After a long hiatus… tanks — a lot!

I’ve haven’t blogged anything in almost 9 months, but I’ve been very busy.  I spent a lot of time working on the my RV-12.  The condition inspection (more specifically, my updating the radio and adding ADS-B In/Out (a new GPS antenna and a new ADSB-In antenna) really kicked my butt.  It dragged on and on.

But through it all, I kept grinding away at the tanks.  It was really slow going.  Mostly I think that this was mostly mental.  I knew that I would have to break out the ProSeal and I kept prevaricating and didn’t get to the end.    Well, finally, I just decided it was time to dive in, so I did.  There aren’t a lot of pictures because my hands tended to be covered in grey, icky goo most of the time.  These pictures will cover many months work.

 

The fuel and drain fittings went in much more smoothly the second time through.  I was finally getting the hang of working with the sealant and got my riveting groove back after being out of practice for so long.  I got a nice squeeze out and made sure to thoroughly cover all the possible places it might leak.

For some reason, I was really looking forward to getting the fuel caps installed.  Maybe it’s just the nice contrast between the anodized red filler and the (not so) shiny aluminum.

Next, there is a lot of back riveting to do.  I tried masking off the areas around the stiffeners, but found that (1) it didn’t really help keep things clean and (2) it made it hard to form a nice bead of sealant.

I took the leading edge stands and built a little rotating adapter that I strapped to a low bench.  This proved very handy for getting a good angle for the riveting work.  This put the wings at a comfortable height and allowed me good access to both sides.

Another thing that proved handy was having small plywood backing boards.  These fit inside the ribs and made them straight and stiff for inserting whilst covered in sealant.  Also, if I needed to, I could give them a gentle tap with a dead blow hammer to get them to sink into place.  I highly recommend making a pair.  They just flip over to do the other tank.  One is long (for tapping) and the other sits inside the flange to give some strength when bolted together.

I also cut another piece of plywood cut slightly bigger than a rib.  This was useful for gently spreading the skins apart when I was sliding the ribs in.  It helped get the skin into the right shape and made just enough room to slide the next goopy rib into place.

 

The riveting was very messy.  I got everything together though and obsesses over covering each rivet head.  The J-stiffener was pretty hard to get in with enough sealant.  The instructions suggest that you can slide it in without touching the skin, but I found that I dragged off some of the sealant anyway.  I added a little more on the insertion side and it seemed to achieve good squeeze out.

 

I needed to fabricate the vent line.  One open end sits at the highest corner of the fuel tank (near the filler cap).  It comes back to a fitting on the inside rib (where the flare fitting is).  It was my first flare (I used my father-in-law’s flaring tool, so I didn’t have to buy one).   It came out very nice with no cracks.

 

In April, I was headed out to a conference near Portland, so I had to stop in at the mother ship.  It was a Friday, so the factory floor was empty, but I still got a nice tour and got to sit in the original 14A!  It was much roomier than I expected (and a bit taller).  It certainly reinvigorated my desire to get working again.

When I got back, I finally got around to fabricating the fuel floats.  I know some people put in capacitance senders, but this seemed so simple and basic that I didn’t want to stray from the plans.

   

Then it was time to seal up the rear baffle on the first tank.  I was pretty nervous.  I checked everything multiple times.  I had a lot of trouble, though, with the pull rivets.  I kept getting sealant in the puller which would then seize.  My trusty Stanley puller gave up the ghost, but I finally got everything pulled.

I took the first tank home to do the leak testing.  I put the balloon on and it seemed to hold air.  I took a dip in the pool and checked back a couple hours later and found that it was totally flat.  That weekend, I got some bubble juice to try to track down the leak.  It was at the balloon joint itself.

So off with the pink balloon and tube and on with a directly connected green balloon.  I added a little Gorilla tape to buffer the clamp so that it wouldn’t cut the rubber.  This one held for 24 hours.  One tank done!

So I did the second tank last weekend.  Brought it home.  Put a lucky green balloon on and….

There was a definite leak at the corner of tank inboard rib and the tank attach bracket.  Sigh!

It could be worse.  I think that I can vacuum in some thinned sealant to get a better seal (or maybe some LockTite).  If that fails, I can reach it by taking off the fuel level sender (yuck), but at least there is a hole that I can reach it through (or a tube attached to a syringe anyway).

In preparation for attaching the tanks and leading edges, I worked on finishing the leading edges.  I had skipped fitting the landing light lenses because it was cold (in NY!) when I last touched these.  It was a balmy 96 degrees F in the afternoon, so I was less worried about cracking.  The first lens has a small gap.  I hoped that I would get a better fit.  I’ll just use some silicon or something to make it watertight after final install.  The second on went on very nicely and I achieved a nice fit around the leading edge.  I changed my technique for the second one and drilled and clecoed the holes directly into the lens after the first rough cut (3/4″ margin).  This let me push harder on the lens from the inside and get that tighter fit I was trying to get.

So next steps are to patch the leaky corner in the second tank.  I’m hoping that it won’t be too hard to get to.  It takes a while though between iterations since I have to let the sealant cure a bit before testing.

Next, I will do the first rough assembly of the wings and fab the control rods.  There’s also a service bulletin that I need to get to that increases the doubler at one of the control mounts. I may even get the pitot mast mount installed.  I’ll wait to close up the bottom skins for a while so that i can get started on the fuselage.

 

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