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Thread: Decks, sub-decks

  1. #1
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    Default Decks, sub-decks

    We are about to put a new deck on a large classic sailing boat. Currently it has the original traditional laid deck, but we will put a ply sub deck and teak on top.

    I would like some oppinions on plywood. Some shipwrights have quoted on using "marine ply". An Oakham based plywood. Others using a Lloyds approved mahogany Ply. Is marine ply soutible for a deck?

    also fastenings.... joining the plywood to the deck beams is it worth going for silica bronze or will stainless steel be fine?

    Thanks

  2. #2
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    Default Re: Decks, sub-decks

    Occume has low rot resistance. It's main attribute is it's light weight,thus, lotta occume kayaks.
    IMO plywood decks are good and teak decks are good. But not together.

  3. #3
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    Default Re: Decks, sub-decks

    As you will see, new decks wont be cheap, and you wont want to do the same job twice. You will get a 20 year guarentee (read the small print) with marine mahogany, and 15 year with marine Okumme (everyone spells that differently), such as that from Robbins Timber in the UK, they ship everywhere at reasonable cost.I have used hardwood WBP exterior plywood, same glue as marine, but it was an exceptional batch of plywood with zero voids that i have even found in some panels sold as marine quality. Im not a real fan of teak overlays, and the only succesfull ones have no fixings down through the ply, so that needs each strip to be weighed down onto an unholy mess of epoxy. Traditional and modern stickums i have seen fail over time, water gets under the teak and over a long time your plywood, even good stuff, will rot. Me, i would just sheath the ply with glass/dynel and epoxy and a nice non slip paint.
    Stainless fastners will be fine on deck. I suppose you are going to have to import this material? There is Joubert in France, Robbins in the UK, Bowa in Denmark and obviously Bruynzeel plywood in Holland. All make reputable top quality and guarenteed boards, you might ask a quote from each out of interest, delivery cost seem to be all over the place in the EU, but Robbins have always been excellent value.
    How big a deck?

  4. #4
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    Default Re: Decks, sub-decks

    Classic sailboat! Got some pictures?
    Teak Decking Systems http://www.teakdecking.com/index.php...d=1&Itemid=101
    They have been around a long time.
    They provide service and shipping world-wide.
    They will recommend a plywood substrate and fastening system.
    Yea, they are expensive, The company AND teak decks. But you know that.

  5. #5
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    Default Re: Decks, sub-decks

    We took care of a lovely55’ Rhodes yawl, built by Abeking and Rasmussen in 1950 for my customers father. Over the years we had done spot repairs to the traditional, caulked teak decking. But the time had come to replace. As we removed the teak deck strikes we could see the very beginnings of water intrusion into the beams and knees.
    The decision was made to leave the trunk cabin in place as it sat on a substantial carlin, and we also left the substantial teak covering boards so as to not disturb the built up bulwark and caprail assembly. The original strikes were 1-3/4” thick, and in places had been sanded down to 5/8”. We felt that substitutingthe ply for the original caulked strikes would apply supply the stiffness the old system had given the structure.
    We went with 2 layers of 1/2” occoume ply that conformed to the BS6068 standard, staggering the laps and with all edges sealed with epoxy as well as bedded between the layers with thickened epoxy. We fastened the ply to the deck beams, but did not glue it. There was enough width and thickness left in the covering boards to rabbet outboard the second layer of ply as well as the actual teak strikes.
    The teak planking was 5/8” thick and 1-3/4” wide, and laid in thickened epoxy, being sprung we temporarily fastened these with screws and fender washers that were drilled in the seams. These were removed after cure and the holes filled with epoxy using a cardboard caulking tube we filled with epoxy that was about heavy cream consistency.
    The seams were filled with Detco 2 part thiokol(sadly no longer made) from a caulking gun and then the proud cured caulk removed with a slick, and then the entire deck faired with a disc sander.
    We now had a new deck that would give another 50 years, and not leak, and no plugs for water to get into. Because the underlying deck structure was in such good shape the job was simplified, keeping the cost down, as opposed to removing and replacing toe rail, caprail, covering boards, maybe some deck beams, etc.
    A wonderful contract to get, a fabulous boat, and a committed owner.

