Kevlar/epoxy canoe and "gelcoat"

Discussion in 'Boatbuilding' started by lazypaddler, Apr 29, 2013.

  1. lazypaddler
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    lazypaddler New Member

    I am going to build Kevlar/epoxy canoe in female mold but this time I would like not to have just plain Kevlar look but I want some color and UV protection. The question is how to achieve it when using epoxy. I don't want to paint this boat after de-molding.
    1. I am familiar with polyester gelcoat but I don't know if that can be used with epoxy laminate. Technically it wold be epoxy over polyester (not vice versa) so in theory it should work but still I am not going to do that till I hear that somebody else did it successfully.
    2. The other option would be some type of "epoxy gelcoat" and I saw products on European market but I haven't find US (affordable) product.
    I know I can pigment epoxy but that wouldn't help UV protection?
    Commercially build Kevlar canoes are sometimes gelcoated but I think they use vinylester resin not epoxy.
    So basically I am looking the way to have color hull, with UV protection but without taking extra time to paint it (paints don't work on canoes anyway since they scratch to easily) .
    I appreciate all advice.
     
  2. ondarvr
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    ondarvr Senior Member

  3. pauloman
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    pauloman Epoxy Vendor

    you can tint epoxy but it will still UV yellow and change its color. Consider epoxy not to b e color stable.

    serious folks often remove the gel coat on new boats and replace with a 2 part lpu coating.

    there are 2 part clear coats with UV protectiion that will slow or stop UV yellowing of the epoxy under it.

    paul
    progressive epoxy polymers inc
     
  4. ondarvr
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    ondarvr Senior Member

    I don't know of anyone that removes the gel coat from new boats and then paints them, many yachts do get painted, but removing the gel coat wouldn't be an advantage.

    I'm sure at some time someone has done it, but what do you gain?
     
  5. PAR
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    PAR Yacht Designer/Builder

    I don't know of anyone intentionally removing gel coat, just to paint, but I suppose it's been done. I know it is during wholesale blister repair, but this is a different story. There is an epoxy compatible gel coat, though not inexpensive, it looks a lot better then traditional gel coat and is considerably tougher too.
     
  6. idkfa
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    idkfa Senior Member

    please share PAR, tks
     
  7. Landlubber
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    Landlubber Senior Member

    Try vinyl ester.....many colours.
     
  8. lazypaddler
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    lazypaddler New Member

    What is the name of the brand?
     
  9. ondarvr
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    ondarvr Senior Member

    It is in the link I gave you.
     
  10. ondarvr
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    ondarvr Senior Member

    Paul has posted this on other forums too, when questioned about it he never responds. So there is no way of knowing exactly what he is referring to.
     
  11. PAR
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    PAR Yacht Designer/Builder

    I have answered this previously and assumed some Goggle time would yield some results, but apparently not.

    There are a few choices - tie coats, for traditional gelcoat, epoxy gelcoat and epoxy compatible gelcoat.

    Crystic gelcoat 252PA is an epoxy gel coat, Crystic gelcoat LS 30 and 97PA are compatible gelcoats. They have a few others, but I only know of these off the top of my head. Of course there's CCP's IMEDGE ECT 120, but they didn't want to hear about this one. There are others and new products in this vain are showing up regularly. I'm fairly sure Gurit has a product too.
     
  12. susho
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    susho Composite builder

    In mould coating, a PU based coating used in the mould, directly compatible with epoxy resin.
    Or a skin coat, after a polyester based gelcoat, apply a vinylester/csm skin, layup with epoxy after that. A bit heavy though, but I've used it on 6 and 12 metre boats successfully.
    Or a tie-coat instead of a skin coat, but a quite heavy solution again.
     
  13. T0x1c
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    T0x1c Junior Member

    Interesting article:

    http://www.oneoceankayaks.com/Epoxtest.htm

    Anyway I wouldn't leave an epoxy unpainted, even with a hot post-cure.
    If your canoe is directly exposed to sun, the epoxy Tg temp. can be attained and the structure is ruined.

    There are compatible gelcoats, but there is no point using gelcoat over epoxy unless you don't mind about weight (but then, what's the point of using Kevlar?)

    An epoxy paint is very solid, base + 2 coats will improve waterproofing and bring UV protection. Leisure marine ones are very expensive, try and use industrial ones used for tankers steel protection.

    If you really don't want to use paint, then use a color pigment (the whitest the better for T°), take an epoxy with high Tg, post cure as per epoxy manuf. recommendations.

    Edit: if you're not confident with gun spray painting, you can use a roller, fine sanding is long but easy with epoxy painting.
     

  14. lazypaddler
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    lazypaddler New Member

    I am OK with painting, I just wanted to save time and take advantage of female mold and use gelcoat like coating for epoxy/kevlar laminate.
    Plus paint doesn't take abrasion very well. I can spray it with Awlgrip but it won't look good very long...
    Manufacturers like Wenonah often leave surface uncounted but I am not sure what resin they use. It might be vinyl ester which is another option I consider.
     
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