Varnish Issue

Discussion in 'Materials' started by Phil Westendorf, Mar 1, 2017.

  1. Phil Westendorf
    Joined: Jun 2012
    Posts: 35
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Saginaw, MI

    Phil Westendorf Junior Member

    HELP! I have made a new pair of 8 ft. Oars and after finish maching them I added two coats of neat epoxy with 6 oz. glass on the edges of the blades (25" long section). This is the third pair of oars I have made, this is first time this issue has bit me.

    This pair is made from Doug Fir with Blk Walnut accent stripes in the blades.

    So here's the problem, after the third coat of Epifanes High Gloss applied to the oars, the fourth coat and now the fifth coat also has a cracked finish on just the blades. The first two cioats were thinned 50% and 25% with a high quality thinner. For the third and subsequent coats I added additional Varnish to the left over "thinned" varnish to increase the ratio closer to 100%. I guess it's approx. 80% varnish and 20% thinner.

    Each coat was sanded w/ 220 grit sand paper after the previous coats were "cured" (24 hrs minimum).

    The "cracked finish" is only only on the flat surface of the blades (both oars, both sides). The shafts are Ok, just like they should be.
    The fourth coat was cured in the garage, minimum temp about 45* (was 60* during the time I applied the varnish and for 2-3 hrs after), So I moved them in the basement for the application of the fifth coat, min. temp 70*. Same result......
    Anyone have any suggestions as to what I am doing wrong. :?:
     
    Last edited: Mar 1, 2017
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    In lower temperatures, varnish can take longer than 24 hours to fully setup. Over a sealed surface (epoxy) you wouldn't thin varnish anymore than necessary to remove stipple and/or brush marks. Out gassing usually doesn't make finishes crack, just bubbles and pinholes, though I have "forced" things to dry both chemically and with elevated temperatures and made it crack.

    Since the third coat went down okay, I suspect temperatures delayed the cure on the fourth coat, which also affected the 5th, even though it was warmer when applied. Simply put, even though some areas of the 4th coat might not have had any cracks yet, they just needed the solvents in the 5th coat to soften the "surface tension" of the 4th coat in these areas and cracks formed.

    Unfortunately, I'm pretty sure you know what needs to be done. Let the oars sit for a few days, then sand back into the 3rd coat and prep for more coats (again). Which Epifanes product did you use? There are several and their basic stuff is a modified alkyd, which usually isn't a troublesome product to use. I'll assume you're not using one of their isocyanate/alkyd formulations, which can be more challenging to apply.
     
  3. Phil Westendorf
    Joined: Jun 2012
    Posts: 35
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Saginaw, MI

    Phil Westendorf Junior Member

    PAR,
    Thanks for your feedback which seem to me to be spot on. I have left the oars in the basement (mid sixties) and plan on leaving them there for a couple more days and then do as you suggest. I'll take it down to the third coat and then add a new forth coat @ 100% and let it cure for a few days. I'd like to get a fifth coat on, but I have to deliver them to a customer on the 12 Th. of March. It's going to be tight. I used Epifanes High Gloss Varnish which I have used on a drift boat, cedar strip canoe and several other oars and related things. This was the first time i have had this kind iof issue using this varnish.

    Thanks again,

    phil w
     
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