Aluminum Gas Tank Installation Question

Discussion in 'Boat Design' started by 84EdH, Aug 24, 2012.

  1. 84EdH
    Joined: Aug 2012
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    84EdH Junior Member

    Hello everyone. New member here.

    I have a 1979 Century 3000. I have done some restoration work and am ready to put the gas tank back in the boat.

    The tank is a 36 gallon aluminum tank. .090" thickness. Dimensions are as follows: 54" long 22" wide 7" deep. It has two 6"x1.5" brackets welded to each of the long ends of the tank. It is supported on each end by cross members between the stringers.

    the floor of the boat steps down about the middle of the tank. Front half of the tank is about 2" off the hull, the back half of the tank is about 5" off the hull.

    My question is this: Does this tank need support on the bottom, or is it enough to have it suspended on the end brackets?

    Any help appreciated!
     
  2. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Did it have support to begin with?
     
  3. 84EdH
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    84EdH Junior Member

    I dont know. I pulled the tank in the process of replacing rotted stringers. The floor of the boat under the tank had rotted plywood over about 2" of wet foam. I dont know if the front half of the tank sat on the floor or just above it.i
     
  4. philSweet
    Joined: May 2008
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    philSweet Senior Member

    How old is the tank? The reason I ask is that they usually don't last more than about 12 years or so in a saltwater environment. May last a good bit longer in Pittsburgh. I'd check with other owners to see if it's is worth putting the old one back in at all. If you are glassing the deck over top of it, I'd be inclined to go new. Is there any pitting at all?
    Have you done a pressure test?
     
  5. 84EdH
    Joined: Aug 2012
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    84EdH Junior Member

    thanks for your responses.

    the tank looks like new. no pitting. still shiny. brackets are strong. the boat is inside in the winter, so not a lot of wear.

    the deck is built to have access to the tank, and will not be sealed away.
    so I have no problem using the old tank.

    back to the install though. are 36 gallon tanks, this wide hung on just the end brackets? I have thought about different methods to support it in the middle but the more I read......foam, no foam, coating, no coating etc. the more confusing it gets
     
  6. 84EdH
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    84EdH Junior Member

    forgot.....this is the original tank 33 years old.
     
  7. jonr
    Joined: Sep 2008
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    jonr Senior Member

    Why do the tanks last only 12 years in salt water environments? Can this be prevented?
     
  8. Moreheadnc
    Joined: May 2008
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    Moreheadnc Junior Member

    When my new aluminum tank goes back in I will be taping a layer of cellophane to the tank, bolting it in place, then pouring 4 LB poly foam in the bottom and then 2LB on the sides. The cellophane is to make removal easier. My tank has a protective barrier coat on it should any water somehow find its way into that area of the boat.

    Just how I am going to do it, another opinion.
     
  9. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    84EdH

    Welcome to the forum :)

    Firstly it is significantly easier to answer your questions with pictures and/or drawings/diagrams.

    Secondly the thickness 0.09" or in real language 2.3mm is very thin, even for a 33 year old tank. Just because its bright and shinny doesn't mean there is no loss of thickness!

    Thirdly, do you know what grade aluminium it is?

    What philSweet means, is that have you pressure tested the tank (only the tank) to ensure there are no leaks? Whether the tank is built-in or stand alone, it must be leak free! Thus pressure test it. In your language you should pressure test it to around 2-3psi for several hours, as a minimum.
     
  10. Submarine Tom

    Submarine Tom Previous Member

    Yes welcome to the lions den... I mean forum.

    Is the tank baffled inside?

    Any bracing or supports inside?

    Have you looked inside?

    With a sewage camera?

    If you stand on it supported only by the ends does it buckle?

    Is there a plastic replacement available in that size?

    Do you have any pictures you can post?

    Enough questions for now...
     
  11. 84EdH
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    84EdH Junior Member

    well thanks for the welcome everyone!

    the .090 thickness was imprinted on the tank.
    yes there are baffles....I have not seen internal supports....looking with a small mirror
    I would be afraid to dent the thing if I stood on it...I am sure it would buckle
    I dont know the material
    I never had a leak that I was aware of, no gas smell etc.
    I would be interested in a plastic replacement in a comparable size 21x7 to 9 in deep x53 1/2 long would be the custom size I would order

    also, I have not pressure tested it. Not sure how to do it.....block off vent tube, install sender with gasket,.......but how to get air into the tank with a pressure gauge?
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    You could use a primer bulb off an outboard tank to pressurize it, if it retains the pressure there are no leaks.
     
  13. 84EdH
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    84EdH Junior Member

    will that squeeze bulb push 3lb?

    also, I just read the label on the tank

    Skyline Industries 5052 H32 aluminum

    I will try to post a couple of photos,
     
  14. 84EdH
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    84EdH Junior Member

    ok, i need help... how do you upload photos?
     

  15. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    You just fill it up with water/oil whatever, with a hose. Have a bucket/funnel on the end of the hose and raise it up.

    Rough rule of thumb, 1psi = 2 feet

    So raise the funnel/bucket by about 6 feet above your tank top, and just leave it for a few hours.
     
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