Varnish vs. UV additives

Discussion in 'Boatbuilding' started by JosephT, Jul 12, 2011.

  1. JosephT
    Joined: Jun 2009
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    Location: Roaring Forties

    JosephT Senior Member

    I just finished building a cedar strip canoe. The candy coat of epoxy was the last coat I've put on it. Now I would like to apply a UV blocker to protect the epoxy. As you might expect the UV coating is to protect the epoxy, and I am hoping there is a UV epoxy additive that goes on clear, yet protects well.

    Q: Is there such a product?

    It appears West makes a "420 Aluminum Powder" that contains some UV resistance, but is it clear? I want to preserve the color of the wood so a pigmented UV blocker (e.g. UV epoxy paint) is not what I'm looking for.

    If no good products exist I'll probably go with Schooner's Gold varnish.

    Thoughts? Suggestions?

    Thanks,

    Joe
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Aluminum oxide powder looks just like what you would think, aluminum. It's used in high heat situations and under paint to protect from UV. It's not clear at all.

    Your choices for clear coats are three fold; traditional alkyd varnishes, which dry damn slow and impart an amber hue to the work, single part polyurethanes, which dry much faster, are harder and more durable, plus have better UV protection, but can be difficult to repair and lastly the LPU's which are also polyurethanes and much more durable. The polyurethanes can be had without the amber color too, but also can be more difficult for the novice to apply well, especially the LPU's.

    Clear coating any epoxy is just a stop gap measure as UV is still getting to the substrate, though at a reduced rate. If you keep the clear coatings in good condition they can last for many years, but if you let them get away from you, though neglect, the substrate will be damaged and there's hell to pay to fix it.
     
  3. JosephT
    Joined: Jun 2009
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    JosephT Senior Member

    Thanks so much for your advice PAR. I will likely go with the case of Schooner's Gold I bought. I vaguely recalled a surfski company in the UK stating they painted their carbon boat with a clear "UV" blocker epoxy coating of some sort. I haven't seen such a product on the market, so I thought I would check.

    I don't mind varnishes, I just wish the surface finish was a lot tougher like epoxy. For most epoxy boats I have built (e.g. fiberglass or carbon) I have always used a lighter colored pigment to block the UV rays. In this case the boat is 100% natural so Schooners it is.

    Cheers,

    Joseph
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Schooner is a fairly soft clear coating. Both the single and two part polyurethanes are harder and more durable the the traditional alkyd varnishes like Schooner. I like Bristol finish, which is a two part polyurethane and very durable.
     
  5. brian eiland
    Joined: Jun 2002
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Perhaps you can tell me. Years ago (like early 70's) I used a varnish recommended to me called Bristol Fashion. I was told you could apply an additional coat the next day without the traditional light sanding that was recommended at the time for most all varnishes of that day. I was also told it would hold up better in tropical sunlight much better. Both of these claims appeared to be true.

    If I remember correctly I think it had a 10% additive of polyurethane ( relatively new product in those days).

    I've often wondered if this Bristol Finish is the same as the old Bristol Fashion??
     

  6. JosephT
    Joined: Jun 2009
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    JosephT Senior Member

    Thanks PAR, I may have to relegate the case of Schooners to the wooden floors of my house and check out that Bristol polyurethane. I have used polyurethane on another boat (over white oak planks) and agree it's tough as nails compared to varnish.

    Thanks again :cool:
     
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