Installing alloy fuel tank in fibreglass boat

Discussion in 'Boatbuilding' started by Landlubber, Mar 11, 2016.

  1. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Hey fellas,

    Looking for the latest best practice for the installation of an alloy petrol tank in a fibreglass runabout.
    More specifically, what to put under the tank to prevent rubbing thru. I know it is not rubber cos of the carbon factor, but would appreciate the latest thoughts please. Ta, John
     
  2. Barry
    Joined: Mar 2002
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    Barry Senior Member

    Need some more information
    1) is it gas or diesel. inboard or outboard if gas
    2) Where is the tank going to be installed, in the engine compartment or in any other space where the air between the engine compartment and the fuel compartment (where the tank is to be installed) is shared
    3) are you installing a sending unit on top of the tank
    4) is it one tank or two
     
  3. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    My plan was to use plastic strips stuck to bottom of tank and then stick it all into the underfloor compartment I have just rebuilt and glassed into the boat.
    No sender unit, single tank about 800mm x 300mm x 2M

    Ta.
     
  4. Barry
    Joined: Mar 2002
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    Barry Senior Member

    H24 of the ABYC standards book, Gasoline Fuel Systems comprises 17 pages of requirements
    I will try to hit some of the high points but realize that not all requirements are included
    1) Valves for drawing fuel from the system are not allowed ( ie you cannot rely on a closed valve at the bottom of the tank to hold back the fuel. A tapered plug fitting is fine
    2) Hoses will comply with SAE J1527 Marine fuel hose
    3) Cork gaskets are not allowed, ( sending unit)
    4) Tank connections shall be accessible through a port or hatch
    5) Tanks shall be restrained so they do not move more than 1/4 inch (6.4mm)
    I would recommend straps over top of a material, non metallic, non moisture absorbing, not abrasive, that is glued to the tank
    6) All non integral tank supports, chocks, or hangers shall be separated from metallic tank surfaces by a non-metallic, non-moisture absorbing, and non-abrasive suitable for the purpose (eg neoprene, Teflon, high density plastics) permanently bonded to the tank surface with an impermeable, non-hydroscopic adhesive (poly urethane adhesive)

    Re mounting, I would not recommend gluing the entire tank to the bottom of the enclosure for if the adhesive failed from hull flexing, you will have created a space
    where water can sit and cause corrosion of the tank. See below

    7) Metallic tanks must be installed above flat surfaces shall be separated from the surface by at least 1/4 inch air space when filled with fuel and the flat surface shall be self draining

    8) Metal tanks shall be installed where they cannot be reached by normal accumulation of bilge water in the static position

    9) the filler hose requires 2 hose clamps and they must be stainless 300 series. Note many automotive clamps have a stainless band and a galvanized metal worm. They would not meet the code.

    10) Fuel fill lines shall be self draining, ie no dips, Same for the vent, there should be an inverted U so the that fuel will drain down and any water egress into the line will go out the vent

    11) minimum inside diameter of the vent line shall be 7/16 inch

    12) Flexible fuel line in the engine compartment will meet the local requirements for your country (USCG TYPE A1 OR A1 -15) (some USCG A hoses are not designed to be clamped)

    13) 15 inches of clearance required between the vent fitting on the hull to any engine or other compartment inlets

    14) There should be an anti siphon fitting on the draw line

    15) The tank and any other metal components that are filled with fuel shall be grounded so that its resistance to the boat ground is less than one ohm (includes metal deck fill)

    16) Due to galvanic corrosion, you can not have any copper fittings, screws, bolts etc in contact with the tank, aluminum fittings or stainless 316 series are allowed

    17) I could not find the clause, but I do not believe that you can have the fuel draw off the bottom of the tank. You need a dip tube, non copper, so that in case of a fire, and the hose burns through, you will not have fuel continuing to feed the fire



    Again, this is a shortened version of the US regulations and it may not be applicable to your area.
     

  5. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Thanks so much for all that mate, have installed to your directions exactly.
    Fingers crossed it lasts many years.

    Thanks all those that responded, John
     
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