Curing problem

Discussion in 'Fiberglass and Composite Boat Building' started by Josip N, Oct 16, 2018.

  1. Josip N
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    Josip N Junior Member

    I dont know here or how to begin, so excuse me if some information are out of order or something. The story goes.. We laminated a transom according to lamination plan etc. and when we demolded it, it warped, like someone inflated a ballon between gelcoat and the mold. The laminate itself looks ok on the inside of the ship and no delmination is seeing. Color is ok too. It's just that gap between gelcoat and the mold. Any suggestions and help are appreciated.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Any pictures ? I'm not that clear about what you are saying.
     
  3. Josip N
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    Josip N Junior Member

  4. rwatson
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    rwatson Senior Member

    All the same photo, it's hard to tell if its the bottom bulge or the top one.

    In any case, it looks like some sort of expansion of the top layer, and it delaminated from the rest of the panel. I wonder if we are looking at gas pressure from a badly mixed section of layup ?

    It will be interesting to get some expert opinion on the reasons.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't make much of the pics, unfortunately.
     
  6. gonzo
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    gonzo Senior Member

    It is hard to tell what the photos are showing. There should be one that shows the overall boat, then some close-up details. To start with:
    What resin did you use? Is there a core? Moisture in the core can produce steam when the resin cures.
     
  7. Josip N
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    Josip N Junior Member

    Rest of the boat is just fine.. Concerning the pictures, it is white gelcoat and I tried taking photos from different angels to show the hole but it doesnt show, you can only distinguish it by hand.. Let me try to explain.
    Material is laminate sandwich with PVC core using polyester resin.. Exact resin and gelcoat I can say tommorow when i come to work again. Now the hard part, how to describe it?
    The gelcoat is spooned (is this the right word?) to the mold on the rest of the boat, except in this place. On this part its like gelcoat got lifted from the mold towards inside of the boat during vacuum infusion and now you can practically put a basketball on that place between gelcoat and the mold. Hope you understood me this time
    @gonzo Moisture was my first taught too, i'll have to check the logs for temperature and moisture
     
  8. JosephT
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    JosephT Senior Member

    I see a big bulge in your pic...thought it was a step in the transom for a moment. I suspect contamination between the laminates is the root cause (moisture or some other chemical). Another thought, there may be a remote chance the vacuum was reduced or lost at some point during resin infusion. Worst case...there was some back pressure applied.

    Unfortunately, you'll obviously need to re-work this area and be sure the core is contamination free, and the resin & gel coat is properly mixed. It can be hard sometimes to monitor all areas of a layup.
     
  9. BlueBell
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    BlueBell Ahhhhh...

    It would be interesting to know why
    but the bottom line is, it has to be cut out and repaired.
    I would suggest the real question is, how?
     
  10. Josip N
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    Josip N Junior Member

    @JosephT you see correctly. It is like a bulge, but towards inside. But there are no sharp edges or something like that, only curved smooth ones. There are no cracks..
     
  11. rwatson
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    rwatson Senior Member

    Just a thought, if you drill a small hole, will it subside as pressure is released ?
    If it does, you may only need to inject some epoxy, and compress the bulge until it cures.

    YOu might need to "flush" the interior out with epoxy, but since its just under the gelcoat, its not structural.
     
  12. kapnD
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    kapnD Senior Member

    Would be interesting to see a core sample of the affected area.
    Also a close examination of the mold in the area is in order, there might be a pinhole.
     
  13. fallguy
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    fallguy Senior Member

    how thick is the layup there?

    maybe it exothermed?

    You'd think it'd discolor though then.

    Intriguing.
     
  14. Josip N
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    Josip N Junior Member

    I cant say, not that I dont know, its that I cant (company policy). What can i say is that there is 5 layers of CSM225 (2layers) and rowing ranging between 300-900 g/m2. On that particular sport we also have a core PVC of 20mm thickness (weight is trade secret). On top of that it goes another 4 layers of warious rowings.

    Laminate from the inside looks good. Mold is going to be inspected in the next few days since it needs to go to get polished etc and we will see what is happening on that particular spot.
     

  15. gonzo
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    gonzo Senior Member

    I don't understand how the density of the foam is a trade secret. Simply measure the volume of a piece of foam, take the weight and calculate the density.
     
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