Gelcoating over fiberglass matting

Discussion in 'Fiberglass and Composite Boat Building' started by rich99uk, Aug 31, 2013.

  1. rich99uk
    Joined: Jan 2006
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    rich99uk Junior Member

    Hi all
    I have just fiberglassed the bulk head of the cabin and need to gelcoat it.
    It is a large area and I would like the gel coat to be smooth.
    The issue is the area as been fiberglassed with matting ans is not smooth. And of course when i apply gelcoat it will be all bumpy.
    What is the best way round this? Can i skim the area with filler before I gelcoat or do i just keep applying layers of gelcoat then sand??
    Any Ideas?
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    G'day, I doubt gelcoat is what you are wanting here, if you sand off any sharp high points on your lamination and apply flowcoat, which is a waxed, pigmented resin with a matt finish, you will be well on your way to an acceptable finish. A long-used final touch is speckle paint, which disguises the surface unevenness making it more agreeable to the eye. But it depends on how much of a perfectionist you might be.
  3. rich99uk
    Joined: Jan 2006
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    rich99uk Junior Member

    Hi thanks for the reply. I have white gelcoat which I have a wax additive i can add to make it go off and not sticky i guessing thats the flowcoat.
    Would it be best to build the layers one gellcoat with out the wax then another coat with the wax?
    I used to put a peice off plastic over the flowcoat to make it smoth while drying but it such a big area that wont be easy
  4. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    LP paint is what you want to do. Choose one, Alwgrip, Imron, Sterling, etc and stick with whatever brands recommended fillers and primers.

    Knock down the high spots, prime, then fill, sand, prime and paint.

    Why did you mat the entire bulkhead? In Poly or Vinyl Ester?

  5. sean9c
    Joined: Jan 2011
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    sean9c Senior Member

    You could coat and sand gelcoat until you get it flat and then do a final coat of gelcoat but you're wasting gelcoat and gelcoat is hard so it's tougher to sand. You could flowcoat it with finishing resin but flowcoat does just that, it flows, being a vertical surface it runs.
    I'd lightly softpad the surface to knock off the big lumps, skim coat it with polyester putty, block sand that out then gelcoat.
    You could use LP but that's a whole different look. Super shiny which also means that you're prep has to be that much better in order to get a good result. Also a lot more expensive.
  6. Yobarnacle
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    Yobarnacle Senior Member holding true course

    You could glue on melamine or formica laminate.

    a lot of commercial vessels use laminate on interior bulkheads.
    Easy to wipe clean, and impervious to Clorox (most prevalent soogee is Clorox and water)
  7. waikikin
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    waikikin Senior Member

    Great Idea Yobarnacle, he could even contact mold some thin fiberglass sheet with gelcoat off melamine/formica/glass & glue it on with core bedding putty, any joins could be patched in.
  8. richard gray
    Joined: Mar 2013
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    Location: port coquitlam

    richard gray Junior Member

    cello finish gelcoat

    on old method but some may use it. you take cellophane or similar, gel will not adhere to it, and lay on flat or convex surface , masking tape three sides and stretch gently to forth side and mask off, so you get an area of 2ft X 3 or4 ft or what ever size of cello edges. so the masking tape encloses it.the cellophane can now be steamed of heated to shrink ,tight to hull. cut a short slot at top and pour in 1 oz of cello finish for every sguare ft of area. use rubber roller to roll out the resin to to all edges, roll out bubbles to edges, let harden. remove cello, sand all edges and lap new cello frame 1" lap on first area and repeat. called cello finish Google it?
  9. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    It isn't mentioned how smooth is smooth or what really are the requirements here. Is it a yacht or a workboat, how involved do you want to get etc. You could sand it with 80 grit, paint it with gloss latex porch and floor enamel, sand it again with 120 and another coat of paint and then it's plenty smooth enough for body contact and easy to wipe or scrub clean.

  10. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Indeed. What finish is the topic starter after? You can knock down the high spots, grit 80 is OK, but I would probably use grit 40. Any small dimples might be filled with some polyester putty, and quickly after (and after a quick scuff with grit 40) you can apply the waxed gelcoat. Most people do not achieve a smooth finish, but that is usually due to too thin layers. Apply one generous layer, and you have a finish that is acceptable for workboats, cheaper polyester sailboats, etc. Also more expensive and luxurious boats have that finish behind all doors. It is cheap, fast and effective. A speckle paint (topcoat in anothr colour) can add to the experience.
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