Covering a ply deck with Dynol and epoxy

[apindrans]

Corio Vertue has a 20mm thich ply deck which has been covered with deck paint. The surface is looking very tired and is flaking so I thought I would sand back to bare wood, prime, and re-paint the deck.

This seemed a very simple solution until a local boutbuilder showed me the results of a Dynel, and epoxy finish on a ply cabin top for a motor cruiser. The results were impressive but how would such a treatment work for an old wooden yacht? Some questions are:

Preparation: Does the deck have to be sanded back to bare timber for applying the cloth and epoxy, or can it still have remnants of paint for bonding.

Rigidity and flexing: The plywood deck does not go all the way to the edge of the hull but stops at a 100mm wide shelf that runs the length of the boat, and provides a base for the staunchions. To me, bonding accross this joint may cause a failure due to differential flexing. Is this the case, or should I apply the Dynel accross the joint.

Bonding to edges of hull/cabin: Is any preparation/finish required where the cloth and epoxy meet a vertical surface?

Dynel seams: I've read the literature, and it shows the joins overlapping, and then being cut while still wet. How is this possible when you have a 1m. wide sheet of epoxy saturated Dynel between you and a seam? One solution given to me is that when the epoxy has cured gently grind down the bulge to the level of the cloth, and fair away any imperfections.

Covering: Standard primer, undercoat, and deck paint?

I'm happy working with wood, but mixing epoxy and cloth on top of wood is a new experience.

[redsail]

Sounds like the perfect time to cover your deck with painted canvas tacked down all around with brass tacks laid over roofing gum. Best to take the canvas out over the deck edge and cover the edge of the canvas with a moulding . Good luck.

[WFK]

You're right, you've got a lot of issues here. To really do a deck properly it should be stripped of everything including toerails, and guards so you have a place to terminate the cloth, otherwise you're just asking for problems down the road.
For the BEST results, epoxy needs to be applied to new plywood, but if you think you'd like to move ahead with this I think you can have good results as long as theres no paint, and is well sanded to ceate a bond.
This 100mm shelf is an issue because I'm to assume that it's a piece of solid stock timber used as a covering board, and you're right, that joint could be a problem because of movement. I would think this area is well backed up but even at that, epoxy and cloth really isn't intended for coving large pieces of solid stock.
There are several ways to address the area where the cabin meets the deck but in your case there may be a piece of trim that covers that corner and this is where I'd terminate your cloth. Remove the trim, cut your cloth and after curing re-bed the trim. If there is no trim, one will have to be made.
There really needs to be no overlap when doing epoxy cloth, and what you read is correct. When doing your cloth work a small overlap while the epoxy is wet followed by a cut with a fresh razor blade through both layers makes for the perfect joint.
Hope this helps.
Bill

[westinghouse]

Dynel seams: I've read the literature, and it shows the joins overlapping, and then being cut while still wet. You can mitigate this back-burner by dry fitting your cloth. It's not perfect but it's good. Gently grind? I don't know that one.


Bonding to edges of hull/cabin: Is any preparation/finish required where the cloth and epoxy meet a vertical surface?
Here you have to decide that the deck/cabin joint is tight and go up, or that it moves significantly and the cloth stays on the deck only. A piece of molding at this seam to match the brow is usually the solution to scenario B and a nice fillet is the solution to A.

Good luck, this job inevitably takes way longer than you think it's going to. It's a rigorous job, and likely not necessary (and that's an argument for doing it, I'd say).

Nice boat,
Eli

[DougWilde]

I covered the deck of my Windward 15 with Dynel. Tried a couple of different ways to joint the fabric. Had not thought about grinding, then overlapping with a final grind. I actually like that idea.

Before you do the deck try some test samples using different techniques and see how they work. Well worth the time and effort. Additionally, if you have not done this type of sheathing before, the practice will pay dividends when you tackle the Big Show.

Just as you would remove deck fittings before laying the cloth, remove the margin boards or whatever at the sheer.

Very important: before applying your finish, bring the completed deck up to the maximum temperature your boat likely will face when outside. If that means 100F+, then do it. Otherwise there will be a final cure and possible print through dockside, as your boat bakes in the sun. Been there...done that.

And finally, this is an irrevocable change to your boat. The traditional canvas and tacks lets you change your mind latter. With epoxy and dynel it is a done deal until you replace your deck.

Doug Wilde

[Bob Cleek]

Okay, Apintrans, forget everything that's been posted above. Some is generally accurate and some is way off the mark. (Sorry, guys...)

