Canvas Hull Durability

[Ronin NW]

So I'm still mulling over ideas for a tender design, and recently found a beauty in Billy Atkin's Handy Andy, which went on to be built in droves by Penn Yan in the 40's. It's eight feet of cedar and canvas, and described as weighing only 90 pounds minus the rig!
http://www.boat-links.com/Atkinco/Dinks/images/HandyAndy-1.gif

She's cute as hell (that sheerline would match the mother ship like a dream), carries 3 comfortably, and is light enough to hoist on deck. I may change to a spritsail rig (mast forward or canted forward) to reduce the spar length for storage. In my naivety, she doesn't look horribly difficult to build, since the filled canvas, rather than tedious joinerwork in the planking, keeps her afloat.

My concern and question here, is of course the canvas. After doing a bit of research, the most definitive info I can find on the durability of canvas is, "it lasts longer than most would expect." Which means absolutely nothing to me! I'm looking at her for a tender (as she was intended), and that may include rocky beaches... there've even been barnacles sighted in Puget Sound. Can I trust the filled canvas? Can I harden the bottom with something more abrasion-resistent (at the risk of adding weight, no doubt)? It's been suggested that Handy Andy could be built in Lapstrake, but I'd like to suss out this canvas thing before I start spiling...

And thoughts, suggestions, or advice much appreciated!

-Scott

[ 07-09-2004, 12:46 PM: Message edited by: Ronin NW ]

[Don Maurer]

Can you put a sacrificial keel board and bilge runners on it?

[Boomkin Joe]

Scot,

You might soak it with hypalon. Or replace it with heavy-duty truck tarp. Or w/ ballistic nylon, like the one that's used in luggage-making, or heavy-duty polyester tent floor lining, or w/ kevlar.
I don't know if you can soak ballistic nylon w/ hypalon, but that would be interesting, especially if the keel and other rubbing places are lined w/ reinforcement strips.

[Wiley Baggins]

Beachcomber stole a march on me while I hit the Google trail. I think that using a more modern coating like hypalon might well improve the durability albeit at the expense of greater weight. Here is a link to a Google search for "hypalon durability paint." (http://www.google.com/search?hl=en&ie=UTF-8&q=hypalon+durability+paint) You may be able to find the coatings more cheaply at a roofing supply house.

[ 07-09-2004, 02:02 PM: Message edited by: Wiley Baggins ]

[Thomas Garber]

I can say, I spent three weeks running the rapids of Northern Ontario, in a canvas canoe many years ago. We always hit rocks. Once in a while one would spring a leak. We just flipped it over, dried the rip, glued a patch on, and went on down the river. I will also say, I never remember the canoes as being light weight. Those portages were a back breaker.

[Fitz]

You might also ask your question here at the WCHA:
http://forums.wcha.org/index.php?s=1a14443ab7a0ed43feda6d793386b92e

I'm a wood canvas canoe nut and fan, so very biased. I don't know your particular conditions, but the filled canvas skins are more durable than you might expect, and are easily maintained, repaired, and replaced.

You could also use heavier canvas to increase durability, if that is your major concern.

[Dan Lindberg]

To add to Fitz's comments,

When a traditional filler is rubbed into canvas, the surface becomes very hard, as the filler is basically lynseed oil and sand, and will slide off objects easily. It can be cut however on sharp objects. The filler is then either painted (with the paint of your choise) or covered with shellac (as the old time Maine guides did, easier to maintain)

However, knowing how I try to keep my W/C canoes away from rocks, if you envision it being pulled up regularly on rocky beaches, I'd try something else.

Heavy glass/kevlar layer with multiple keels??
Don't know.

Dan

[Corso]

this might be stupid as epoxy has never been mentioned so it might be that you absolutely dont want to use it, but even non glassing the boat instead of canvassing (it's canvassing in english isnt it?), you could try (if compatable whith what would be underneath)varnishing with 70% epoxy resin, 25% graphite powder,5% colloidal silica (#s 423 and 406 for west system i think). It cures to a really hard surface, and if used with kevlar its said to be almost bombproof (i wouldnt waste the money for the kevlar though)

[Ronin NW]

So I just found the "Should I fiberglass my canvas canoe?" FAQ at WCHA (thanks, Fitz): http://forums.wcha.org/showthread.php?s=5cfa7967eaffa35b9c5818d7ee1c6ae7&threadid=12
They're pretty vehemently against it, for understandable reasons, but it raises questions regarding the difference between canoe and more substantial boat construction (not that this would be much stronger, but I recon that larger frames, transom, keel can make a big difference).

How much would a wood-canvas boat actually "flex" by intention? (I know my baidarka and I'm not expecting that!) Also, if I stick with canvas but use stronger resin or goop, is it likely to soak through the canvas and coat the underlying wood?

Thanks so far!

