Deck canvas

[ianc1200]

Any experts on here? For years I used to have painted canvas decks. About 2006 got fed up with having to lift both hatches/tabernacle/guards rails/windlass/cleats/fairleads/toerails/quadrants to recanvas and succumbed to ply/epoxy etc. Net result the decks separated from the ply, the deck planks rotted, did partial repairs 5 years ago, but now rot in deck beams, beam shelves, lodging knees etc. All up and will be replaced with iroko. But I'm going back to canvas & painting - at least I (partially) understand it, and know apart from annual painting the canvas needs replacing after so many years. I think there is also an advantage by getting it up every 5 years or so, you can see what's going on and detect suspect areas whereas you can never see what's happening between ply and the deck. (BTW I used Robbins Elite & it rotted to nothing....)

My question is about the type of canvas to use. When I was at Freebodys (on the Thames at Hurley) they criticised the canvas I used - I sourced very heavy/thick canvas. They said I should use thin, almost nylon quality canvas. Any views?

 

[johnlilley]

Hmmm. That's unfortunate. Your experience with ply & epoxy sheathed deck is not good. Do you know why the water got beneath the ply as generally this method should easily last 30 years or more. It sounds as if you followed the "rules", that is everything lifted off deck including toe rails & rubbing strakes. New 6mm ply nailed & glued to deck planks, Epoxy & glass cloth sheathing (not just epoxy resin/paint) overlapping deck edge and raised up side of coachroof and all other upstands & then bedding quarter mouldings over the edges of the sheathing & rubbing strakes over the top of the sheerplank & on top of the sheathing fully protecting the edges of the sheathing.

I see many timber vessels where this has been done with no problems at all. Sometimes see problems caused by leaking chainplate piercings & deck fittings, stanchion bases etc. but these are obviously preventable, so I would think about plywood & epoxy sheathing again really if it was me as you should not have to make any repairs for many decades. The other benefit is that once the ply is fully secured to the deck , this has the effect of making the vessel much more rigid & helps stop the vessel twisting and moving as is often the case with old planked decks where each plank can move very slightly against its neighbour due to aging fastenings & aged planks.
Canvas cannot add any strength.

 

[ianc1200]

Thanks John. The ply was put done by me but (the late great) Peter Freebody gave me a lot of advice as I was doing it. My opinion is there are so many penetrations of the deck - must be at least 100 screw holes, 30 - 40 bolts for the guard rails it was always bound to fail. With the canvas I'm not looking for strength but a covering which won't in itself cause problems. The original 1951 deck was douglas fir or pine T & G Vee jointed 3/4" thick, I replaced that in about 1988 with 1" thick douglas fir T & G etc. What's going back is 1" iroko T & G Vee jointed, we are replacing most of the deck beams in laminated iroko and I have the iroko for the beamshelves, but not looked too closely at those yet. Hopefully it will see me out!

 

[johnlilley]

Just be aware that iroko will be a lot heavier than the original 3/4" as built deck and will almost certainly have a limited affect on the stability depending upon how much freeboard you have and the overall size of the deck.
There are methods of improving the risk of stanchion base leaks such as mounting the bases on timber pads that are fully bedded to the deck before fitting the bases. This does make a difference. The same goes for other areas of through deck fittings.

Finally, be aware that a canvas covered deck will almost certainly not be a good sale point if and when selling in future, but that might not be any issue for you.
Good luck either way.

 

[Wansworth]

Why not use cascover,did a deck of a nic 36and a hillyard3 tonner

 

[ianc1200]

Thanks - where would you get Cascover & is it OK to paint? Essentially I want to put lots of paint on the deck, stretch canvas etc overand then put more paint down.

 

[Wansworth]

Why not use cascover,did a deck of a nic 36and a hillyard3 tonner

No idea,I assume it’s still used to cover underwater part of wooden boats to deter gribble,list a nylon cloth impregnated with a resin,but the details I have forgotten.Or course nothing wrong with a canvas deck either

 

[Kukri]

I can remember that deck canvas was a thing; it came in very wide rolls and yes, it wasn’t particularly thick or closely woven. I last bought some from Frank Knights in Woodbridge in 1986.

There is the question of whether you lay it in wet paint or allow the paint on the t&g to dry. This used to be a Controversial Point.

 

[Wansworth]

Hillyards used woven glass mat and resin on their new decks …….a while back?

