Fuel tank oil canning

[Luke68]

I am having trouble with one of my main fuel tanks oil canning, if I lightly push on the filler neck the top of the tank pops down so one side of the neck is about 1/8" lower than the other, I can pull it back by using a bar but can't figure out how to make it stay. I know steel can be heated and then rapidly cooled the make it shrink but I'm a little hesitant to try that on aluminum. Any suggestions would be great Luke Huismannn

[Battson]

I agree that heat treatment would need careful thought, you will probably change the microstructure of the alloy in the process. Now that might not be a problem for the fuel tank, compared to say a wing spar, but you would want to take advice on the subject first.

​You could consider running a heavy weld bead along the outer skin to stiffen them? But if that doesn't solve the problem, then it could lead to cracking.

Also, does this problem happen when the tanks are in the wing (and under pressure from the tank straps and wing skin stiffeners), or is your tank as yet uninstalled?

[Luke68]

I have the tank in the wing and have tried different tensions on the straps but it doesn't seem to have much affect on the oil canning, when I get everything good and snug it takes slightly more pressure to make it pop but it still won't stay where I want it. I might take the tank to the local welding shop and see if they have any ideas, possibly welding the skin or cutting the neck out and welding it so it works with where the tank wants to be.

[Mark Moyle]

There is a trick Kent White showed us in class. Heated the aluminum causing it to bulge out. Then while the aluminum was hot and using what looks like a really coarse file....designed for aluminum...Kent ran the file across the bulge. Shaved perhaps a few thousandths off. Shaving off that little bit held the aluminum. When it cooed off...same. Give Kent White a call at TM Technologies.... He can walk you through the process....and you can purchase the correct file from him. Mark M. Sent from my iPad using Tapatalk HD

[KyBearhawk]

I would love to know how you solved this once you get it fixed.

[Luke68]

I managed to get the fuel tank to stop oil canning, I just heated it with my torch and used an L shaped bar to reach inside the tank through the filler neck and push up on the low spot in the skin, then I cooled it with a wet towel. It took six or seven try's in different places to get all of the oil canning out.

[Battson]

Hey pleased to hear you got it sorted!