On Canvas, epoxy, and filler

[nmerrill]

Let me start by saying that I am new to the Canvas Wood Canoe world.
I recently acquired "The Book", and have read archives of this list for a while, but if there is some post out there that answers these questions, please point me to it!
I'm just curious about a few things....

So, the recent discourse in the Cecofil et al. project by Mike got me thinking about epoxy and glass (blame Todd). I understand that "Glassed" boats are a horror for several reasons, however, I still wonder about a few alternative ideas...
It seems that epoxy is really a superior "filler" compared to that used typically - or if not a filler, a finish. From what I have read, it seems that epoxy is frowned on due to bondage to the wood (expansion/contraction issues) and makes future recovering a nightmare. But it is harder, and rot proof - and makes what ever fabric it is impregnated into rot proof.

What if the bondage to the wood was eliminated? Seems that a coating of some sort (mould release solution) or an under layer, like a thin heat shrink material (window plastic?), could be used to keep the epoxy off the wood.

Additionally, once you are talking about using epoxy, why stick with canvas? Canvas is prone to soaking up water, and prone to rotting. Also, I suspect that canvas would use way to much epoxy to wet out, and result in an overly expensive and heavy boat. Why not use a light glass cloth or other suitable cloth? Does epoxy interact favorably with Dacron? Would Dacron impregnated with epoxy still exhibit explosive tearing?

As for flexibility, in my experience, thin layers of glass and epoxy are very flexible and resilient, though I am sure that certain epoxies are better than others.

I suppose that a thin layer of epoxied fabric might show some imperfections of the hull that a filled canvas wouldn't. A suitable underlayer might help there though.

BTW, I think that traditional materials are warranted in some/many situations!

Someone must have been here before...
What am I missing?

Nathaniel
Vermonter planning a spring canvas project

 

[Blue Viking]

First....Let me answer your primary question....Are you looking to make a canoe float or are you planning on a canvas restoration?....If you are just trying to get a thing that will float on the water, then by all means try anything you want....BUT...If you are restoring...RESTORING!...Then the primary object of your project should be to rebuild in the manner that it was originally made.... There are easier softer ways, but those who came before us, or are among us still, believe in the theory of how themasters made them did so by trial and error a long time ago and came up with a canoe that they felt could survive all the hardest use. have you ever seen an aluminum or "plastic" canoe that went through some white water or rapids? Most are either smashed to smithereens or damaged beyond repair...Wood and canvas is supposed to be flexible to survive that...

Well!...I have said my piece about using other stuff...Tom McKenzie has developed some materials that are a little more on the modern side but they keep to the basics....If your from vermont, maybe you should plan a weekend trip and head on up to Maine and meet Rollin Thurlow and see how a master constructs and restores... Just to walk in and see a masters shop is an experience in itself.

Good luck, I wish you well, and I am sure you will get some responses to your questions that will address you issues.

"Life is not detrmined by how many strokes of the paddle it takes to get there, but rather in the JOY of the journey"...(BlueViking)/B]

 

[peter osberg]

I agree with your logic, which is why I have posted a routine that uses a non-adherant layer, layered dacron, and epoxy filler sequence. The explosive tearing concept is more applicable concern with a canvas cover than dacron one, though it is firmly lodged in some people's minds, and is not an issue with the routine I described. peter

 

[Todd Bradshaw]

It's sure lodged in my mind. Maybe that's because I used to test Dacron for it under the guidelines of the FAA as part of my employment and have seen plenty of it - or the fact that I can take a piece of brand new 10 oz. Dacron with a small slit in it's edge, give it one sharp tug and split it right down the middle. The fact that you even mention canvas in the same sentence indicates very clearly that you don't understand what explosive tearing is. It would actually be quite difficult to find a non-spandex woven fabric, synthetic or natural, that is less prone to explosive tearing than cotton canvas is. Cotton can certainly be torn, but explosive tearing is a specific term and requires specific mechanical properties to even take place. Cotton canvas does not fit those parameters

And no, epoxy-coating Dacron will not stop or lessen the possibilities of explosive tearing. It actually makes it more probable by limiting the amount that the yarns can move relative to each other, further concentrating the strain on one yarn at a time. Don't get me wrong, I really love Dacron. I use hundreds of yards of it every year and have for over two decades. If you need abrasion resistance, U.V. resistance or dimensional stability under a load, it's one of the best fabrics available, but in terms of tear strength the same properties which yield that stability reduce tear strength as they do so.