  6. #6
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    Default Re: Decks, sub-decks

    As wizbang says – replace the Teak decks with Teak decks - no ply. Or Ply decks and no Teak.

    But if you really must lay teak over ply, then you need to choose the best, most rot-resistant ply that you can get – genuine BS1088 and a durable species which Occumé really isn't – or a genuine Lloyds approved marine ply, again not Occumé. The problem with both is that there is a lot of bad ply out there with BS1088 or "Marine" stamped on it. Remember that the British Standard is only enforceable in Britain. So you need to be sure that you are getting it from a reliable supplier – like skaraborgcraft mentioned.

    Stainless steel screws ought to be OK for fastening the ply to the beams and carlings etc. I would glue the butts in the ply with epoxy and then coat the entire surface with two coats of epoxy, making sure to remove any amine blush and sand the second coat to a good matt finish. Personally I would use WEST system materials.

    Then lay the teak without fastenings, bonded with epoxy – you hold it down while the epoxy cures with temporary fastenings in the seams (screws and fender washers as #5 is a good scheme). Then fill the screw holes with epoxy,

    Depending on the thickness of teak you can either fill the seams with an epoxy/graphite mix (for thinner teak) or a deck caulking compound (for thicker teak) – usually a one-part or two-part polysulphide. With the polysulphide system it is usual to lay a bond-breaker tape in the bottom of the seams to allow the polysulphide to stretch and shrink in a regular fashion.

    For such an expensive job like this I would consult with the WEST system people to get their recommendations – they are very good, have been in the business a long time and are very helpful.

    Fastening through the teak, with plugs over the fastenings, is going to fail at some point and water is going to get into the ply and it is going to rot. The basic service life of the deck will essentially depend on the depth of the plugs – probably about 5mm to 6mm – and how well they were glued in. You will likely get a longer service life from a 6mm thick epoxy-bonded, epoxy/graphite seamed deck at less cost.

    Cheers -- George
    To be truly free to live, one must be free to think and speak.

    A C Grayling

  7. #7
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    Default Re: Decks, sub-decks

    Thanks for the correction on the BS1088, it definitely was that, the BS6065 is the lesser grade. We talked with the owner about laying down T & G first to match the original detail on the underside of the teak, which had a V- match edge. We finally epoxied and then pre-painted the underside of the first layer white.
    We always got our ply panels and hardwoods from Edensaw over in Port Townsend, so felt we were paying for and receiving a genuine stamped product. The job could have been cold molded with layers of Alaskan Yellow Cedar as well, the first layer would have been laid parallel to the centerline and been T&G.
    The vessel is out the family now, was in San Diego last I heard, and like a lot of big refits I don’t have current info to see how this work has stood up over time, about 15 years now.

  8. #8
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    Default Re: Decks, sub-decks

    Thanks all for your comments.

    Understood that hat the general thought is that either ply deck or teak deck. But we must end up with a pretty teak deck on top. When this boat was built it had almost 50mm thick teak planking, to come back to original build thickness it would take half a rainforest in solid teak. We are 23m on deck and just over 5m beam.

    my feeling is that the plywood is not a place where you should try to save money. But a couple of stories above suggest a well sealed quality marine ply might suffice. The difference in cost is around €10k. But I will be checking with more suppliers suggested above.

    we intend to leave bullworks in place and rebate a scalf joint under. However this may change as we assess condition of knees and frame ends.

    i have spent the day removing interior head liners, which I don't intend to put back. We have had some water ingress, but the spruce deck beams look in astonishingly good condition.

    With caulking compounds, a lot of people a going off sikaflex these days; lots of bad batches. Was thinking TDS. Any experience here with TDS?

    Excuse me for not giving details of the boat, but I don't want this to show up on google searches for her. But I would be happy to photograph the process and share if there is interest.

    Thanks
    t

    edit
    also yes, the intention is to glue the teak to the ply. No fastenings.
    Last edited by Rhodes_ketch; 11-14-2017 at 01:17 PM.

  9. #9
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    Default Re: Decks, sub-decks

    ...it is usual to lay a bond-breaker tape in the bottom of the seams...
    What's "bond-breaker tape"? Explain, please?

