Gelcoat problem - help

Discussion in 'Fiberglass and Composite Boat Building' started by silenthunter, Sep 20, 2010.

  1. silenthunter
    Joined: Jan 2010
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    Location: Chile

    silenthunter Junior Member

    Hello, I did my first 3 meters boat. blisters appeared in the hull which I broke and I want to repair, how I can repair? Today I put gel coat but is a bit complicated on the vertical surfaces coz gelcoat slips.

    I also would like to know what I can use or what type of material put after the gel to coat to prevent the formation of these blisters.

    I ultilizeon my boat: gelcoat/mat450/roving600/mat450 in my boat

    Sorry for my English my language is Spanish

    I attached pictures of the problem

    Thank you very much;)
    Bruno.
     

    Attached Files:

  2. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Those are air bubbles left behind due to inexperience in rolling out the skin coat.

    You can thicken the gel coat with silica (aerosil or cabosil) and use it as a putty to fill the voids. After it cures you'll need to sand and buff.
     
  3. silenthunter
    Joined: Jan 2010
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    Location: Chile

    silenthunter Junior Member

    I use a alu roll to get out the bubbles, i dont see it. Maybe i need to use a special mat first? not 450?
    thanks
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    As you do more fiberglass work you will get much better at seeing the air and rolling it out. Until then you get to practice doing repairs, this motivates you to do a better job of rolling.
     
  5. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    What do the numbers 450 and 600 mean? Is it the weight? Did you laminate all three layers at one time? Mat is easy to get into tight spaces, once it's in place it will stay, but working on roving in one place can pull it out of other places you've already worked, and you might not notice.
     
  6. silenthunter
    Joined: Jan 2010
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    silenthunter Junior Member


    Yes is the weight. One layer first, next day the other two.
     
  7. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    ...450 grams/square metre, the weight of the reinforcing glass used.

    i would suggest that you use a very light glass against the gelcoat too next time, use tissue or some other csm if that is the way you wish to build.
     
  8. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

    That is a very tight corner you have there. You should fill it up with "bog" first. That is a putty mixture of resin and thickening agent such as aerosil, cab o sill or cotton flox.

    I normally use a "tie coat" first. a veil cloth or surfacing mat, 30 to 50 grams/m2, followed by a resin rich CSM 300. Only after that I use CSM450.

    As the other forum members have suggested, it takes some experience. it is a good idea to roll out the tight corners first then move outward or if that is not possible, lift the dry end of the mat untll you are satisfied that the corners have wetted out properly. You need a helper if you are new to glass layup. Somebody to hold the dry end of the cloth while you are wetting it out. This way you will reduce or prevent "bridging".
     
  9. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    What kind of resin are you using, polyester or epoxy? Thatweight mat seems heavy for the first layer. Air bubbles are hardest to see against white gelcoat, you have

    to look very close and know what to be looking for to see them. You want to lay roving onto a wet mat surface, otherwise the bond is not so good and you usually

    get lots of tiny air bubbles.
     
  10. tunnels

    tunnels Previous Member

    The first layer of glass onto the gelcoat you need to take a lot more care and attention !:mad: You can see what happens when bubbles are left and not rolled out properly , Even when it has all hardened you need to very carefully check with a light and look for bubbles ! :idea:These can be carefully opened and filled with resin before the next layers of glass are applied ! An extra couple of hours rolling can save you many hours of repairs and trying to cover the repairs so they cant be seen . Its never a race to see how fast you can get the job done !!
    Take your time and look at what you are doing .:D:p
     

  11. tinhorn
    Joined: Jan 2008
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    Location: Massachusetts South Shore.

    tinhorn Senior Member

    That's a tough place to roll out. I'd lay a narrow strip of mat over those strips, just wide enough to cover them with a few inches extending onto the hull. Then you can focus on this trouble area. Use a corner roller, and be very careful as you roll the top of the strip--very easy to drag the 'glass, creating a bubble.
     
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