wrinkles in spray-on gel coat repair?

Discussion in 'Materials' started by mac26d, Aug 27, 2007.

  1. mac26d
    Joined: Aug 2007
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ontario

    mac26d New Member

    Howdy all

    I am in the midst of a f/g repair and am in the gel-coat finishing stage. I was spraying the gel coat (with air dry) and the gel coat started to wrinkle in small areas (about 5-10% of total area). I don't believe there to be anything special about the areas that are wrinkling, i.e. all the area were prepped the same way.

    If anyone has any ideas I would appreciate it.

    Thanks in advance

    mike h
     
  2. dberr
    Joined: Mar 2007
    Posts: 19
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    Location: Toronto

    dberr Junior Member

    Been there, ...

    I have been having "challenges" with gelcoat this summer too. I was spraying gelcoat into a mold and had prerelease problems. The replies to my question on this thread were very helpful: http://boatdesign.net/forums/showthread.php?t=18566
    (I don't know how to set up a link yet)
    I have since had the same problem you are describing while brushing gelcoat into the mold for a steering console. It looked to me like the cause was thin gelcoat. I have also had wrinkled, or alligatored, gelcoat when spraying into a mold which I am sure was caused by a small amount of acetone in the gun in addition to thin gelcoat. I have learned that it takes a lot of practice to spray gelcoat correctly. Unfortunately, you have to practice a bit with expensive material.

    db
     
  3. patrik111
    Joined: Sep 2003
    Posts: 58
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    Location: Sweden

    patrik111 Junior Member

    Cause

    This is caused by migration of styrene through the mold.
    If the mold is prepped with PVA (Poly Vinyl Alcohol (I think)) this problem should go away.
     
  4. mac26d
    Joined: Aug 2007
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ontario

    mac26d New Member

    thanks

    Thanks for the replies.

    I have since sanded and resprayed the suspect areas. I'm still not sure what actually caused it, although surface prep may have been part of the problem despite my efforts.

    Second time around after thickening up the gelcoat slightly and ensuring the surface was clean there were no problems.

    mg
     

  5. fiberglass jack
    Joined: Dec 2005
    Posts: 463
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    Location: toronto

    fiberglass jack Senior Member

    wrinkles in a repair sound like you sprayed the area and waited to long for the gel to flash off before you sprayed again, with gelcoat you got to let the gel flash off but if you wait to long the frist layer will have set up and the second coat will attack the frist and wrinkle, it may also be that you over build the spray and the presure from the gun will blow the gel and this will look very simalar, the flash time with gel is only a few minutes just enough to let the acetone flash off, next time try using duratec high gloss addative 50 50 mix you will realy notice a differance the gel will lay almost like paint,
    dberr prerelese is often caused by to much gelcoat is the relese near corners or areas that you may over passing the spray patern, once you learn to spray the mould you should be fine , every mould is a little different and you got to learn a patern to spray, the pva also helps as it is a wax free surface, to much wax will often cause the release also, but first find out if the wax you are using contains silacone if it does the pva will fisheye so its not a good idea if your looking for a good finsh,
     
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