QuickBuild RV-8 Fuel Tank Leaks Showing Up as Paint Bubbles Around Rivets

[Carlosanlley]

I’m looking for some advice regarding a fuel tank issue on my RV-8.

My fuel tanks came assembled as part of the QuickBuild wings. About three months after I first started adding fuel for tank calibration and testing (before the airplane ever flew), I began noticing paint bubbles forming on one of the fuel tanks.

The bubbles appear to contain fuel and are forming between the tank skin and the paint. Most of them are centered around rivet locations, which leads me to believe that I may have a tank that was not properly sealed during assembly. The opposite tank shows no symptoms whatsoever.

I’m attaching photos of what I’m seeing. At this point I probably have 10–12 affected spots, with some of the bubbles reaching up to about 1/2 inch in diameter.

My question is: Is there any proven method to seal leaks like these without having to work from inside the tank? I understand that I’ll need to completely drain and defuel the tank, but I would really like to avoid disassembling or opening it if possible.

Has anyone successfully repaired this type of leak from the outside, perhaps using an approved sealant injection method or another technique?

Any experiences or recommendations would be greatly appreciated.

Thanks!

 

[Mikeyb]

It’s an observation that goes way back. Good luck.

Paint Blisters/Fuel Tank Rivets

Six or seven reports been filed on another thread on the problem of paint blisters over fuel tank rivets. I sent a summary of those reports to Van's in an attempt to determine what is causing the phenomenon. This is an on going issue that started on my airplane over 2 years ago. I thought I...

vansairforce.net

 

[Mike S]

Has anyone successfully repaired this type of leak from the outside, perhaps using an approved sealant injection method or another technique?

Single data point for you-----green locktite worked for me, but it was on a top skin rivet.

Dan Horton did a deep dive (typical Dan) on this problem a while back and you can find his results via search.

 

[DCBrown198]

I had a couple if leaks. The green Locktite did not get it.

Somewhere on this forum someone suggested I try MarineTex. It's an epoxy putty that is highly regarded in the marine world. Sand very smooth like bondo. It has worked very well for me. No more leaks.

 

[MIKE JG]

Ugh, that stinks. I feel for you. I'm currently building my tanks (still...) and using plenty of tank goo to cap each rivet tail as well as a type A sealant after applying the normal type B.

Wonder if Vans would send you a new tank?

I swear someone should start a business of just building RV tanks. I'd pay the premium had I not already started on mine.

 

[MIKE JG]

Ugh, that stinks. I feel for you. I'm currently building my tanks (still...) and using plenty of tank goo to cap each rivet tail as well as a type A sealant after applying the normal type B.

Wonder if Vans would send you a new tank or pay the cost to have one built for you?

 

[8MikeXray]

Pull the tank, cut an access hole in rear web, replace the affected rivets and reseal. Not that difficult to do and it is the proper way to seal your rivet leaks.

 

[Mike S]

I swear someone should start a business of just building RV tanks. I'd pay the premium had I not already started on mine.

Steve Barns has been doing that for some time as I recall.

Fuel Tank Build / Rebuild Services

Experimental aircraft part, accessories such as propellers, fairings, tailwheels, Whelen wat lights, propeller balancers, crow harnesses / seatbelts

fairings-etc.com

 

[Quotafiller]

Green loctite didnt work for me. I found a guy selling specific blind rivets that worked. Drilled old ones out. Covered new ones in proseal and got lucky. Ill try to find contact info.

 

[Mike S]

I found a guy selling specific blind rivets that worked. Drilled old ones out. Covered new ones in proseal and got lucky.

IIRC Vans had them.

 

[Roy Thoma]

See HFS's post #7 at https://vansairforce.net/threads/fuel-tank-rivet-shows-some-blue….241285/#post-1910800

 

[DanH]

When were those tanks produced?

Pull the tank, cut an access hole in rear web, replace the affected rivets and reseal. Not that difficult to do and it is the proper way to seal your rivet leaks.

Dave's re-formed rivet works fine, but if you have more than a few with blisters, chances are you also have some waiting to happen. May as well bite the bullet...

Access holes; four rear, one end web, and the sender hole..



Sharp fly cutter works fine.



Closed end rivets.



Sealant under the flange, pull the rivets, then overcoat.



I recommend a joggled cover plate. It's insurance, relating to the 200-300% elongation spec for proseal. Without it, a 0.001" thick sealant layer under the flange can fail with a 0.003" shear strain. There is also a tension load on the rivet.

 

[Mikeyb]

When were those tanks produced?



Dave's re-formed rivet works fine, but if you have more than a few with blisters, chances are you also have some waiting to happen. May as well bite the bullet...

Access holes; four rear, one end web, and the sender hole..

View attachment 120254

Sharp fly cutter works fine.

View attachment 120255

Closed end rivets.

View attachment 120256

Sealant under the flange, pull the rivets, then overcoat.

View attachment 120257

I recommend a joggled cover plate. It's insurance, relating to the 200-300% elongation spec for proseal. Without it, a 0.001" thick sealant layer under the flange can fail with a 0.003" shear strain. There is also a tension load on the rivet.

View attachment 120258

What’s the best way to form that joggle?

 

[Phil Sprang]

I've cut the hole with a fly cutter as well. Go slow, sub 10 RPM. After I made practice cuts with the fly cutter and hole saw, I made the real hole with the fly cutter.

I'm also a big fan of type A ProSeal over top of the type B.

 

[Z32MadMan]

Weep No More - KITPLANES

When a fuel-tank repair means crafting your own rivets.

www.kitplanes.com

 

[Breezy]

I’m looking for some advice regarding a fuel tank issue on my RV-8.

My fuel tanks came assembled as part of the QuickBuild wings. About three months after I first started adding fuel for tank calibration and testing (before the airplane ever flew), I began noticing paint bubbles forming on one of the fuel tanks.

The bubbles appear to contain fuel and are forming between the tank skin and the paint. Most of them are centered around rivet locations, which leads me to believe that I may have a tank that was not properly sealed during assembly. The opposite tank shows no symptoms whatsoever.

I’m attaching photos of what I’m seeing. At this point I probably have 10–12 affected spots, with some of the bubbles reaching up to about 1/2 inch in diameter.

My question is: Is there any proven method to seal leaks like these without having to work from inside the tank? I understand that I’ll need to completely drain and defuel the tank, but I would really like to avoid disassembling or opening it if possible.

Has anyone successfully repaired this type of leak from the outside, perhaps using an approved sealant injection method or another technique?

Any experiences or recommendations would be greatly appreciated.

Thanks!

View attachment 120205View attachment 120206View attachment 120207

Carlos,

I see this often during Condition Inspections. Can't say whether it is associated with QB tanks.
My -8 has slow built tanks and occasionally the paint bubbles at the rivets like yours. My guess on cause is either a very small fuel droplet leaking at the rivet gassing under the paint, or solvent trapped during paint prep that also gases under the paint.

I suggest trying this before thinking of repaint, I have taken a very fine pointed awl or straight pin and carefully prick a hole on the trailing edge of the bubble. As close to the separation point as possible. The paint often shrinks and flattens out. You may have to give it a few days to a week. This has fixed 6-8 rivets on my tanks and other aircraft as well.

Good Luck!