Integrated fuel tank in a Jon boat?

Discussion in 'Metal Boat Building' started by thudpucker, Aug 16, 2008.

  1. thudpucker
    Joined: Jul 2007
    Posts: 885
    Likes: 31, Points: 0, Legacy Rep: 453
    Location: Al.

    thudpucker Senior Member

    I want to have a Welded Aluminum fuel tank created inside the Seat.
    Does anybody know of a Jon boat with an integrated Fuel tank?

    I have a 15' Al Weld (Bryant AR) Jon boat. It's a good boat.
    I have a question on the Fuel tank.
    The Foam floatation is in the seats. It should float, gunnels up, fully loaded, because of this foam.

    So the question is:
    Would a Gas tank float as much as the same volumn of Foam?
    Is there any law against me doing such a thing?
    Have any of you had experiece with an idea like this?
  2. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    1 cubic foot equals 7 1/2 gallons. A gallon of gas weighs around 6 1/2 lbs. Unless you have foam that weighs 49 lbs a cubic foot, it won't float as much.

    A cubic foot of water weighs about 62#.
    A cubic foot of gas weighs about 49#.
    A cubic foot of foam weighs about 4#.
    A cubic foot of foam would support or float about 58#.
    A cubic foot of gas would support about 13#.
  3. kmorin
    Joined: Apr 2005
    Posts: 185
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    Location: Alaska

    kmorin Senior Member

    Tanks as Seats


    If the boat's seat is replaced with a tank then I'd suggest you make the tank on the bench- fully finished in all details before it goes in the hull. I'd suggest that the tank be made the shape/volume/size of the seat with two 'ears' or horizontal flanges at the top outboard ends to bolt or weld to the skiff's internal framing.

    This way the tank is completely separate from the boat and more likely to be a safe installation and if the seat is attached at the bottom at the top of longitudinals you could add angles or tabs to make these connections to the new tank/seat.

    The new seat/tank can't be counted on for reserve buoyancy if you swamp so you'll probably have to add foam in some other void in the hull- maybe under a foredeck, or under the floor's if there is a deck? You might consider adding foam under (very) thin riveted covers along the gunwales if there is no other place to add it once you replace the seat with a tank. IF you can choose the foam - pick styrene as opposed to urethane which deteriorates into acids that eat into aluminum hulls.


  4. thudpucker
    Joined: Jul 2007
    Posts: 885
    Likes: 31, Points: 0, Legacy Rep: 453
    Location: Al.

    thudpucker Senior Member

    You guys are a wealth of info.
    I have a call into Al Weld up in AR. but have been too busy to pursue the effort.

    The Coasties inspected my boat one time. There are a different set of rules for integrated tanks.
    And since the exxon Valdez spill, even tankers must have a double hull.
    So the Coasties will be the last bunch I ask, as their rules may change again before I get this project completed.

    I appreciate the tip on the Styrene foam.

    My intent was to cut a large area out of the Seat. Then have a tank welded up that would drop down into the hole. I was going to have the tank welded to the top of the seat.
    Then make fuel port and supply hose fittings come up high on the back of the seat.
    After all this, I may not do it. I haven't gatherd all the info yet though.
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