[Fitz]

I was thinking about this some more. What kinda beach we talkin' here?

If the boat spends most of its time in deep water and the beach is round rocks (not sharp or jetty, or sharp bedrock) and you take care of your boats, I bet you don't have to worry.

I routinely get out of the wood canvas canoe in the water and lift it onto the shore. After all, we are only talking about a 90 lb boat. Care in landing would be taken with a wooden hull boat too.

You are going to scratch the paint, but if you take care of the boat, I suspect canvas damage is a non-issue.

I touch up the paint every few years.

Re: the size of the boat - many canvas canoes with sponsons and/or sail rigs for example weighed more that 100 lbs. and Pen Yan and Old Town built wood canvas small motor boats and run abouts, car toppers all about the same size of your proposed boat. They lasted for years and are easily repairable.

Canvas and filler is relatively cheap and dare I say it - fun to do. If it doesn't perform to your satisfaction, it comes off in 10 minutes and then replace it with something else.

Best of luck with what you decide to do.

[ 07-09-2004, 10:44 PM: Message edited by: Fitz ]

[Corso]

I was actually referring about painting only the bottom, not soaking the canvas with the resin.
Had experiences (not boats) using other kinds of fabrics, instead of glass fiber, with resins. I dont know what kind of canvas would be used on the boat but with some fabrics (syntetic) the resin make them become... brittle id say, it sort of "cook" them, so they are like non existant, others just soak the resin but they dont really bond together so in cases of cracks the resin itself cut the fibers, in the best of the cases the resistance of the whole fabric+resin was poor because the fabric wasnt "primed" to bond with the resin (sorta like using glass prepared for polyester with epoxy resin).
(here im talking about airplane models with failure of structural parts during the flight, i dont think that a canvas over wood is subject to those stress conditions but still could be ruining a nice boat)

[Three Cedars]

I've built a number of skin on frame kayaks some with 15 oz canvas which was painted with alkyd house paint mixed with 1/3 boiled linseed oil. Those kayak skins are holding up well. Puncture resistance is ok but with a heavier boat you would be more likely to be running it up on shore and it is that steady abrasion on the keel and chines that would be a concern . Rub strips could go a long way with protecting the skin.

Synthetic skins of heavy tightly woven nylon are very durable, much better than canvas . Nylon and polyester in heavier weights are available from George Dyson at , Dyson, Baidarka & Company
435 West Holly St., Bellingham WA 98225
telephone: 360-734-9226 — fax: 360-671-9736

A two part flexible resin is the ultimate for coating but a lot of SOF kayak builders use a one part satin exterior polyurethane or a roof coating such as Black Knight brush grade roof coating .

Corey Freedman can fill you in on the particulars of which skin and coating to use at http://www.skinboats.com/

[Fitz]

Well, the difference here between the SOF kayaks and the boat in question is the Filler. As Dan mentioned above, the filler fills the weave and produces a rock hard surface.

[Ronin NW]

Small world, and it's all coming back to me... I actually built a baidarka a couple years ago, not with Cory, but I bought a skin and his secret 2-part polyurethane off him. So, I'm very familiar with that but thought from the get-go it would be out of place. SOF is meant to flex, whereas filled canvas should be hard (due to filler) and well supported by direct and solid backing of cedar.

I wonder how a sacrificial keel and runners will affect the boat (may not look as good upside-down on the deck ;) ), but unless I go the kevlar route, that may be the way to go, at this point...

[Wooden Boat Fittings]

.
I built a wood-and-canvas kayak way back in 1960 and she's still going strong. Cotton canvas of course, but I can't off-hand remember whether it was 15 or 18 oz. No filler (it hadn't been heard of, I shouldn't think,) just marine paint. At least five or six coats initially, and many more over the years. It made the canvas tough and leathery, but allowed it to stay flexible.

Outside the canvas there's a full-length semi-sacrificial softwood keel and two short bilge keels (really just runners.) None of these has been replaced, but most of her beachings have been on sand so the timber's taken a fair bit of abrasion. I didn't use her in whitewater much, and the canvas itself has never been damaged (which of course was what the timbers were supposed to make sure of.) Contact-cement / patch / paint would have been the repair method of choice if necessary. However, I'd be wary of puncturing the canvas on a sharp edge of rock, whatever the finish treatment was.

As far as the paint soaking through the canvas is concerned, yes it did a bit -- enough to make the inside unsightly. So when I'd finished painting the outside I painted the inside in "canvas-colour," which successfully hid the bleed-through.

Mike.

http://www.woodenboatfittings.com.au/public/kareela-s.jpg

Edited to add: This was not a canvas-sheathing-over-timber hull, but stretched canvas over a rib-cage of softwood stringers some 6" apart (themselves supported by five transverse plywood frames.)
.

[ 07-13-2004, 05:51 AM: Message edited by: Wooden Boat Fittings ]