epoxy not waterproof?

Discussion in 'Materials' started by magwas, Dec 19, 2009.

  1. TollyWally
    Joined: Mar 2005
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    TollyWally Senior Member

    I've used talc and baby powder in a pinch. Not everyone approves.
  2. magwas
    Joined: Oct 2009
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    magwas Senior Member

  3. apex1

    apex1 Guest

    The relevant info is in your head already!

    A coarse grain filler makes a poor bond and / or a far too high resin consumption for glueing. You need something like flour. I´ve heard some people use plain chalk, but do´nt quote me on that.

    For fillets the raw sawdust is a perfect and cheap material, though screening is necessary (your mosquito net might work).

    The resin manufacturer "West Systems" provides a good tutorial on his websites

    Merry Christmas
    and thanks, I am going better a bit!
  4. nukisen
    Joined: Aug 2009
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    nukisen Senior Member

    Nice thread! :)
    Specially as I am about to almost do the exact same procedure myself. Exept for I am going to us glassfibre rovingnet for strengthen up the construktion.
    Hope I will manage to do this.
  5. nukisen
    Joined: Aug 2009
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    nukisen Senior Member

    Maybe we are able to get experience of each other as I do also planing to build a boat out of 3,1mm board plates. I suppose I have to give a first layer before I cover it with glass fibre roving sheet. And also after that I will cover as many layer as it will be smooth and shiny again.

    As the epoxy price for me is no longer a big problem I hope to manage to build a boat that is actually useful and works well.
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Simply put, log onto www.westsystem.com or www.systemthree.com and down load their user's guides. It will walk you through fillers, hardeners, mixing and all the basic stuff.

    As a rule there are two types of fillers, fairly smooth and round or fairly rough and long. This describes the physical dimensions of the materials.

    The smooth and round items are also light weight and used for fairing surfaces. They have very little, if any structural value and are just used to smooth up surfaces.

    The rough and long materials are generally fibrous in nature. These tend to interlock with each other when mixed in resin. This interlocking makes a very strong material when cured. Milled 'glass fibers, shredded cotton, silica, wood flour, etc., if viewed under a microscope are very fibrous and ideal for improving the structural composition of cured resin.

    You can use wood chips and/or shredded bits of rope if you want and they'll make good filler materials, though you'll probably have a difficult time controlling the amount of epoxy you use, which is why we use the really fine versions of these fillers. Ideally, the fillers you employ should be in powder form.
  7. nukisen
    Joined: Aug 2009
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    nukisen Senior Member

    This is very usefull and knowledge increasing information.

  8. kengrome
    Joined: Jul 2006
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    kengrome Senior Member

    I bought talc by the sack to use for sandable filler too, it works great. baby powder is usually made of talc, although you should read the label because some baby powder is made of corn starch.

    Just add cabosil (fumed silica) to prevent sagging.

    My favorite for really strong joints is pulverized limestone, it works great and it is cheap although it is not a lightweight filler. You can buy it at an agricultural supply store. Cement works great too (especially if you cannot find the lime) although it produces a gray filler rather than cream colored or white like the limestone.

    These are all mineral fillers that do not absorb epoxy so they are very predictable when mixed with epoxy. One thing though, the lime and cement are hard like rock when cured (because basically that's what they are) so don't expect to sand them easily. Talc is rock too but it's the softest naturally occuring mineral so it sands relatively easily.
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