View Full Version : Canvas Deck
07-02-2001, 03:58 PM
I decided to use 3/8Ē okume plywood on the decks of my catboat. Iíll screw it in place with dolfinite bedding compound at the seams and edges for a good seal and the ability to disassemble at a later date. Talked to Kirby about using white lead past under the canvas and he is sending info to me on the system they recommend. The thought occurred to me while ordering the dolfinite that it may be usable in place of the white lead past. I donít have it in hand so I donít know if it is even the right consistency for the job. I guess Iím asking for comments from people of experience with canvas decks.
07-03-2001, 09:47 AM
Hmmm... Interesting idea. Never heard of anybody using dolphinite for that purpose so probably there's a reason not to. Lot's of folks would argue that epoxy/dynell would be a longer lasting approach, but we're not talking a huge, complicated structure here are we? And white lead/canvass certainly has a long tradition. I'd be curious to hear of your impressions with the dolphinite for bedding your plywood to the deck framing. I'm still debating what to use myself. Right now I'm thinking either the dolphinite or silkaflex. Something less "permanent" than 5200 at any rate. Looking around the local boat stores all I've ever seen on the shelves is something called "Dolphine Marine Bedding Compound" (I think that was the spelling...) Is this just the "eco-friendly" version of Dolphinite? If so, where can you still get the "real" stuff?
07-03-2001, 06:54 PM
Art, you will find Sikaflex pretty permanent when used as a deck bedding. I ripped off an old bit the other day and it parted the ply laminate before the joint. White lead + putty would break apart easily but how often do you lift your deck?
07-03-2001, 10:06 PM
Canvas will draw the oil out of the Dolphinite, makeing it useless. Some woods will do the same. Seal or oil the wood first. If you oil the canvas to prevent this dry out,you might find out why your not supposed to leave rags soaked in linseed oil laying around(spontaneous combustion!). Dolphinite will add no strength to the joint between the deck and the beams, 5200 will. You might need heavier ply and fastenings if the boat was designed to have 5200 here and you don't use it. Never change any aspect of someone elses design, unless you know more than they do.
07-04-2001, 01:59 AM
Well, good point... But unfortunately, my boat was designed long before 5200, Sikaflex or probably even Dolphinite. For that matter the plywood sub-deck I'm contemplating wasn't likely around then either... Then again, I doubt I'll feel "too" guilty about forgoing the traditional laid canvas on cedar decking called for in the plans when I'm out there sailing, watching the rigging stresses on a boat that I put together one piece at a time, learning as I went! Perhaps the poor bastard who comes along after I'm gone and finds himself faced with re-doing the decks will curse me, but I kind of like the idea of somewhat "tenacious" deck to sheer/beam joints. (And that extra longitudinal stiffness won't hurt either...) Still wondering whether Sikaflex might not have some sort of other characteristic or property that would argue against it's use for this purpose?
07-05-2001, 04:52 PM
There really is NO point at all in going to the trouble of laying a canvas deck over plywood. The purpose of the canvas deck is to waterproof a planked subdeck which is designed to move. This is why your canvas is laid over Irish felt and then painted with white lead (if you are a purist) or plain old paint. You DO NOT lay canvas in some sort of googey bedding compound for lots of good reasons, some stated above. These days, Dynel and epoxy is the only option over plywood subdecks (which don't, and aren't intended to move at all.) Be sure to CPES your plywood very well, particularly the edges. Fasten it well to the deck beams. Dolphinite would do well, but why not some super glue. You don't want it to move anyway. If you have to pull up the plywood, I guarantee you will have to replace deck beams by then anyhow, so what's the difference? Look at the search feature for past discussions on Dynel/epoxy and canvas deck sheathing. You will not be able to tell a good Dynel job from the canvas if done right. The Dynel will last 100 times longer with 100 times less maintenance.
