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Permalink Reply by Gordon Van Alstyne on March 30, 2014 at 8:46pm

You need to talk to an engineer at the factory.  My knowledge is limited, but it looks like there was severe bending and creasing that took place.  I would think that the working of the aluminum to flatten it out, heat or no, has weakened the metal.  Whether or not it would come back to bite you in the future is something that I can't answer.  It would depend on the loads placed on it.

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Permalink Reply by Chris Aysen on March 31, 2014 at 7:28am

Christopher - On picture 3 I notice you have a line from a permanent marker. The line disappears where the welder heated (& hammered) that means the metal received enough heat to anneal it. The affected area seems to be quite lengthy? This area could develop problems down the road; when the wing is all closed up. Myself, I would replace it. The bends on pictures 6 & 7 are not as much of a problem because there does not seems to be any heat or hammering evidence. Unless they are on the same tank as picture 3 they probably would not need replacing. I'm not an engineer. Just my two cents.

Chris

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Permalink Reply by Christopher Jon Brown on March 31, 2014 at 9:33am

Thanks for the comments. Pic 6 & 7 are the before pictures and 3 is the result.  I used a heat gun to remove the cork and used laquer thinner to remove the residue and it took off the marker.  I used the marks   to position the tanks each time from the original install. Then washed out the tanks with soap and water 8 times to get the gas fumes out.  the length of each bend varied with this one being the worst about 5 inches. I was amazed how flat he got them and that they didnt leak and fit fine and no metal is gone. I'm going to call Caleb and see what he says.  I figured they welded in the bungs and cap mount and that metal is still good and the little heat he used to work the metal would not hurt it but it is a fuel tank and with the fuel sloshing might put loads on it that would make it crack but just cant seem to find anything on the internet about this situation.  And if possible not buy two tanks and shipping and cutting the holes and all the testing again and the time associated with this, just hoping for a miracle.

Best Chris

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Permalink Reply by Paul Bonasera on March 31, 2014 at 9:47am

Most alum fuel tanks are built from 5052 which is easy to weld and not heat treatable. So even if the 6061 was heated till if was annealed it should be ok. Let me know if you decide to buy new tanks i'll buy those from you as I believe I would run them....

IMHO Paul

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Permalink Reply by Christopher Jon Brown on March 31, 2014 at 12:21pm

Thanks for the info and the offer and it is 6061 T6. I'm going to use them!!!!!  Talked to a few engineers and they said it could crack down the road maybe 300-400 hours later or NEVER due to the metal being weaker but more ductile and only having 20% of the strength of the original but the surrounding metal being less ductile and stronger COULD cause a crack after repeated vibration and flexing  due to fuel sloshing.  There really is no load on the metal so I'm going to use them and if a crack develops down the road years from now, I'll fix it then which would be a weekend adventure.  Also they said that if a Small Crack would develop and show signs of a leak, it wouldn't be a giant split in the metal with fuel gushing out all over the place so I'm going to give them a whirl.  Back to the airport to button up the wings and burn in the brakes. Believe me I'll be checking these areas at preflight very closely every time for any sign of a leak.  And remember THROW THOSE ANTI SLOSH DISCS AWAY UNLESS YOU HAVE ANOTHER VENT IN EACH OF YOUR TANKS IF USING THE CESSNA CAPS.

Best Chris and thanks

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Permalink Reply by david junkins on April 15, 2014 at 5:12pm

I don't understand.  What is an anti slosh disc?  dave

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Permalink Reply by Christopher Jon Brown on April 15, 2014 at 11:57pm

on the cessna fuel caps there is a little rubber disc that lets the cap vent when suction is applied to the fuel tank,but when fuel is sloshed from a steep dive, pullup or uncordinated turn the rubber disc covers the vent holes and doesnt let the fuel flow out of the vent holes on the fuel cap. heres a link with a picture http://www.zenith.aero/photo/cessna-gas-cap  In a cessna fuel system there is an additional vent line so when that anti slosh disc closes the tanks can still vent pressure built up in them so they dont puff up like mine did.  I think I will Probably go to a gooseneck vent on the original caps so there is positive pressure going into the tanks like on older planes that dont have additional vent lines.  Oh by the way the tanks are doing great, with just some taxi testing and with the Rotax it wheelies super easy and the ground handling is excellent, cant wait for first flight soon.

Best Chris

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