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  • Fuel cap question

    Anyone see a problem with mixing 6061 and 7075 aluminum together? Or will I be doomed for corrosion issues? Reason I ask is I have a bunch of 7075 that I could make the main two cap bodies out of. I know I should keep the tank bung 6061 for weld ability. The center piece will also be 6061. Dan scratch build patrol #243
    Dan - Scratch building Patrol # 243.

  • #2
    Can't answer that, but a related question. What about welding the 6061 bung to the 5052 tank? Is that OK?
    Doug
    Scratch building Patrol #254

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    • #3
      I think the alloy differences will not be the issue. But galling on the threads may be.

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      • #4
        I think the alloy differences will not be the issue. But galling on the threads may be.

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        • #5
          Another fuel cap question related to the "tightness" of the cap: I bought the main tanks and caps from AviPro a couple years back and just now got around to unpacking them.

          The fuel caps seem to take a LOT of persuasion to go in the filler hole. I put a little lube on the seals and it didn't help much. Will this change with time? What sort of work-arounds have you tried? Could it be the seals dried out and solidified after sitting in a Ziploc bag for a couple years? Thanks.

          Nic

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          • Mark Goldberg
            Mark Goldberg commented
            Editing a comment
            Occasionally we hear this. If using some grease on the o rings with the o rings uncompressed - doesn't allow the gas caps to go in and out OK - then there are a couple things. Fuel Lube is usually NOT recommended for the gas caps because it is slippery that normal fitting gas caps can loosen and be lost on a flight. But if the caps are too tight after grease - this Fuel Lube can make them work sometimes.

            Other option is to take .005 off the body of the gas cap where the o rings sit. Mark

        • #6
          I would put a touch of fuel lube grease on the threads. We had the aluminum bolt gall up so bad that we had to get a new gascolator. The O rings locks and seals the gas cap in the fuel neck. We carefully worked the fuel tank neck to get a fit that allowed the cap to come out with a comfortable fit. We did that so the cap was not such a tight fit that it needed fuel lube to be able to pull the fuel cap out. We also put a cotter pin in the bottom of the cap bolt so we do not accidental loosen the cap so far as to drop the lower part into the tank.

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          • #7
            If you don't grease the threads, you will have a bad time. The caps lock up so tight and so suddenly, that one day you simply cannot get them out...! Guess how I know.

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            • jaredyates
              jaredyates commented
              Editing a comment
              If you are lucky, this will happen at home. I was not lucky!

          • #8
            Today I finished installing my AVIPRO supplied tanks and fuel caps into my plans-built 4-place wings. One of the caps would not go into the filler neck, but it was the aluminum body of the cap that was too big to go in. Close inspection revealed that the filler neck was out of round. I used a sanding belt to slightly reduce the diameter of the cap. It now fits OK, and the rings seem to work well after applying Bob’s recommended lube. I also lubed the threads.

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            • Bcone1381
              Bcone1381 commented
              Editing a comment
              What is Bob's recommended Lube?

          • #9
            The lube is called EZ TURN.

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