Light canvas/filler options?

Rob H.

Curious about Wooden Canoes
I have only used traditional canvas/filler, but am considering restoring a canoe for a man who wants it to be lighter: "Whatever you have to do," he said. The canoe is currently 18 feet, fiberglassed, and too heavy for him to consider it usable. Since cuting out the middle three feet and sticking the ends back together seems unreasonable, I thought looking for lighter "canvasing" material might be a better idea.

Any suggestions?

Rob H.
 
I would suggest finding a much smaller canoe and covering it with dacron. The lightest canoe that I have ever paddled was a wooden frame covered with clear plastic that Tim Hewitt made at a WCHA Assembly many years ago.

Benson
 
"Clear plastic skin over canoe stringers/form"

Wow! I am considering throwing some time into a clear plastic skin on a touring kayak I've built. It normally is covered with 6 to 10 oz canvas, then airplane doped to stretch and seal, then enamel painted to protect and waterproof. I was considering plastic just for fun and also to see how light I could build it while realizing the fragility of it all...
If Tim Hewett could explain how he did it, that would be a great help.
I have also considered using a heat shrink plastic (as used in large boat storage) for the skin due to the anticipated problem of plastic not having a thread pattern "bias" which enables canvas to stretch and form around curves.
 
How to skin a cat or a canoe:

Dacron is able to make for a lighter canoe, yes. Number 12 canvas will too but to a lesser extent. But maybe try to look at the problem from a different angle. How about a small cart? how about a type of roof rack that allows you to load one end and then the other. Maybe by doing things a little diferently you can still enjoy the canoe without major changes to the canoe itself. I built a simple cart from scraps and a couple of wheels. It allows a small woman to move a canoe around easily. For portages that do not allow a cart, how about taking a young, strong protege'? there's more than one way to skin a cat.
 
Randy Johnson said:
If Tim Hewett could explain how he did it, that would be a great help.

Tim has been very busy recently and hasn't posted a message here in many months. My recollection is that heat shrink plastic was used although it may have been ordinary construction or vapor barrier plastic. The experience of watching a canoe move through the water from the inside was very strange.

Benson
 
Light canvas/filler options

Thank you gentlemen for the comments. I'd like to read some information about how to/how not apply the Dacron. Suggestions?

Any idea about what an 87 lb. wood/canvas might weigh if it became wood/dacron?

I will also explore the possibility of different loading and carrying options which might make the canoe usable for the owner. Great suggestions.

It's really too nice of a canoe to put back in a barn.

Rob
 
Pam Wedd has used dacon successfully for a number of years. I spoke to her about it at the Assembly. She applies the dacron in the same manner as canvas and uses a latex filler which is much lighter than tradtional filler. I saw several of her canoes done in this way. They looked beautiful. Her personal canoe was done in this way. She pointed out that after a number of years of service, the main diffenence is that it does not protect the wood as filled canvas does. If you scrape on underwater obstructions it leaves pressure groves in the planking. Given that, after a good many years use, her personal conoe still looked great. There is indeed a very substantial savings in weight. I also recall that a canoe was recovered and filled using dacron and latex filler at the 2004 Assembly. Perhaps someone who was involved in that project could add some input. Sorry, but I did not get the details as to what weight dacron was used and exactly what kind of latex primer filler was used. It looked like plain old gray latex primer. I suspect the dacron could be purchased from a sailmaker supply.
 
The Old Town Canoe Company catalogs between 1966 and 1974 listed a 15 foot canoe covered with dacron and known as the featherweight. The weight was 46 pounds while the identical lightweight model with a light canvas covering was 58 pounds. Their 18 foot Guide's model with heavy canvas was 85 pounds for comparison. I would guess that the weight savings with dacron on your canoe would only be about 15 pounds.

My solution to the heavy canoe problem is an old snowmobile trailer. This also doubles as a temporary dock if the edge of the pond is marshy and a real dock is not available. Good luck,

Benson
 
Thanks Andy and Benson for the comments. I'll have to pass this on to the owner and get his input.

