Spar Urethane

Discussion in 'All Things Boats & Boating' started by Victory 1, Jun 6, 2013.

  1. Victory 1
    Joined: Jun 2013
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    Location: Hawaiʻi

    Victory 1 New Member

    How many of you out there are fans of this stuff for wood surfaces?

    I got away from this stuff when a woodworker friend of mine suggested poly-urethane since it flows

    better(?) So I got a lot of practice with polyurethane even to the point of using a foam roller, then got

    good at spraying with a HVLP gun.

    Two weeks ago I finished some outrigger canoe booms by spraying spar urethane and it turned out good

    but not spectacular.

    So on to a new pair of booms in the final spar urethane applications. My intentions were to brush on the

    first two coats then do a top coat by spraying through the HVLP gun.

    I decided to use a brush to do the top coat, and I think it looks even better than a HVLP sprayed coat.

    Looks like Iʻll be using Spar Urethane from now on.

    Any more tips for great looking Spar Urethane application?
  2. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    welcome to the forum,

    they are really same product except the "spar" usually implies more UV protection. Normal interior polyurethane has little to no UV stablizers, extirior rated PU has more, and the "spar" or "marine" has even more. the UV stablizers alters the color and perhaps the texture of the finish, though this varies from brand to brand.

    All urethanes break down in the sun, and some are more brittle than others (but are harder so have better abrasion resistance). All manufacturers have slightly different formulations of adatives to make them more suitable for various applications, putting in UV protection is just one of them. I do not know that spar varnish or spare polyurethane is any different from other exterior grade PU finishes, but likely has some other properties that might make it more suitable for exposed bright work. I would suspect, if it is not just marketing, but rather intended for use on actual boat spares, it might sacrifice surface finish quality and color for more durability and extra weathering protection.

    There also does not seem to be any correlation with price and durability, you can spend anywhere from about $25 a gallon to $180 a gallon for "spar varnish" from various manufacturers. The more costly finish from the specialty marine supplier is not necessary any better than the more moderately priced exterior finish.
  3. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    With Varnish the higher the solids content, the more UV durable the varnish. Check the data sheet. Epifanes has traditionally been the varnish with the highest solids content. Its the industry standard "Good Stuff ".

    I only use polyurethane varnish on surfaces that will be walked on .

    Polyurethane is a HARD varnish and is very troublesome to repair.

    The advantage to polyuerathanes is fast dry...coat on coat, no sanding.
  4. Victory 1
    Joined: Jun 2013
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    Location: Hawaiʻi

    Victory 1 New Member

    My first real attempt at brushing spar urethane.


    With more practice I think I will continue this process.

    The urethane seems to harden fast and it is very handleable quicker than I

    am used to (as in less tacky feel).
    Last edited: Jun 7, 2013

  5. Victory 1
    Joined: Jun 2013
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    Location: Hawaiʻi

    Victory 1 New Member

    Couple more photos of booms - ʻiako in Hawaiian.


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