 

[Hacker]

We’ve finished the restoration of a 100+ year old Truro oyster dredger (Falmouth working boat). During this we replaced the stem which had rotted but then found the decks had gone as well. All ripped out and replaced with 18mm marine ply. We the sheathed this and then covered it with straight laid leak on top (all bonded down and caulked). We painted the ply with accelerator, wetted out with resin, laid one layer of combi mat (CSM layer down) and the fully wetted and rolled. Care needed to ensure that the edges are bound down properly over the deck edge. Deck, covering boards and rubbing strake made sure there was no area for water ingress.

 

[ianc1200]

There is the question of whether you lay it in wet paint or allow the paint on the t&g to dry. This used to be a Controversial Point.

Agreed! I was a wuss and wouldn't put loads of paint down, afraid it would get everywhere you didn't want it. Tended to put minimal amount on the deck, stretch the canvas over and paint over. Freebody said use cheapest paint you can buy, and put lots on the deck, stretch canvas and paint would come through.

 

[Sumara of Weymouth]

I canvassed the decks of my first yacht back in 1980's. I certainly laid it onto wet paint which was basically a mix of all the old oil paints left on the shelf. I couldn't remember the weight of the canvas so I have just consulted George Buchanan's excellent book "The Boat Repair Manual". It states that the canvas should be 10 oz. He says lighter canvas will not withstand rough usage and heavier canvas is difficult to stretch. That chimes with my memory. You can buy canvas from Whaleys in Bradford and it comes up to 9' wide. I would go for loomstate canvas and certainly avoid any fireproof treatments. Although I have only canvassed one deck, I have canvassed many thousands of metres of theatre scenery. It is important to keep the warp and the weft running square. Oil based paints have less effect on shrinkage so you will need to pull the canvas quite tight. If you apply it onto wet paint a small wooden block can be pushed over the surface of the canvas to force the paint through. The canvas will then stick down to the deck. If you apply it onto a dry deck you would be able to lightly dampen it with warm water to make the canvas shrink. There is a bit of an art to getting this right, if you have stretched it too tight it will pucker up behind the tacks. On scenery, strong timber frames could be bent into banana shapes, so the forces are considerable. For this reason I feel laying onto wet paint then forcing the paint through with a timber block is the safest method. Hope this has been some help.

 

[Kukri]

^A perfect answer.•^.

 

[Wansworth]

I canvassed the decks of my first yacht back in 1980's. I certainly laid it onto wet paint which was basically a mix of all the old oil paints left on the shelf. I couldn't remember the weight of the canvas so I have just consulted George Buchanan's excellent book "The Boat Repair Manual". It states that the canvas should be 10 oz. He says lighter canvas will not withstand rough usage and heavier canvas is difficult to stretch. That chimes with my memory. You can buy canvas from Whaleys in Bradford and it comes up to 9' wide. I would go for loomstate canvas and certainly avoid any fireproof treatments. Although I have only canvassed one deck, I have canvassed many thousands of metres of theatre scenery. It is important to keep the warp and the weft running square. Oil based paints have less effect on shrinkage so you will need to pull the canvas quite tight. If you apply it onto wet paint a small wooden block can be pushed over the surface of the canvas to force the paint through. The canvas will then stick down to the deck. If you apply it onto a dry deck you would be able to lightly dampen it with warm water to make the canvas shrink. There is a bit of an art to getting this right, if you have stretched it too tight it will pucker up behind the tacks. On scenery, strong timber frames could be bent into banana shapes, so the forces are considerable. For this reason I feel laying onto wet paint then forcing the paint through with a timber block is the safest method. Hope this has been some help.

Greatreply

 

[Bodach na mara]

Someone mentioned Cascover, which was nylon fabric applied over resorcinol (eg Aerodux) glue. Given the name I thought that it was Cascamite glue which was a one-pack casean glue and that was not known as resistant to water or durable so I was never tempted to use it. I did at the time use a lot of Aerodux glue for moulded wood structures. I saw several boats with Cascover decks and while it seemed to last longer than canvas it did eventually leak and removing it was a right b****r.

I repaired the leaky decks of my old 6-metre by nailing on exterior douglas fir ply over the pine planking and it lasted for a few years before I sold it. I saw it in yards a few times over the next few years and finally saw its remains lying under the pier at a yard in Port Glasgow.