    Alex

  10. #10
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    Default Re: Decks, sub-decks

    I have seen several times where a layed deck was properly dried and faired smooth, left as a sub-structure, and then covered with well bedded ply,,,,no gaps in the bedding, and then glassed, right over the covering board and over the plank edge. In one case the ply was laid in 6" wide strips, layed diagonally, to ensure good bedding. I have not seen any of this work fail.
    I would not put teak onto ply,,,,, ever.

  11. #11
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    Default Re: Decks, sub-decks

    ...it is usual to lay a bond-breaker tape in the bottom of the seams...


    Pitsligo " What's "bond-breaker tape"? Explain, please?"

    The TDS caulking (paying compound) should NOT adhere to the bottom (the plywood)of the seam. Only the sides for expansion and contraction reasons.

  12. #12
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    Default Re: Decks, sub-decks

    Let' see, 1975 to 2017 , teak over ply and still going. I wouldn' replace the teak again but my friend with our near sister ship just had the teak veneer removed and found no issues with the ply. Same boat builder as us 5 years newer.

  13. #13
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    Default Re: Decks, sub-decks

    It was L. Francis Herreshoff himself that taught me how a deck should be laid. It was his opinion and mine as well that the deck is an integral part of the strength of the entire hull it covers. I still remember the sound of a hull whose newly laid deck begins to ring like a bell as the deck caulking is driven causing it to take up and add to the structural integrity of the entire boat just as a girder will in architectural engineering. I have been laying decks for well over fifty years, nearly sixty, and have yet to find that a deck laid over plywood is superior to one laid in the traditional manner. In fact, in every case I have worked on a deck that has a sub deck made of plywood, the plywood has rotted out from under the plaking above it and ruined the structural integrity of the hull.

    My own preference is to lay down a sub deck made of Alaska Yellow Cedar, it doen't rot, made of for and aft tongue and groove staving. These staves can be pre painted prior to laying in order to make the overhead less pain to deal with for paint work. If greater stiffeness is needed, lay a single course of glass over it and then plank the decks with vertical grain stock of the designers choice set in luting/bedding compound. The choices I prefer are VG Douglas Fir, Eastern White Pine, Teak, Port Orford Cedar,
    or Wyche Elm. I have seen boats that were built in Australia that used Eucalyptus for decking too. All of these woods are rot resistant. The fir is of the lowest resistance. This should be stock that is milled to have a proper V'd caulking grove. Decks should then be caulked using a deck seaming mallet. And payed with Jefferies Marine Glue and not rubber caulk!
    This is the manner of construction that will provide a long lasting and easier to maintain, in the long run, wood planked deck.
    Jay

  14. #14
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    Default Re: Decks, sub-decks

    If you are worried about the cost and impact of a solid teak deck (and you should be!), could you be convinced to try another hardwood?

    Ipe, iroko, and others would work very well at a fraction of the cost of teak.

    My own boat is ply deck with VG fir bedded on top. It is not what I would prefer. When there is a leak through the top "pretty" surface, which there will be, it is not detected from below and will just sit and eventually rot. Or the leak will travel and eventually come out in a different place than it went in, making tracking it down very difficult. Modern seam compounds (sika, TDS) will fail eventually as well leading to undetected rot.

    Fully fiberglassing a ply deck and then bedding down the teak with no fasteners is the best way if you must go that route. Any leaks then stay above the fiberglass layer and out of the ply.

    A solid timber deck is probably longer lasting, more honest, and certainly easier to repair.

  15. #15
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    Default Re: Decks, sub-decks

