Tuesday, February 27, 2018

Left fuel tank - Sealing process described in detail with photo's

Tonight I took a few extra pictures of the sealing process I use (not easy to do with very sticky rubber gloves on).  Van's recommends that you buy two orders of sealant (about a quart total) to complete the RV-10 fuel tanks.  So far I have completed the right fuel tank with the left tank well on its way and I've used maybe 1/2 of the first batch.  So, I assume they expect that you will use far more than I think is necessary. 

Below are some step by step pictures and description of how I am sealing the tanks.  Granted this is only one part (the fuel cap flange) but the steps apply to all mating surfaces.  The idea is to get two barriers of sealant so that if one fails the second will prevent fuel leaks.  Some areas this is not really possible but in most it is.

End ribs with fuel penetrations installed/sealed

First step is to get the tools out.  This is a 10cc syringe that I use as a mini caulking gun.  Oh, and lots of rubber gloves...

Syringe loaded up with enough Sealant for tonight's sealing steps.  Tonight I installed the fuel cap flange and the drain flange.

There are really only a couple of places that fuel can get out on this fuel cap flange.   Past the skin/opening interface and past the rivets.  In this picture you can see that I put a bead of sealant around both the outer and the inner rings to act as double barriers for the first situation.

Its not really visible in this picture but this batch of sealant prevents the fuel from leaking past the rivet holes.  This is a bead of sealant around each dimple.  The fuel flange will sit on top of this area.

Each rivet needs to be sealed as well so in this picture I am dabbing sealant into each dimple on the outside of the skin using a q-tip twirled in sealant.  This is done just before I put the rivets in place.

Rivets pushed into place and the area around the rivets is gently cleaned up with MEK so that the tape used to hold the rivets in place (and protect the skin while back riveting) sits tight against the rivets and skin.

Then the fuel flange laid on top of the skin with the rivets poking through the holes.  Notice that there is already a bead of sealant showing up around the outer edge.  Thats barrier #1.  The rivet sealant is barrier #2.  Each opening actually has two barriers of sealant on them so that if one fails the second should prevent leaks.

And finally this is the "cap" of sealant that I place on top of the shop head of each rivet after it has been set.  This acts as the second barrier for the rivet holes.

This is the drain flange inside the fuel tank with the sealant cap applied.

And this is the outside of the same drain flange.  If you look close you will see sealant around each rivet as well as the edge of the flange.  This is after I had used some MEK to clean up the excess sealant that squeezed out.

Sunday, February 25, 2018

Right tank curing, Left tank on the bench

I managed to get the right tank to the point where I need to let the sealant cure for a week or so before a leak check.  Now its on to the left tank.  Much of the prep work was already done (cleaning up edges, riveting nut-plates on the Z brackets, making the new anti-rotation brackets) so this should go a little faster than the right tank.  As of today I managed to assemble, final drill, trim, countersink, disassemble, debur, and dimple all the parts.  Next up is the reassembly with sealant.  I hope to get it to the point of a leak test in the next week because the RV-9A annual inspection is due in March and I plan to start that the first full week of March. 

Hopefully it will warm up a bit before then because the hangar is darn cold right now with an outside temp in the 20's.

Took this snapshot from one of the security cameras in my hangar this morning.  Notice the temperature INSIDE the hangar is 30.5 degrees Fahrenheit.  Brrrr.  I'm not going to be doing the annual in those temps that's for sure.

Riveting complete, now it waits for sealant curing.  I left my fuel tank caps at the hangar so I used some tape to cover the fuel inlet while it waits.

The other end of the tank with rubber gloves covering the fuel outlet and the return line fittings.  Not really sure why I didn't just use a finger from the glove instead of the whole glove....

Monday, February 19, 2018

Right fuel tank, almost done

I spent a lot of time on the right fuel tank this past week.  In fact since this was a nice 3 day weekend I spent the majority of it in the garage.  I got the right fuel tank sealed up and almost rivet complete before my back decided it had had enough for the day.  A little more riveting on the back baffle and then its time to let the Proseal cure enough for a leak test.  :-)

Ribs cleco'd in place with sealant.  Took a whole box of cleco's but the skin is nice and tight.

Inside view of the cleco'd tank.

And this is about 6 hours later.  All of the ribs are riveted with the exception of the farthest forward 3 rivets on the top side.  I still have to install the tank attach bracket before I can fasten the aft half of the inboard rib.

Top of the tank in the same state as the picture above.  I could not reach those last 3 cleco's on each rib so I took the fuel tank to the airport and had Harry help me finish those rivets.
Top J-Stiffener riveted in place.

Inside view of J-stiffener riveted in place.  Still have not finished encapsulating the shop heads with sealant in this picture.
Aft rib half riveted in place.  You will notice the fuel return fitting and the vent fittings installed in this picture.

