Gelcoat mixing additves?

Discussion in 'Materials' started by wrbowcal, Feb 3, 2011.

  1. wrbowcal
    Joined: Apr 2010
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    Location: Crowsnest pass, Alberta

    wrbowcal Junior Member

    First off I don't know much about gel coat just a couple vids on utube.I need to know what I was told by the kid that sold me my supplies is correct for application as I don't want to loose over $500 doing it wrong.I will do my best to try and explain this.what I have is 2- 5gal pails half full of white gel coat, lots of MEKP and 1 pint of what he calls air dry?....told for the first coat mix acetone to thin then the catalyst(MEKP) to the gel coat mix and apply,He said it will not go hard just tacky.Then for the final coat(the other pail)add the pint of air dry into the 2.5 gal then acetone then MEKP and this will harden the tacky first coat when set.
    I just purchased a 2qt canister sprayer that has a 1.4mm and a 2mm nozzle cheap a little over a $100.00,not professional equipment but I hope it will do the job.Does this recipe sound OK? No writen instructions on anything all poured from bulk containers? Oh can I mix the MEKP to the same ratio as poly resin at 100 parts to 1 for min approx 1 hour before it starts to harden I can get the shop up to about 70 deg .thanks
     
  2. mark775

    mark775 Guest

    There are those here that are better qualified than I to guide you but there is much that is wrong with this plan. Wait a day, at least, there are many eager to help with this. To start, I don't believe you should thin the first coat with acetone. The first coat does harden - it's just that the outermost links to oxygen molecules. The "air-dry" has to be a brand of surfacing agent - it keeps the oxygen from the surface and forces the linking to happen to each other, rather than oxygen, thus a hard surface. Yes, use a cheap sprayer. Don't mix large batches or it will kick from its own heat and disappoint. Work safe, there are some bad chemicals there.
     
  3. idkfa
    Joined: Sep 2005
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    idkfa Senior Member

    thin with styrene and not acetone, and no more than 10%.
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    How you plan to use the gel coat will determine the spray equipment and methods. What is the project?.

    It sounds like you plan to spray a large surface ???

    From your description of the spray gun I can't tell if its a siphon gun or a pressure pot?

    Thinning is not recommended, but is done at times, it depends on the project and what you want as a final result.

    Air Dry is a regional term for surface agent, it is wax dissolved in styrene.

    With a little more info people here should be able to walk you through it
     
  5. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    Typically gelcoat is catalyzed at 1.5 to 2%

    Use the 2.0mm tip for your sprayer the bigger the better

    Thin with Styrene or MEK they say 10% but reality is with your spray equipment you may need to go a little more (but you degrade the gelcoat some by thinning)

    I think you will be in big trouble if you mix / catalyze 2.5 gallons of material at one time. AT 70 degrees F and 2.0% catalyst you have aprox. 30 minutes to work, that means spray your material and wash the gun out.

    The surface seal is a paraffin wax in solution with Styrene, set it in the sun before you use it and shake it up well. Add to final coat at around a 5% ratio or what ever ratio your supplier stated and make sure to mix it in very well with your gelcoat
     
  6. wrbowcal
    Joined: Apr 2010
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    Location: Crowsnest pass, Alberta

    wrbowcal Junior Member

    Alright,Ok I will buy styrene for sure for thinning and just thin to 10% .The spray gun is a pressure pot gun with 2 hoses 6ft long that go to the 2qt canister 45 psi max so I have to thin to spray.I have a couple HVLP guns I can use for above the water line. The project is to gelcoat the new stringers, ribs,bilge bulkhead and floor (Just one coat),and the hull under the water line on my bayliner 2750 (2 coats).I hope I have enough gelcoat? To prep the hull would I sand with 80grit? I need a supplied fresh air system Im sick as a dog from glassing the stringers yesterday even with a fan,respirator and tyvek coveralls didnt help?
     

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  7. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Acetone is really a bad choice for thinning. Styrene is somewhat better. If you want a good product, use Durated Clear additive. The last coat of gelcoat needs wax, because it is air inhibited. If you let it open for too long, it will absorb humidity and become a sticky mess. With Duratec you donĀ“t have that problem
     
  8. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    You may find it easier and faster to just use a roller to Gelcoat the above mentioned parts of the boat.

    If you are not aware the gelcoat you spray that you probably want to shine and look very smooth like you see on a new boats hull will not be achievable by spraying. You will need to sand out all the orange peel with progressively finer grits of paper then polish out with a buffer and compound. If you don't care cool or if you already know my apologies
     
  9. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    For the bilge its not going to make much of a difference on what mix you use, but you will need the surface agent (air dry). I typically just roll the bilge and floor areas, spraying can be messy, dirty (over spray) and stressful when new to spraying gel coat.

    Air dry is just styrene and wax, so adding it is just like adding styrene to thin it.

    Adding anything to thin gel coat will degrade it, typically it reduces the weather, crack and water resistance, so whatever you use, add as little as possible.
     
  10. wrbowcal
    Joined: Apr 2010
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    Location: Crowsnest pass, Alberta

    wrbowcal Junior Member

    I looked for styrene today and could not find it in the small town Im from but will get it.acetone is not an optioin now, just for cleaning the gun and pot. Hey! rolling the interior is what im going to do it will save a huge amount of time masking etc.Thanks for the tips.
     
  11. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Remember, your air dry is styrene with wax in it, so you do already have styrene, but add as little as possible, because styrene will degrade the gel coat too.
     
  12. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    You can use MEK to reduce your gelcoat for spraying
     
  13. tunnels

    tunnels Previous Member

    I got a pretty good sence of humor but this takes he cake and the tray !! Where do these peole come from ????
     
  14. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member

    I'm at a lost here, MEk v Mekp? but.... no anyway!

    Maybe you could use a little resin to thin with if no styrene is available.
     

  15. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    MEK is a solvent and is totally different than MEKP (catalyst). Some people do use it to thin gel coat, I don't use it, but it does have a history in the industry.
     
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