Gluing bulkhead

Discussion in 'Fiberglass and Composite Boat Building' started by mrdebian, May 22, 2022.

  1. mrdebian
    Joined: Apr 2021
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    mrdebian Junior Member

    Hi all,

    I got a friends kayak for a demo day and saw that the bulkhead leaks (see attached image) from two places eventhough it looks that there is mat and resin there.
    What is the proper way to quick fix this?
    Is it going to work by sanding a little bit and simply put around the bulkhead on the place where it joins with the hull cabosil?
    A putty filler I guess will work the same?

    Thanks
     

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  2. fallguy
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    fallguy Senior Member

    How does a bulkhead leak?

    You mean it is leaking from a wet cockpit to a dry locker?

    Or is it leaking through the hull?

    If just across the bulkhead spaces; this is caused by the fillet a/o glass being too light. Typically a 6 oz woven with no fillet has a high potential for pinholes. The ideal fix would be sand with 60 grit for an inch or so each side, a lighr fillet of epoxy and silica a/o another light tape, but you might go less work with a bead of caulk..
     
  3. mrdebian
    Joined: Apr 2021
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    mrdebian Junior Member

    It leaks from the cockpit, not the hull.
    What do you mean by saying a bead of caulk?
    From what I can see they used most likely two of 300 gr mat to join the bulkhead to the hull.
    It is difficult to work as you don't have easy access, it is inside the cockpit at the end.
     
    Last edited: May 23, 2022
  4. fallguy
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    fallguy Senior Member

    So, there is a pinhole somewhere.

    In the picture provided, I don't see any tabbing at all. Not saying you are wrong.

    You can fashion a piece of 36-60 grit sandpaper on a stick and then you could try to sand the seam on each the hull and bulkhead some. Then lay plastic in the cockpit footwell area for drips and lay a piece of heavier glass in there. It should be well consolidated. If you have a laminating roller, you can also tape it to a stick for reach.

    To apply the tape from 5-6' away; you may need to make a jig for the tape. Something like a piece of angle iron. You'd wet the tape on a table on a piece of plastic and then lay it onto the jig.

    Some creativity to hold the tape on during the transfer may be needed. Think like sewing thread or something you can leave on until a few days cure that can be removed easily or not at all.

    I'd use something much heavier for tbe repair; probably a 3" wide piece of 1708 which is 600/225, but not less than 400g biaxial if you can't make a fillet.

    Then pressing the glass into the corner is imperative or it can leak behind the edges. Typically this is done with fillet material. You could try to fillet it remotely, but is pretty hard to do well. Perhaps a 3" wide trowel on a stick. Epoxy and fumed silica about 1:2 by volume adjust per viscosity of epoxy.

    Good news is noone will see it.
     
  5. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    It depends on on if the existing laminate is too thin, or too weak.

    If it's strong enough but just thin, you can get some 3M 5200 or similar and smear it over that area, or the entire radius.

    If it's too weak, then glass it as fallguy said. As he said, thin layers of cloth are susceptible pin hole leaks.
     
  6. mrdebian
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    mrdebian Junior Member

    @fallguy the 400 biax won't be a problem to lay it up as it is like 90 degrees angle. Why not adding a 450 mat for example?
     
  7. DogCavalry
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    DogCavalry Senior Member

    Mat is not appropriate for epoxy work.
     
  8. fallguy
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    fallguy Senior Member

    This is not fully true, my friend.

    Mat backed fabrics are useful with epoxy when fast build of thickness is desired; for example, all glass moulds. Or can be used for tabbing with great weight penalty.

    Mat's binders will not break down with epoxy, so mould conforming will not occur, but epoxy doesn't seem to be impeded by the binders in any work I've done..

    Here, if you only have mat, you could use it..the fillet and epoxy and some roughing up with sandpaper are needed.
     
