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Thread: Grit check

  1. #1
    Join Date
    Dec 2016
    Location
    Bethlehem, PA, USA
    Posts
    49

    Default Grit check

    So I did a bunch of reading and searching on the forums here and want to get a gut check before I start since I'm new to this.

    I'm building my own version of an 19' lumberyard skiff. I've just finished putting on the second coat of 6 oz cloth with epoxy resin. Now I'm thinking about sanding and priming. I'm planning on using 80 to 100 grit sand paper before moving onto a high build primer. Does that sound about right?

    Thanks.

  2. #2
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    50,664

    Default Re: Grit check

    I'd longboard with 80# to prevent making ripples. If that looks really fair, prime away. If not then spread microballoon-thickened epoxy and again with the long board, spread a thin coat of epoxy to fill the surface microballoons, longboard, and prime.

    Prior to each sanding, wash the hull to prevent smearing any blush. Look to the WEST manual. https://www.westsystem.com/instructi...product-guide/

    Total Boat has a good overview of fairing. https://www.totalboat.com/fairing/

  3. #3
    Join Date
    Jun 2000
    Location
    Madison Wisconsin
    Posts
    10,250

    Default Re: Grit check

    In general, nicely sanded epoxy resin is a better primer than any primer. Standard procedure for my glassing has always been to roll on thin filler coats of epoxy (as many as it takes as people and their rolling technique and resins vary) until the cloth texture has completely disappeared, then roll on one more coat as a sanding cushion. Filling with resin only makes a much tougher surface than adding microballoons or other filler powders. Yes, it may take up to five or six thin filler coats, but they go on in about fifteen minutes and you just need to wait long enough between coats for the stuff to stiffen up enough that the application of the next layer doesn't disturb it. For health reasons, you should let the epoxy completely cure for about a week before sanding it smooth. Failing to do so can expose you to the toxic dust and you risk becoming permanently allergic to epoxy. Then wash off any blush and sand it to 80 grit and then maybe to 100-120 grit.

    Once you're done sanding, it should be baby butt smooth and defect-free, with no real need for any sort of high-build primer.

  4. #4
    Join Date
    Dec 2016
    Location
    Bethlehem, PA, USA
    Posts
    49

    Default Re: Grit check

    Thank you both for the info. I do have a bit of epoxy left, so a few coats will be going on.

  5. #5
    Join Date
    Jan 2000
    Location
    Cushing, Maine
    Posts
    4,190

    Default Re: Grit check

    I do love 80 grit especially for working boats. Rarely does anything get finer.
    Ben Fuller
    Ran Tan, Liten Kuhling, Tipsy, Tippy, Josef W., Merry Mouth, Imp, Macavity, Look Far, Flash and a quiver of other 'yaks.
    "Bound fast is boatless man."

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