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Varnish the outside?

Discussion in 'Wood and Canvas' started by johnmetts, Aug 1, 2019.

  1. johnmetts

    johnmetts Curious about Wooden Canoes

    Hi everybody,

    Any ideas on varnishing the outside of the canoe before stretching the canvas on? Seems like a coat of shellac and varnish would aid in waterproofing.


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  2. Rob Stevens

    Rob Stevens Wooden Canoes are in the Blood

    Lots of discussions on that topic here. Some prefer thinned varnish rather than linseed or other oil. Fewer use shellac.

    JSRIII Curious about Wooden Canoes

    I think that many recommend an oil finish such as linseed oil because it breathes. A finish like shellac or spar varnish is less likely to breathe. IMHO, sealing both sides of the wood planks would be similar to having 2 vapor barriers in the wall of your home. If moisture were able to get between the inside and the outside it would be more difficult for this moisture to dissipate. In a house wall this can cause mold and defeat the benefit of the insulation. In a wood canoe it could promote wood rot.

    I have a similar restoration project just beginning and I will be oiling the outside wood with linseed oil as I believe Old Town did during the original build.

    I also believe that with a wood and canvas canoe, it is the canvas, the filler and the paint that provide the barrier to keep the water out, not sure that varnishing the exterior of the planks would do any more.
  4. Rob Stevens

    Rob Stevens Wooden Canoes are in the Blood

    I suggest you search "linseed" here. Many believe it feeds mildew.

    JSRIII Curious about Wooden Canoes

    I should have clarified. "Boiled" linseed oil. Raw linseed oil takes weeks to dry and during that time frame could be subject to mildew growth. "Boiled" linseed oil contains drying agents that allow the oil to dry rapidly and is usually dry within 24 hours. These drying agents also can cause difficulty with rags or brushes used during application and can spontaneously combust if not immersed in water so care should be taken.
  6. Todd Bradshaw

    Todd Bradshaw Sailmaker

    Linseed oil (which is flaxseed oil in the health food store) is edible. Adding driers and other chemicals to it to make "boiled" linseed oil (generally no longer actually boiled in the current process) may make it no longer edible for us, but it does not mean that it can not still serve as a food source for rot, whether or not it has dried to the touch. Some of us refuse to use it on anything for that reason as well as its tendency to sometimes turn the wood black. YMMV

    The supposed "breathability" issue is another one which is controversial. The fence around my backyard is totally breathable (old treated lumber), yet after years of the wood getting wet and then "breathing out" the moisture (just the way canoe ribs and planks do, because they actually do get wet in use) something has happened. They apparently breathed out a lot more than just the recently picked up moisture. The boards now feel more like Styrofoam, because a lot of whatever it was that made the boards solid structural wood is now missing. If I wanted to, I could easily kick or punch my way through my fence. I have seen the same thing happen to old canoe ribs and planking - dried out, shrunken and brittle, and caused mostly by water soaking in and "breathing" out.

    I don't know what the best all around answer is, but I think you have to put the drying out dangers on a par with the wet rot ones. Personally, I lean toward sealing the outside of the planks pretty well and preventing most of the water from getting in there in the first place. Varnish or something like multiple coats of Deks Olje #1 (an oil which dries fast and doesn't turn black) would probably be my choice. With more emphasis on keeping what naturally comes inside the wood in there, rather than worrying too much about keeping other stuff out.

    The other potential value to using varnish is that it may help to preserve the varnish on the inside of the canoe's planking. Boat wood which is partially varnished or painted, and partially bare has a tendency to allow water to enter the bare areas, spread toward the other, under the varnish or paint, and often eventually lift them. The result is usually big flakey bubbles of paint or varnish film, which may eventually also be joined by weathered, discolored wood.
  7. OP

    johnmetts Curious about Wooden Canoes

    Thanks to all for the insights. WCHA folks are the best,
  8. pklonowski

    pklonowski Unrepentant Canoeist

    I've been struggling with the varnished interior/oiled exterior for W/C canoes as long as I've been hanging around this forum. While in my 20s, I was "schooled" in cabinetry/furniture building; we built high-end stuff: curved exterior balconies, arched entries, roll top desks, frame & panel walls, fauncy fireplace surrounds, etc. I learned that any finish applied to one side of the wood absolutely must be applied to the other side of the board, to prevent differential expansion situations due to fluctuating humidity.

    Many years later, after I'd left the trade, I started building paddles, and I was faced with the situation of laminating woods for blades, where the woods and grain directions being used were listed in Bruce Hoadley's "Understanding Wood" text as having very different expansion characteristics, due to changes in humidity. Indeed, I found that the laminates that ended up in the grips of my paddles behaved differently over a year's time than the identical laminates (same board, same grain) in the blades... expansion lines became evident after less than one year in the grips, but not the blades... the grips were oiled, the blades were 'glassed & varnished. Some smart guy told me to use laminating epoxy (e.g., West System 205 Resin/207 Hardener; other brands will work fine) as the first finish coat (no 'glass; just epoxy). This seems to have completely eliminated the expansion lines, in the grips.

    What this would seem to indicate is that there may be some advantage to varnishing the exterior of the not yet canvassed canoe, just as you would the interior...

    I'll note that this is theoretical; I have yet to restore a W/C canoe. The 1918/19 Old Town HW in my shop is awaiting my retirement. I'm really curious about this issue, but have no real experience with it. Thoughts of more experienced builders/restorers would be appreciated!
  9. Todd Bradshaw

    Todd Bradshaw Sailmaker

    One thing that I find interesting is that I really doubt that the early builders who basically developed and, at least to some extent, standardized wood/canvas canoe construction probably had no intention to build a boat which might last 80-100 years or more. Making one which could be restored in the next century and still look good enough to be put on display probably wasn't high on their list of priorities. I don't know for sure, but I suspect that the intended lifespan was more along the lines of maybe 25 years with good care. That might allow the elimination of some of the preservative steps practiced on other types of wooden boats - things like bedding all wood to wood joints and certain rot and water resistant wood treatments.
  10. Dave Osborn

    Dave Osborn LIFE MEMBER

    I oiled my first restoration and have varnished close to 150 hulls since.
  11. Just1moredave

    Just1moredave Enthusiastic about Wooden Canoes

    This may seem obvious, but if you varnish, make sure you chase down any drips or runs before installing canvas. DAMHIKT.

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