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PostPosted: July 14th, 2018, 8:33 am 
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Location: n/e ontario
A quiet solo paddle this morning, I was distracted and ran over a sharp rock that put a 3 inch tear in the canvas on the bottom of the canoe. How do I fix this... long term.


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PostPosted: July 15th, 2018, 5:55 am 
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This reply from Pam Wedd of Bearwood Canoes near Parry Sound:

Oh, too bad about the rip. Yes you can fix it. I make little cuts at both ends, at right angles from the cut, so that it makes a very side but short H. did that make sense? The you can open the cut up a bit, gently and put a piece of canvas underneath. The little side cuts just let’s you open it up a bit to work the canvas inside. Now, the best stuff you can use is called Ambroid, but not sure if you can get it anymore. It is model airplane glue. You just work a bunch in to the patch and the backside of the old canvas and then push the flaps down and tape it closed. Sometimes that is good enough, sometimes I fill the cut with epoxy thickened with some micro balloons, sometime I sand the paint hard and put a patch on the outside too.
If you can’t find Ambroid glue then you could try contact cement - just put it on like the ambroid, not like you normally do contact cement - put it on, lots to soak in to the canvas then push it together.. I guess you could use epoxy too.


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PostPosted: July 15th, 2018, 8:39 am 
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Part of the care she takes is not to glue any canvas to the filler as when its recanvas time the canvas will just stick doggedly and perhaps pull out some wood splinters. My friend ( a cohort of Pam's) used to use duct tape and sand off the shiny and paint over.


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PostPosted: July 15th, 2018, 12:34 pm 
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Ambroid is no longer made. It was designed for use with canoes. There's a contact cement type glue available in every hardware store that works quite well. It's called Seal-All and is available in small tubes. The cloth patch can be put on the surface instead of inserted beneath the existing canvas. In that case, fray the edges of the patch about 1/4". That will taper the patch a bit and it will be stronger as a result. An alternative is to use pipe lagging compound such as this one: https://ca.henry.com/roofing/hvac-coati ... ng-coating You paint on a coat of the compound, embed the patch and cover it once, at least, with more compound. Three or four coats will make the patch invisible. This material is dead simple to work with, dries fast and contains nothing toxic or even unpleasant to be around.


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PostPosted: July 16th, 2018, 6:29 am 
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You might want to put a barrier under the patch of canvas to ensure that won't stick to the wood. I'd use a bit of the stretchy food wrap stuff from the kitchen on the wood, then put the canvas patch on it. That way nothing will bond if whatever you use to glue it soaks through the canvas.


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PostPosted: July 16th, 2018, 6:44 am 
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Quite right


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PostPosted: July 16th, 2018, 8:04 am 
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Ambroid used to be used for model airplanes as well... this is the alternate now according to the modeler boards.

https://sigmfg.com/products/sig-sig-ment

Something tells me that ambroid was used in the old days because there wasn't the choice there is now. IIRC it was celluloid dissolved in acetone... maybe something more added since it was more expensive than the cheaper acetone-based glues.

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PostPosted: July 16th, 2018, 8:26 am 
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Well, there was more to it... it seems there was an aircraft grade Ambroid and I remember it was more flexible than the cheap stuff. All you could ever want to know about Ambroid in the thread below. Duco may be another alternative.

Quote:
Ambroid has only three organic solvents in it. They are ALL hygroscopic. Acetone and Isopropanol are two of them. I got the MSDS from the manufacturer of this Nitrocellulose cement. What makes Ambroid work so well in comparison to other solvent cements , on wood, is that it will absorb the water in wood and will therefore penetrate deeper than the others. Also it is strong, hard but not brittle. One irony of nitrocellulose is that it is in fact more flammable when dry than when it is in solvent form. The material solid, is in fact stored in Isopropanol to reduce its combustion properties. Go figure. This is the main reason the cement actually contains Isopropanol. The other sweet part is that it can be plasticized very easily with vegetable oils. At this point it shrinks a lot less and flows better. When I thin it out to make a coating, depending on what I am putting it on and how quickly I want it to dry and also how I am applying it, the main solvents I use are Acetone (never MEK), Glycol Ether, Butyl Alcohol and Toluene, This really reduces shrinkage and allows easy application even with an airbrush. Unfortunately, once you use Toluene and Butyl Alcohol, it becomes no longer hygroscopic (nether of these two solvents are) and can blush while drying. It also reduces the adhesive properties of the "dope" from its original state. For the average person, Acetone is going to be the only viable solvent for Nitrocellulose. The main difference between Nitrate and Butyrate dope is that Nitrate thinners contain Acetone and Butyrate thinners contain MEK. Unfortunately the average hardware store thinner contains both of these. Also Nitrate thinner contains Toluene while Butyrate contains Xylene. The HW store kind contains both plus petroleum distillates. This is a NO NO for any aviation grade dope thinner. This really reduces adhesive properties but aids in flow characteristics.


https://www.rcgroups.com/forums/showthr ... glue/page7

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PostPosted: July 29th, 2018, 7:09 pm 
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RonB wrote:
Ambroid is no longer made. It was designed for use with canoes. There's a contact cement type glue available in every hardware store that works quite well. It's called Seal-All and is available in small tubes. The cloth patch can be put on the surface instead of inserted beneath the existing canvas. In that case, fray the edges of the patch about 1/4". That will taper the patch a bit and it will be stronger as a result. An alternative is to use pipe lagging compound such as this one: https://ca.henry.com/roofing/hvac-coati ... ng-coating You paint on a coat of the compound, embed the patch and cover it once, at least, with more compound. Three or four coats will make the patch invisible. This material is dead simple to work with, dries fast and contains nothing toxic or even unpleasant to be around.


We'll work on buddy's canoe right after we finished installing the new rack and undercover tonneau covers for kayak mount on his truck. There are three 2ish-inches tears on the canoe he bought used. The Seal-All seems a good one to try.


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