07-05-2001, 08:18 PM
Bob's wrong. I'm always looking for an opportunity to say that because he's an arrogant bugger and he's usually right. My dad built his boat in about 1973. It has ply decks canvassed over. I think the decks were glued and screwed to the deck beams. The canvas was laid over red lead paint. Then painted with enamel with some sand in it. Its been repainted from time to time, and is still going strong. There's no way though that dynel will look or feel the same as canvas. No way you'll get those nice double stitched seams. No way you'll get that ever so slightly soft feel under hand or foot. A dynel deck trying to look like canvas seems to me to be a bit like those plastic boats with plank grooves moulded in to look like wood. They fail.
07-06-2001, 10:42 AM
No, Bob is not wrong. Seams in a traditional wood/canvas deck allow water trapped between the canvas and wood to seep thru and drip on your head. No way for the water to get out thru the ply, so it will lay there until it eventally starts rot. Red lead will help, but once the ply cracks and the water gets to the next layer, its a goner! Better take a hard look at those nice soft decks, as they may well be soft spongy rotten ply core!
07-06-2001, 12:42 PM
"You will not be able to tell a good Dynel job from the canvas if done right."
In so far as this, I'm inclined to agree with Phil, Bob (and Dale) is wrong. But then one wonders what a "good" job and "done right" means. Personal experience with the dynel deck of Praire Isander obviously fails to meet either criteria. My ego remains intact with glass layups but suffers from Dynel poisoning.
The deck of my Haven 121/2 is canvas over planking set in white lead, the canvas scrubbed in hot water and painted while still wet...it looks beautiful. I saw a Pisces 21 at Mystic Seaport a couple of years ago and thought the deck was canvas covered, it looked beautiful. It wasn't canvas, it was covered with dynel and epoxy. I think they both look great.
07-06-2001, 03:43 PM
Arrogant, no... usually right? Well... LOL
To keep a canvas deck alive takes meticulous care. You have to be ruthless about keeping up the paint surface. Once ANY moisture penetrates the paint coating, rot begins, not necessarily in the wood, but certainly in the canvas. The paint will crack over time and then the water soaks the canvas, which being mostly covered with paint, holds the moisture between the canvas and the deck. Then there is the whole "deck shoe" issue, which canvas requires. One sharp edged heel (like those guys in the yards who wear the steel toed lumberjack boots) and your canvas is history. Canvas is definitely traditional and when done well, looks great. It is the necessary way to go when the deck below is laid, to permit the deck to move while the canvas stays put. (Hence the Irish felt underlayment.) To get the canvas look, Norm, try sanding the nap down a bit on the Dynel before you put the next coat of paint on. If that doesn't do it, or if you want a really smooth Dynel surface, lay down some sanding primer paint, or even think epoxy with microballoons in it and then sand that.
And, sorry... but if you think double stitched seams look cool on a canvas deck, each to his own, but that isn't what you want in a canvas deck. The whole object of the enterprise is to avoid exposed seams, as said. (Which is why decking canvas is sold in wide bolt widths.) If you must live with a seam, it is the preferred practice to run them down the center line (minimizing it where it runs through the cabin, cockpit, etc.) and then cover that with a wooden trim board.
But, if you really love canvas, and you don't mind replacing it completely every five or eight years (assuming you really take good care of it), well, go for it! LOL
07-06-2001, 04:13 PM
As one who is contemplating replacing a cracked and deteriorating canvas deck in the near future with no great relish, I sure think dynel over plywood would be nice to have, particularly for new construction when you already have the plywood. I'm debating whether or not to replace a badly-built canvas-covered laid deck (well, let's be tactful and say "built to a price") with plywood/dynel. The added structural strength is attractive too. Yes, the canvas looks great when it's in really good shape, but I think I'd rather be sailing than replacing deck canvas again.
07-10-2001, 01:25 PM
Bob and Dale are right on. Sure, there's always someone who will have a five hundred year old this or that which turns out to be the exception that proves the rule. Canvas was designed to accomodate the movement between planks of a laid deck. The white lead added some rot-resistance for the inevitable water that works its way through the canvas. It's a great system when used with laid decks.