Rob
 
Aircraft Spruce carries both certified Cetex (sp), another certified dacron and uncertified dacron, the uncertified stuff goes for about 5/yd if I remember correctly. They also carry several different filler materials and offer installation books/guides. These are all offered for aircraft but if the methods are proven and certified for aircraft, they likely will work on a canoe also.

I would be interested in knowing what and where the material can be found that was used at the 2004 Assy. I plan to do a few test panels and then a canoe.

Dan
 
I am wondering about fillers and which dacron to use. I checked the Aircraft Spruce site. Their dacron is predictabley very light weight maxing out at about 3 oz. I checked a sailmaker supply. They sell dacron in the 10 oz. plus range, but it is expensive - about $30 a yard. They sell it in 54" widths. I suspect the sail cloth might be more suitable for canoes.

That leaves the question of fillers. I believe the filler used at the 2004 Assembly was some sort of aircraft dope. Unless my memory fails me I think it smelled like lacquer. It was gray in color and appeared to have substantial solids in it. I should have asked more questions, but at the time I wasn't as interested in dacron as I am now.

Has anyone out there had any experience with using dacron? The weight difference makes it very tempting to try.
 
Andy,

I thought that AS sold a 4.3 oz, in addition to the 2 lighter weights.

As for the filler, there is (for aircraft) 2 different types (materials) that they use, and per the installation instructions I got, one has to be used 1st to "wet" the fabric, as the other doesn't stick to it, and then the 2ed is used to finish the "fill". With aircraft, only the 1st coat is brushed on, they spray all the rest. (I'm not going to do this.)

Within the filler tyes, each can be had in 2 versions, a shrinking and non-shrinking mix, they recommend using the non-shrinking. They say to apply the fabric and heat it using a calibrated iron at a specific temp to get the fabric tight. Then don't tighten it any farther as it may fail.

I got samples of the 4.3 oz to make tst panels, then the canoe. I'll probably use the non-certified fabric as it's cheep and then the prescribed dopes.

Also, the dopes all come in several colors to help know when it's all uniformly covered. Not sure if that's needed/important for canoes though.

Note, that all this info is from reading the catalog and instruction manual, and not personal experience so take it for what little it's worth. :)

Dan
 
Dan,

Thanks for the info. I believe you are correct about the weights of dacron AS sells. The dacron sold for sails is much heavier. You can check it out at http://www.sailrite.com/

As an old model airplane builder, I'm familiar with the butyrate laquers they use on real airplanes.They would probably make for a beautiful finish on a canoe, but might be on the brittle side when compared to oil base paints such as Kirby. Synthetic coverings were not available in my day, but my nephews tell me that heat shrinking synthetics are in common use on models today.

I'm really curious about the results of your test panels and I'd sure appreciate it if you keep us posted. To add to the quandry, I'm 90% certain that Pam told me she uses a latex primer as a filler. It might be interesting to include a test panel of latex.

I live near a small airport and I believe they do aircraft refinishing there. I'll poke around there and see what I can learn and pass it on.
 
I don't know about the '04 assembly, but the demos at Keuka College Assembly and the Assembly where the 11' canoe was built and won by the Dells used Cecofill for filler. Cecofill is the aircraft fabric filler that is supplied by WCHA member Tom MacKenzie and can be used as a filler for both dacron and canvas.

See http://www.aircraftfinishing.com/cecofill.htm for more details. For canoe builders, I understand that Tom offers the best price.

It should also be made clear that there are different forms of dacron. The dacron used to cover canoes (and aircraft), like Ceconite, is a heat-shrink fabric. Dacron sailcloth is not heat shrinkable... At one time, Gil Cramer was offering heavy dacron fabric, perhaps 9 oz...? I keep waiting for Todd Bradshaw to chime in with his experience with dacron.

