thoughts on finish in a mold

Discussion in 'Fiberglass and Composite Boat Building' started by brokensheer, Feb 23, 2012.

  1. brokensheer
    Joined: Jun 2009
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    Location: So. Md

    brokensheer Senior Member

    I am talking about a v bottom power boat mold in the area of 14' to 17' . I am building the plug from wood, I am told to get the plug to an 800 grit finish, cast the mold and then polish the mold up to the 2000grit finish I am looking for, my question is why would I not want the plug as highly polished as possible!
     
  2. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    I am a big fan of polishing the plug to a high gloss, however, sometimes due to the materials used, this is not possible. Then polishing the mould can be easier.

    But beware, polishing a big mould can be a tedious task, even if it was just for the reason that you glide around in the mould like crazy. Spraying the bottom of the mould (the Vee) with Spraylat can help. Then at least you ca walk around, instead of fall around.
     
  3. brokensheer
    Joined: Jun 2009
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    Location: So. Md

    brokensheer Senior Member

    Thanks Herman, this mold I am speaking of is the forst of two the 14' we can reach it all from the outside!, I do know how fun it can be to slide around inside of our 23' mold,,

    Thanks
     
  4. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    It is a whole lot easier to fair a positive/convex plug than a negative/concave mold. You can finish a plug with anything that leaves a smooth surface. Do it up like bodywork on a car, put on a sandable hi-build primer, fair that out with grits comparable to what an auto body repair shop would and finish with an auto paint. Lightly buff, wax 4 or 5 times, pva and then make the mold. You want the plug as pretty and finished as the final product will be. The finished mold should only need a very light buffing, if even that.
     

  5. brokensheer
    Joined: Jun 2009
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    Location: So. Md

    brokensheer Senior Member

    Thanks SamSam
     
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