I am guessing from your description that Corio Vertue is a Cheoy Lee built Vertue sloop. I have Patience, Vertue SN 136, built by Cheoy Lee and I've done the repair your describing. I'll walk you through it.

What you have at the covering board (you called it a shelf) is a true covering board fastened above the deck beams. If it is built as the rest of the similar Cheoy Lees, this covering board is rabeted at the inboard edge. There is a trim strip laid in this rabet and a caulking seam between the trim strip and the covering board. The seam where the plywood decking butts up against the covering board is covered by the trim strip. (The trim strip looks like a single decking plank up against the covering board.) Where the deck has been covered with fibreglass (as was the original construction... yours may have been removed), the edge of the fibreglass runs over the edge and into the trough made by the rabet in the covering board. It too, then, is covered by the trim piece.

In order to dynel and epoxy the deck, you will need to remove the trim strip between the covering board and the plywood. Remove the bungs and screws, etc. Try not to bust it up or you will have to make another to replace it.

When you get back next to the Highfield levers, you may find them fastened over the trim piece and the devil to remove. You may wish to simply cut the trim piece at that point and grind a groove between the trim piece and ply deck into which your fabric edge will go. Otherwise, you have to remove all the hardware that is in the way. Nasty job.

Once you have removed all the trim running next to the covering board, you must remove all the trim against the cabin sides, around the bitts and so on. Again, you have to remove the bungs and screws and hope it doesn't all fall apart in your hands, especially the curved pieces! I use a brad point drill bit to drill out the bungs. The point bottoms out in the middle of the screw slot. I then use a Dremmel tool with a dental burr in it to clean out the screw slot. When the slot is clean, I take out the screw. When the screw comes up, the remaining bung at the bottom of the hole comes up and out with the screw. The drill insures that you have a clean hole to rebung, rather than one all chewed up on the edges. There are a LOT of screws holding that trim down!

Now, sand your deck fair. It is certainly necessary to get all the loose paint and fibreglass off. A heat gun and scraper will take off the worst of it. You don't have to go down to absolutely bare wood. Epoxy is very aggressive stuff and eats right through paint. The important thing is to have a fair amount of wood exposed is all.

Now, lay your Dynel and wet it out with epoxy. Run the edges into the trough in the covering board rabet and up against the cabin sides. I use the green lacquer proof tape for all epoxy work, as epoxy will lift all other tape. I tape up about a half inch on the cabin sides, wet it out beyond that and when half cured, I take a sharp razor blade and cut along the taped edge and remove the waste.

There are many ways to do a seam with Dynel and epoxy. Generally, one edge is simply lapped over the other wetted edge. The "hump" will be rather small. Now one way to deal with it is to just grind it fair. Works fine.

Another easier way to do it is to wait till the deck is dry and then tape a strip like a king plank down the middle of the foredeck where the seam runs down. You then take epoxy thickened with sanding filler and spread it between the tape. When that hardens, you sand it flat and remove the tape. You are left with a neat smooth "king plank" seam. The Dynel on either side will look much like painted canvas. The nap will show through and make a good non-skid surface. If you want a smooth surface, simply coat the Dynel again with epoxy thickened with sanding filler and sand it smooth. On my boat, I kept it smooth and then taped off areas, put a coat of epoxy between the tapped areas and poured sand on it... wait for that to cure and vacuum up the excess sand. Paint over it. Perfect non-skid.

This, if done carefully, will produce a very strong, abrasion resistant surface. It can be sanded and painted as you wish when it needs touching up.

Oh, and then you get to replace all the trim... after you've made replacements for the parts you broke... and then strip all your varnish and re seal it with CPES and then eight coats of varnish.

Just that easy.... sort of.

BTW, Cheoy Lee's method of butting ply up against the covering board is really unusual. I've never see it elsewhere. At the time our boats were built, plywood was probably something new to the application it was used for. They treated the plywood as if it were solid traditional deck planking. If you really wanted to go whole hog, I suppose you could remove the ply and lay a teak plank deck right up against the covering board!

Also, I should mention that I had significant leaking problems in the seam between the trim strip and the covering board, even though I had gooped it up good when I put it in. The deck seam compound (3M 101) hardened and cracked in the seam between the trim piece and covering board after a couple of years. I ended up routing the seam out with a Dremel and caulking it traditionally with cotton cod twine. I then painted the caulking cotton with CPES and stopped it with Teak Deck Systems seam compound. No problem for a couple of years now, knock on teak!

Good Luck!