Cheers,
Dan
 
You rang???? I can't imagine trying to cover a canoe with regular Dacron sailcloth. It has totally different properties from the ceconite-style Dacron used for heat-shrunk aircraft applications or the old Featherweight canoes. To start with, it's already been heat-shrunk about as far as it's going to go. Then it's been fixed with resin (melamine or epoxy). Nearly everything that's done to process raw Dacron into sailcloth is done to keep it from stretching and/or changing shape. It's made flat to stay flat and will likely self-destruct long before you ever get it even close to being canoe-shaped.

Especially in light weights like 4-6 oz. or less it's also important to understand Dacron's tear strength. The Dacron fibers (or any polyester fiber for that matter - Dacron is simply Dupont's trade name for their polyester) are quite strong and resist stretch better than most other synthetics. They're also decently abrasion and U.V. resistant, but they tend to take tearing or ripping force one yarn at a time in woven applications. Where the woven yarns in a hunk of nylon will tend to stretch as a localized group when tearing force is applied, spreading the strain over a lot of yarns, Dacron yarns tend to try to take that force one yarn at a time. This is because they don't stretch enough to help each other out. The first yarn stresses until it breaks, then the second, the third and so on. It happens so fast that it's called "explosive tearing". You can take a piece of very heavy Dacron sailcloth (10-12 oz.) cut a small slit in one edge, grab either side, pull hard and it will split wide open. The same is not usually true of nylon, acrylic, cotton canvas, and most other synthetics, which will at least put up a fight as stressed yarns are helped by their neighbors. If you can pull hard enough to pop the first yarn on Dacron, you can easily tear the piece in half, so a fairly minor tear could end up 15' long if the force isn't removed. Sailcloth is also frequently treated with stuff like silicone, so finding filler materials which will stick well to it may be a problem.

The heat shrink-types of Dacron have these same tearing properties and should be used with care if the canoe is going to come in contact with rocks. The fact that the fabric is shrunken into canoe shape as part of the covering process may build in a little more stretchability than sailcloth has, but it's still very light and they're still Dacron fibers and limited in durability and elasticity.

I believe that the sailcloth which was tried out for canoe covering was North's "Oceanus", which is a heavy canvas-like fabric developed for square-rigger sails. It might work and at least can be stretched (or at least distorted from a flat state) to some extent, mostly because it has far less stabilizing stuff on it. The lightest weight is 7 oz. (measured in sailmaker's yards which are 36"x30" and once processed sail fabric is often as much as 25% or so heavier than the quoted weight). A very similar fabric is Richard Hayward "Clipper Light" canvas, made in England. I haven't used much of it because these fabrics are too heavy for the small sails that I build (makes a hell of a dog bed though) and could possibly be a good non-rotting substitute for cotton canvas on canoes, saving a certain amount of weight. I would imagine that durability-wise the Oceanus and Clipper 7-8 oz. fabrics would be similar to the light-to-medium weights of cotton canvas. They're fairly smooth though and absorb less liquid, so you might save more weight by needing less filler. Cost-wise, expect to pay $20-$25 per yard, 54" wide, so they aren't going to be cheap.
 
A source for heat shrink dacron is Platt Monfort of geodesic boat fame. You can also look at using polyester or nylon (Available from George Dyson, Baidarka & Co.) which are both tougher than the dacron. The nylon water shrinks but has a tendancy to slack in cold/ high humidity situations. I use the nylon on my traditional skin-on-frame kayaks but I would no t use it on a canoe. The nylons also do not work well with waterbased finishes. Dacron will be the lightest option.
 
In order to make a big heavy canoe lighter, it is my position that you need to find 10 ways to save one pound rather than 1 place to save ten pounds.

A lighter skin, yes. But if you have Ash gunnels and thwarts, and seats, I'd also consider changing them over to lighter woods.

A while back I had two nearly identical canoes in the shop. One had Ash gunnels inner and outer, the other had Spruce, as well as slimmer trim pieces. You could really feel the difference.
 
That latex filler might have been a lagging compound such as Bakore. Its used for coating the insulation wrapping of steam pipes. I've used it a couple of times. I wasn't excited about the results. They were OK, but that's about it. More work that usual to get a good finish.
 
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