Gel Coat reactions

Discussion in 'Boatbuilding' started by Leon01323, Jan 24, 2011.

  1. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    Hey guys,

    wonder if any of you could shed some light on this problem, i waxed a piece to day to make a mould of it and when i sprayed my gel coat on it and in patches it kind of like bubbled up and left little circles where the gel coat would not stick. if i sprayed more on sometimes it would fill in these holes and others it would not.

    any ideas.... all i can say is i thin my gel coat with thinners so i can spray it easyier and use meguiers mirror glaze wax.

    any ideas?

    Thanks
     
  2. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 145, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    To obtain the proper layer thickness you need a much higher viscosity.
    If you don't want to use a brush or roller like the rest of the world, I think the only alternative is airless spraying without any thinners.
     
  3. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    Hey, Thanks for the reply. The only problem ive had is that the guns to spray the gelcoat are very expensive for what i am doing..

    Not tried brushing on my Gelcoat as i had not seen that done.. will give it a go and see how the finish turns out.

    Thanks
     
  4. gonzo
    Joined: Aug 2002
    Posts: 13,766
    Likes: 431, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Thinners are not the right product to thin gelcoat. It should ideally not be thinned at all. The voids are full of wax and will be really difficult to get anything to stick. You need to sand and de-wax before making a gelcoat repair in those areas.
     
  5. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    Ah wicked. I was only worried about brushing the gel coat on as I did not want to leave brush marks. Just done a trial piece a small one and will see how it comes out. I've had no probs with the pieces I've pulled out that have been sprayed with thinned gel coat. It's just a really thin layer.

    Thanks
     
  6. gonzo
    Joined: Aug 2002
    Posts: 13,766
    Likes: 431, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    There will be no brush marks. The surface of the mold is the negative of what the finished product will be.
     
  7. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    just popped out the test piece that i did and there were no bush marks..... i was only worried that if the bush marks went through to the mould surface that it would ruin it..

    a lot thicker coat as well as stated which means it comes out a bit nice with very smaller air bubbles now not being a problem i think.

    all is well do you think that it was the thinners that was causeing the reaction?

    Thanks
     
  8. gonzo
    Joined: Aug 2002
    Posts: 13,766
    Likes: 431, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    That was probably part of the problem. As the thinners evaporated, the fumes get trapped.
     
  9. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    that sounds like logic to me:D...Thanks for the help once again guys greatly appreciated
     
  10. rxcomposite
    Joined: Jan 2005
    Posts: 2,006
    Likes: 185, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    What thinner are you using? Styrene is the only accepted thinner. Not more than 20% by volume. Acetone will work but dulls the finish and makes the gel coat brittle.

    For your small part a wet film thickness of 4 to 5 mil is enough. Ask for a wet film thickness gauge from the supplier. It is free.
     
  11. rxcomposite
    Joined: Jan 2005
    Posts: 2,006
    Likes: 185, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    It is called "Fisheye"
     
  12. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    ive been using "CELLULOSE THINNERS" from where i buy my products

    http://www.cfsnet.co.uk/cgi-local/s...of_Copy_of_x.html#aACT001_2d001#aACT001_2d001

    If i pva the mould and once dry spray on the gel coat i never get a reaction. If i try an spray onto a previously gel coated product i get the reaction. Could this be where who ever made that gel coat product finished with a layer of gel coat with wax and thats why i get a reaction, or could it be the mould wax where its not been buffed off correctly?

    Thanks
     
  13. gonzo
    Joined: Aug 2002
    Posts: 13,766
    Likes: 431, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    That is also called laquer thinner. Use it only to clean.
     
  14. Leon01323
    Joined: Dec 2010
    Posts: 95
    Likes: 1, Points: 0, Legacy Rep: 27
    Location: England

    Leon01323 Junior Member

    But you can thin paint with it?
     

  15. gonzo
    Joined: Aug 2002
    Posts: 13,766
    Likes: 431, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Yes, if it is laquer.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.