Re-testing fuel tanks

December 22nd, 3h

Given that I redid the fuel caps for both left and right fuel tanks, I had to retest both tanks. So, I redid the pressure test with the sraying of soapy water.  The test passed.  So, now the fuel tanks are complete.

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

 

 

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.

 

Riveting/Sealing Fuel drain, caps and Ribs

April 11th, 14th, 18th, 20th, 21th, 22nd, 27th and 28th, May 2nd 47h

Riveting the fuel tank ended up taking a lot of time.  The procedure of the riveting is very similar to the one of the stiffeners.

On April 11th, I riveted the fuel drain and caps with back riveting, for both tanks.This took about 6h.

On April 14th, we did two ribs. This took about 4h.

On April 18th, we did one rib. This took about 2h.

On April 20th, we did two ribs.  This completed the left tank inner ribs. This took about 3h.

On April 21th, we did five ribs.  All of the right tank inner ribs at once.  We definitely improved and speeded up our process.  We learned that it is more efficient to do multiple ribs in the same time, so we tackled 2 together, then we tackled 3 ribs at a time. This took about 6h.

On April 22nd, I prepared the 2 outboard rib.  I had to custom cut a 6D rivet to fill the holes in the rib, then rivet it with sealant.  Then, I prepared the reinforcement plates, drilled then and riveted then with the sealant to the outboard ribs for both tanks.  Then, I roughed all the surfaces for all inboard and outboard ribs and the rest of the parts that mount to the inboard ribs. This took about 5h.

Then, I did couple little side tasks, which took about 3h.:

• Testing the fitting of the 2 tanks with the baffle and the z bars, now that the ribs are riveted.

• Priming the z bars, so that they are ready to rivet to the tank once the fuel tank is complete.

On April 27th, I riveted the outboard and inboard rib for one of the tanks.  The riveting was easier since it can be done with the pneumatic squeezer, so it can be done with all one person. This took about 6h.

On April 28th, we riveted the outboard and inboard rib for the other tanks. Then we riveted the horn and reinforcement plate for both inboard ribs.  This took about 3h.

Then we moved on to the vent line, fuel pick up tube and fuel sander.  We started preparing the vent line, but then we realized that we need to flare the pipe, and I did not have a flaring device.  So, we decided to move on until I get one.  Then we look at the fuel pick up tube, we went though the instruction of creating the custom one, but then I decided that getting an upgrade from Vans with the mesh is a better option, so we decided to move until I purchase that one.  Then we move on to the fuel sander, for which we riveted with sealant the plate nuts, for both tanks.  This took about 3h.

On May 2nd, I took on the task of examining the flushness of the rivets and cleaning all the outside fuel tank sealant around the rivets.  The left tank, which was the first one we did had way more tank sealant around the rivets and it took about three hours to clean. The right had way less fuel tank sealant and took only about an hour to clean.  Then I went through both tanks marking any rivets that were not smoothly flush with the surfaces and sanded those rivets to get a nice flush finish.  A couple of rivets were a little too high for sanding according to the MIL specs, so I removed those rivets in order to reset them.  Afterwards, I added protective tape to keep the metal protected against corrosion until it gets painted. This took about 6.5h

Riveting/Sealing Stiffeners

April 6th, 7th, 8th 2019, 11h

Riveting using the fuel tank sealant is a missy time consuming job.  We decided to tackle half of the stiffeners at a time so that we can be done in one hour while the sealant is still good. The method we used is as follow:

• Clean very well all surfaces, rivets and clekos with Acetone.
• Add type to all inside surface we did not want any sealant in.
• Add a good layer of sealant to the stiffeners.
• Put the rivets in and add backing type.
• Rivet
• Add more sealant to the edges of the stiffeners and the head of the rivets.
• Remove all type and clean with Acetone.
• We had a couple rivets that did not go very well, so we replaced them.

Right Fuel Tank Prep

April 5th, 6th, 7th, 2019, 15h

After getting the new z bars for the right wing tank, I went ahead with preparing this tank to catchup to the left one:

• Drilled the z bars middle holes.
• Checked the fitting of the fuel skin with the drilled z bar and the baffle,  I had to make some very small modifications.  By the end the filling looked good.
• Drilled the rest of the lower holes in the 6 z bars
• Attached plate-nuts to the z bars: drilling holes for rivets, deburring, counter sinking and riveting.
• Attached the z bars, and checked the fitting again, it looked good.

• Attached the baffle, and drilled the lower holed for the 7th z bar.
• Attached plate-nuts for the 7 z bar to the main spar: drilling holes for rivets, deburring, counter sinking and riveting.
• Attached baffle and the ribs and drilled the rest of the top holes in z bars.
• Attached the Skin to the ribs and baffle.
• Drilled the holed in W-423 attachment plate.
• Matched drilled all Skin holes with the ribs and baffle.
• Counter sinks the holes in the skin for attachment with baffle.
• Debbured all holes in the skin, and stiffeners.
• Smoothed the edge of the skin.
• Dimpled all holes in the skin and stiffeners.
• Roughed the surfaced in the skin and and stiffeners for better attachment with fuel sealant.