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Not your typical fuel tank woe

ShortSnorter

Well Known Member
After agonizing over to wet rivet or not, sealant dispensing methods, and everyone opinions, I completed my fuel tanks back in November and the initial leak test with soapy water and balloon passed with flying colors. About a week or so ago I ran across a thread from a builder who was having issues with producing acceptable tubing flares. It was then I learned that I used the wrong flare set (automotive) when making the vent lines in for the tanks. That's when I went down another path of endless thread scouring about potential vent blockages/leakages etc. I was worried that although leak free, I may leak fuel through the improper vent fitting once the vent fitting was submerged in fuel. My curiosity couldn't take it anymore, so I decided to do another leak test with Avgas. Long story short, no leaks from the inboard rib vent fitting when submerged in fuel. Which brings me to......

While inspected each rivet in the tank for blue dye, I was scraping off bits of dry proseal from around the rivets. My heart sank when I found this:

2m3iutu.jpg

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It seems that during my wet riveting, proseal madness, I overlooked a rivet. This hole is filled with dry proseal and is leak free. It is just far enough away from the filler cap that I can not reach it. Here is a picture I tried to snap holding a mirror through the filler neck (the red in the lower left is the filler neck). The red arrow points to the pick piercing through the sealant.

ibkkjo.jpg


Here are my initial thoughts in order of least to most invasive:

1) Do nothing other than fill the dimple completely flush with sealant and pretend like it never happened.

2) Put a blind rivet in and attempt to smoosh a big dollup of sealant on the shop head using some sort of reaching device (i.e. mirror, etc)

3) Cut an access hole in the back and put the the correct rivet in place. (This seems like overkill)

Any other ideas or suggestions? I hate to cut into a leak free tank just for the sake of one rivet.

Thanks in advance!
 
The RV12 uses a special blind rivet for its fuel tank and you install it wet. You might talk with Vans but this seems like an option. A second option is to install the correct rivet. It looks close enough to the fuel cap to get a small bucking bar inside.
 
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The RV12 uses a special blind rivet for its fuel tank and you install it wet. You might talk with Vans but this seems like an option. A second option is to install the correct rivet. It looks close enough to the fuel cap to get a small bucking bar inside.

The AK-42H rivet is a flush, closed ended pull rivet. You will have to drill the hole out to 1/8", then use a countersink/hand deburring tool to bevel the hole enough to make the rivet sit flush. However, the tank skins are quite thick, so you shouldn't have any issues there. Just do a little at a time and test with the rivet until it is flush.
 
A custom bucking bar holder with a small bucking bar should allow a normal rivet to be used. Move on to other jobs and think it over for a while.
 
The AK-42H rivet is a flush, closed ended pull rivet. You will have to drill the hole out to 1/8", then use a countersink/hand deburring tool to bevel the hole enough to make the rivet sit flush. However, the tank skins are quite thick, so you shouldn't have any issues there. Just do a little at a time and test with the rivet until it is flush.

A custom bucking bar holder with a small bucking bar should allow a normal rivet to be used. Move on to other jobs and think it over for a while.

Either of these suggestions are good options.

The first one has been done successfully many times.
 
Good advice

I agree with the sleep method. After several days of thinking about my problem, I have always come up with a solution that works.
 
I have used the special closed end pop rivet to fix a leak on the bottom of my tank.

This is the fix recommended by Vans.
 
Gents - I appreciate all of the valuable feedback. I think I'm going to go the blind rivet route for two reasons: 1) Its fast and easy; 2) I could see dropping a bucking bar or whatever into the tank and dinging it up (even though its the bottom skin)

Next question: Should I pretty much use the same procedure for riveting the Z-Brackets and swirl the rivet in sealant prior to insertion and then attempt to reach with something and dollop sealant on the shop head of the rivet for good measure?
 
on the top side of the tank and in that location. How much fuel could that rivet hole ever see?

I would put some epoxy filler over it and continue.

I have used normal 3/32 pull rivets on the bottom of the fuel tank with good success.

I drilled out the leaking rivet and stuffed proseal into the hole and buttered proseal on the rivet before installing. A little dab of proseal on the head. leak fixed.
 
Next question: Should I pretty much use the same procedure for riveting the Z-Brackets and swirl the rivet in sealant prior to insertion and then attempt to reach with something and dollop sealant on the shop head of the rivet for good measure?

If you can reach the shop head there's no harm in it. But if you can't reach in and get it without undue effort I wouldn't bother.
 
on the top side of the tank and in that location. How much fuel could that rivet hole ever see?

This was my part of my rationale for leaving it. The other reason for leaving it was introduction of debris into an otherwise debris free tank (i.e. bits of cured sealant, metal shavings) without the assurance of getting it all back out.

If you can reach the shop head there's no harm in it. But if you can't reach in and get it without undue effort I wouldn't bother.

I definitely cannot reach it with easily with or without a tool. I'm sure I could come up with something though to smear it on if need be. I guess it really isn't necessary. There have been no issues with the zee brackets.
 
I spent a few minutes in the garage today and was able to successfully enlarge the hole to 1/8" with minimal debris. Just for grins I went through my rivet collection and to my surprise I had a bag of AK42H rivets. The rivet fits snugly in the freshly drilled hole but my question lies with the CS. I dimpled a piece of scrap with 1/8" dies and the rivet really didn't sit much different than the picture below which is sitting in a 3/32" dimple. I know it was mentioned earlier in this thread to CS a little at a time until it is flush but my concern is the potential to disturb the sealed sandwich of the stringer and the skin. Although unsightly, is it totally incorrect to leave the rivet proud as shown or are my concerns completely unfounded?

snh3zt.jpg
 
***Update***

In an effort to close this thread out and provide some photos for archive purposes, I have implemented the recommended fix by CS the already dimpled hole and installing the closed end blind rivet wet. As I'm sure many on here may or may not be willing to admit to the same, I found myself with analysis paralysis. This entire fix was done in 30 minutes, including mixing and cleaning up proseal.

As shown in the previous post, the blind rivet sat slightly proud but I was nervous about CS the already dimpled hole. Solution: Try it out on scrap first. Needless to say it was was a non-issue.

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With the rivet installed I was able to seal the back side of the rivet by bending a long strip of HVAC aluminum to the right angles to apply the sealant.

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