How Thick Can I Fill with Epoxy over Balsa Cored Fiberglass Floor?

Discussion in 'Fiberglass and Composite Boat Building' started by naturewaterboy, Jul 14, 2008.

  1. naturewaterboy
    Joined: Sep 2006
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    Location: key largo, florida, usa

    naturewaterboy Steel Drum Tuner

    I replaced the balsa core on my flybridge floor. I put two layers of glass (biaxial bonded to mat - so I have mat-biaxial-mat-biaxial) using an epoxy resin. I tried to keep everything as flat as possible, but I will need to fill a lot in some areas.

    I thought about filling the lowest spots with epoxy-milled fiber-cabosil - A mix of about 4 volumes of epoxy, 1 volume of milled fiber and enough cabosil to thicken. Let this set up and then fill closer with just epoxy-cabosil.

    Is this OK to do? What limits on thickness are there? Should I do several thinner layers?
     
  2. Landlubber
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    Landlubber Senior Member

    naturewaterboy,

    Just how deep are you expecting to fill, if over 3-4mm, you should look at doing some more laminations in the hollowas, then you only have slight detents to fill. Too much filler is never a good thing. It contracts and expands at different rates to the base, and eventually lets go.
     
  3. naturewaterboy
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    naturewaterboy Steel Drum Tuner

    I'll have to measure, but a good point to add layers rather than filler.

    If I do use filler, does it help to put some milled fiber into the resin rather than use all cabosil?
     
  4. alan white
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    alan white Senior Member

    I have found that it is better to fair prior to glassing so that the filler is locked in and the outer surface is consistant. This solves the problem of sealing the filler, which saves epoxy.

    Alan
     
  5. Landlubber
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    Landlubber Senior Member

    soooo true alan, it is always best to do a job once and do it right, unfortunately that is not the case, so now he has to repair the damage.
     
  6. naturewaterboy
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    naturewaterboy Steel Drum Tuner

    Measuring the worst low spots, looks like I might need 2mm of filler. What do you recommend for filler - milled fiber, cabosil or microballoons?
     
  7. mango madness
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    mango madness Junior Member

  8. naturewaterboy
    Joined: Sep 2006
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    Location: key largo, florida, usa

    naturewaterboy Steel Drum Tuner

    Mango,
    thanks for the link. Good description - you put a lot of work documenting your work. Thanks for sharing. Your project looks a lot like mine. I've taken some pictures but not as many as I thought I would - I usually remember to take a picture when I've got gloves full of resin.

    I've installed about 30 square feet of balsa core. I haven't finished any of it yet - just trying to get all the rotten core replaced and get it waterproof before we see a hurricane. I have to fill and sand a lot of area. I have done a bit of glass work on other parts of the boat and on several other boats. Sure like sanding epoxy filled with microbaloons, sure hate sanding epoxy filled with milled fiber. But the milled fiber has to be lots lots stronger. I've replaced a lot of deck, and I don't want any cracks after I'm done. I think I'll try to fill as much as I can with milled fiber and cabosil, then try to keep the microbaloons very thin. Does this sound like a good plan?

    BTW, very fine spousal unit there! Nice photography (her and the boat!)
     
  9. the1much
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    the1much hippie dreams

    epoxy doesnt crack if its under the glass like poly?,,,,,see, im learnin,,hehe :D;)
     
  10. Landlubber
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    Landlubber Senior Member

    Polyester resin is not generally compatible with epoxy under it, epoxy over poly is OK, just not under it normally. Therr are problems with the poly not setting correctly because of the epoxy underneath...just be aware of this.
     

  11. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    ya,, i knew not to mix the 2,,,just as we all know,, i dont mess with epoxy,,hehe,,and with poly i know that you dont glass over filler because you end up with cracks there in a few years.,,i just automatically thought it was the same with epoxy,,hehe ;)
    thanks LL ;)
     
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