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Old 10-03-2016, 04:14 PM   #1
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Deck project

Ever since buying the boat 7 years ago I knew I would someday have to tackle the cockpit deck situation. Well that day has come and it's looking like a massive project (what else is new?). Nothing rocket science mind you but a lot of work. I wanted to post a few pictures and ask your opinion on a couple of points at the same time. So here we go.

My initial idea was to remove the teak and put a few layer of fiberglass like I did on the foredeck and the sides last year. (It worked very well.) But upon inspection I quickly realized that the plywood underneath the glass was completely rotten and it would be pretty much pointless to build anything on that.

http://www.trawlerforum.com/forums/a...1&d=1475524958

It became obvious that the most logical way to proceed would be to remove everything and start from scratch. Furthermore two of the beams supporting the deck are in pretty bad shape so I might as well replace that as well.

http://www.trawlerforum.com/forums/a...1&d=1475525112

So here are some questions to you. Why was the deck made up off small pieces of plywood (about 5 inch by 5) instead of larger pieces? Would it be a bad idea to use pieces that would be bigger (let's say 2 feet by 2 feet)?

I most likely won't be able to fit an 11 feet long beam in one piece so I'm thinking of laminating one in place with a few 8 foot long boards. Would regular 2x4 work? I was originally thinking of using hard wood boards like oak but since it's a lot more expensive I want to have your opinion on that.

Here are a few more pictures.

http://www.trawlerforum.com/forums/a...1&d=1475525617

http://www.trawlerforum.com/forums/a...1&d=1475525617

http://www.trawlerforum.com/forums/a...1&d=1475525786
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Old 10-03-2016, 04:44 PM   #2
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I would make any new beams the same size as original. 2x4s look like an amateur fix. Ideally the deck should be as few pieces of plywood, the better. The beams look painted so fir will do a fine job. Use clear fir or buy oversize and rip to size avoiding knots. Halibut schooners are fir and some over 100 years old are still fishing.
I would do the deck in 3/4" plywood with 2.0 rsm and epoxy. I'd also make a cove around the edges and roll the cloth up the sides a couple inches. You can feather the top edge when cured. That way the deck is like a mini tub and won't leak through the sides. My own decks are done this way.
Before you put the plywood down, clean and paint the lazerette while it's easy.
Epoxy the plywood to the beams to stop flexing and stop any small leaks from rotting the beam tops. Use stainless drive screws, no nails. Epoxy resin, not polyester. If you later put down teak on top, use a syringe to put some epoxy down the screw holes so water has no path to the plywood or beams.
I use to do this for a living.
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Old 10-03-2016, 05:13 PM   #3
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So here are some questions to you. Why was the deck made up off small pieces of plywood (about 5 inch by 5) instead of larger pieces? Would it be a bad idea to use pieces that would be bigger (let's say 2 feet by 2 feet)?


A bit of clarification please - a ply core deck consists of a bottom layer of glass, small squares of plywood then the sealing top layer of glass (then teak on top) Your question and in particular the shot taken from the lazarrette looking at the underside of the deck seems to show that that bottom layer of glass has been removed to show the ply core? - did you do this?
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Old 10-03-2016, 05:22 PM   #4
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Quote:
Originally Posted by Brisyboy View Post
So here are some questions to you. Why was the deck made up off small pieces of plywood (about 5 inch by 5) instead of larger pieces? Would it be a bad idea to use pieces that would be bigger (let's say 2 feet by 2 feet)?

From reading many threads here on this regarding typical Taiwanese Trawler construction, this seems the norm. Scraps were used as filler. Decks, cabintops, sides. What you see is how it was done (like it or not)

Not the "Best" way of course, but likely the cheapest...
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Old 10-03-2016, 05:45 PM   #5
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Was this a cored fiberglass deck? That is, 'glass on the bottom, chunks of core - could be anything handy - scraps of plywood or anything - chunks of end-grain balsa, and 'glass on top. The chunks don't matter; the balsa you buy is in chunks glued to a 'glass scrim. Better (and not at all unusual) construction would ensure that the chunks are separated from each other by resin so that a leak can only rot one chunk.

