gelcoat repair

Discussion in 'Fiberglass and Composite Boat Building' started by rturbett, Apr 10, 2009.

  1. rturbett
    Joined: Aug 2005
    Posts: 155
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    Location: FINGER LAKES, NY

    rturbett Senior Member

    I need to fix numerous scrapes and gouges on a sailboat. The scrapes are straightforward gelcoat work. The gouges are adout 1/4" to 3/8" deep. They reach the fiberglass.

    My question is how thick can I use gelcoat? Should I nearly fill the gouge with epoxy first?

    The largest gouge is the size of my thumbnail.

    Thanks,
    Rob
     
  2. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    If it were me I would fill the gouges with some high density filler, which you can mix up, or easier for you just by The 3m vinylester repair putty.

    In general gelcoat should not excede around .030 of an inch a 1/4 inch is .250
    in reality you could build it up thick , but it will probably be too brittle and crack again.
     
  3. Itchy&Scratchy
    Joined: Jul 2008
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    Location: Oxford & South Africa

    Itchy&Scratchy Senior Member

    Mix a bit of gel with colloidal silica to make your gel paste-dont make it too dry otherwise it will crack, should be the cosistency of peanut butter but still be able to see bit of shine from the gel in it if that makes any sense.:confused: Fill up the gaps , sand down and do you gel repair over that.:)

    Good luck
    regards
    Justin
     
  4. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    That sounds really deep. Replace the hull to be safe :D

    Just joking.

    Itchy&Scratchy has it about right. When you apply the gelcoat you can stick cellotape over it to give it a smooth(er) finish, it makes for less sanding.

    If you have long deep scrapes that is almost through the hull I would suggest you question the strength in that area. Even when fixed up as above the filler would not contribute to any strength. A bump against the hull in this area may cause the original thin hull area to tear / seperate and make water.
     
  5. rturbett
    Joined: Aug 2005
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    Location: FINGER LAKES, NY

    rturbett Senior Member

    Thanks,
    I would really like to replace this hull-anyone want a Pearson 23 sailboat?

    I will fill in the worst ones with epoxy first-

    Any hints on how to mix gelcoat colors to get a Buff/ cream white?
     
  6. Typhoon
    Joined: Mar 2009
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    Location: Australia

    Typhoon Senior Member

    You buy this stuff called pigment paste. You'll have to carefully mix several batches of resin.paste and record amounts (easiest with accurate scales) and let it set. It will change colour a little when is sets. Be sure to sand and buff a portion of teh hull to colour math to, or you will be matching to a faded colour.
    As for thick gelcoat, I remember attempting to drill a hole in a brand new Princess motor yacht and a piece of gelcoat about teh size of a tennis ball broke off. It was around 3/8" deep and not at all well bonded to the substrate.......

    Regards, Andrew.
     
  7. rturbett
    Joined: Aug 2005
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    Location: FINGER LAKES, NY

    rturbett Senior Member

    I was wondering what pigments get mixed in to get a buff white
    the colors offered in the repair kits are very bold

    Rob
     
  8. Wynand N
    Joined: Oct 2004
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    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Real reason for the cellotape is to keep oxygen off the gelcoat to help it cure. Some others ways are to mix some wax with styrene into the gelcoat or to spray a pva over the gelcoat repair to help it cure. The wax will rise to the top of gelcoat acting the same as the tape or pva.

    In short, gelcoat are made to be used in a mold and the side on the mold will cure//hardens because the oxygen is cut off and the laminate side will stay semi hardened/cured or tacky (for quite a while) so the fibreglass laminate will stick to it properly.
     
  9. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Hi Wynand,

    I think you meant flow coat ?

    With flow coat the wax rises to the surface area
    With gell coat the wax rises to the bottom ie against the mould.
     

  10. AroMarine
    Joined: Jul 2005
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    Location: Atlantic City NJ

    AroMarine Junior Member

    Fanie, NO wax in gelcoat in the mold for making parts. Wynand's got it. Wax only get's added to a repair or respray to seal out the air. Also wax can affect the final color if not used correctly. PVA has always worked better for me.
     
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