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  #1  
Old 01-25-2020, 04:51 PM
Saville's Avatar
Saville Saville is offline
 
Join Date: May 2014
Location: KBVY Massachusetts
Posts: 1,261
Default Left Tank Leak - Looking like a new tank

Well this was the year for the prop inspection and as that was going to take several weeks I decided to so the annual 4 months early - lousy flying weather in January and February anyway.

But the other reason I downed the plane was that I had developed a small leak in the left hand tank. You'd wipe the underside of the wing clean and the next day there would be a track a few inches long. Nothing major but enough to bother me.

So the prop came off and and the annual completed (few minor adjustments to be made), and the tank came off.

The leak is in the lower seam about 3/4's the way outboard:



Turns out that someone had buttered up the entire outside of the seam with Pro Seal but...the sealant never cured - you can wipe it off with your finger:



So then it was observed that just about every fastener hole along the top spanwise edge had a small crack on the underside. The conjecture is that maybe the screws were turned too tightly or that the dimples were not created squarely - or maybe both.

Anyway this tank has been a problem from the start. Firstly the tank vent B-nut on the inside was never tightened down so I had to remove the access plate, reach in there and tighten it. And the pass-through the rib for the vent was sloppily put on and leaked so I also removed it, put new fittings in Pro Sealed it and it was good from that point on. There was also Pro Seal on the tip of the vent near the fuel filler cap partly blocking the vent.

So it looks like a new tank. I suppose one could try to remove the skin and reskin the structure but the time taken to drill out all those rivets must be close to just constructing a new tank. And this one I can inspect as it's being built.

Well that's the fun of EAB and buying someone else's airplane. I'm not complaining...these things happen: Only if you build it yourself do you reduce the chances for surprises. But the prop might be back on before the tank is built and installed.
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Last edited by Saville : 01-25-2020 at 04:56 PM.
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  #2  
Old 01-25-2020, 07:01 PM
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Gregg,

Cut access ports in the rear wall, re-seal as necessary, live happily ever after.





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  #3  
Old 01-25-2020, 07:23 PM
Northernliving Northernliving is offline
 
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Location: Boston, MA
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Default

Quote:
Originally Posted by Saville View Post
Well that's the fun of EAB and buying someone else's airplane. I'm not complaining...these things happen: Only if you build it yourself do you reduce the chances for surprises. But the prop might be back on before the tank is built and installed.
If you don't want to build tanks, I think Evan Johnson is still building tanks. Evan took over the tank building business from Don London who built RV tanks for many years. I might be able to dig up his contact info if you are interested.
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  #4  
Old 01-25-2020, 07:30 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by Saville View Post
Turns out that someone had buttered up the entire outside of the seam with Pro Seal but...the sealant never cured - you can wipe it off with your finger...
Probably because there were fuel fumes/residue weeping into the proseal as it "cured".

Your tank is definitely repairable....do as DanH suggested, open up the tank in the bays where the leak is located and seal inside the tank after is it completely dry and free of fuel. You should then be good to go.
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  #5  
Old 01-25-2020, 07:31 PM
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RVbySDI RVbySDI is offline
 
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Quote:
Originally Posted by DanH View Post
Gregg,

Cut access ports in the rear wall, re-seal as necessary, live happily ever after.





Take the advice from one who has experience with this (7 times worth of experience, go ahead and do a quick search to see some of my posts), this is the only way you are going to successfully seal leaks in a leaking fuel tank.
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  #6  
Old 01-25-2020, 07:37 PM
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A2Jake A2Jake is offline
 
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Quote:
Originally Posted by DanH View Post

Cut access ports in the rear wall, re-seal as necessary, live happily ever after.
Dan,
Are these tanks you built that developed leaks later in life ? Or??. ?

Reason I ask, I have new 2005 vintage QB tanks that have never flown that I don't trust the Philippine builders Vans had at the time.
I was thinking to re-seal just as you have here before paint & fly.

J.

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  #7  
Old 01-26-2020, 05:47 AM
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decathlon737 decathlon737 is offline
 
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Default Seal Tanks

As one of the early guys that got bit by leaking QB tanks, around 2006 / 2007 era, I would urge everyone to open the rear wall and reseal tanks properly. The work performed inside tanks by the QB personnel that I have witnessed was performed by obviously untrained labor. I repaired mine in 2009 and never another problem. At the time I had several friends in the flying and building stage that had me do a reseal on their tanks without a future problem. Do not paint tank installation screws so they can be removed with minimal damage to paint if needed. Also install flushing washers under screws to help protect paint. Save yourself time and labor later by doing this during the build.
YMMV
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  #8  
Old 01-26-2020, 06:58 AM
Northernliving Northernliving is offline
 
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Location: Boston, MA
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Quote:
Originally Posted by A2Jake View Post
Dan,
Are these tanks you built that developed leaks later in life ? Or??. ?

Reason I ask, I have new 2005 vintage QB tanks that have never flown that I don't trust the Philippine builders Vans had at the time.
I was thinking to re-seal just as you have here before paint & fly.

J.

~
I'm aware of a local 8 builder with QB tanks around the vintage you mentioned that developed leaks. He basically did what Dan prescribed. The leaks developed shortly after his first flight but before it was painted. No problems since.
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  #9  
Old 01-26-2020, 07:15 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by A2Jake View Post
Dan,
Are these tanks you built that developed leaks later in life ? Or……. ?
Reason I ask, I have new 2005 vintage QB tanks that have never flown that I don't trust the Philippine builders Vans had at the time.
I was thinking to re-seal just as you have here before paint & fly.
Those were brand new QB tanks, vintage 2005. They were indeed a mess, but that's another story.

Closed end pop rivets, installed wet.



Perhaps not strictly required, but I recommend a sealant joggle around the perimeter of the cover plate. It guarantees structural loads cannot shear the sealant line.

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Last edited by DanH : 01-26-2020 at 07:34 AM.
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  #10  
Old 01-26-2020, 07:33 AM
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Saville Saville is offline
 
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Quote:
Originally Posted by Sam Buchanan View Post
Probably because there were fuel fumes/residue weeping into the proseal as it "cured".

Your tank is definitely repairable....do as DanH suggested, open up the tank in the bays where the leak is located and seal inside the tank after is it completely dry and free of fuel. You should then be good to go.
Well - referring back to my OP - there's the cracks in the screw holes along the top of the wing that the mechanic mentioned. I need to see those for myself. If there are as many have cracks as he says then the tank skin is no good.

If the skin is no good then at that point it's either a re-skin or a new tank. I think I'd opt for a new tank.
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