oppps theres a two holes in my fiberglass fuel tank

Discussion in 'Fiberglass and Composite Boat Building' started by gaztric, Oct 23, 2018.

  1. gaztric
    Joined: Mar 2018
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    Location: australia

    gaztric Junior Member

    Hi

    I have a dilemma.I went through the process of gel coating my ski boat and got it looking reasonable nice.(currently upside down in my back yard)
    I thought before I proceed and work my way up to the finer grade sand papers than polish.I shall mark where I want to put the fins
    Well as the title says I put two holes straight through into the fiberglass built in fuel tank.
    I have rang around ski boat builders but they were not much help.

    Has anyone done repairs for this kind of mishap before? that could give me some pointers.
    What kind of fiberglass,epoxing catlist etc i need to repair the problem.
    I have never done any fiber glassing only the gelcoat work.

    The two holes go from the under side of the boat into the tank.The holes are about 6mm each.

    Thanks in advance.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    So, you have drilled holes in the bottom of the boat to attach the fins ? And the bottom of the boat is actually also the bottom of the fuel tank ?
     
  3. fallguy
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    fallguy Senior Member

    The tanks must be removed from the hull and the hull must be repaired/modified and then the tanks repaired.

    Once you get it apart; you can stud for the fins with a modified bolt.

    Ouch. How did you intend to attach the fins?
     
  4. fallguy
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    fallguy Senior Member

    You may need to raise the tank up for clearances, so see if you have any space to do so as well. You can't have the tank rubbing on even a modified bolt.

    Take a picture of this fin as well and post it here
     
  5. gaztric
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    gaztric Junior Member

    yes stupid me I know the tank is not removable it is built into the boat and is fiberglass the tank is at the back of the boat.I drilled the two holes correct at the front of the fin and the two holes at the back of the fin went through into the tank. I shall try and get a link to a video up.
     
  6. gaztric
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    gaztric Junior Member

    Unfortunately tank is one molded in so its apart of the boat.My explanations are not the best.The fins will be attached with stainless steel bolts nuts and washes maybe with a plate before the washers.I shall try and get a video.
     
  7. fallguy
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    fallguy Senior Member

    I can only advise removing the tank and replacing it with a not built in.
     
  8. JamesG123
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    JamesG123 Senior Member

    Did they at least not laugh at you?

    What is the gap between the bottom of the fuel tank and the hull?

    If you didn't need to use the holes you put in the tank (for your fin), and the space between the tank and hull is small/touching, the fix would be a relatively simple one of injecting a large quantity of thickened epoxy into holes to seal both.

    Probably what you are going to have to do is (carefully!) cut out enough of the bottom hull to patch up the tank, and then repair the hull bottom. Extra points for making a plug you can glass in that has mounting bosses for your fin's bolts.
     
  9. JamesG123
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    JamesG123 Senior Member

    Probably not practical as the tank is most likely built into the upper or inner lining moulding of the hull, so removing it would mean chopping up a large portion of the rear hull and then rebuilding it.
     
  10. gaztric
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    gaztric Junior Member

    Okay I hope I have done the video link right this video was for someone else but hopefully you guys will get an understanding of what I did.
    I will be putting a fin under the ski pole utilisizing two off the holes already there. And hopefully moving the fin forward just in front of the tank .I should of looked before I drilled the holes amazing what I can do with no sleep.

    Link
     
  11. gaztric
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    gaztric Junior Member

    I did think that but id rather move the fin forward just in case i accidentally run the fin into a log or bank it on some rocks and put a hole in the tank.

    Hahaha yes they had a laugh.My wife got home and she said whats wrong I had a tear or two in front of her after all the work I did doing the prep for the gelcoat.Then gelcoating.
    I shall read more of the posts tomorrow I best be off to sleep now.
    Thanks every one for the posts so far.
     
  12. JamesG123
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    JamesG123 Senior Member

    Oh that should be an eazy fix. Grind down to glass around the offending holes, and then fill it with resin and chopped mat topped with a piece of ply glass. Lightly ream around the inside of the tank with something like... a flat bent nail chucked into a drill to clear away the fuel residue and give the epoxy that goes inside something to adherer to.

    Definitely buck your relocated holes on the inside with a good sized piece of stainless plate not just washers so that if (when) you do ground your fin, it will spread the stress over more of the hull glass.
     
    Last edited: Oct 23, 2018
  13. fallguy
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    fallguy Senior Member

    Interesting setup with a hull tank.

    Gonna need to drain any fuel and sand down the area with the two holes. Sand about 4" oval around the holes to just past the gelcoat and to a feather edge. You will want a few inches of glass not gelcoat each side of the holes.

    Then get some mat and I would use epoxy as it is best. Fill the holes with thickened epoxy - thicken 2.5 to 1 by volume with cabosil. You will need say 1 ounce of epoxy and 2.5 oz cabosil or less actually. Let them cure and come back and sand again the entire area with 40 grit paper.

    Then I like to use plastic and a sharpie and trace the shape of the hole and make progressively smaller patches. You would be making say three patches minimum, each an inch smaller diameter or so.

    Cut out the plastic templates and tear out mat shapes like the templates. Tearing the mat is better for improved bonds.

    The entire patch can be done in a single go. I would lay the biggest patch first. If you find you are too low; you can add another piece on the fly. Too high is not great, but it looks like the hull could be faired up there some anyway.
     
  14. fallguy
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    fallguy Senior Member

    It would be good as James says to use a rat file on the hole edges to rough them up for bonding.

    Make sure to change your fuel filter fairly soon a few times after you startup. It is gonna be fouled with shavings.
     

  15. fallguy
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    fallguy Senior Member

    Good study video.

     
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