Now, there's nothing WRONG with putting canvas over plywood. It'll work to a point. But it won't let you take advantage of the best qualities of plywood--its stiffness and stability. Because of that stiffness and stability, you can use a harder, stiffer and more durable cover, like epoxy and dynel. Canvas won't last as long as dynel and epoxy and it surely won't be as durable, except in the unusual case. On the other hand, white lead smells much better than epoxy and is slightly less toxic. Tastes Good Too!
If you use canvas, make sure you seal the ply real well with CPES, because once the water gets under the canvas, it's a gonna stay there until the plywood rots all the way through.
[This message has been edited by Scott Rosen (edited 07-10-2001).]
07-11-2001, 12:51 AM
You know I was just thinking, Bob is probably right again, so I guess I'm going to have to give up that idea of building a traditional carvel boat, and go instead for the more stable ply, and then glass over that. Or since the glass itself is pretty strong, and very stable, I'm thinking maybe if I build a hull out of something really lightweight, maybe balsa, and glass that inside and out, but then if water gets in, the balsa will rot, but maybe if I use foam for the hull, and glass that, and still put on a nice teak toerail or something, then I'll really have a wooden boat to be proud of. Jeez but the maintenance on that toerail is going to be a drag. LORL.
07-11-2001, 07:31 AM
Time to pipe in again. I own the canvas so Iíve already started down the road. The lead paste is expensive enough that I could go the dynel route at no additional extra cost. Thatís the economics of it. But this is not about money is it? If it were, we wouldnít be messing around in wooden boats would we?
OK, Dolphinite is out, just thinking out loud on that one. The argument against canvas are that what you should use boards instead of plywood against all recommendations in all the books Iíve read. The reason for using the poor substrate is so when the deck leaks because of a ridge caused by a lifting edge of one of the boards, or just because twenty years from now when the paint begins to fail the dripping water on your head gives you feed back that your deck has failed.
I guess I have few questions.
Is the failing of a canvas deck so subtle to a concerned eye that water would be accumulating under the canvas long before you would notice it from looking at the deck surface? So the only way to evaluate the condition of the canvas is by observing the leaky or rotting condition of the substrate.
When the dynel deck accumulates several coats of paint in fifteen or twenty years and the paint needs removal, what do you do to the surface to renew that look and feel of a traditional canvas deck?
The deck on my boat is not very extensive. The side decks on this fifteen foot catboat are just wide enough for your foot sideways. The foredeck is too small to take a walk on for any good purpose and is totally accessible from the cabin sliding hatch. I see little need for foot traffic.
To replace the deck at a later date, removing the cockpit coaming and the entire cabin is not a big deal. By then the fender could probably be replaced and the toe rail is not that difficult to remove either. So in fifteen or twenty years by replacing the deck I will have a new and refurbished top sides with a brand new canvas deck as compared to the dynel deck that looks like I donít know what? The ability to replace the canvas and the look is what attracts me. The aging and deterioration of the apearance is what bothers me about the dynel. Is the canvas that fragile?
Why are the beetle cats still using canvas if it is so bad? Still undecided but you can see where Iím leaning.
07-11-2001, 08:55 AM
Beetle cats use canvas because they also use cedar planked decks. As far as using canvas on the catboat, it's your boat, do what you want. With the occume ply you could just seal (CPES) and paint it, you don't really need a covering. I just looked at a 25' catboat built by a builder for himself that had canvas on ply decks. The canvas had failed in the last several years(the boat was built in 1966) but the plywood was still fine. When canvas fails you will know right away, it generally will split or tear which is quite noticable.
[This message has been edited by holzbt (edited 07-11-2001).]
[This message has been edited by holzbt (edited 07-11-2001).]
