Need help with shrink

Discussion in 'Fiberglass and Composite Boat Building' started by Bradley Adkins, Sep 24, 2020.

  1. Bradley Adkins
    Joined: Sep 2020
    Posts: 2
    Likes: 0, Points: 1
    Location: Missouri

    Bradley Adkins New Member

    Hey I’m having trouble with gel coat repair patches shrinking I suspect it’s due to too much heat from buffing but I figured I’d ask someone more familiar with this stuff than I. I catalyze correctly and wait a nearly 24 hours before I sand and after I buff it to a polished shine I notice it always sucks in a little I’m away from work currently but I will get pictures posted tomorrow any help or advice is appreciated
    Thanks
    Brad
     
  2. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    That is barely enough time for the solvents to evaporate. If you want to speed up the cure, use a heat lamp.
     
    fallguy likes this.
  3. antonkov
    Joined: Mar 2010
    Posts: 43
    Likes: 8, Points: 8, Legacy Rep: 20
    Location: Vancouver,BC

    antonkov Junior Member

    I just mentioned the shrinking issue in another thread. Depending on the type of polyester you are looking at 2% or more of linear shrinkage (5-13% volumetric). Seems like everybody using a common, basic kind of PE is dealing with it. Among the solutions is to compensate for it beforehand or to use special (i.e. more costly) resins or additives.
     
  4. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I usually lay a thicker than necessary coat of gelcoat and sand it down after. The other solution is to finish with a gelcoat/Duracote mix and spray the last coat on.
     

  5. Bradley Adkins
    Joined: Sep 2020
    Posts: 2
    Likes: 0, Points: 1
    Location: Missouri

    Bradley Adkins New Member

    I believe we use a vinyl ester gelcoat I always apply it thicker than needed and sand down I’m going to try the heat lamp thanks for the advice.
     
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