Epoxy fillers

Discussion in 'Boatbuilding' started by Manie B, Sep 4, 2008.

  1. Manie B
    Joined: Sep 2006
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    Location: Cape Town South Africa

    Manie B Senior Member


    What do you think is the best material to mix into epoxy to make a putty to fill in corners.

    I have read the latest TCP and see that it looks like a white powder possibly Talc or Silicone


    In the past i used a relatively fine saw dust - it is definately strong - but difficult to sand down smooth in the corners. Sawdust / epoxy putty is difficult to apply and leaves a ruff surface when cured, that basically has to be sanded down for painting and blush removal.

    I am stuck between something that i know is strong and hard work - or do i go for weak and light work.

    Have any of you guys had strenght concerns the way that TCP is doing his filleting:?:
  2. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    Depends on the strength requirements. If none 5/1 microballons/cap-o-sil it's quite easy to sand.. chance more sil if some stres is expected and in sawdust, microfibers, hardfiller or "chopped" fibers (in that order) to gain more stength. I do the "chopped" from biax leftovers with a kitchen mixer..
    for instance 1/1/1 microballons, sil and "chopped" fibers..
  3. the1much
    Joined: Jul 2007
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    Location: maine

    the1much hippie dreams

    ya i use cabosil and i take scissors and cut up whatever glass i got laying round.
  4. kengrome
    Joined: Jul 2006
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    Location: Gulf Coast USA

    kengrome Senior Member

    Hi BManie,

    Many corners in a boat should be filled with a structural filler putty, not a fairing putty. If this is what you need then I suggest talc because it is the easiest to sand of all the structural fillers.

    If the filler is only for cosmetic purposes you can use microspheres or microballoons to make 'fairing putty' which is even easier to sand but very weak in terms of structural strength.

    And if the putty you make sags too much you should add some fumed silica (one brand is Cab-O-Sil) which in some places is also known as 'stop sag' for obvious reasons.

    Milled fibers and the larger chopped glass fibers like Jim is referring to will make the filler stronger but they also make it harder to sand, and from your original post it seems you desire a more easily sandable filler -- so don't overdo it with these stregthening additives unless you want to make the sanding more difficult than it already is with your sawdust filler.

  5. Manie B
    Joined: Sep 2006
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    Location: Cape Town South Africa

    Manie B Senior Member

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