Thinning polyester resin with Acetone

Discussion in 'Fiberglass and Composite Boat Building' started by valvebounce, Apr 4, 2017.

  1. valvebounce
    Joined: Dec 2010
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    Location: manchester uk

    valvebounce Senior Member

    The two drain holes in my splashwell are 3/8" higher than the splashwell floor.
    This leaves water in the splashwell,which gathers dirt in the water.The boat is stored on my drive and is left uncovered part of the time.
    The water forms a "D"shape.
    I have levelled the boat port to starboard,and wound up the jockey wheel to tip the boat to the stern.
    I have sanded the "D"shape plus and inch,and the bottom of the inner transom area.
    I laid up 3 thicknesses of csm to gain the height against the transom.
    It has left the surface a little lumpy,and shrunk slightly below the drain holes.I have sanded
    it down,but it is still slightly uneven.
    Seeing as there is not a lot of strength value required,I am considering thinning the polyester resin with Acetone and pouring it into the level of the bottom of the drain holes and letting it find it's own level.
    Can anyone see why it won't work?
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Use MEK instead and though it'll weaken the cured resin, it doesn't really matter, because you're just trying to level out the bottom of the splashwell.
     
  3. valvebounce
    Joined: Dec 2010
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    Location: manchester uk

    valvebounce Senior Member

    Hello Par,thanks for your reply.
    Is MEK an American product or an abbreviation?(or can't you spell it,Haha)
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Methyl ethyl ketone ? Styrene monomer is used to thin polyester resin, but none of it should be necessary for what you are doing ?
     
  5. valvebounce
    Joined: Dec 2010
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    Location: manchester uk

    valvebounce Senior Member

    Hi mr E,
    Because radius's in the splash well are difficult to sand,the idea is to let the resin flow flat.
    The resin on it's own doesn't flow too good,I want to duplicate the area where the water was lodging.
    I'll be Gelcoating the area to finish off.
     
  6. valvebounce
    Joined: Dec 2010
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    Location: manchester uk

    valvebounce Senior Member

    Hi Mr E,
    The idea is to let the diluted resin flow and find it's own level,resin on it's own stays too proud
    and sanding the radius's in the s/well is quite awkward.
    Sort of replacing the lodged water level with resin.
    I'll be gelcoating the area to finish it off.
     
  7. Canracer
    Joined: Aug 2009
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    Location: Florida

    Canracer Senior Member

    How thick will the leveling layer be after it's cured?
     
  8. valvebounce
    Joined: Dec 2010
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    Location: manchester uk

    valvebounce Senior Member

    The layer will be about 1/4" against the transom,maybe slightly less,and tapering to infinity as it gets towards the bow.
    It will form a "D" shape about 4" wide in the middle.It will be going over the glassing I have just completed and sanded.The s/well is 2' wide at the transom.
     
  9. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    1/4" of unreinforced resin will be very weak, and most likely start cracking, putting gel coat over it will slightly increase the likelihood. Thinning it with anything will make it even more brittle and weaker than it would be to begin with.

    Add more glass to the area and then just skim the surface with a filler.
     

  10. valvebounce
    Joined: Dec 2010
    Posts: 549
    Likes: 11, Points: 18, Legacy Rep: 124
    Location: manchester uk

    valvebounce Senior Member

    Thanks O,maybe filler is the answer
     
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