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Thread: Teak on Mahogany ply on teak deck beams.

  1. #1
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    Default Teak on Mahogany ply on teak deck beams.

    Hello, i'm new to this forum, have been reading some posts and found it to be really interesting.

    Im looking at buying a 30ft sailboat. One thing that has been grabbing my attention is reading about how bad it can be to have teak layed on ply.... In the photo i've attached you can see some mould in the forpeak on the ceiling. Im concerned that this could be the ply (9mm mahogany) with moisture entering from the teak deck and not just mould setting in from a not very well ventilated forpeak.

    The teak is 19mm which has worn down to about 14 to 15mm in places a few of the screw heads are showing.

    Saying all this though the boat is in good order apart from this issue.

    I would really appreciate any comments / information anyone could relay to me about this.

    Thankyou.


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  2. #2
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    Default Re: Teak on Mahogany ply on teak deck beams.

    There have been many threads concerning this dillema! If you can do a bit more sleuthing with a qualified surveyor you might find that the mold is mainly surface invasion due to poor ventilation. But, I do not advocate this kind of construction as it, nearly always, guarantees this kind of result, "rotten plwood sub decking under the teak overlay!" I deeply regret having to make this comment! A good wooden boat surveyor would be a must for getting a true picture of the condition of those decks!
    Jay
    Last edited by Jay Greer; 11-04-2018 at 03:02 PM.

  3. #3
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Thanks Jay for your reply,

    Yes it is a shame for sure, having this boat surveyed soon aswell..... Ive been hoping for some kind of magic moment where this is just not going to be a problem, but looks like it might be...

  4. #4
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Neil, are you handy with tools and do you have enough free time to devote to laying a new deck if the boat flunks survey due to the deck problems that may need fixing? You will need to stress these money pit issues when bidding on such a boat!
    Jay

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    Default

    Looking at a survey as an investment is usually a mistake. Many people will buy the boat because of the cost of a survey, rather than do it again. There are just too many good boats out there with better construction. Teak on plywood run! don't even look back!
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

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    Default Re: Teak on Mahogany ply on teak deck beams.

    Impossible to say really looking at a photo. You'll see more looking at the deck. But if screw heads are exposed you can be pretty sure water is getting into the ply.

  7. #7
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Im a furniture maker by trade , hmmm its a bit dissapointing, will have to review situation.

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    Not so hard to rebuild a deck on a 30 foot boat if you can handle some tools. But factor it into the price.


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    Default Re: Teak on Mahogany ply on teak deck beams.

    We are looking to sail around the UK in 2020 so would need to get that work done next year. Would have to do alot myself and with a friend to reduce the costs and get a shipwright to oversee and guide me through some tasks. I am confident in using tools and working wood to a good accuracy. I guess id have to decide either to only replace the bad bits (thats if there is rot) or go for new deck. Id definatly need some advice from the surveyor though.

    The boat is a one off Helford cutter, iroko on oak carvel planking, shes setup as a rugged long distance sailboat. Paul Gartside design, built in the UK 1983. She is lovely!

  10. #10
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    Default Re: Teak on Mahogany ply on teak deck beams.

    That teak is incredibly thick for an overlay on ply.Usually it is in the 6mm-9mm range;your mould may have other causes.Can u post pics of the deck and any portlights,hatches ventilators?

  11. #11
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    Default Re: Teak on Mahogany ply on teak deck beams.

    The foredeck has a samson post, stay sail self tacking boom fixing and windlass which are fixed to the centre blocking on the deck. You can see in some of the photos. Id say the teak has worn down to approx 14mm in certain areas. Yes the owner has said its an unusually thick teak deck.

    The hatch is at the front of the coach roof and not in the deck.

    cheers
    Neil
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  12. #12
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Why not make an offer subject to a clean survey?
    If the deck is bad, then negotiate a price reduction.
    All you risk is the cost of the survey.

  13. #13
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    Default Re: Teak on Mahogany ply on teak deck beams.

    The mould could just as well be a badly ventilated forepeak. If the ply is rotten it will sound dead and be soft to a knife point or spike – also I would expect the paint to be peeling and some wrinkling of the grain of the face veneer.

    From the photos of the deck, it looks to be very nicely laid. But it has obviously worn to the extent that some screw heads are now showing – which may just be that they weren't very deeply countersunk in the first place.

    Also in some of the photos, especially the last one, it looks like the seam paying has started to lose adhesion on the sides – and also the paying is very hollow. This hollowness could simply be that the deck is very dry so has shrunk to its minimum – and the seams will return to normal once the deck swells up. It could be that there isn't a bond-breaker in the bottom of the seams (perhaps unlikely considering how well the deck is laid). Or it could be that the paying material is coming to the end of it's useful life, has lost flexibility and thus adhesion to the teak.

    A simple test is to wet the deck and watch to see how it dries up. If it stays wet along the edges of the planks after the remainder has dried, that is an indicator that water is getting into the join between the paying and the teak.

