Redoing fuel caps

December 7th and 8th, 10h

I decided to redo the fuel tank lids after checking with Vans.  The issue happen when  torqued the bolts after the sealant was dry.  I added fuel tank sealant to the outside of the bolts, but Van said that it is not enough.

So I went ahead and removed all the bolts from all the lid for both the left and the right fuel tanks.  Then I spent many hours cleaning the lids, the holes and nutplates.  Then I reset the bolt with wet sealant again.


Attaching Fuel Tank & Flipping Wings

October 5th and 6th, 6h

Given that we had 2 bolts that did not work well with the second fuel tank attachment, we want ahead and removed the second tank.  Then we replaced the bad platenuts.  Then we attached the fuel tank again.  The second time, it worked great.

Afterwards, we proceeded to flipping the tanks into the new cradle. We looked for any twist, and we measure less then 1deg, which is pretty good.



Attaching Fuel Tanks

August 29th, 9h

Attaching the fuel tanks was a bit time consuming.  The fitting is pretty tight, and having fuel tank sealant in the edges did not help.  So, we have to do couple trials to makes small adjusted, removing some sealant, to get the tank to fit.

Finally, we got the right fuel tank to fit pretty well.



Then we moved on to the left one. The fitting ended up pretty good as well.  However, we ended having a bit of troubles with 2 bolts going into the platenuts attaching the spar to the Z-bars.  we decided to get back to those bolts later.




Fuel Tanks Closing and Testing

August 19th, 21th, 26th 11h

I finished closing the second fuel tank: the tank lid and the duel sander.

Afterwards I moved on to testing the 2 fuel tanks. I emailed Vans about the leak in the fuel cap observed in the first tank.  According to them, small leaks in fuel cap are ok since it is in the highest point in the tank, so they asked for adding tape to the fuel cap for the sake of the pressure test.  As well, they pointed a nut that I could adjust to tighten the pressure between the fuel cap and the flange.  After tightening the nut, the leak was way small.  Then I added tape for the test.

After many trials to get a good seal between the balloon and the air vent fitting, I was able to get a good seal and test both tanks.  Both tanks passed the test.

There was no babbles when I sprayed soppy water.  There was a small deflation in the ballon in one of the tests that is expected because of a decrease in temperature of about 20 deg Fahrenheit between the 2 days.  There was an inflation in one of the balloons all the way to explosion after 24h, explained by an increase in temperature between the days.  So, temperature plays a big role in the size the balloon maintains and the deciding factor in the test is the absence of babbles when spraying with soapy water.


Closing the Fuel Tanks

August 15th, 17th & 23rd, 23h

First we started by verifying all the sealant inside the tanks.  We swept each tank few times, filling any tightly hole we saw with sealant.


Then we went ahead with closing the tank, we put the baffle and z bars in with cleakos, then we went ahead filling all the holes with wet rivets. We used pop rivets for the center z bars and solid rivets for all the edges. Then we verified that the bottom internal corner stayed open, we put big blob of sealant in the outside corners, and we made sure that there is good fillets on all the edges.



Following, we put the closing lid and the fuel sander. Everything was set wet, including the screws.


After closing the tank, we waited a couple days, then we tested one of the tanks.  I used the Vans testing kit to close the the fuel line, I attached a bike pump to the fuel drain, and I attached a ballon to vent line.


I pumped air in.  Unfortunately there is a huge leak since the tank is not able to hold pressure.  The leak is not from any of the seals we created, but from the Vans fuel tank cap/flange. The small seal in the fuel cap between the lid and the flange is not able to hold pressure  So, we need to replace the fuel cap and maybe the flange.


The Vans fuel cap/flange used

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Sealing Miscellaneous

May 24th, 25th,  15.5h

After getting the main part of the fuel tank done, I moved on to finishing the last details before closing:

  • Fixing few rivets:  first there was few rivets that were not flush, above the mil spec.  So, I removed those rivets and reset new ones with fuel tank sealant.
  • Vent line: first I needed to flare the vent line.  It is very important to get the flare well done, since a bad flare can lead to leaks in the fuel tank.  So, first, I purchased a flaring device and testing it in some extra pipe I had, the flare looked great.  Then I went ahead and flared the vent line for both tanks.  Afterward, I fit the vent line in both tanks, through all the ribs and fuel cap tab.  Then, I bent the line so that it is pointing to the highest point in the tank.  As well, I tested tightening the nuts.  Everything looked great.  Then it was time to add the tank sealant in to seal the input of the vent line for both tanks.
  • Fuel pickup tube: I bought the pre-made fuel pickup tube, so it came already with a flare.  So this one was easy.  I fitted in the tank.  Then I riveted the anti-rotation bracket with sealant.  Then tightened the nuts.  All looked great.  Then I moved to sealing the fuel pickup input for both tanks.
  • Fuel sander:  this one does not need to be sealed in until closing the tank.  But for completion, I added it in to see the fitting of everything together and test for any interference.  All looked great.
  • Removing fuel sealant from the edge that meets with the leading edge:  after testing the fit of the fuel tank in the main spar, with the leading edge, the fuel tank was a little too high.  This was because there was a bunch of fuel tank sealant a† the edge of the most outboard rib that added material causing the tank not to be flush.  So, I removed the excess fuel tanks sealant., leaving only few millimeters at the outside of the rib for sealing.