Obviously, plain old fir plywood and wood beams would make a perfectly adequate deck and would last as long as the paint did (ordinary workboat construction). Just as obviously, encapsulated plywood and encapsulated wood beams would be perfectly adequate and would last as long as the encapsulation was not breached. Better, I think, would be a cored fiberglass structure and adequately-sized hat channels for the beams/stiffeners (and if the core is balsa or scraps of plywood, don't drill holes in the fiberglass).

I wonder if whether I'd make up this deck, lazarette hatch and all on a handy work surface rather than in the boat. I'd figure out some easy way to drop the assembly in onto ledges that formed the perimeter gutter.
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Old 10-03-2016, 06:59 PM   #6
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Originally Posted by Brisyboy View Post
So here are some questions to you. Why was the deck made up off small pieces of plywood (about 5 inch by 5) instead of larger pieces? Would it be a bad idea to use pieces that would be bigger (let's say 2 feet by 2 feet)?


A bit of clarification please - a ply core deck consists of a bottom layer of glass, small squares of plywood then the sealing top layer of glass (then teak on top) Your question and in particular the shot taken from the lazarrette looking at the underside of the deck seems to show that that bottom layer of glass has been removed to show the ply core? - did you do this?
Yes, that is exactly the way it was built. I started by poking through the bottom layer of fiberglass only to realize the core was all wet and rotten. That's when I decided to take the circular saw and cut everything out from the top to expose the beams.
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Old 10-03-2016, 09:42 PM   #7
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Too late now but I think I would have left the bottom layer of glass there and re done the wood filler with new top glass, or just lay it up with glass only. Either way you could still put new teak down if wanted.
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Old 10-03-2016, 11:53 PM   #8
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Along with considering the above, I'd be thinking if the access hatch has been adequate or if you want to add any for additional access. I had a single 24 x 24 lazarette hatch originally and added an additional 38 x 48. Easy access now, also moved the genset there. Make sure you do any wiring, exhaust, plumbing, or any other mod that involves that area while you're rebuilding the deck.
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Old 10-04-2016, 12:02 AM   #9
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As Steve said above, I've read and heard that some Taiwan yards recycled wood from pallets and packing crates in order to economize on construction materials.

I once inspected a 44' Marine Trader with a lazaret like yours - just a big, soggy mess. A P.O. had stripped the original teak decking off, glassed-over the plywood, and painted it with anti-skid. Obviously, a short-term fix. The rest of the decks had been similarly treated. That boat needed what you're doing, to gut everything and rebuild, but it was hard to see where that project would end.
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Old 10-04-2016, 02:20 AM   #10
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Have you considered a foam sandwich core? My boat, and Brisboy`s, have foam cored decks, it does not give the problems scrap bits of timber shoved together do.
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Old 10-04-2016, 07:43 AM   #11
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Too late now but I think I would have left the bottom layer of glass there and re done the wood filler with new top glass, or just lay it up with glass only. Either way you could still put new teak down if wanted.
Believe it or not, the bottom layer of glass was in bad shape in some areas. The core was so wet for so long that mold made its way through. Anyway that layer was really thin and I'm not sure it would have been very useful to keep it.

Thanks for all the input so far. It confirms some of the ideas that I already had and gives me new ones. I will of course take the time to make it nice and pretty down there while it's all open and easy to access. I will keep the original access hatch because the size is good and I don't want to redo the entire frame anyway. But I will also consider adding a smaller one on one of the sides. I changed the water tanks a few years ago and the new ones are smaller. There is a considerable amount of space on the outside of the tanks where I can (and do) store some stuff but getting to it is not easy.

Glad to see I don't have to use 5'' x 5'' pieces of plywood to rebuild! Good god. I was wondering if there was some technical reason why it should be done like this. Now that I know it was just to save costs, I will use 3/4 ply and make pieces as big as possible. I'm guessing this will add stiffness so that's a good thing. Before installing I will put a layer of glass underneath to replicate the original and protect the wood from the humidity inside the lazarette.

