Float Coat cracks in inner hull

Discussion in 'Fiberglass and Composite Boat Building' started by SeaWeavers, Sep 18, 2019.

  1. SeaWeavers
    Joined: Sep 2019
    Posts: 2
    Likes: 0, Points: 1
    Location: UK

    SeaWeavers New Member

    Hi

    I've discovered some cracks on the vertical length of what I think is the transon wood edge. I've used a dremel to investigate and the cracks seem to be gel/float coat cracks only. The gel coat is quite thick along the vertictal edge, when the boat was manufactured in looks like they chamfered the edge of the wood with gel coat, it seems.

    Image here: Screenshot https://prnt.sc/p7qnlb

    This is my first ever GRP repair so was wondering if someone would be able to give some advice.

    Do I:

    1. Keep sanding around the cracks until I expose the GRP and then do a full glassfibre repair?
    Or
    2. As it's only thick gel coat cracks (and it's only the inside of the boat thats affected), do I use a epoxy filler or gelcoat filler to fill up the trenches I've made and then float coat over the top?

    It's really hard to get to the area in question as it's behind the seat/engine with very limited arm movement so I'm hoping the second option is viable!

    Many Thanks
     
  2. fallguy
    Joined: Dec 2016
    Posts: 3,058
    Likes: 354, Points: 83, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    1. Verify source of crack. Grind to glass and verify no glass damage below. If it is just in the gel; go from there.

    Ondarvr is the local expert on gelcoats, but if you think it is thick; that might be the cause in itself in which some material removal (sanding) might be best as well.
     
  3. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    I bet the cracks are not being helped by being on the plywood or wood transom.
    Wood swells in the presence of moisture.

    There are a dozen "types" of Gelcoat,
    https://www.aoc-resins.com/pdf/tech-exterior-compare-gelc.pdf

    and I wouldn't use ANY of them straight over Plywood or Timber. Polyester resin is not a great encapsulator, and Gelcoat has poor structural properties on variable substrates.
    ie. It cracks ( surprise)

    At the very least I would do a good grind back, and lay glass fibres and Epoxy, before building up any future surface coat.
     
    fallguy likes this.
  4. SeaWeavers
    Joined: Sep 2019
    Posts: 2
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    Location: UK

    SeaWeavers New Member

    Great thanks for the information. I thought I might have to grind back to expose the fibreglass. Will be tough as there's hardly any room to get to it without taking apart the engine.
     

  5. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    If there’s glass under the cracked gel coat, and it’s not cracked too, then there is no concern and it can be left as is.

    If the glass is cracked, or there’s no glass and it’s just wood, then it needs to be repaired, which won’t be easy if there’s no room.

    It’s very common for thick gel coat to crack as soon as it’s flexed, that doesn’t mean the laminate underneath has a problem though.
     
    Last edited: Sep 19, 2019
    fallguy likes this.
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