Interior Fuel Tank Repair

[Crossbow]

Interior Fuel Tank Repair

Good morning!

I have a problem that I hope some of you all may be kind enough to help with.

I am working on the fuel tanks for an RV-8, and while the tanks do not leak, however there is a problem with the capacitance plates in one of the tanks. Specifically, in the right tank there is a short between the plates and/or the plate wiring and the fuel tank itself; and of course, for the capacitance plates to properly function, then there needs to be electrical isolation between these items.

Now then, this is really annoying since I checked, checked, and checked some more during the construction process and there was never an electrical problem until I checked again after the leak test.

Anyway, it is now necessary to cut at least one access hole in the rear baffle plate so that I can get inside of the fuel tanks in order to effect repairs.

Therefore, do any of you all have any advice for doing just that?

I checked the VAF archives and I did learn how the process works in general: drill out an access hole; make the repair; then use pulled rivets, aluminum sheet, and Pro Seal to patch over the access hole.

However, I do not know the specifics of the process, such as:

Just what type of pulled rivets should be used?

What size should the access hole be?

And what should be the spacing on the rivet holes?

Thanks much in advance and please let me know if you need anything clarified.

[Mel]

I've done several repairs of this type. Back when we used the wrong "slosh compound", we had to remove it. We cut 4" holes in the baffle with a hole saw. Installed cover plates with pulled rivets. You can use any puled rivets you like as long as you coat them good with pro-seal. Most people use the "closed end" rivets, but it's not necessary.

[Crossbow]

Originally Posted by Mel

I've done several repairs of this type. Back when we used the wrong "slosh compound", we had to remove it. We cut 4" holes in the baffle with a hole saw. Installed cover plates with pulled rivets. You can use any puled rivets you like as long as you coat them good with pro-seal. Most people use the "closed end" rivets, but it's not necessary.

Thanks much for the data!

And just one more question, what spacing do you use on rivets? Or put another way, do you recall how many rivets that you used to seal the 4" hole?

[C-GRVT]

Have a look at "Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair" (you can find it on Google of you don't have it) for acceptable aluminum repair/patch technique, including rivet spacing and pattern. I cut and covered access holes in one of my tanks, and I recall that the acceptable rivet pattern for a circular hole cover was two rows of rivets spaced equally around the circumference of the cover plate - you will find a illustration in the book.
Bill Brooks
Ottawa Canasda
RV-6A finishing kit

[Mel]

Originally Posted by Crossbow

Thanks much for the data!

And just one more question, what spacing do you use on rivets? Or put another way, do you recall how many rivets that you used to seal the 4" hole?

I believe we used 12 rivets evenly spaced.

[Crossbow]

Originally Posted by C-GRVT

Have a look at "Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair" (you can find it on Google of you don't have it) for acceptable aluminum repair/patch technique, including rivet spacing and pattern. I cut and covered access holes in one of my tanks, and I recall that the acceptable rivet pattern for a circular hole cover was two rows of rivets spaced equally around the circumference of the cover plate - you will find a illustration in the book.
Bill Brooks
Ottawa Canasda
RV-6A finishing kit

Good call!

I have a copy of that book back at my shop and I will look up this point later today.

Thanks much!

[Crossbow]

Originally Posted by Mel

I believe we used 12 rivets evenly spaced.

Mucho thanks Mel!

I knew that you would save my life yet again and please have a good day.

[Crossbow]

Good morning!

I just wanted to give you all an update on this issue since you were so good about helping me when I needed it.

I found the culprit problem. It turned out that one of the bolts used to secure the Outboard Capacitance Plate was not quite seated correctly. I think that it shifted just a tad during the riveting process (where I used a Rivet Gun as opposed to a Rivet Squeezer) causing the plate to make physical contact with this bolt, and since this bolt is in physical contact with the Fuel Tank itself, therefore a short to Fuel Tank was developed.

In any event, by simply loosening that bolt a bit, then re-tightening that bolt, it fixed the problem.

It was considerably annoying (to say the least) to have to cut three access holes just to make a one minute fix, but at least the fix was made.

So my next job is to patch up those access holes and hopefully that will fix the problem for good.

Thanks again!