    I'm intrigued. The shyness of Google search suggests maybe a charter vessel? A 23 metre Rhodes ketch. Sounds stunning. I'm also intrigued that you have the deck off but haven't yet chosen your sub deck material. But that happens sometimes. My boat is 17 metres, built in 1974 with teak over ply decks. I understand from the builder that they have always been problematic. They are now due for redoing, which in my case is going to mean removing the teak, cutting out and replacing sections of rotten ply, probably adding a thin skin of ply to bring the thickness back up, and covering with dynel. The failures are all where water has entered the sub deck where there are fasteners. Most fasteners are fine, even where screw heads are now exposed, but where there are problems, fasteners are the cause. Or other protrusions such as chain plates. The lesson is of course to do everything to avoid water ingress via fasteners or other protrusions. I'd avoid teak, because whatever you do, the teak will move with wet and dry cycles, glue or sealant lines will fail and water will get in. I'd probably tend to prefer something more flexible than epoxy to set teak strakes into, so that when it does fail, the underlying membrane of epoxy is less likely to be breached, letting water into your ply. I'd spend my money on doing everything possible to keep water out of the ply, rather than on the ply itself. Whatever ply you use will fail if it gets wet. It may take 2 years or 5 years, but all ply will rot if water gets into it. So save your 10k euros on the ply, and put it into making every protrusion as fail safe as possible. Drill oversized, fill with epoxy, then redrill. Find a good sealant for fittings, good quality butyl tape seems to be the most reliable. If the boat is going to have daily care and attention, so that the decks can be wet down daily, do consider traditional decks as Jay suggests, possibly not teak given cost and availability. Would love to see a picture of the boat.

  16. #16
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    Default Re: Decks, sub-decks

    Teak is not essential for decking, just, long lasting! White or Alaska cedar is as long lasting, lighter but soft and prone to abrasion damage. I might add to the post I wrote above, that I dip every screw that is used on boats I build in bee's wax! Bee's wax will not support fugus and it lubricates and seals the fastening from moisture as it is driven. During the driving, it heats slightly and soaks into the surrounding end grain, thereby, sealing the wood from moisture intrusion and rot infection.
    If I need a break from the routine of the day, I put on some good music and sit next to the wood burning stove with a tuna can of melted bee's wax and a box of scews to dip. Takes no time at all to dip 100 and, my brain gets a bit of a rest thinking of cruising in the boats I have built.
    Jay

  17. #17
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    Default Re: Decks, sub-decks

    This would not be her, as she is said to have teak deck beams. But just so's we know the sort of thing we might be talking about

    http://www.sandemanyachtcompany.co.u...3dd1ea577a.jpg

  18. #18
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    Default Re: Decks, sub-decks

    No comment Phil

  19. #19
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    Default Re: Decks, sub-decks

    Quote Originally Posted by gilberj View Post
    I have seen several times where a layed deck was properly dried and faired smooth, left as a sub-structure, and then covered with well bedded ply,,,,no gaps in the bedding, and then glassed, right over the covering board and over the plank edge. In one case the ply was laid in 6" wide strips, layed diagonally, to ensure good bedding. I have not seen any of this work fail.
    I would not put teak onto ply,,,,, ever.
    This has been seriously considered. However not to take the opportunity to inspect and repair beams, knees and frame ends would be a wasted opportunity.

  20. #20
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    Default Re: Decks, sub-decks

    With reference to Iroko for laid decks - we built a couple of boats (not as big as this - in the 50' range) with Iroko decks and they were never as satisfactory as Teak – and those were the days when we could buy an Iroko log 40' long and 5' across the butt, so you could absolutely choose the best timber for the job. It really does shrink and swell rather too much to make a leak-proof laid deck. These decks were caulked and paid with Jeffrey's Marine Glue – maybe they would have been more satisfactory with modern deck compounds. But a true laid deck still needs to be caulked, so, for polysulphide or similar, the seam shape needs to provide a caulking bevel and then the upper part needs to be rectangular.

    For traditional work I agree wholeheartedly with Jay - dip all the fastenings in wax – as a lifelong vegan-vegetarian I wouldn't use beeswax – but carnauba wax is equally satisfactory. But with modern epoxy bonded work, wax is not good - dip in epoxy instead. Personally I would also stick with Jeffreys for a traditional laid deck – it maybe needs more maintenance, but the maintenance is simple and low tech – and can be done pretty much anywhere – no special primers, bond-breaker tapes, mixing polysulphide components etc. And the more you tread on it the better it will be!

    However you do it, and as careful as you may be, a Teak over Ply deck is unlikely to be as long-lived as either a traditional laid Teak deck or a simple ply deck, covered in Dynel or glass cloth and epoxy.

    Even building aluminium alloy yachts as we did, with the teak simply bonded with a special two-part polysulphide - no fastenings – the water still managed to get under the Teak eventually – there are simply too many metres of deck seam which can fail.

