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  #1  
Old 06-10-2020, 10:11 AM
1001001's Avatar
1001001 1001001 is offline
 
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Default Fuel tank baffle line of leaky rivets -- Advice?

After feeling really good about building one fuel tank that had no leaks upon pressure testing, I confidently undertook to seal and rivet the second one. as a new fuel tank expert, I knew exactly what to do, and it all went swimmingly well.

Until the pressure test.



Fortunately, everything is very well sealed, except for about 15 rivets on the top inboard edge of the baffle (the suds below are just from running down the tank skin). I am at a loss to understand what happened here, but I assume that it was an inadequate bead of sealant on this edge. I don't get why, though, because sealant squeezed out the rear side of this joint when it was assembled. There is a nice bead along the back side, but clearly, air is leaking in the front (internal) side and reaching the rivets.

I can see a few options for repairing, but would like some advice, if you'd be so kind...

1. Drill out these rivets, and reinstall with sealant on the heads (I didn't apply sealant to these rivets originally, assuming the bead inside the tank would be adequate). This would be super easy, but have the greatest likelihood of not working, or failing later in the life of the tank.

2. Drill out these rivets, pry the skin back and clean the faying surfaces of any sealant remaining, squirt some sealant into the gap, cleco it, shoot a few rivets for structural integrity and then try a new low pressure test to see if it worked, then drive the rest of the rivets. This seems like it would work, but there's a chance shooting new sealant wouldn't cover the whole gap. Also, a chance that I could just end up damaging the sealant bead inboard and outboard of the repair. The cleaning part would be really difficult.

3. Drill out the rivets on the entire top of the baffle and try to apply a new bead after cleaning.

4. Pull the level sensor and try to apply sealant from the inside through that hole.

5. Cut a hole in the baffle, reseal from inside, and apply a repair plate.


What would you do? What has the best chance of working?
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  #2  
Old 06-10-2020, 10:28 AM
wilddog wilddog is offline
 
Join Date: Feb 2008
Location: va.
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Default

I would do #1 and if it still leaked do #4. Save #5 for last. You will probably destroy the tank trying to pry off the rear baffle without dissolving the Proseal with something. If the baffle does have to come off, I would send it out to Weeps No More and let them fix it. Cost more but you will get a tank that will not leak.

Last edited by wilddog : 06-10-2020 at 10:33 AM.
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  #3  
Old 06-10-2020, 12:06 PM
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Thanks, I may try that. Probably will drill the rivets, stuff some thinned proseal in the holes, then pull a vacuum on the tank to see if I can draw any sealant in there.

Can anyone tell me about the Van's baffle access plate kit? I have seen people say they use a 5" hole saw to cut access holes. Is this the correct size for the Van's kit? They don't specify the diameter.

Also, does the kit come with only one plate and rivets or are there other pieces? Again, Van's store description leaves a lot to the imagination.
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  #4  
Old 06-10-2020, 12:53 PM
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az_gila az_gila is offline
 
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Why drill out the rivets?

Use Van's repair kit and a 5 inch hole saw to redo the ProSeal filllet on the inside surface.

The local Ace hardware guy said I was the only person ever to buy his 5 inch hole saw...

Yes, it's one plate and the associated sealed pop-rivets per kit.
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  #5  
Old 06-10-2020, 01:09 PM
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wirejock wirejock is offline
 
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Default Tank repair

Tough call. I think I would drill the leaky rivets and cut a hole in the baffle in each bay with leaky rivets. Fix the seam from the inside, replace leaky rivets with sealant and close up the baffle with the Vans covers.
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  #6  
Old 06-10-2020, 02:07 PM
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Quote:
Originally Posted by az_gila View Post
Why drill out the rivets?

Use Van's repair kit and a 5 inch hole saw to redo the ProSeal filllet on the inside surface.

The local Ace hardware guy said I was the only person ever to buy his 5 inch hole saw...

Yes, it's one plate and the associated sealed pop-rivets per kit.
I'll probably try the drill-out and reseal rivet method first while I'm waiting for the repair plate kit to arrive.
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  #7  
Old 06-10-2020, 03:43 PM
pa38112 pa38112 is offline
 
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I would do #5. You will get a good seal without having to remove the rivet, and the plates will be there for future access.
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  #8  
Old 06-10-2020, 04:07 PM
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KCBerner KCBerner is offline
 
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Default pressure

I see you have a different setup than the balloon and schrader valve setup and you have a pressure guage. For my own information, what pressure did you test at?
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  #9  
Old 06-10-2020, 05:01 PM
Ralph Inkster Ralph Inkster is offline
 
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I saw a severely bulged tank at 3 psi. Caution!


"I'll probably try the drill-out and reseal rivet method first while I'm waiting for the repair plate kit to arrive."

Personally, I'd drill the rear baffle off & re-do it, but Gil's suggestion is a close second as fuel hasn't touched that sealant yet.
Any short cuts today will haunt you when you least want it too later.
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Last edited by Ralph Inkster : 06-10-2020 at 05:10 PM.
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  #10  
Old 06-10-2020, 07:24 PM
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Quote:
Originally Posted by KCBerner View Post
I see you have a different setup than the balloon and schrader valve setup and you have a pressure guage. For my own information, what pressure did you test at?
Up to 3 psi. The gauge is calibrated 0-15 psig. I originally used a Magnehelic gauge calibrated up to 2 inches of water column for the first tank. I switched to this new gauge to test at a higher pressure, knowing that too much might exceed the acceptable loads. I fear I may have overpressurized and stressed the tank, damaging the bead in the area in question. I plan to visually inspect the bead with a borescope or mirror if I have to cut access holes.

My estimate of the pressure capability of the tank: So if the tank is 8.75" high, given that the specific gravity of 100LL is 0.68-0.74 by spec, the tanks should be designed to handle up to THIS WAS INCORRECT, SEE POST BELOW FOR CORRECTION static pressure equivalent. Basic rho * g * h.

Last edited by 1001001 : 06-10-2020 at 09:14 PM. Reason: WRONG calculation see below!
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