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Kayak and Canoe Design Bulletin Board
waterproofing an antique kayak
Posted By: Paul Jacobson In Response To: Antique kayak (Billy Bob)
Date: Monday, 19 July 1999, at 1:07 a.m.
> I own an antique kayak that is made of canvas. I wish to make it
> water-tight again. What should I use on the canvas to do this?> Thank you
> Billy Bob
Gee, there are lots of materials you can use. A lot depends on the condition of the canvas and whether you are planning ot use this boat for recreational purposes, or if you want to preserve it for museum display.
If this is really an antique you might not want to do anything to it. Some artifacts are best `preserved`, and not `restored'. In this case you don't paddle it, you conserve it as an investment, and hopefully sell it for a small fortune at some time in the future, (keep dreaming about that fortune) or you donate it to a museum and take a tax writeoff.
If this is just an old boat, and you want to make it waterproof so that it can be paddled again, go over the skin very carefully to see if there are any weak areas. If the canvas has deteriorated during the years then it would be better to replace it with new canvas. There is no simple process that can restore the strength to old canvas, so even if you made it watertight, it would be fragile and rip easily. This is of course a `worst case scenario'. Klepper's old fabric hulls had a reputed life span of over 25 years if they were stored well. Yours might be in good shape, too.
Next, if your boat was commercially made you might want to try to find the manufacturer and either get a replacement skin (already waterproofed) or ask about the process they used originally, and whether they supply materials for repair.
If the boat was privately made then you might try to figure out what was originally used and duplicate that.
If all else fails you can try applying your own waterproof coating and hope that it will adhere. Without the benefit of any analysis of the current coating there is no way of knowing in advance what would be compatible, but you can try something in a small area, and if it doesn't stick, try something else.
The list of possible coatings ( by no means complete):
Thompson's Waterseal, a commercial waterproofing compound for decks used to list canvas as one of the materials it could be used on. The last can I looked at no longer lists canvas, and I don't know why this was dropped. ( A wild guess would be that people used it on tents, and the coating was not flameproof, so they quit promoting this use) A gallon can is about $10 at almost any hardware store. Ace and True Value and other hardware stores may have a generic or house brand of a similar material for a few dollars less.
Paraffin, a solid wax used for making candles, and sealing jars of jelly, can be dissolved in gasoline or naptha and painted on. The solvent soaks into the fabric, dragging wax with it, and evaporates leaving the wax behind. A simple home made process that was popular a while ago, but a VERY dangerous process. Nonetheless, it is possible that this was used on your boat. You will be able to see and feel the waxy nature of the fabric if this was the original process. If you try to repair it with the same materials, be very careful. Mix very small quantities of solvent and wax. Work outside, away from buildings and trees. Keep TWO dry chemical fire extinguishers handy. Wear a respirator, and only do a small area of the boat at any time. Don't smoke and stay away from sparks.
Paint: Most any oil based paint will do a good job of waterproofing canvas. If the original skin looks like it has been painted, put on another coat of paint. Lightly sand the original base. The new paint will seep through any hairline cracks in the old layers and provide a nice flexible layer.
Some people use urethane, polyurethane and epoxy base paints. Others use latex porch and deck enamels. Whether a coat of paint will stick has a lot ot do with the nature of whatever is already on there. If you have no idea about the current coating then trial and error may be your only course.
Thre are paints sold at boat shops for painting and recoating the huls of inflatable boats. They seem to bond well to the rubber or plastic materials that these boats are built from. You might want to look at these products.
Roof coatings: Old boats (going back centuries) covered their hulls with tar to keep out the water. Native Americans used it to seal the seams on their birchbark canoes. About the only use for tar these days is for paving material and roofing material. As a roofing material it is easily found at most hardware stores. Tar is a mess to work with, and the boat is rather ugly if you cover it with tar. I do not recommend it. There are some elastomeric rubber roof coatings that are now on the market (Snow Roof or Snow Cote) which will provide a strong, UV stable, watertight coating. I'm using this on a kayak I'm currently building. Samples of the material I saw at the store were thick and strong. I put on three thin coats (about 1/2 gallon) and I think that should do, although I may just put on a few more coats for good measure, and to use up the rest of the gallon.
liquid vinyls: You can get vinyl based paints and inks designed for screenprinting at art supply stores. These are called Plastisol inks, and they are used for printing T shirts, among other things. The come in a lot of colors. Most of these need a few minutes of high temperatures to cure properly. In a screen printing operation this high-temperature heat is usually supplied by passing the printed garment in front of heat lamps for several minutes. You could make an array of heat lamps and slowly move it around the kayak to cure the ink, if you went this route.
Liquid rubbers, natural and synthetic: Natural rubber, or liquid latex can be found at art supply stores where it is sold as a modeling compound for making molds for plaster casts. It can also be found at theatrical supply stores, and partygood stores around Halloween as it is used for making masks and disguises. I understand that ``adult toy'' stores also sell liquid latex. (Don't ask me how or why it is used as I am not sure, but the impression I get is that it is used for something kinky. If you told them it was for a boat they would probably grin and think ``Yeah, right''). You can brush on liquid latex and let the liquid evaporate, leaving behind a thin layer of pure rubber. I understand that a bit of ammonia will cause the latex to coagulate or polymerize. Heating with sulphur will cause the stuff to vulcanize.
Synthetic rubber compounds include silicones, neoprene and Hypalon. Hypalon is really tough stuff used commercially to cover the fabric used in whitewater rafts, and chemically related to neoprene. You can get gallon cans of the stuff through George Dyson, the author of a book on Baidarkas ( a type of Kayak). I don't have his e-mail address handy, but if you look for a Baidarka builders group online you should be able to get it through them. He also sells liquid neoprene. If you want small quantites of liquid neoprene you can try getting it at a SCUBA diving supply store, where it is usually available and sold for repairing wet suits. You can find some silicone compounds that might be suitable at art supply stores. I've never played with them, but these are also used for making molds for plaster casting. They come as two part mixes that seem to set up rather quickly, so I guess you would want to do small batches and apply them to small areas as fast as possible. They would cure into flexible and durable rubber coatings. Other silicone materials you might try would be one-part silicone caulking materials, such as used for automotive or bathroom tub sealing applications. Try applying them with a squeegee or a trowel. I don't know of anyone who has tried these things on a kayak, though. If you try one of these silicones let me know how it works, or if it works.
Urethane: Campmor and other camping supply stores sell a liquid urethane material for recoating the floors of tents to restore the waterproofing. This is a urethane compound which is milky to clear, water thin, and can be brushed on with a cheap brush. You can use this on the ``wrong'' side of the fabric as it will soak into the fibers, bonding tightly. If your current kayak skin has the waterproof coating on the outside you might try this on the inside. This would preserve the look of the boat. The problem would be getting at all the recessess of the inside of the boat. The far ends tend to be confined and hard to reach. Urethane treated nylon is frequently used for less-expensive waterproof garments, like raincoats and ski jackets. ( the more expensive ones are made from Goretex or have some fancy ``breathable'' coating on them) A pint of this stuff should be under $10.
There are probably several (many) other things on the market that would work, but these are the ones I know about. Hopefully one of them will work for you.
Best of luck in your project.
Paul G. Jacobson
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