    That's not to say don't do it - just recognize that it is likely to be a shorter lifespan, so the cost must be amortized over fewer years.

    Cheers -- George
    To be truly free to live, one must be free to think and speak.

    A C Grayling

  21. #21
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    Default Re: Decks, sub-decks

    A lot of excellent input here, with a wide variety of experience and recommendations. After I put the wrong plywood spec in my first post, I started questioning what I was remembering about this job. So, I went to the computer and found my Labor and Material records, the work was completed in August of 1999, and we did use BS1088 Okoume from Edensaw.
    Looking through the record it did jog more recollections, like how frightening it was to see the evidence of water intrusion, but fortunately no damage to the structural members. Also how far down the deck had been sanded and been worn away from chemical cleaning over the years
    Most of the entry points appeared to be from fasteners, which were silicon bronze screws, in some areas a seam was the culprit. I cannot remember if the owner had ever re-caulked the deck seams, they had been reefed and filled with thiokol at some point before we started taking care of the boat. Interestingly, the owner chartered the boat when he was sent to Europe to oversee Hewlett-Packard Packards first offshore factory. The two gentlemen who chartered it owned famous boats themselves- Barlovento and Orient. They replaced the standing rigging with rod and this yawl was raced very hard on San Francisco Bay. The two gentlemen owned a little business called Barient, the name came from combining the two boat names, this yawl also had a full complement of Barient winches.
    I was glad we did not try to reef and caulk the deck after seeing how thin it had gotten in places, certainly re-laying New teak pieces would have been an option, caulking and paying them, though I would have un-hesitatingly used Detco Thiokol Deck Caulk.
    The extent of the damage that had came via the fasteners was uppermost in my mind, and bonding the teak to the sub-deck and having no penetrations made a lot of sense, along with having a full depth seam to allow wearing away.
    I also found that we added a Carlin type piece to the cabin side, in order to rabbet the landings of the ply and new deck, as well as keep the sander and deck cleaning materials away from the varnished cabin sides.
    Sadly, since the boat went out of our care when the owner passed away, I can’t critique all the decisions and methods we used with the passage of time to either ‘prove’ their merits or convict myself of a mis-guided plan or execution.

  22. #22
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    Default Re: Decks, sub-decks

    What any boat owner chooses to use in the way of materials is a matter of either personal experience or personal investigation as to what works or what does not work in the sense of how long the system of construction will last and how expensive it will prove to be in terms of maintenance. Common Sense based on experience is a great leveling tool! Speculation based on hearsay is entirely another thing that can reach deep into ones bank account and or life span while waiting for expensive repair work to be done!

    This statement is not intended to relflect the opinion posted above by Paul Schweiss. However, I can state, from my own experience, that Okoume plywood has only one virtue. That is that it is very light in weight,21 to 25lbs. per cubic foot. When compared to teak at 51 to 65lbs per cu ft and other structural materials used for boat building this is very light indeed! This is why many designers and boat builders, who seek to keep a vessel light in displacement use it. However, Okoume plywood is extremely expensive and very low on the scale of rot resistance, a characteristic that causes many seasoned boat builders to not favor of its use for a vessel that is intended to live a long life! A well built wooden boat of well chosen materials should be able to last sixty to one hundred years depending on he type of maintenance and repair it is subject to during its lifetime.

    L Francis Herreshoff once said that a person inspecting a wooden vessel that is near one hundred years of age should inspect her with bowed head and cap in had out of respect for the knowledge of her builders and of the skill that went into her construction! For this reason, I urge those of you who desire to build your dream ship to take these well proven factors into consideration.
    Jay

  23. #23
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    Default Re: Decks, sub-decks

    If she has to have teak deck, the a fully glassed plywood subdeck would be my first choice. And if its not already clear, dont use any fastenings. Not used any TDS. Last big deck i was involved with (30m) used sika (aluminium deck).
    You really need to get your decking from a supplier who knows what they are doing. We once had to send back several tons of machined decking as it was poor stock for the job, we ended up purchasing the baulks and ripping it ourselves. Its too big and expensive job ,to have to do it twice. Thats a classy looking boat, even if its not the one......

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