Build Log RV-10 #1

Blog for a Vans RV-10 Airplane Build

Fuel Tanks

Started July 1st, 2010  115 Hours

Well, today is the start of the dredded fuel tanks.  After reading many other builders logs it seems that this is no easy or fun process and has been making me nervous to even start.  But I guess the only way to get them done is to dig right in and get going.

The first parts of the directions are not so bad as it is just putting everything together with clecos and match drilling all the holes.  As many other builders have said - the directions get a bit harder for every section that you move on to.  This meaning that they leave out some of the steps that should be a given now.  For example size of holes, fluting, what should be dimpled and countersunk and what needs to be done to each part or hole before final assembly.  Not bad just need to understand this so that you do not forget.

To begin I took all the parts that were marked for the fuel tanks and prepared them.  This included separating some of the z-brackets, tank stiffeners and vent line clips.  Got all these separated, deburred and the ones that needed it, primed.

Then on to fabricating the full length tank stiffeners that go on the top top side of the tanks.  Clecoed them and the small stiffener plated to the bottom skin.  Make sure that you read the direction on the inner most bottom tank stiffener as they need to be trimmed and the inner most hole redrilled.  Also, not these on the stiffeners so you do not put them in the wrong place during re-assembly.

Clecoed all the tank ribs in place for both tanks.  Match drilled all the holes of the ribs to the skin then finished drilling all the holes in the top stiffener. Then cleco the tank attach bracket to the tanks and ribs.

The directions do not mention what to do with the holes in the tank attach bracket but drill to final size.  After looking at other builder logs and the fact that the thickness of this piece is quite thick, it is about impossible to dimple.  So I went ahead and counter sunk the holes that match the skin and also the ones that go to the upper and lower shim pieces.

I did not choose to use the fuel caps that came with the kit but chose to upgrade to the lockable ones.  After receiving them in the mail, I was pleased that I made this choice.  They are much better quality and the do not need to be bent to match the skin curve.

The z-brackets are now primed and dry so I went ahead and attached the nut plates per instructions.  Then clecoed them along with the rear tank baffle to all the skins and ribs. Final drilled all the holes per instructions.

Drilled out the screw holes in the fuel tank skins to a #19. 

The next step takes a bit longer and make sure that you fully read the instructions as you do not countersink every hole that attached the skin to tank baffle.  They tell you to leave a few of them  to maintain proper alignment.

Before dis-assembly of the tank, I went through and labeled all the parts  so that it will go back together in the exact same position it was match drilled for.

I have to leave this process for a bit because I am not going to use the float fuel system that are in the instructions.  Instead I am going to come up with capacitive fuel guage senders.  Vans does not offer a kit for the RV10 at this time so I am going to make one.  This will be documented in another section called Capacitive Fuel System.

I got all the parts fabricated for the capacitive fuel system done so I can now move on to finishing the tank construction.

All the parts for the tanks have been deburred, dimpled and countersunk per the instructions.  The instructions are now requiring you to think about the process more as they do not specifically tell you to do steps that you should already be aware of doing.  For example, deburr every hole, not telling you what exact holes to dimple, etc.

Started final assembly on the tanks by mixing up some of this great pro seal stuff.  This is a process that I have been dreading from the very start.  Instead of applying the pro seal with a stick, I picked up some syringes from our pharmacy that have quite a big opening to make it easy to suck up the pro seal, and just about the right size to lay out a nice layer.  Worked great for me, although never tried any other method, so could be totally wrong.

Got all the tank stiffeners gooped up and clecoed onto the skins.  Tried at first to buck the rivets normally, but then has this great thought to try and back rivet.  Much better idea, not sure why I was lacking this judgement earlier.  Made a huge mess trying to do it the other way.

All tank stiffeners are done and on to the ribs.  I made up two ounces of proseal at a time which covered two ribs, top and bottom.  This worked out pretty well as by the time I was done riveting the second rib, the proseal was already starting to set up.  Bad part is that after each set of two ribs, everything must be cleaned before moving on to the next two.  The clecoes were the worst to clean.  Finally started to soak them in MEK over night and wiped off the next day before doing any more ribs.

Kept moving on with assembly in the order that the directions tell you.  Besides dealing with this very messy proseal stuff, it actually was going pretty good.  The biggest thing that bothered me the most was the amount of time it was taking me.  Seemed like I was never going to get to the end.

Well, finally getting close.  Got everything together except for the rear baffles.  I decide to waste some time to check for major leaks by filling each tank with water.  It also was to help clean out all the sanding mess I made from trying to get rid of all the proseal I ended up with all over the inside of the skins.  Glad I did this as I ended up with 1 rivet in each tank that had a very slight leak.  Not sure where it was coming from but decided to remove and replace these two rivets.  Now that I have become nervous that I have  a couple of leaks I decided to go around every seam with proseal.  This means every rib inside and out, top and bottom, along with all the tank stiffeners and the j stiffener.  Probably not needed but I do not want to have to cut into the rear baffle to fix leaks later.  I wanted to feel 100% that there was not going to be any leaks.

Before installing the rear baffles, I had to finish up the install on the capacitive fuel system.  That is now done.

Lastly, finished up the proseal and rivets for the rear baffles.  Once everything was dry, I sanded off all the excess proseal I had on the outside of the tanks and sprayed on a final coat of primer.

I am going to let the tanks sit for a couple of weeks before I do a pressure test. Have heard a couple of stories of builders that tried to do it to soon and the pressure pushed out the proseal and ended up with quite a few leaks.

Be back in a few weeks to finish up this section.

Well, with a lot of stress, I decided to pressure test the fuel tanks tonight.  I am pleased to say with much relief that neither tank leaked.  Yipeeeeee!!!!

The only thing left to do now is hang the tanks on the wings.  Started to do just this tonight and notice that I need to shave a bit off of the skin of the outer side.  This is due to the skin overlapping the leading edge.  Used a beld sander on low and only needed to take about 1/32 off.  Pretty easy.

I am leaving the balloons on the tanks to see how long they stay pressurized.

But for now, the tanks are on the wings so I am calling them complete.  On to the next section.

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