Orange Peel

Discussion in 'Fiberglass and Composite Boat Building' started by aaronhl, Sep 14, 2022.

  1. aaronhl
    Joined: Aug 2012
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    aaronhl Senior Member

    Does it come down to spray technique and tip size, how do you guys deal with orange peel? Seems like I am only able to start with 220 wet to knock down the peel after spraying gelcoat or even Duratec...I get better results with an air sander+water because it doesnt leave behind as many scratches as hand sanding with paper.

    1/8" tip seems too small to spray the peanut better and 1/4" seems too large to give more peel

    Educate me on how you get a mirror finish without scratches because I think I am screwed from the beginning having to start with 220
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Are you referring to orange peel of aluminium?

    There is not a lot you can do..as it is a grain boundary issue from forming/drawing of the sheet of metal.
    It really depends how deep the grains go from the deformation in forming/drawing. Until you try sanding it...you wont know.
     
  3. aaronhl
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    aaronhl Senior Member

    No I am talking about the texture of gelcoat after spraying it on the outside of a boat or plug, not inside a mold nor anything to do with metal
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Ahh yeah, my bad, i read the post too quickly....doing too many things at once!
    Sorry about that...

     
  5. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    Gelcoat is actually intended to be the first layer of a laminate made on a mould.Using it as paint brings it's own problems.You are unlikely to get a high gloss finish straight from a spray gun.The alternative is to use paint to cover the boat as it has different characteristics but will still require compounding at the very least.
     
  6. gonzo
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    gonzo Senior Member

    Spraying with Duratec should give you an automotive quality finish. If you want a show finish, like a good gelcoat, polishing should be all you need. I am not sure what you mean about the peanut.
     
    ondarvr likes this.
  7. fallguy
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    fallguy Senior Member

    He is referring to peanut, as in butter, and referencing the thickness of the gc. (methinks)

    I am not a gelcoat guy, but I would think orange peel and viscosity are related somehow.

    Sorry I don't have more to add. Sort of lurking the post to learn what I can. I have a jetski repair in my future.
     
  8. aaronhl
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    aaronhl Senior Member

    Yes exactly gelcoat has a high viscosity so it's like shooting peanut butter and its not smooth like auto paint, auto paint is like water...

    My concern would be for a final finish of a mold plug, I don't get how you can just shoot duratec or gelcoat and only have to polish, the texture needs to be more than cut, it has to be sanded

    Maybe I will play around with the tip size and thinning some of the duratec using a dump gun (no luck with hvlps) too see how I can cut down on the orange peel texture so I have less to sand
     
  9. fallguy
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    fallguy Senior Member

    The expert on gelcoat is @ondarvr ... a few others are also wise, but have not responded here
     
  10. comfisherman
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    comfisherman Senior Member

    I watched a few local guys and came to the conclusion the solution is to shoot it thick with orange peel and then spend several days with 220....
     
  11. gonzo
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    gonzo Senior Member

    If you spray gelcoat 50/50 mix with Duratech clear additive, the finish is the same you can get with an automotive enamel. The light orange peel can be finished with a compound like 3M Finesse. If you need to cut more, it is probably the spraying technique. You shouldn't have to use a coarser grit than 800 after spraying.
     
  12. ondarvr
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    ondarvr Senior Member

    Yes, gel coat is difficult to spray and get a good finish without a little chemistry assistance.

    Duratec when used as recommended should give you a very smooth and high gloss finish. Whether this finish meets the desired goal is up to you, but light sanding and buffing will yield an even better finish.

    Every gel coat is different, but I can normally spray this blend and start sanding with 600 to 800 grit. This doesn't mean you can do it every time, but most of the time on surfaces that don't have challenging geometry you can get a very good surface.

    For tooling you can add it to the tooling gel, or buy the Duratec top coats designed for this purpose, they spray and level more like paint. Some shops don't sand and polish these products, they go straight to mold release.

    This works if you don't need a perfect surface, or if the part is going to be painted later. But it doesn't take much to sand and polish out the minimal amount of orange peel you may get if you need a better surface.
     
  13. ondarvr
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    ondarvr Senior Member

    I will add, you need at least a 2.5 mm tip in an HVLP gun to get a good finish, and for larger surfaces an even bigger tip.

    And don't spray it with a typical automotive paint type pattern, too much air can result in more orange peel. You need to flood the surface a bit more and get the mix to flow into a continuous smooth film.
     
  14. aaronhl
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    aaronhl Senior Member

    Mixing the duratec high gloss with gelcoat, what PSI do you spray out of a 2.5mm tip?

    Could you guys share some other spraying techniques since it's not like an auto pattern?
     

  15. ondarvr
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    ondarvr Senior Member

    35 PSI or so, but the more important factor is the volume of air, it needs to be reduced. You don't want a wide highly atomized fan, the droplets need to be a little larger
     
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