  9. mrdebian
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    mrdebian Junior Member

    It is made with polyester resin the kayak so I assume I can use the same resin to do the repair, no need for epoxy?
    @fallguy by saying fillet you mean cabosil?
     
  10. Blueknarr
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    Blueknarr Senior Member

    Polyester will work
    Cabosil can be added to thicken resin when making fillets.
     
  11. fallguy
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    fallguy Senior Member

    You can use either resin, but the area must be sanded for either one, then cleaned and then make a fillet of some kind. All the work must be completed from a distance. The reason I'd use epoxy is because it will forgive errors better due to its waterproof(ness) and bond strength.
     
  12. wet feet
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    wet feet Senior Member

    Just use a strip of mat wide enough for the job,with polyester resin.The important thing is to make sure the mat is rolled out well enough to spread out the strands and not leave them looking just like versions of the same mat on the roll.My experience of using glass tape in small boats was that there are likely to be leaks through the weave and well consolidated mat closes the gaps between it's fibres and I see no reason why other types of woven cloth would behave differently.

    This thread bothers me a little because we are considering a simple,small boat with a small problem that can be easily overcome.Yet we have recommendations for materials that are overkill for the job and which,if echoed in a professional environment would kill the prospect of an economical and effective repair.Would the posters like to advise us of the comparative prices in their localities for epoxy and polyester resins so that we may see if they have local prices that make such recommendations sensible?
     
  13. fallguy
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    fallguy Senior Member

    Threads with open ended content or easily answered threads can quickly devolve to polemics and cheap shots.

    You want to compare costs professionally?

    I will.

    Let's assume the cost per ounce of poly resin is 25 cents and the cost for epoxy is $1.

    For a 17" fillet, he needs one ounce of resin.

    For a 2" tape, he needs like 2 ounces, but we'll round to 3.

    So, for the difficult to reach location, you are quibbling over whether he needs to spend $1 on polyester resin or $4 on epoxy. A difference of $3.

    In a professional environment; this job is all labor. Say an one hour job at a friendly shop rate of $80. Add two bucks for the fumed silica and the glass.

    The difference between epoxy and resin is thus.

    epoxy. 85
    poly. 82

    So, you are bothered with the prospect of spending $3 for a superior repair that is less likely to leak?

    The epoxy, for the non-professional will also shelf for a very long time.

    And for the professional; it doesn't matter.

    And for the non-professional; he can used what he's got if he preps the area.

    To be frank. He could probably paint brush epoxy up in there, no glass and seal the pinhole.

    For the non-professional, many people work attached to their homes and the stench of poly is also awful.

    Also, many yak builders in these parts do so with epoxy, so the notion someone defaults to epoxy may not be nonsense at all. You certainly would not start to recommend poly if you were unsure, and when he first posted, he simply said resin, not which one.

    End rant.
     
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  14. DogCavalry
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    DogCavalry Senior Member

    To follow @fallguy , if I had to do a patch in an extremely difficult area to reach, the superior secondary bond performance of epoxy over polyester would make it no choice at all. Polyester would be an extremely poor choice. A false economy.
     
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  15. wet feet
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    wet feet Senior Member

    So we have established that epoxy is much more expensive.Is it essential?Not really.A small boat built of polyester doesn't have to have alternatives just for the sake of it.I also doubt that anybody will be paying $80 an hour for the work.I despair of the trend to use epoxy as the universal cure for any boat problem that needs fixing and the bigger the boat,the bigger the leap in cost.I would estimate that upwards of 98% of all boats are built with polyester on a global basis and just as in the days of wooden boats,the economic driver for professionals is keeping the cost down by using appropriate solutions.Or pricing yourself out of the market.It is no bad thing to apply the same discipline as an amateur,unless one has abundant funds to throw at a project.Which leads me to point out that amateur built boats tend to be harder to sell when the time comes and the price has to be suitably low to tempt buyers.Leading to a poor return on the time and money consumed.Just for the record,I have used over a hundred tons of epoxy products over the years-but only when necessary.
     
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