caulking planks

Discussion in 'Wooden Boat Building and Restoration' started by JimHog, Oct 26, 2006.

  1. motorbike
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    motorbike Senior Member

    There is no mystery to caulked boats, you just need to know what youve got to deal with. If your boats is well fastened with good timber and the seams are tight its a piece of cake, if its a sloppy old workboat you need big gear and lots of muscles!
    Painting dark colours is generally not advised but you can try it if you want. Recaulking is easy, you never remove old cotton, you just bash in more with the right sized iron. Its not hard! just make sure you dont bash it more than 3/4 of the plank depth and that the hammering is even. Taper the cotton etc when adding more. The best way is to hire an experienced (older) boatbuilder for a day and watch. If you can pick it up in a day- well you should consider a glass boat.

    You can pay the seams with either putty or something like sika 291 underwater. Above the waterline use putty. Remember its the cotton holding the boat firm and waterproof- the sika or putty is essentially to hold the cotton in and to make the boat look nice, although they do hold a lot of water out as well. Personally I like Sika, but you must clean the seams and prime with grey primer or sika primer for it to work. Its really fixes them.

    Again the cotton is the main part and you need to attend to this well. The putty or whatever is secondary.

    good luck and dont be afraid to get stuck in and do it as there is a lot of bullsh*t out there suggesting its a hard to learn dark art.
     
  2. BATAAN
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    BATAAN Senior Member

    Par is absolutely right here.
    Back in the stone age when I thought I was a hot carpenter and was taught how to caulk by being physically pushed under an ancient, rotten, leaking 100 foot wood barge at $5 per hour, and there were still 4 members of the Caulker's Union in San Francisco, the whole thing was explained to me thusly:
    "The caulking ain't just to keep the agua out kid, it turns a basket into a bowl, now get to work under that basket of a barge or you're fired!"
    "But I'm a carpenter, not a caulker."
    "You're either a caulker or an unemployed carpenter, take your pick."
    So I spent the next several weeks caulking overhead in a 3' space as vile fluids tasting of the graveyard leaked in my face. But the barge went back to work making money for its owner and I still had a job.
    An uncaulked wooden boat is like a basket, all parts are free to move to accommodate stress and the thing flexes a lot under load.
    Caulking turns it into a bowl, rigid and unwilling to distort, because one has effectively driven continuous wedges between the planks over the whole thing. There is no way any caulk/sealant can do the same job.
    Sealant for "paying" over the caulking can be everything from nothing but paint (formerly common on the topsides of wooden tugs), to $7 per-hundred-pound-bag Portland cement below the water, to common window putty, fancy and expensive 'seam putty' with a boat on the label which is pretty much the same thing, red lead putty, shingle cement and many others, all with plus and minus points. Urethane sealants are one choice but I find they fail in long strings when they go bad and it all comes out at once, sometimes pulling the cotton with it, plus this is the most expensive choice.
    Even a clinker hull needs the rabbet caulked. Here is a job I did 2 years ago. I used varnish to prime, then seam putty over the cotton.
    The last pic is caulking and painting an old hull on the beach between tides. This is something we did a lot back in the 70s and nothing but oakum and cement is practical in this type of work.
    For a small, new hull with carvel planking, just pick something from a designer who understands wooden boats and do it the way he says.
     

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  3. Landlubber
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    Landlubber Senior Member

    ...for paying we used whiting and boiled linseed oil, works a treat and hold any paint used over it.
     
  4. BATAAN
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    BATAAN Senior Member

    Whiting is cool stuff and we used to mix it with white lead to make very durable putty. Can't do that anymore. I like the whiting and linseed oil paying idea. Around here some use asphalt "wet patch" roof cement mixed with dry portland cement until it's quite stiff, then troweled over the oakum. This is referred to as bear **** and forms a flexible yet hard and very durable underwater putty on big craft.
     
  5. Bob Smalser
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    Bob Smalser Junior Member

    Don't forget centerboard trunks. Even the trunk posts in a plywood-and-epoxy boat need caulking if the builder had the wisdom to mount the trunk traditionally instead of with more glue.

    [​IMG]

    They are the weakest place in the hull...all eventually require repair...and it's nice to be able to do the repairs using a screwdriver rather than a Sawzall.
     
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  6. PAR
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    PAR Yacht Designer/Builder

    I use to design my cases with a traditional caulk seam, but now rely on the new sealant/adhesives available. The case can be easily removed with a hot putty knife once the fasteners are pulled.
     
