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Thoughts on coating wood with epoxy

  • October 21, 2013 3:36 PM
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    Message # 1418493
    Deleted user

    After having just built a new bowsprit for our boat a little over three years ago I discovered that sat the laminated Doug Fir bowsprit had almost rotted completely through and was pretty lucky not to have a failure of the rig. The old sprit was made from local lumber yard wood and was evidently wet and considering that I completely sealed the spar in epoxy as a water barrier coat it actually appears to have rotted from the inside out. I am now in the enviable position of making a new sprit and was able to procure a beautiful vertical grained old growth beam that came out of an old building rumored to have been cut in the mid 1800's.

    I am trying to decide if I should coat the spar in epoxy, my instinct is this does not allow the wood to breath and may cause more problems than it solves. The other issue I have had issue with is paint does not seam to adhere properly my spars that are epoxy coated, even after dealing with the amine blush issues, am always going back and spot repairing and painting.
  • October 21, 2013 11:27 PM
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    Reply # 1418745 on 1418493
    Deleted user
    Not sure what happened in your case, but sealing a wet wood with epoxy is not so good.

    But 2 things I have found to be true.
    wood not exposed to air (under water 100% of the time I mean "100%") and wood not exposed to water (dried and sealed wood) do not seam to rot.

    example 1   the trees brought up from the swamps or from the bottom of lakes, make some really nice lumber.
    example 2  the old barn wood and some old house timbers from the 1600's still look great.

    both could be eaten by insects and bugs, but should not show rot.

    For good rot you need moisture and O2 (air) so 100% sealed should = no rot, but 99.9% sealed can lead to rot.

    Everything has mass transport, O2 movement, epoxy is pretty slow on this issue, so it makes a good reduction in air and water moving in or out of the part, varnish is less, but still ok at reducing the movement. 

    So a good varnish = ok
     a well oiled part = ok
    an epoxied and painted part = ok 
    But all should be dried under 15% and ideally be under 8% moisture.     
    Hope this helps

    Norm

    Oh SS does not rot. Just in case you wanted to know
  • October 27, 2013 12:05 PM
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    Reply # 1422362 on 1418493
    Anonymous member
    It's easy to miss, but did you epoxy seal the holes that ran through the bowsprit?  I like to epoxy prior to varnishing. Epoxy builds much faster, sand smooth and varnish. But if you do all that then drill for the rollers and then drill for the platform and then drill for the head stay and then drill for the end piece and then drill to attach it to the deck you have now added a multitude of points for water and air to mix and damage the wood. And if you use carriage bolts after you pull the head into the wood creating yet another entry point.

    The last wooden sprit we had  made we sealed with (after drilling all the needed holes) with Cuprinol and then epoxied and then varnished. Don't know how long it lasted, about 5 years when we sold it and the current owner has never said he needed to replace it. The last pics in 2005 looked like it still had the one I put on which would have given her about 15 years.  Like I said, can't guarentee it wasn't replaced sometime without my knowing it.

    Ciao
  • February 22, 2014 11:19 AM
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    Reply # 1503760 on 1418493
    Deleted user
    Hi, A previous owner had Awlgripped (epoxy painted) allot of pieces on my W32 Sunrise, Awlgrip does not breath and sticks to the surface of the wood  like a strong thick hard heavy film. The areas where there was chafing like on the Samson posts, developed rot by moisture entering through the bare,worn wood. On the bowsprit where the cross members that supported the bow pulpit were screwed down there were also problems. The new wood parts I am constructing to replace them are rot resistant hardwoods and primed with epoxy penetrating epoxy (nasty) and then marine varnished or painted.
    Seems to me that the treatment for marine 'doug fir' is oil and varnish or oil paint. I think the old timers used allot of linseed oil cut with turps for better penetration. Any holes drilled downward need to have a weep hole drilled to the hole and/or be constantly re-bedded.
    I guess that softwood needs to breath more than hard woods, softwood can soak up allot more water than hardwood (and quickly) so it's probably better if it can breath. The water usually cannot get out the way it got in (through a scratch or screw hole etc.) unless it becomes a vapor and even then, it's not all getting out again. If you are in a cold climate moisture saturation can be a big problem with the frost expansion that pulls all the fasteners loose and thereby lets in even more moisture!
    The wood also plays an important role in it's own preservation. I recently purchased a large amnt. of old factory floor beams that were not well protected from the weather (all the same species and age, some were rotted and others were not. The grain and pitch content made the difference in weather resistance. The doug fir used should be a dense high marine grade for a sprit, I would spare no expense for that piece of wood considering how much trouble it is to install and how vital it is to the survival of the boat. Cheers