the aileron stiffeners with the Scotch-brite wheel.

I needed something mindless to work on, so I cut, trimmed, and shaped the aileron stiffeners. These pics show the progression. 1) Cut them apart with the band saw, 2) rough cut the tapers with the band saw, 3) clean up the tapers with the belt sander:

Drilled and deburred the edges and holes in all of the aileron brackets in preparation for priming. Adele helped by removing all of the blue plastic and sticky tags.

[Note: It’s difficult to figure out what holes need to be countersunk on the brackets. I ended up neglecting to countersink 4 holes that would have been easier to do at the unassembled stage. See the entry from Aug 25, 04.]

Drilled out the rivets on the left tank in the corner that was leaking. I drilled out about 8 rivets. I scraped and sanded the ProSeal off of that area as well. That stuff really sticks. MEK helped get off the last little bits. I guess it hadn’t completely set up yet.

I mixed up another tube of ProSeal and used a putty knife to jam it down into the seam between the skin and baffle flange. Re-riveted and cleaned up. [Note: don’t put the ProSeal on this heavy over the shop heads. It makes it difficult to put the tank on the main spar. Also, it would have been easier to fix this by just reaching inside the access panel. Oh well, 20-20 hindsight.]

The left tank still has leaks. The one corner that I thought wasn’t leaking actually is leaking at two of the rivet heads. Since they are pretty slow leaks, I was able to get some descent pressure in the tank this time. I soaped up the entire tank and those two rivets are the only places making bubbles. You can see the bubbles around the upper rightmost rivet. The rivet 4 to the left was also bubbling, but not in this picture for some reason.

I haven’t had much time to work on the plane lately. I’ve been trying to fly everyday to get the private pilots license finished up. Having this kind of backward progress is definitely frustrating at a time when I’m not making any forward progress anyway. I guess there is one small bright side. My daughter pointed out that the tank will be very clean from spraying soap all over it (and rinsing afterward).

To anybody making their tanks, don’t follow Van’s instructions where it says to put on a small bead of ProSeal. Make sure you have a healthy bead of ProSeal along the tank/baffle seam. I’m planning on buttering up the baffle flange good and plenty on the other tank.

Finished off the skin to main spar flange rivets on the left leading edge. Just have to set the rest of the rivets connecting the leading edge ribs to the spar web.

Also started prepping the aileron attachment brackets. Got all of them deburred.

Finished off the dimpling of the left inboard bottom skin. All of the skins are now ready to go.

In between waiting for Julie, I started working on the aileron brackets. I mainly just figured out what parts go with what.

Julie helped me rivet more of the left leading edge ribs to the main spar. We got two more ribs done. It is very difficult to rivet the -4 rivets in there with the offset rivet set. I have the pressure turned up to 95psi and it’s still slow going. I’m wondering if a 3X rivet gun would work better.

After two ribs, I could tell Julie had had enough. We got the two end ribs riveted plus one more, so I figured I could pull LP4-3 blind rivets on the rest. Only one rib has descent space for pulling rivets. I couldn’t even get my ground-off pop riveter on the other two ribs. I’ll either have to pull them from the forward side or grind off even more of the pop riveter.

I decided it was OK to set the skin rivets at this point. I’m committed to putting the leading edge on at this point. I squeezed most of the bottom skin/main spar flange rivets before calling it a day.

Did the leak repair on the left tank. I got some plastic syringes from the drug store. They didn’t have a very small tip, but I was able to fit a tip for inflating basketballs onto it. It was difficult to squeeze the ProSeal through it, but it did go through. I used that to squeeze ProSeal into each corner. I then placed a bead of ProSeal along the edge of the baffle along where I drilled out the rivets yesterday. I used a putty knife to shove the ProSeal down into the joint. That worked well. I then riveted it back together and covered everything around the baffle in ProSeal. Fingers are crossed. Again.