Outboard rib with the extended range fuel transfer fitting installed....with LOTS of Proseal...I kinda went overboard on this one.

I took this picture so you could see the vent line end.  I curved it a bit around the fuel filler opening and then bent it up close to the skin.  This should allow less fuel to burp overboard when the fuel expands due to heat.

The vent line fittings are encased in Proseal (after torquing them down) to make sure there are no leaks that might limit how much fuel I can put into the tank.

Outside of outboard rib.  Not much Proseal here because there is a nice filet of sealant on the inside (see pictures above).

This is a vent line snap bushing penetration.  I put a little left over Proseal on the vent line and the fitting to keep them from vibrating and possibly cutting through the bushings.  Not likely but hey, I had some extra Proseal.

A nice shot looking into one of the fuel bays.

Fuel level sensor and float installed.  This is the empty position with the float on the bottom of the fuel tank.

And this would be the full position.

And this is how things stand as of this evening.  The Z brackets are riveted on and all thats left are the side rivets that should be pretty easy to install with the squeezer.  No Proseal required on these so I guess I am pretty much done with Proseal for this tank.

I poked my phone camera into the fuel filler opening to take a couple of pictures of the back baffle seal.  It looks pretty good in every location I can see.  Only a leak test will tell for sure though.  This picture is looking outboard at the end rib.

And this picture is looking inboard at the 2nd rib in.  The top left "line" is the baffle seal and you can see a bead of Proseal along the entire length which is exactly what I was hoping to see. 

Friday, February 16, 2018

Proseal Take 2

Still working on the right fuel tank.  I did get to fly this week though.  Harry, Jeff, Paul, Mark and I met at Jefco for a little breakfast and then Harry, Jeff, Mark and I flew on up to Friday Harbor to meet up with some Fall City folks.  (Ben, Kathy, Jeff, Salima ,Larry, Mary, Dave).  We walked down to the water front to have some lunch.  It was a very nice day for flying and it showed as the sky was full!

Parked at Jefco for breakfast.
Harry and Jeff off my left wing on the flight back home.

Fuel cap base with sealer and cleco's
Back side of the fuel flange.  Nice cap of Proseal over each rivet shop head.
I got a little carried away back riveting the fuel cap...I forgot to add the tape to protect the skin so it scuffed up a bit.  No biggie since the skin has to be scuffed for paint anyway.

Finished up the stiffeners on both sides of the tank.
Stiffeners back side with nice cap of Proseal over rivet shop heads.
Stiffeners after I had back riveted them but before removing the tape and cleaning the heads a bit.
Stiffener rivets cleaned up a bit shows the proseal around the head of the rivet.

Fuel drain port sealed and cleco'd to the outside bottom skin.

Fuel tank drain flange on the outside of the fuel tank.  Riveted but not yet cleaned up completely.

Friday, February 9, 2018

Proseal take 1

Yep, this week I finished up the prep work and started the sealing the right fuel tank.  I'm trying to be a little more stingy with the Proseal this time so it doesn't get all over everything but who knows how it will end up.  Once you mix it up you only have about 90-120 minutes of working time before it hardens up.  They say you can store it in the freezer for a few days and I actually did mix up the first batch, and stored it in the freezer. It worked out pretty nicely the next day.

Most people don't care to work with this fuel tank sealant but I really don't mind.  It can be fun seeing how neat I can make it... at least until I find a leak...then its not so much fun.

Here you can see where I scuffed up the inside of the fuel tank in any location that will have the sealant applied.  This is supposed to give the sealant something to stick to.  Not sure about that because Proseal sticks to anything!

What you are looking at here are two extra penetrations I am putting into my fuel tanks.  The one on the left is the anti-rotation bracket that will allow me to put a bulkhead fitting in place in case I ever decide to install long range fuel tanks in the outer wind leading edge.  The one on the right with the fitting in place (for test fit) is where the fuel pump return flow will enter the tank.  The hole right beside it is the vent line penetration.  There will be another anti-rotation bracket installed here...well actually its already installed but not in this picture.

And here is what that same fuel return line fitting looks like riveted in place and prosealed.

This is what the outside of that same fitting looks like.  Notice I put some sealant under the rivet heads so they don't leak.
The vent line port is riveted in place, the tooling holes are filled with 3/16" rivets and the fuel pickup port is riveted in place.

Same part, other side.  This is actually the inside so all the rivet tails are covered in a cap of proseal.

I had a little extra Proseal left over on Thursday night so I started putting these stiffeners in place.  They are only cleco'd in place for now.  Once the Proseal sets up for a bit I will come back and finish with rivets.  This process helps with the mess.