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Marine Spar Varnish vs Poly Urethane

Discussion in 'Wood and Canvas' started by slk, Sep 17, 2019.

  1. slk

    slk Enthusiastic about Wooden Canoes

    Ok guys from my previous post's I am doing a wood and canvas canoe , with the exception of finish. I am clear coating with fiberglass cloth. I am about done with the epoxy finish, and it is looking good. Next step I need to protect the epoxy with some sort of UV coating. So my question is Varnish or Urethane. I like the urethane idea because I could spray that and get a great finish. Spraying varnish is a disaster with the bubbles. IDEAS???

    Steve
     
  2. David Satter

    David Satter LOVES Wooden Canoes

  3. Todd Bradshaw

    Todd Bradshaw Sailmaker

    Be aware that the inclusion of UV protective compounds into varnishes or urethanes is by no means automatic, so check the can carefully. If they are not specifically boasting about the product's powerful UV resistance, then you don't want it. Many of the typical coatings basically have none, and a couple hundred hours of UV is enough to start breaking down epoxy resin.

    For large-ish products like boat and canoe hulls, many of us have found rolling and tipping paint or varnish to be the easiest way to get a gorgeous finish without a lot of effort or equipment. If you haven't studied it, you should. Do a decent job of it and folks will think you sprayed the stuff. These boats were both done out in my driveway over smooth-sanded epoxy resin coatings (naturally, the first step on any similar project is to sand the resin baby-butt smooth) star (2).jpg
    N3.jpg . The varnish is Captains Varnish and the paints are Brightside, all rolled on using Gougeon yellow foam epoxy rollers and tipped with cheap chip brushes. I have spray equipment on hand, but think rolling does a better job, with a lot less cleanup and overspray hassles.
     
  4. OP
    OP
    slk

    slk Enthusiastic about Wooden Canoes

    Todd that boat looks beautiful....................

    I have 4 coats of epoxy on right now. How many do you guys usually put on before you start sanding for the varnish finish?

    Steve
     
  5. David Satter

    David Satter LOVES Wooden Canoes

    we've do a few glass and epoxy bottoms over the years on small boats or Grand Lakers. Depends on the weight of the cloth. Four seems enough to fill the weave of the cloth. Wash the blush off if needed then sand for varnish. Here's an American trader I reglassed and varnished with a brush. 10-15 captains varnish. The guys who do the strippers would know more about the finishing process. american trader, Dave White 005.JPG american trader, Dave White 005.JPG
     

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  6. Todd Bradshaw

    Todd Bradshaw Sailmaker

    The thickness (or not) of a coat of resin will vary a lot, depending on who is applying it and how much pressure they tend to use, what formula of resin they are using, what the working temperature is and even how many minutes it has been since you first mixed that particular batch of resin. Therefore, applying a set number of filler coats and expecting the results to be the same from boat to boat is awfully inaccurate. Best bet is to determine how many coats to add by the actual results you are getting. The rule of thumb that we always used was to apply thin coats (they tend to drip and run a lot less, requiring less clean-up sanding once all the coats are on) and to roll coats on until the weave texture has totally disappeared. Then add one more coat as a sanding cushion, so that you won't be cutting into the glass during the final sanding. It's not unusual to end up with five or six thin, rolled-on filler coats, with new ones being applied as soon as the previous coat has stiffened enough that you won't disturb it with the roller. You may end up working around the clock for a day or so, depending on your hardener speed, but the time needed to apply a coat is only a few minutes, followed by some drying time before the next one.

    No sanding is done between coats. In fact, it takes epoxy a week or so to harden completely to the point where the dust is no longer an allergy threat. If you're smart, you will give the boat a week or so to fully cure before you do any sanding on the resin, because you seriously don't want to develop that allergy. It would keep you from ever being able to work with epoxy again.
     
  7. OP
    OP
    slk

    slk Enthusiastic about Wooden Canoes

    One thing I am finding out with the marine spar varnishes is that all of them I have read the spec's on says do not use below water line. The last one I did years ago I used McCloskey Man-O-War and it lasted with years of use, and it even said do not use below water line. Do any of them say they can be used below water???

    Steve
     
  8. Todd Bradshaw

    Todd Bradshaw Sailmaker

    What they are talking about are situations where you might leave a boat sitting in the water for extended periods, which can peel most enamels or varnishes in a few days. Remove the boat from the water when you aren't paddling and you won't have a problem - as seen on thousands of strippers over the past 50 years or so. UV is still your boat's greatest danger. The rest is just common sense and maintenance when needed.
     
  9. OP
    OP
    slk

    slk Enthusiastic about Wooden Canoes

    Ok guys I have the epoxy on the canoe all sanded. What do you recommend to wipe it down with to get all of the white dust off before varnishing? I just did not want to use the wrong chemical/thinner. Is water and a rag ok, or will that smear the white dust around?

    Steve
     
  10. Todd Bradshaw

    Todd Bradshaw Sailmaker

    Water is generally effective and one of the least likely substances to introduce contamination which might mess with the varnish. There are certainly solvents which can be used, but the purity of what you find in the hardware store is always an unknown, so many of us tend to avoid them. The other considerations are concentrating on lifting the dust off with your rag and maybe a vacuum, rather than just smearing it around, and making sure the rag itself is clean. Some paper towels, for example, are even treated with a bit of silicone to make them resist water and hold up a little better when wet. Any transfer of that stuff to your boat can be a serious problem for varnish.

    Some sort of big, fairly soft dusting brush can also be handy to have, as can a tack rag, though some of the water based finishes say not to use a tack rag, as any residue it leaves can be a problem with the water-based varnishes and lacquers. It doesn't seem to be a problem with oil-based varnish.
     
  11. 1905Gerrish

    1905Gerrish LOVES Wooden Canoes

    Steve,
    My vote is denatured alcohol inside if you think there is any chemical residue after blowing the canoe out with compressed air.
     
  12. OP
    OP
    slk

    slk Enthusiastic about Wooden Canoes

    Ok guys I have the outside varnished. Now I have to do the inside. As a rule of thumb how long do you have to wait for the varnish to harden up to be able to have it sitting on it's bottom while doing the inside. On the can of my varnish it says drying time of 8 hours, but I know that is just a suggestion. I do not want to have the impression of a towel/padding on the bottom of the canoe. Once ya start the inside you are more or less committed till it dries.

    Steve
     

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