Seams corked only below the waterline, but not above.

Discussion in 'Wooden Boat Building and Restoration' started by Sather, Jun 13, 2015.

  1. Sather
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    Sather Too many boats

    Anyone familiar with the practice in wood boat design, perhaps older trawlers, whereby the seams above the waterline are not corked and faired. And if so, any problems inherent to that design to watch out for?
     
  2. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    You'll have to be more specific about your concerns/questions. Are we talking about a partial carvel, with something else above the LWL or possibly something different. It seems counter productive to "harden" up the planks below the LWL, yet leave them hanging on their fasteners above. Please clarify.
     
  3. Sather
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    Sather Too many boats

    Thanks for taking the time...
    Yes, Carvel style, Sather built, 1970. Boat has been moored in a dry region for a few years. Seeing daylight between planks above waterline, but below she's tight and no leaks.
     
  4. SamSam
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    SamSam Senior Member

    Sinking sounds like a likely problem. Give more details in 10,000 words or less. Or a picture. Are you looking to buy it?
     
  5. Sather
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    Sather Too many boats

    Thanks SamSam,

    Not so much a sinking issue, however Im not in the know of a normally practiced boat building style where we don't see calking all the way up to the caprail. Like I said, below waterline she's calked and payed. The waterline is high as she is commercial fish built. Just thought I might come across an old timer who has seen this before.

    Thanks.
     
  6. PAR
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    PAR Yacht Designer/Builder

    Carvel builds have to be caulked to impart the mechanical lock, the structure needs to be both water tight and structurally sound. There's no exceptions to this rule, unless the hull has had something done, such as spines, maybe a sheathing, possible veneers, etc. all would be present in some fashion, even if on the hard for several years. There's no advantage to edge set planking and there's a lot of structural loses, if the boat is used like this, not to mention leaks. A close inspection would possibly reveal a combination of build methods, maybe carvel below the LWL with batten seam above or some other adaptation to the basic carvel build. Can you post a photo of the above LWL seams up close, particularly the really open ones?
     
  7. SamSam
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    SamSam Senior Member

    Maybe you're talking about the bulwarks having open seams, which is above the level of the deck. That doesn't matter much, if at all.

    The water line is at the level of the water. Open seams at the waterline are a big concern and a definite sinking issue.
     
  8. Sather
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    Sather Too many boats

    Definitely ABOVE the waterline. Picture not possible at this time. Talking about the outer planking, from inside looking out, DAYLIGHT... NO COTTON-NO SEAM filler. Edge to edge construction. Seems odd to me too... That's why Im askin. Never seen it before.
     
  9. waikikin
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    waikikin Senior Member

    It is possible, some builders have set up like that, more typical on small racing yachts like Dragons & 5.5metres, although some others, I've heard of a crayboat builder that used various coins as clearance set up, some edge bruising techniques also employed & relies on the boat staying wet & similar in sealing concept to the clinker/lapstrake timber to timber sealing,, also I believe- from the source(Maltese & Greek) that some Mediteranean built vessels are built with faying plank edges & roughly paraphrase that "English boats "*hit built.... need cotton/oakum to keep outa water.... where I from planks perfecto & caulking only for old boats, when you build boats on island everyone know a good boat, when fisherman no come home... B***** M*******"
    Nevertheless that doesn't solve your problem, you may be able to cut some bevel with an appropriate rake, we make from files & heat/bend & grind to suit profile required, then you can caulk & pay as usual.

    Jeff
     
  10. SamSam
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    SamSam Senior Member

    The thread went from 'Seams corked only below the waterline, but not above'

    to

    'Definitely ABOVE the waterline.'

    but you still have the same questions.

    Y̶ᴇ̶s̶ᴛ̶ᴇ̶ʀ̶ᴅ̶ᴀ̶ʏ̶ ̶I̶ ̶ᴡ̶ᴇ̶ɴ̶ᴛ̶ ̶ᴛ̶ʜ̶ʀ̶ᴏ̶ᴜ̶ɢ̶ʜ̶ ̶ᴀ̶ ̶ᴄ̶ᴏ̶s̶ᴛ̶ʟ̶ʏ̶ ̶ᴀ̶ɴ̶ᴅ̶ ̶ᴘ̶ᴀ̶ɪ̶ɴ̶ғ̶ᴜ̶ʟ̶ ̶ᴘ̶ʀ̶ᴏ̶ᴄ̶ᴇ̶ᴅ̶ᴜ̶ʀ̶ᴇ̶ ̶ᴛ̶ʜ̶ᴀ̶ᴛ̶ ̶ʀ̶ᴇ̶ǫ̶ᴜ̶ɪ̶ʀ̶ᴇ̶ᴅ̶ ̶ᴍ̶ᴇ̶ ̶ᴛ̶ᴏ̶ ̶ʜ̶ᴀ̶ᴠ̶ᴇ̶ ̶ᴍ̶ʏ̶ ̶s̶ᴘ̶ɪ̶ɴ̶ᴇ̶ ̶ᴀ̶ɴ̶ᴅ̶ ̶ʙ̶ᴏ̶ᴛ̶ʜ̶ ̶ᴛ̶ᴇ̶s̶ᴛ̶ɪ̶ᴄ̶ʟ̶ᴇ̶s̶ ̶ʀ̶ᴇ̶ᴍ̶ᴏ̶ᴠ̶ᴇ̶ᴅ̶.̶

    Please, I don't have much time...what is it that you want to know?
     
  11. PAR
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    PAR Yacht Designer/Builder

    I have also seen some edge set planking jobs, though they often had edge hardening treatments, they usually didn't hold back the wet for long.
     
  12. Sather
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    Sather Too many boats

    Okay. Thanks for your insights.
     
  13. peterjoki
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    peterjoki Junior Member

    Hey Sather,

    A picture would be really helpful. The building practice you describe doesn't sound familiar but a lot of possibilities should be considered.

    Restoration, poor caulking causing the seams to have lost their filling for any reason, intentional removal by a previous owner. From what I gather the boat doesn't take on water.

    If the boat is used in calm weather exclusively, the extra ventilation is more than fantastic for the longevity of the structure and boating experience. Provided everything stays dry.

    Please post us a picture when possible. We can all learn from these rare cases.
     
  14. sdowney717
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    sdowney717 Senior Member

    The builder of my Egg Harbor 37 1970, above the waterline, planks are edge set with a small caulking bevel into which was stuffed fine cotton threads the size of kite strings. This was then covered over with white seam compund.

    Now what do you suppose happens to white linseed oil seam compound after so many years? It all cracks open turns rock hard, lets in water which then causes edges of planks to rot. It just does not look good at all.
    Some seams did show daylight all the time, anyway after replacing rotten wood, I repayed all the seams with acrylic latex caulk DAP Dynaflex 230 last haulout. When it cures, it forms a pretty hard rubber. I managed to make it look very good. I wanted to see all the planks edge seams.

    So here it is all dug out that old cracked seam compound. It was not easy.
    [​IMG]

    This was how I did it.
    [​IMG]
    Here I repaired some of the plank edges with new wood glued in.
    Also shows the white DAP caulk. After some light seam sanding and painted with kilz123 latex primer it looks really perfect. Dap Dynaflex 230 is a waterproof caulk.
    It will never crack open.
    [​IMG]

    Closer view of seams filled, hand sanded seams and painted. The DAP caulk can be wet sanded easily after a few days of cure.
    [​IMG]
     

  15. gonzo
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    gonzo Senior Member

    The caulk is part of the hull's structure. Taking out the cotton and replacing with only an elastometer the hull. The planks will be allowed to move longitudinally between each other instead of forming a panel.
     
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