07-11-2001, 10:21 AM
OK, you can have it both ways if you want. Why not sheath the plywood deck in epoxy/fabric, then lay canvas in the traditional fashion over that? More work and expense, I realize, but it's not a very big boat. Has the following advantages:
- Dimensionally stable base (stiffens the boat, canvas lasts longer).
- Plywood is well sealed so if the canvas leaks it won't cause damage.
- Epoxy/Fabric sheathing is relatively quick and easy since it doesn't have to be faired very smooth.
- Looks and feels like a traditional deck.
- Canvas can be replaced when it wears out or gets too much paint on it.
- The type of fabric used isn't critical, since it will be covered with canvas. Fiberglass, Dynel, Xynole, whatever - it's just to reinforce the epoxy layer, really.
- An epoxy/fabric sheathed deck under canvas should last just about forever.
I realize this may seem a little like those carbon-fiber masts with a layer of wood veneer outside (I saw a section of one at the MAS epoxy booth at the wooden boat show BTW - about 16" diameter with around 1" walls, maybe 1/4" of wood on the outside, weighed nothing, very impressive), but there are real functional as well as aesthetic advantages to having a removeable sacrificial layer on the deck.
[This message has been edited by Keith Wilson (edited 07-11-2001).]
07-11-2001, 09:05 PM
I think Keith is on to something here. It would be interesting to soak the canvas with CPES before painting it too. If it works as well on fabric as on wood, the canvas may last a lot longer!
07-11-2001, 09:43 PM
I'd definitely soak canvas in CPES for openers, but then, I soak everything in it these days. LOL
Hey, look... we aren't reinventing the wheel here. There is no point in picking your belly button lint over this decision. This is one of those... "ya axed a question and ya gots an answer.... now don't argue about it!" If you want the text book answers, you got them. Plywood deck = dynel (etc.) and epoxy. Planked deck = traditional canvas.
As for your questions (sigh... can't you just take it on faith?)... Your canvas will probably leak water underneath the day you lay it down and only worsen from then on. Somewhere, likely the minute you walk on it, if not sooner, there will be some little pinhole or whatever. Water is amazing how it can find its way downward. Now, since you've done (almost) such a great job sealing it... the moisture that does get below is going to STAY THERE right up against your zero-rot-resistant plywood. While you are at it, forget your twenty year timeline for canvas decks. You will pay hell trying to keep a canvas deck servicable for twenty years and, given a miracle, if you do, your decks will rot out long before. Now, if you are doing a "museum quality" restoration of a classic vessel which is going to be covered or stored indoors, like a Beetle cat, for instance, and it has a planked deck because it is very traditionally built (which your ply deck isn't... but so much the better for dimensional stability and strength), by all means use the canvas. Otherwise, save yourself the grief. Sometimes, only rarely, something new, like dynel and epoxy, comes along which is better than the old tried and true. Usually, as here, it is the result of an entirely new material (dynel and epoxy).
Now, I suspect you spent money buying that canvas and you are trying to avoid getting stuck with it. Never fear. There is no end to the use canvas can be put. Start running up some nifty covers for this and that. Make hanging bags for the cabin. Tease out the strands and knot up some McNamara lace curtains... the opportunities are endless!
07-12-2001, 02:33 AM
Go with the canvas, its what you want, what you've got, and you'll be happy with it. If there is some rot in the ply in 15 years, which is entirely possible, fix it. All I can really say is my dear old dad put it on his ply decks 27 years ago, with a couple of stitched seams and all, he's not a maintenance fanatic, and its probably due for replacement around now. I can't see why his should be exceptional.
07-12-2001, 08:59 AM
<I think Keith is on to something here. It would be interesting to soak the canvas with CPES before painting it too.>
S'what I did recently when I canvased and CPES'ed my new hatch. Catch me in about 10 years and I'll let you know how it's holding up.
