Fuel tank mounting

Discussion in 'Boatbuilding' started by tuantom, Jun 21, 2009.

  1. tuantom
    Joined: Jan 2005
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    tuantom Senior Member

    I think I may have blundered my fuel tank. I used beads of 5200 in a herring bone pattern and placed my gas tank right on that with 1/8" spacers in the corners to keep something of an air space underneath.

    This was done about 24hrs ago in a last minute change from the original plan of using foam. So it occurs to me this morning that 5200 is pretty strong stuff and that this may be more permanent than I want.

    I guess my question is: Do I just leave it alone and hope I don't have any problems in the forseeable future? Or do I lift it the tank out and come up with a new plan before the 5200 fully cures?
     
  2. TollyWally
    Joined: Mar 2005
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    TollyWally Senior Member

    If I thought I could pry it up now I would. Personally I'd want more than 1/8" clearence. Ventilation is a good thing regardless of the material in question.
     
  3. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Regular 5200 takes up to a week to cure, the faster you get it out the better.
    5200 alone is not enough to mount tank, so why are you using it. It is better to mechanical attach tank, and make sure that it could weight of tank full of fuel. What happens if you boat get thrown 3 or 4 feet in air? Will tank stay in place?
     
  4. tuantom
    Joined: Jan 2005
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    tuantom Senior Member

    Yeah it'll stay in place. It's a belly tank and is held down,but not supported, from the floor above it. It originally was foamed in a supposedly isolated compartment; but somehow water found it's way in there and saturated the foam anyway.

    The 5200 is just meant to keep it supported a bit off the base of the compartment so if water gets in there again it can go to the new drain hole in the back.

    I won't know till tonorrow how cured the 5200 is.
     
  5. mark775

    mark775 Guest

    "somehow water found it's way in there and saturated the foam anyway." Always.
    Aluminum fuel tanks should have welded-on angle attachment points and be supported only from these points. Powder coat. When the stainless bolts rot the aluminum in twenty years, move the bolts to new holes. This is one place where foam should never be used IMO.
     
  6. mydauphin
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    mydauphin Senior Member

    I also paint outside of AL tanks with Zinc Chromate primer spray paint .., Good protection for $10 and 10 minutes of work... Wear a mask
     
  7. Ike
    Joined: Apr 2006
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    Ike Senior Member

    Absolutely make a proper mounting system for the tank. Foaming in a tank is a sure way to destroy it. You definitely need to get it up off the bottom of the compartment so air can easily circulate.

    I disagree. Why paint a tank that has a natural coating on it that protects it from corrosion? see Aluminum Boats and Tanks: To Paint Or Not To Paint? http://newboatbuilders.com/docs/aluminum.pdf To do it right you have to prep the aluminum correctly and even then it won't last. Aluminum is best left unpainted. If left unpainted, supported properly and kept dry the tank will last twenty years or more.
     
  8. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The painted aluminum tanks will pit corrode if there is any scratch. That is particularly so with electrolisis. Instead of a small amount eroding from the whole tank, it all comes out of a small spot and makes a hole.
     
  9. mydauphin
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    mydauphin Senior Member

    Wrong, Ije and Gonzo. Let me tell you why. I said paint it, I mean with zinc chromate primer. The purpose of it is to prevent a little corrosion that happens when something touches or falls on aluminum. When it gets wet, the zinc chromate, breaks down and it realize the zinc and chromium to the scratch and helps protect AL when it wont oxidize.
     
  10. tuantom
    Joined: Jan 2005
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    tuantom Senior Member

    What about coating the tank in epoxy rather than paint? Assuming it was properly prepared, wouldn't that do a fair job of isolating the tank? Maybe even use some lightweight cloth for abrasion resistance.

    BTW - the tank lifted out without much fight yesterday. I'm thinking I could use the same method with my herring bone pattern; but use some 1/4 inch plastic strips sandwiched between the 5200. It'll get the tank a little higher up and I'll be able to lift it out in the future if needed.
     
  11. TollyWally
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    TollyWally Senior Member

    If it were me I'd really think about ventilation.
     
  12. Luckless
    Joined: Mar 2009
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    Luckless Senior Member

    The problem with that is if you epoxy cracks and pulls away from the tank, then it will trap moisture there. This will hurt the tank far more than help it.


    Ideally if you have to put your tank somewhere that it could risk getting hit, then I would suggest looking into getting some kind of protective mesh cover that stands off 1/4 inch or more, with 1/4 inch holes. This should let the air flow around and any water fall away. The mesh/slatted cover should bend and dent before the tank takes damage.
     
  13. tuantom
    Joined: Jan 2005
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    tuantom Senior Member

    Unfortunately that's about the most ventilation I can give it. If I raise it any more than a 1/2" off the base, it'll be into the floor above it.
     

  14. TollyWally
    Joined: Mar 2005
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    TollyWally Senior Member

    LOL,
    Nothings easy is it?
     
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