The Dacron which interests me the most for possible canoe covering is Oceanus sailcloth, which was built to mimic cotton canvas. It's a combination of both spun fibers and continuous fibers. This type of yarn construction and the subsequent weaving of it builds a certain amount of "cushion" or potential elasticity into the cloth which normal, thin, hard Dacron doesn't have. Even though the yarns themselves will have similar limited stretchability, the twist and the up and down path that they take during the weaving process will build a bit of slack into the fabric. The idea of something very similar to a cotton canvas canoe skin that is far, far less prone to absorbing moisture , rot proof and though it might support mildew and mold, immune to being eaten by them is pretty interesting.

I suppose one could lay up a non-connected fiberglass skin, but I'm not sure it's worth the trouble. You would need a barrier layer, both to prevent sticking and because fiberglass doesn't bridge cracks between planks or tack head dents very well without some sort of solid backing (comes out like screenwire over the gaps, and filling the little holes is a real pain). Fiberglass isn't really resin-saturated fabric as much as it is fiber-reinforced resin - and there is a difference. Trying to make a thin, light, stand-alone waterproof layer would probably require multiple layers of very light (maybe 3 oz.) finely-woven cloth. You want maximum fiber and a minimum of unsupported resin in the mixture, so most standard weights of cloth are most likely too coarse to do a good job without a hull to stick to. I think that by the time you finally got the boat done the traditional and more common alternative methods would be looking awfully good.

Blue Viking - I hate to be the bearer of bad news, but if you'll spend a weekend at any popular whitewater stream you'll see plenty of plastic and/or fiberglass composite boats surviving impacts and abrasion that would absolutely destroy a wooden canoe. I really believe that the whole sport of whitewater paddling has changed drastically during the past 50 years. As it was taught to me, one was supposed to avoid the rocks and the damage that they could do to your boat. The fiberglass boats of the 1970's and '80's showed that they could take more punishment, but could still be holed if you really hit something. These days, the plastic boats will really take a beating and it's almost as if avoiding rocks is purely optional.

 

[Blue Viking]

Sorry if I am a tradionalist, but in my personal opinion, it is not a restoration, especially if it is an antique, if sustitute materials are used. I believe that if Old Town built it with canvas and used a tradional filler, then you are building a canoe and not doing a restoration if you use substitute materials.........Thats just my persoanal opinion but then......thats why I am a canoe NUT! [/B][/B]

 

[nmerrill]

Blue Viking, I fully understand your line of thought - I own an antique motorcycle and road racing bikes that I strive for original with all work I do on them.
I am about to fix an Old Town and will likely do it as a *restoration* - besides leaving the sailing rig that it came with on it - that was not original.
That said, not all boats are rare, nor particularly special, and an alternative covering might not be anymore permanent than canvas - if done correctly.
BTW, are you sure that the old timers wouldn't have used something else -if a better option existed at the time? Of course they would - But then that is irrelevant for a *restoration*, I agree.


Todd, that is exactly what I was envisioning when thinking about this. The backing layer could be a heat shrink plastic (or Dacron). And yes, several layers of fine and light cloth - or even Kevlar! Considering the wood backing, I'm not sure that "multiple" layers would be required, though. And I don't see why you could not "vacuum bag" an entire canoe to help maximize the resin to cloth ratio.
I suppose experimentation would tell.
Obviously, the exercise may be more trouble than it is worth. But then, experiments are what produce progress.


Peter, I recall something about this - did you use plastic wrap as the under layer? I'll have to find your post on the Dacron/epoxy project and look again. I was thinking about the heat shrink window plastic that is used to seal drafty windows in the winter- I have seen rolls of it that are cut to fit for large windows. Seems like that would be an ideal layer.

 

[peter osberg]

On new covers I have used saran wrap as a layer,(to prevent adhesion) as it adds negligible weight.
I firmly believe that a wood and fabric canoe is more durable because virtually any damage can be field repaired, exceeding the survivability (personal experience) of fiberglass, plastic, or aluminum. A requirement I have had to appreciate.
peter