    At 14mm average thickness (if that is indeed the case), there should be plenty of teak left. Provided the ply underneath hasn't started to decay (OK - not so easy to determine that absolutely), then there should be plenty of material left to refasten and re-pay the deck. That's not a quick job. You need to lift all the deck fittings (especially items like stanchion feet). Withdraw all suspect fastenings – probably the majority because they will tended to have countersunk them all to the same depth, countersink them a little deeper and re-fasten, and glue in new dowels; clean out all the existing paying and rout the seams a little deeper before re-paying – following the instructions for whatever paying material you are using (seam shape, seam depth, bond breaker, priming etc).

    If there don't appear to be too many problem areas, you should be able to carry out a holding operation for a year or two or more - re-pay any suspect seams and refasten where the dowels have come out – in other words, an ongoing maintenance program. But eventually the deck will have to be refastened and re-payed – it happens to all teak decks laid this way.

    Get a good survey done by a surveyor who is experienced in traditional timber yachts.

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

    A C Grayling

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    Default Re: Teak on Mahogany ply on teak deck beams.

    Great advice from George. Older wooden boats always need work but if the initial construction was good and the design as well then it will be well worthwhile. Remember by working on the boat one REALLY gets to know the boat thus building confidence in the boat too. Remember what Ratty said to Mole!
    Dennis

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    Default Re: Teak on Mahogany ply on teak deck beams.

    Very few Helford cutters were built. Have you bought this boat are are you looking at the one on Ebay? That mould is typical from a boat left ashore under cover for years on end. There might very well be some moisture wicked into the sub deck, but a good surveyor armed with a tapping stick and a moisture meter should give you a better idea of whats going on. If its the boat on Ebay, your quids in even if it needs a new deck.

  16. #16
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    Default Re: Teak on Mahogany ply on teak deck beams.

    They be plugs, not dowels.

  17. #17
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Thank you so much for all your comments, its a big help to hear from people with experience. The boat is under offer pending survey which is ment to be next Monday (if the winds are not to strong for the crane).
    I will talk to the surveyor and express my interest in the above matters before the survey and then we can see how the boat is. I do know im excited and looking forward to the survey report.
    If I do buy the boat then Im sure I will be on this forum asking questions. Great to know its here, and hopefully I can be of some service/help aswell.
    Cheers
    Neil

    'Lose yourself to find yourself'

  18. #18
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Quote Originally Posted by Phil Y View Post
    They be plugs, not dowels.
    In British yacht building they are called dowels.If the purchase goes ahead it wouldn't be a huge job to remove the screws and increase the depth of the counterbores.Re-paying the seams is a bit more challenging and the worst part is cleaning out the seams.By comparison,squeezing thirty or so tubes of mastic is quite relaxing.

  19. #19
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Quote Originally Posted by Phil Y View Post
    They be plugs, not dowels.

    Ok - semantics, semantics! For some reason at Whisstocks (and other English boatyards) they were always called dowels and the machine that made them was a dowel cutter. It has some provenance I guess coming from German döbel – a plug. It's hard to throw off 35+ years ...

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

    A C Grayling

  20. #20
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    I am currently pulling up and replacing exactly this problem deck, 37ft. If it is useful, the cost for me will be about $12k Australian. Including crane, yard fees and materials.

    The job, if it goes according to plan, will take me about 20 long, 14 hour,dirty days. I have done all the work myself with the exception of some hours from my 12 year old (handy for through deck fastenings), and my brother in law who got in my way for a few hours.


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  21. #21
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    Default Re: Teak on Mahogany ply on teak deck beams.

    Thanks for your message Gypsie, really good to know.

    Here are two videos from mobile phone of me on the deck tapping and also below deck tapping the ceiling.

    https://youtu.be/xQ7DMYKHDY8

    https://youtu.be/nwJZ0FNEE3U

    I'm only tapping with my fingers but an experienced member of the forum might be able to give some feedback.
    Craning delayed as we have strong winds.
    Thanks
    Neil

  22. #22
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    Default Re: Teak on Mahogany ply on teak deck beams.

    I'm not an expert or even close, so don't take my word for it.

    But that looked okay to me.
    Those exposed screw heads will let in water - best cover them in goop soon. The rasied caulking may be a humidity/temperature thing, and shouldn't be a worry.
    Any evidence of the teak 'bubbling'? lifting off the ply beneath. In the areas where rot had progressed in my boat the teak overlay appeared to have seperated from the ply as the ply delaminated.

    That mould on the cabin top, is it clearly from water ingress or could it be due to poor ventilation?

    What are the bolts through the deck for the windlass like underneath? corroded?

    I have no doubt water will get in, or is getting in, and will cause trouble some day. But it looks a while off yet i think. Possible delay by regular oiling to help water run off...... Recaulking under some deck fitting that might be showing some water ingress. Just delaying tactics though.

    The brief glimpse at the interior was tantalising. Any pics of the whole boat?
    "People should be able to access these benefits [Social Welfare] as a matter of right, with no more loss of their own standards of self-respect than would be involved in collecting from an insurance company the proceeds of an endowment policy on which they have been paying premiums for years."
    Robert Menzies - Liberal Party (Conservative) Prime Minister of Australia.

  23. #23
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    Default Re: Teak on Mahogany ply on teak deck beams.

    That mold looks like poor cabin ventilation to me. The deck may have issues, but I don't think that mold tells you much about them.

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