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#1
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Canoe rebuilt with Epoxy
covering with glass fibre and resin adds weight faster than strength. one method of recovering canvas is to use heat shrink dacron. Platt Monfort has an inexpensive booklet of instructions at www.gaboats.com. you'd have to replace any bad wood for strenght but you don't have to stretch the dacron or fill it like you do the canvas. I don't know about making up your own ribs as they are usually half round to save weight. (You could try the oak trim at your local home improvement store if its not full of finger joints.) -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or its returned |
#2
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Canoe rebuilt with Epoxy
I have used the heat shrink Dacron to make a 14 pound canoe of Platt
Monfort's design - for that purpose it works great. It's really strong - for a 14 pound canoe. However, I don't think it's going to work out so great for an 80 pound Old Town. The heaviest Dacron I can find is 1.9 ounces/sq.yard - way lighter than the 6 ounces per yard glass you would probably use for a canoe or the 13-14 oz/yard that #10 canvas duck weighs. (Many people, myself included, use 2 layers of the 6 oz glass on a canoe bottom). Of course I'm comparing apples to oranges to grapes - these are 3 different fabrics with different properties and they are used with different coatings which may be as important as the fabric itself, but my point is: the Dacron is in a different weight class than the glass and canvas fabrics typically used for traditional canoe construction. I believe the main function of the fabric covering on a wood canvas canoe is to make the hull water proof and provide abrasion resistance and increase impact resistance. The way I waterproofed the 1.9oz Dacron was by simply varnishing it - doesn't add much weight, but it doesn't add much abrasion resistance, either, at least not to the degree that 2 layers of 6 oz glass in epoxy will, and not to the degree that #10 duck canvas properly filled with a good hard filler will. There are other coatings used on the Dacron and you could add 2 or 3 layers, but I think you would have to agree, in the context of the Old Town, using the Dacron would be experimental. Has anybody actually tried this? I'm curious to learn what you mean by: covering with glass fibre and resin adds weight faster than strength There are many kinds of 'strength' - impact resistance, tensile strength, puncture resistance, etc. I prepared test panels and dropped a 46 ounce window weight on them from various heights. The damage I saw from a 4 inch drop on a panel with epoxy, no glass, was about the same as from 16 inch drop on a panel with the same amount of epoxy, but 1 layer of 6 oz/yd glass. Judging the damage was somewhat subjective - I measured the diameter of the craters and looked for hairline cracks. I know from weighing a 14 ft canoe before and after glassing the interior that one layer of 6 oz in epoxy added 3 pounds to a canoe which weighed 48 lbs, completely finished. So it would appear that a 6.7 percent increase in weight added a 300 percent increase in impact resistance. This assumes the impact force has a linear relationship to the height of the drop - I don't know enough physics be sure this assumption is valid, but I'm guessing if it's not linear then it's MORE than linear, so my assumption is probably conservative. -- Gary Wright you can see the 48 pound canoe at: http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3617885338 ___________________________________________ In article , (William R. Watt) wrote: covering with glass fibre and resin adds weight faster than strength. one method of recovering canvas is to use heat shrink dacron. Platt Monfort has an inexpensive booklet of instructions at www.gaboats.com. you'd have to replace any bad wood for strenght but you don't have to stretch the dacron or fill it like you do the canvas. I don't know about making up your own ribs as they are usually half round to save weight. (You could try the oak trim at your local home improvement store if its not full of finger joints.) -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or its returned |
#3
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Canoe rebuilt with Epoxy
"Gary Wright" ) writes: Has anybody actually tried this? yes. don't know how many but I heard last year about one shop locally that's doing it. I have no info on how durable it is. Monfort's frames are flexible. The skin has to work with the boat. The skin does not have continuous backup so is subject to puncture. I don't know how well it holds up to abraision on his boats. I imagine any abraision would be concentrated where the skin covers the stringers? On a cedar planked canoe the abraisive action would be spread out over the surface. Dacron on a cedar planked, oak ribbed canoe would just be there to keep out the water - resist moisture and resist abraision. I'd assume it would perform better than on the open framed boats. But hey, ideally a boat never touches anything but water. I'm curious to learn what you mean by: covering with glass fibre and resin adds weight faster than strength There are many kinds of 'strength' - impact resistance, tensile strength, puncture resistance, etc. in this case, the original subject of the thread, it was structural, ie. glassing over the hull (exterior only) instead of replacing cracked and broken wood. fibreglassing a heavy "plank and rib" canoe for structural strength is going to make quite a heavy boat. I haven't done the actual calculations. However if enough epoxy is put on to provide the structural strength then the cedar won't soak up water so there will be some weight savings there over the season. canvas won't provide the structural strength (rigidity) which is what the poster was looking for. the damaged wood would be replaced first before covering with canvas or dacron. I too would like to hear more from people who have used dacron. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or its returned |
#4
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Canoe rebuilt with Epoxy
On Sat, 19 Jul 2003 02:50:23 GMT, "Gary Wright"
wrote: I have used the heat shrink Dacron to make a 14 pound canoe of Platt Monfort's design -///The heaviest Dacron I can find is 1.9 ounces/sq.yard - way lighter than the 6 ounces per yard glass you would probably use for a canoe or the 13-14 oz/yard that #10 canvas duck weighs. ///using the Dacron would be experimental. Has anybody actually tried this? /// Gary Wright you can see the 48 pound canoe at: http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3617885338 Your mention of 'experimental' reminds me that 1.9 oz polyester is a standard covering these days for light aircraft. It needs special goo for gluing to ribs, and paint cover - but works well in that milieu. Brian Whatcott Altus OK |
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