Thinning Epoxy?

Discussion in 'Materials' started by Frog4, Oct 17, 2011.

  1. sabahcat
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    sabahcat Senior Member

    WTF has any of that got to do with anything?
     
  2. tunnels

    tunnels Previous Member

    Using un-catalyzed resin to prime wood with and then putting catalysed over the top !! Is what it has to do with !!
    BAD PRACTICES !!:eek:
     
  3. sabahcat
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    sabahcat Senior Member

    And what has that to do with correctly mixed epoxy with a small amount of thinning agent?
    Tested repeatedly on boats that have sailed countless thousands of miles over decades

    You are comparing apples with elephants
     
  4. michael pierzga
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    michael pierzga Senior Member

    And why would you thin epoxy when off the shelf you can purchase professionally formulated epoxy with different viscosities ?
     
  5. CC Guy
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    CC Guy Junior Member

    Hi Guys I see we have some more thoughts on this, as we can see some manufactures will state there epoxy can be thinned to their spec, along with warming wood should help penetration which again is subject to the viscosity of the epoxy your starting with, the atmospheric condition, position your coating the wood in, type of wood will all play their part.

    The blanket statement of NO thinning is too strong for a world view as it will depend on what you’re doing and what’s available in your part of the world.

    My opinion would be do some simple test yourself before deciding what’s best for you.

    As for my 75% test my aim is to stabilize wood movement not moisture protection which it has done compared to untreated test, which will prevent checking over a long time on a bright finish double planking boat.

    I’m sure many are enjoying this discussion, my test is nothing new and would have already guest my aim.
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    Sack 'em or train 'em! If you're not allowed to do the first and the second doesn't work then move the factory someplace else even if you have to pay higher labor rates.

    Totally agree!

    Better watch out for your customers too!
     
  7. PAR
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    PAR Yacht Designer/Builder

    It's purely mechanics folks, though on a very small level (actually not that small really).

    To stabilize wood moment, you have to stop moisture vapor ingress/egress. This is the simple fact of it all, other wise wood will swell and contract. The only way to do this is to insure less then 3% moisture absorption and start with fairly dry stock. This is why marine epoxies are formulated the way they are, why all formulators recommend 12% moisture content stock and also why the polyesters and vinylesters don't get the job done (they resist at 85% - 87% and 87% - 92% on the 30 day absorption test respectively). If your coating, regardless of penetration amount (hell, it could hover over the surface, so long as it stops moisture), can't resist moisture vapor transmission, below the 3% threshold, then you'll have "gain" or "lose" depending on the current environmental changes. These are the simple physical facts of the testing and analysis preformed since WBP possibilities in WW II discoveries. This is well established and given that all, every single one of the formulators, hang onto these same baselines and moisture content thresholds, speaks volumes about the validity of their (and my) position on the subjects.

    Of course, unless we've all gotten it wrong for the last half a century and you've discovered something special, in which case you'll need more then some garage testing. For example what was the flexural modulus of your thinned goo against your baseline? Assuming a typical 3:1 formulation baseline of a half a million PSI, how did your goo fair? Tensile strength/elongation/modulus? Compression strength? How about hardness (Shore D or Barcol, which ever you prefer)? Naturally, I'd have to ask about water absorption rates too . . .
     
  8. Frog4
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    Frog4 Proletariat

    does this apply to vacuum bagged wood components as well?
     
  9. PAR
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    PAR Yacht Designer/Builder

    Any wood that is to be dimensionally stabilized with a plastic coating, regardless of the method, needs to resist moisture vapor ingress/egress to less then 3%.
     
  10. sabahcat
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    sabahcat Senior Member

    Maybe you missed the bit where I said that the thinned "goo" (20ml of biocide to the litre) was the first coat just to soak into the ply and still leaving the ply looking quite dry.
    ALL other coats were unadulterated, taking care of any of your fears.
     

  11. sabahcat
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    sabahcat Senior Member

    I buy my epoxy in 44 gallon drums and it is already a low viscosity resin.
    I only need a few litres of the epoxy with biocide added to it for the first coat to ply that will be immersed (Tank Baffles and sides or in areas with no access.(the only timber in the build to get the treatment)
    Secondary coatings of unadulterated epoxy to these components I would prefer to use the same "Brand" of resin and apply while green so as to eliminate sanding between coats.
     
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