Cedar Strip Canvas canoe waterproofing recipe

Discussion in 'Wooden Boat Building and Restoration' started by pinecreek, Dec 7, 2013.

  1. pinecreek
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    Location: kawartha lakes ontario

    pinecreek New Member

    Hi, I have recently bought an old canvas covered cedar strip canoe that needs re canvassing. Shes pretty weather cracked , so i am gonna tackle it this winter. I am fairly familiar with the process I just cant seem to find the "traditional" water proofing recipe anywhere...I know for sure that it includes white lead, calcium carbonate , linseed oil and maybe a couple of other ingredients. I had it written down years ago but lost it. Any one know what I am talking about? I am open to new ways of sealing too, just want to keep it original. Thanks, Syd
     
  2. hoytedow
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    hoytedow Wood Butcher

    I think there were more than one "traditional" covering methods, not all of them containing white lead. They would have varied regionally according to what sealants were available, usually varnish or paint, whether made in one's own workshop or bought at the general store.
     
  3. lewisboats
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    lewisboats Obsessed Member

    A couple of coats of oil based paint works well on Skin on Frame, I don't see why it wouldn't work just as well on canvas. It might take an additional coat or 2 due to it soaking in but....
     
  4. PAR
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    PAR Yacht Designer/Builder

    As mentioned, there are lots of formulations and concoctions, some better then others. With modern materials, you'd be best advised to paint the hull (two full coats) with a good quality alkyd paint (high gloss). Scuff the paint when cured and apply the fabric pieces (dry) stretching them out and tack along the edges (deck, keel, etc.). Next wet the canvas with warm water (it'll shrink a bit). Let this dry and apply a protective paint coat (more oil base) over the canvas. The initial coat of paint should be thinned a bit, no more then 15%, but subsequent coats right out of the can. A touch of Japan drier is helpful in the first coat.

    The canvas should be preshrunk cotton duck. White lead is still available from Kerby Paints. Canvas sheathings have to be religiously maintained or they rot and can cause the wood beneath to rot as well. The paint coating needs to be well cared for, kept intact and of sufficient film thickness. These sheathing techniques are "quaint" but not very effective, having been supplanted with more modern techniques and materials. If a decorative piece (the canoe), then this technique is fine, but it'll see more than occasional use, the modern skipper isn't usually prepared for the effort it takes to keep one of these in good shape.
     
  5. DCockey
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    DCockey Senior Member

  6. Petros
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    Petros Senior Member

    I have built a number of skin on frame hulls, which have similar issues, I have used a number of sealants. Unless you are making a museum pace and want it "authentic" I see no reason to use obsolete coatings. I have used cotton canvas with linseed oil mixtures, or oil based paint. these are traditional for canvas hulls, but as you can see the oil continues to shrink as it ages, and get brittle as it ages, so it eventually cracks and even falls off. the most durable combination is either heavy nylon or polyester fabric (8 to 10 oz/sq yd) with oil based polyurethane floor finish, 4 coats min to fill the weave. You can also add pigment to the finish if you want color or add two coats of pigmented oil based paint. As it ages you can add another coat or two every other year or so. this costs about the same as canvas and linseed oil mixture and will last twice as long and weights a bit less too.
     
  7. rwatson
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    rwatson Senior Member

    Yes, thats the way to go. It beats all the old canvas techniques.

    There are a number of 'destruction tests' of ballistic nylon on youtube, that demonstrate just how tough SOF can be, and give lots of confidence around underwater obstructions
     
  8. Petros
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    Petros Senior Member

    there is even a better finish, two part polyethylene floor finish. It is very tough and durable, the problem is it is highly toxic and very costly because of shipping costs. so I prefer the single part oil based polyurethane finish which you can buy at any big box store.
     
  9. upchurchmr
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    upchurchmr Senior Member

    Petros,

    What is the product name of the mysterious 2 part polyethylene floor finish?
     
  10. Petros
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    Petros Senior Member

    Never heard of that stuff! that should read two part polyurethane. that is a typo caused by the spell checker.

    I was just seeing if you were paying attention.
     
  11. upchurchmr
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    upchurchmr Senior Member

    Petros,

    I was hoping you were pointing out another option.
    I'm really not happy with any of the paint I have been using. Takes too long to dry hard.
     
  12. Petros
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    Petros Senior Member

    now that you mention it I had been contemplating a skin-on-frame option where you would take a lot of plastic milk cartons and melt them in a big pot and than spread it on the hull fabric with a squeegee. It was for a boat building contest I do in Seattle on the 4th of july weekend. Both judges and the locals all vote on various aspects of the different home built boats, and it seems going "green" or using recycled materials is popular with many of them.

    the one part oil based polyurethane floor finish seems to cure over night good enough to take in the water if done in a fairly warm environment. The water base cures a bit faster but I do not think it is as durable, and if it is damp or humid (which it is around here most of the year) it cures a milky white color rather than clear.
     
  13. hoytedow
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    hoytedow Wood Butcher

    I repaired a cracked shop vacuum bucket with a milk carton by cutting it into a sheet and melting it on with a Wagner heat gun. It was very easy and left no mess. No pot was required.
     

  14. hoytedow
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    hoytedow Wood Butcher

    Polyfilm can be shaped the same way.
     
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