07-16-2001, 03:45 PM
Hello all, I am new to the group but like what I see here. I just completed canvasing the aft deck on my enclosed cruiser (1940 25'). After fairing the planked deck - tough shape after ripping an old fiberglass job off - I bedded the canvas in 2-part polysulfide rubber (waterproof AND flexible). A few tips: The quart of boatlife type P coveried about 20 sqFt but the 3 hour potlife is optimistic, more like 1.5 hours. The polyurethane roller tears apart when the stuff starts to cure up so I ended up using a plastic 'squeegee' - get a few, one clean for the canvas, one to spread the rubber. Monel stapels kept it all in place. She's all cured up now, ready for primer, light sanding, then final painting. Will repeat process for the cabin top in a few weeks.
PS: I'll also update the group in about 20 years re: longetivity.
07-16-2001, 11:48 PM
Scott, Your using 2 part polysulfide is interesting. I had a conversation with Steve(?) Smith of CPES fame about canvassing, and he recommended that in the strongest of terms. Do you know anyone else who has used this?
07-18-2001, 10:08 AM
I deferred to Steve's advice. I also asked him for thoughts re: polyurethane caulk but he reminded me it is a moisture cure and would skin over before I had a chance to bed the canvas. The 2 part stuff will cure no matter what and does not need to be in contact with the air or need a route for solvent to evaporate.
06-02-2002, 03:25 AM
I have been looking through the forum for a solution for the "dashboard" area of the cabin top of my venerable 1969 Chris~Craft cruiser. The area to which I refer is the area aft of the windshield in front of the helm on the flying bridge. It had a few wrinkles when I bought the boat in 1993. Originally the entire cabin roof was canvassed, but several years ago I had the cabin top glassed and painted with Awgrip, and it has been pretty much bullet-proof.
Last winter water got under the windshield, and under the canvas, which then separated and developed large wrinkles. It has many layers of paint. It appears beyond any help. I had to get the area dried out, and especially under the windshield, then properly caulked. But the canvas under the windshield is hopelessly wrinkled and worse, shrank as it dried out. If I try to wet it again and stretch it back, the layers of paint will certainly preclude its drying out. It is a very difficult area to work on unless you are a midget, and I am not certain I want to replace the canvas. Someone on the Chris~Craft list suggested that I just remove the canvas, fair the substrate (it must be plywood) with bondo, etc., sand it and paint it. I am not certain that would work, though
it sounds easy. Advice? Thanks
06-02-2002, 07:25 AM
Bob and Dale are right.
Last summer I re-did my coachroof which I had done 17 years before with canvas and lead paint.
This time I did it with plywood, epoxy and glass cloth. I don't expect to do it again, this time.
06-02-2002, 07:48 AM
As long as the plywood is not fir, that solution will work just fine. If the plywood is fir, you should cover it with a layer of glass and epoxy to prevent checking of the wood, which your paint job won't prevent.
By the way, I don't recommend using Bondo. It's polyester, so it absorbs and holds water and it dosn't have great adhesion. Use an epoxy filler instead.
06-02-2002, 09:43 AM
Rubber roofing mat..roll on adhesive to ply...deck planking glued to the rubber mat with seams filled with whatever you like...no thru deck fasteners anywhere..no cracking with deck flex from crew members, anchors, sea lions, flying fish, or whatever lands hard on your deck.. smile.gif ..outside the box.. :D
[ 06-02-2002, 09:50 AM: Message edited by: norske2 ]
06-03-2002, 02:42 AM
Thanks, troops. I hate to admit that I don't know how to tell if the plywood is fir, fer sure.
06-07-2002, 02:25 AM
Well, after looking the dash area over and poking around a bit it is obvous that the canvas is history. It has wrinkled further now that it is dry, and with the top sealed with a hundred coats of enamel there is no way it can be soaked and stretched back into position. I believe it is original, and since it was water leaking under the windshield that lifted the canvas, it must have been applied with lagging compound. I would think I can just soak it off, let the plywood dry, then soak it with CPES, fair it with an epoxy filler and paint it. What I want is a smooth white surface. One fellow suggested I just carpet over it, and I haven't recovered yet. Any reason I am wrong?
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