It's a big project but a fun one I find. At least there is room to work, unlike other projects I'v done over the years!
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Old 10-04-2016, 11:50 AM   #12
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The reason that scraps of stuff is used for core, plywood, balsa, or whatever, is that the scraps readily fit the curves and bed themselves in the fresh resin. Even your back porch floor is curved, probably in two directions, to shed water to the perimeter. (Our curve/camber is about 1 1/2", that is, the middle near the salon is that much higher than at the sides, and about 1/2" higher at the middle of the transom.)

Another good feature (as I said above) of using chunks is that it's possible to force/allow/encourage resin to go between the chunks, sealing each one from the next, thus preventing the spread of water and rot.

Your deck was most likely laid up/moulded upside down: a lovely smooth mould, then mould release, then gelcoat, then the top thicknesses of 'glass and resin, then chunks of core, then the bottom thicknesses of 'glass and resin, then the deck beams/stiffeners. Unless you build this thing on shore, elsewhere, you won't be doing that and you will have to do the finished surface last.

You could possibly tab your new work down, inside the lazarette, at the cost of unpleasantness of working conditions, rather than tabbing up and having to clean up the appearance. Probably, you'll need/want to to do both since the inside skin of the bulwark needs to be attached to and sealed to the new deck. Tab to bare fiberglass and not to gelcoat or paint. (Ours is only lightly affixed to the hull. The back porch deck basically hangs on the bulwark top and only a few of the stiffeners are tabbed to stiffeners on the hull.)
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Old 10-04-2016, 12:03 PM   #13
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I'd consider making most/all the framing out of box and/or aluminum I beam.

Then build the deck out of a synthetic core material and glass.
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Old 10-04-2016, 02:33 PM   #14
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What about using cedar to replace the rotten beams? There are nice 4x4 posts at the hardware store. Would that be an acceptable material for this usage?
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Old 10-05-2016, 08:43 AM   #15
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Any input on this?
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Old 10-05-2016, 10:44 AM   #16
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Fotoman, good quality cedar is only a little less strong than fir. 6:7, or so. Means that your new cedar beams would be 7/6ths as wide, or somewhat deeper. Cedar is more rot-resistant than most woods but it will certainly rot. Pretty hard to get good lumber at all, which is why laminated members are favored by engineers; they can count on the properties.

Check your deck's camber; you probably would have to laminate the beams to get the curve and at the same time keep the depth of the beam pretty much as it was. Pretty easy to laminate 3/4" thick stuff; you'd bend the stock against some sort of form and, once laminated, the curve would stand. (I've laminated against blocks of various heights tacked onto a wood ladder, against blocks screwed to a workbench, etc.)

I'd still encapsulate the cedar in epoxy, bearing in mind that any screw/nail hole penetrates the epoxy's moisture barrier. Also bear in mind that cedar is soft and would be susceptible to physical damage which could damage the epoxy. (I made sliding doors and door frames for my home shower using Home Despot's cedar decking back when it was good quality. All components, glass stops and all, coated in epoxy, except for the shower door sill which I covered in 'glass and epoxy.)
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Old 10-05-2016, 11:21 AM   #17
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Thanks DHeckrotte. Good to know cedar is an option. You are right about coating the wood in epoxy. That was part of my plan from the start. The good thing is that now in theory there will be no more water intrusion. Just "normal" humidity. Anyway, in theory. Lol
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Old 10-07-2016, 06:16 AM   #18
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Encapsulating lumber in epoxy is not a good idea....but...encapsulating ply is ok.
If you prefer to have lumber beams dont encapsulate them, just paint them.
Encapsulated ply is a perfectly good way to build & using ply for the beams allows you to part build with gravity helping you then laminate up to full section in place.
Making the beams into a tee section by epoxy bonding the deck ply on top is also possible if using ply for the beams and will give a good result.
If you use marine ply and the underside is internal there is no need for epoxy/glass on the underside, paint is enough. Epoxy/glass on the underside increases strength and life expectancy but isnt easy to do overhead.
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Old 10-10-2016, 09:24 AM   #19
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Thanks for the input. Why wouldn't it be a good idea to encapsulate lumber?
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Old 10-10-2016, 10:38 AM   #20
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Thanks for the input. Why wouldn't it be a good idea to encapsulate lumber?
Moisture content & (lack of) dimensional stability, difference in expansion rate, "conventional wisdom" .
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