The right fuel tank cap flange is not my friend. This same rivet continues to leak. I’ve inspected with mirrors, flashlights, magnifying glass, and fingertips to no avail. It drips the third test just as it has the first two. At this point, it was clear that there was a path for the water to get to that hole from somewhere obscure and slathering proseal on the back isn’t fixing it. I decided to drill it out all together.

I then surgically removed a chunk of proseal from the back of the flange covering the shop head. I cleaned the area well and mixed up a mini-batch of proseal, this time resealing the hole from the front before inserting and setting the rivet. I then resealed the back and put one more generous layer of proseal, basically covering the inside of the skin and flange from the end rib all the way over to the flange.
The good news is that the once-large leak is no more and the rest of the tank was finally behaving. All of this testing time has given me ample opportunity to finish up the leading edges with a bit of help from the Mrs. and a buddy who came over to drink a beer and was voluntold to learn how to rivet in quick order. He now owns 1/100,000,000 of an RV-10!

You can guess how it went by the title. I read another build log and saw the idea of testing the tanks before sealing the rear baffle in with water and food coloring. The guy had taped toilet paper on all the seams to be able to identify weeping rivets / leaking joints. I decided that was a good idea since I’m not in a hurry and it would allow me to fix any spots with Pro-seal instead of having to tear into the sealed tanks.

Boy am I glad I did this.

My dad and I got out the hose and filled up the right tank first. Overall, I’m really happy with my first Pro-seal job. I had one weeping rivet (a solid, steady drip) at the fuel cap flange and a stead little stream at the seam between the front spar and skin. After a little inspection, I think I can see where I didn’t get a complete fillet on that joint, so I’m confident it will be a quick fix. I also had one drop appear on the fuel sender plate after letting it sit for 24 hours, so I’ll beef up the Pro-seal on those as well.

The toilet paper really wasn’t neccessary, so I didn’t repeat the prep on the left tank. We filled it up and were immediately standing in water. I missed a fillet on the outboard rib and it was a pretty good leak there. I also had one weeping rivet on the bottom leading edge of a middle rib that I’ll need to put some more on.

I’m pretty excited that my work was solid and method proven capable. I didn’t use nearly as much as others and my tanks look clean. While I know it wont’ win any awards, it makes me feel better not having the extra mess, weight, and sloppiness inside my tanks. My plan is to fix those few spots after a couple of days of drying and then retest for a few days to ensure they are all set before cleaning and sealing the rear baffles.

With the drilling and deburring complete, it was time to use yet another new tool that has sat in the toolbox for far too long. This is a bucking bar and rivet set that allows you to insert dimple dies and dimple areas that the c-frame can’t get too. It was useful on the leading edges of the tank skins in the middle of the skin. I did learn, however, that the dies don’t like this tool, especially with a side load on them. I broke two sets of dies. A quick call to Avery and a replacement along with the SafeAir1 pitot mast was on the way.

It’s hard to believe that almost all the components of the fuel tank can fit on my little stool.  I scuffed the joint surfaces to promote adhesion for the Pro Seal on all the parts. These are all set for final installation into the skin.

This is where things can get sticky. The biggest advice I read was to be prepared for working with Pro Seal and to wear two pairs of gloves while replacing the outer pair often. Once Pro Seal touches a surface, it doesn’t come off without MEK. I used a postage scale to weigh the components, ceramic tile to mix, and the applicator gun from Brown Tool. All that equaled a clean, easy process of using Pro Seal.

The wife-copilot-cobuilder-photographer came out to help and we started with the stiffeners. I chose to 100% cleco the parts in place and come back for riveting the next day. It greatly reduces the mess and actually makes riveting easier. Kayla the flight engineer dog came out to support the project as well. The next day, I came out to rivet the stiffeners with a dab of Pro Seal in each dimple to seal the mfr head of the rivets. Turned out well with the tank die dimple, as it’s a nice flush surface.

I went solo and finished up the ribs and the j-stiffener for each tank after mixing up yet more sticky stuff. I found that letting the sealant cure for one day was perfect for riveting, so the following day was spent riveting the ribs and j channel. I also went back and put a blob of sealant on each shop head, completely sealing each rivet (hopefully) to prevent any fuel seepage.

The next step is to fabricate the fuel vent lines, which consists of straightening very carefully the aluminum tubing and flaring one end to accept the AN fitting through the end rib. I skipped ahead on the plans and riveted the end rib on before putting the line in, but was able to easily work around it. None the less, it’s a good lesson to stick to the plans. Pro Seal is permanent, so no going back and redoing!

With the rudder all finished, it went up in the ceiling with the other finished components to make room on the workbench for the next project.  Fuel tanks are a key part of each build and one that is often dreaded because of the process and mess that it can make.  I’ve read a lot of how-to’s and gotten a lot of advice and feel pretty confident moving into this stage.  I also invested in a few tools that should make the job a little easier, cleaner, and more effective!

First is to prep just like all other steps.  The previous builder of my wing kit started the left fuel tank, getting so far as to seal the ribs and fuel cap flange to the skin.  However, I want to have the upgraded locking caps and wasn’t comfortable with the sealing job that had been done.  So I decided to order replacement parts and start fresh.  I also used the now scrap tank to practice with was helpful.

Each tank has 14 stiffners that are cut from a single stick of aluminum similar to most of the j channels.  Those are cut, shaped, and deburred then match drilled to the skins.  The ribs are also finessed into the skins, especially the pointy part that doesn’t seem to fit well without a little encouragement with the pliers.  I was surprised at how difficult it was to get all the ribs lined up for match drilling.

The fuel cap flange is contoured to match the skin.  I used some of the double sided tape for trailing edges to hold it in place for match drilling.  One thing to note is that the locking cap looks a lot better and fits a lot better than the stock Van’s unit.  Well worth the extra money for me.

The attache zee’s were next, having been match drilled to the tank spar and having nut plates installed.  These will be primed as will the exterior of the tank ribs.  Nothing inside is primed, as the fuel is corrosive to all but the mightiest of paints.

One piece of advice to heed, make sure nothing is in the tanks that doesn’t belong!  I had used my rubber mallet to tap some pieces into alignment.  I found it after enclosing the tank with clecos to match drill.  I looked all over the garage for that thing!