Wormholes in infusion?

Discussion in 'Fiberglass and Composite Boat Building' started by jim lee, Jan 9, 2009.

  1. jim lee
    Joined: Feb 2007
    Posts: 368
    Likes: 20, Points: 18, Legacy Rep: 247
    Location: Anacortes, WA

    jim lee Senior Member

    We've run into something that's giving us fits. Wormholes in the infusion. We are making molds using infusion and we are seeing where small air bubbles near the gelcoat are causing little gelcoat breakouts.

    What can be done to minimize air bubbles in infused parts? Where do they come from? It looks like perhaps the resin is boiling when its going into the drystack?

    Any hints pointers etc?

    Many thanks in advance!

    -jim lee
     
  2. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Polyester or epoxy? What laminate? Infusion pressure? Infusion height?

    -take care of the right gelcoat thickness (and use a gauge to check this on several places)
    -dry your glass
    -degass your resin
    -get your plug airtight, same for the bag. Test this!
    -use a good quality bag. Not everything on the market is suitable.
    -experiment with the first layer, that goes against the gelcoat. No unifilo please.
    -hand laminate a skin coat (vinylester). Use peelply to get a good bond.
     
  3. MarboMan
    Joined: Nov 2008
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    Location: Orlando FL USA

    MarboMan Junior Member

    Styrene gets excited under vacuum.

    Experiment and see what the bubbling point is of your resin. See how much you can draw on a clear jar with some resin in it before you see the little bubbles forming.
     
  4. jim lee
    Joined: Feb 2007
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    Location: Anacortes, WA

    jim lee Senior Member

    Vinyl ester resin,
    As much vacuum as we can pull around 28 1/4 in Hg.
    An entire array of laminates,
    all small parts from 9' x 9' to about 3" x 2".

    We've been doing a lot of experimentation trying to improve our mold building quality. Surface print-through and dimensional stability. (Reduce warping) This worm hole deal was unexpected.

    I was thinking about trying degassing the resin. We just got a degassing chamber but have not yet set it up. My fear was that the styrene was boiling off. If that's the case, does this limit the vacuum we can pull?

    On our deck mold, the plan is to use a skin coat. But, isn't that just kinda' hiding the problem? The bubbles will not break through the gel coat so much, but they will still be in there.

    What does gelcoat thickness have to do with bubbles in the laminate?

    The glass is in a heated shop, so I'm thinking its pretty dry.

    Thanks again for your ideas.

    -jim lee
     
  5. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Do a test with your glass: Take a small piece, weigh it, then put it in an oven, and weigh it again. This is the only way to tell. YOUR shop might be heated, but where is the glass coming from?

    Gelcoat thickness: If the gelcoat is thin, and might have some porosity, and the plug is not 100% leak free, then you might pull some air. Slowly, so not visible on top.

    Try degassing. Indeed, styrene might boil at 60% vacuum, but still you might take advantage of it.

    About your vacuum level during infusion: try infusion at a lower vacuum level. Say 70-80%. Yes, this is above boiling point for styrene, but the pressure drop at the resin front is dramatic. You might notice some boiling at the front, but that is not critical. However, after completing the infusion, the pressure spreads, and then it might be the case that you are boiling out the styrene at some spots. Your high vacuum level might induce that.

    About skin coat: Yes, partly hiding, but also partly vacuum integrity. And suface quality might improve.
     

  6. Cobra1
    Joined: Feb 2008
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    Location: Az

    Cobra1 Junior Member

    I thought you were suposed to skin it first then do the infusion build up?? Your'e putting this on the gell then trying to infuse it. See if Sparky can help you. http://www.viciousmarine.com . He built the very first infuse boat, so he knows his shiat. Worth a shot or call the manufacturer and explain the issue to them.

    By worm holes you could meen aligator as well, maybe. This is caused by the gel being to thin. The styrene will mess with it big time.
     
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