  7. Joe sabo
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    Joe sabo Junior Member

    caulking a carvel Planked boat with polysulfide

    Hi I have a question about caulking a carvel planked double ended Coast Guard 26 ft whaleboat. I reefed the cotton out and carfully cleaned out the seams of old paint and compound and sealed the seams with Smiths CPES and coated the bottom with Smiths as well. I am now going to put the cotton in. The Planks are 1 " thick and am considering using a polysulfide over the cotton as the boat doesn't live in the water and will be a trailered in and out of the Lakes up here in Upstate NY. the boat hasn't been in the water since fall 2004 so the boat is dry. Question #1 How tight should the cotton be tamped in the seams and how much cotton should be used . Question #2 what is the best polysulfide to use in this case and is a hard epoxy paint OK to use on the bottom as I have already sealed the bottom with epoxy.
     
  8. gonzo
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    gonzo Senior Member

    Usually to train you ear to hear the right ring. I don't know how else to explain it.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Since you've CPES'd her, you have to get the moisture back into the hull and swell up those seams. Other wise you'll launch and the planks will eventually swell (CPES isn't remotely water proof) and it'll spit out all the caulking you just pounded in.

    A weeping hose or garden sprinkler will do and let it run for a week or two. When you caulk your seams, start on the topsides and with some luck, by the time you get to the LWL, you'll have enough skill to do a water tight job, without splitting any planks or breaking frames. As a few have mentioned, it's an experience thing and not easily described. If using proper tools it can be a sound, but it can also be a feel thing. Accurately conveying either is difficult.
     
  10. BATAAN
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    BATAAN Senior Member

    PAR is absolutely right about the need for mechanical joining of the plank edges by pounding the 'wedges' of cotton or whatever between them.
    A carvel boat without caulking is like a big basket, you can twist and rack it in your hands and the pieces slide past each other, but add properly tucked and set caulking, with or without putty and paint over it, turns the basket into a bowl, rigid and much more resistant to deformation and able to spread loads over the entire structure.
    I too have seen jobs that someone did not understand the mechanical need for caulking and just used sticky hardening rubber, either Polysulfide or Polyurethane, and had big failures when the boat was stressed hard. It puts a lot more load on the fastenings and they fail much sooner.
    If the proper out-gauge is present between the planks (1/2" in 10"), almost anything including horse poop has been used successfully for the wedge-forming material pounded in the seams, it forces the planks apart, makes a waterproof joint and does the job.
    On low-budget, soft, old fish boat repairs in the past I have personally used hundreds of wedges cut off flush, when the plank edge was so bad it could not be caulked any other way.
    On others, a long spline cut to a wedge shape has worked in repair to glued-edge boats like Knarrs and IODs where a seam had opened, to restore the glued-edge structure.
    An eastern Canadian method is cotton-caulked seams with routed-in battens over instead of putty.
    In heavy planking, such as tugs, the old common method is no putty in the topsides, just pounded full of oakum, and portland cement as putty in the bottom seams over the oakum.
    West Coast caulking style for over 1.25" plank is a choker of cotton, caulking the job complete, then a line of good soft long fiber oakum over that leaving a seam about as wide as it is deep, then red lead paint, then topside seam putty or underwater seam putty as the location requires.
    "Bear S**t" is a NW USA seam putty mixed from powdered Portland cement and black roofing patch tar, applied below the water over the caulking.
     
  11. BATAAN
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    BATAAN Senior Member

    Good advice.
    Start with the second seam down in the topsides. If you over-caulk your 'learning' seam, you'll push the sheer strake up and off the boat.
    The proper irons are crucial and you only need two for this job, a very thin OO size that you loop the cotton in with in 'tucks' and then caulk it in the seam with, and one about 1/8" for 'making' the cotton or tamping it down evenly.
    The process starts with the butts first, leaving a 1" tail hanging out anywhere you stop, then the seams, crossing the butt tails and trapping them in. All the seams run out at the stem, again with the tails, last seam is the 'devil' or stem rabbet/garboard which traps all the plank tails.
    After these steps you're there.
    The proper caulking mallet (eBay, searches "caulking or caulker or caulk") helps, but for just one boat, a square wooden carpenter's mallet will serve. Not a round one, you can't control the blows right.
    Here's a couple places to look.
    http://www.youtube.com/watch?v=qCxqvjSD4uo
    http://forum.woodenboat.com/showthread.php?115648-Very-dry-carvel-hull-caulking-techniques
    http://www.nwboatschool.org/programs/Course_Detail.aspx?processID=23
     
  12. Joe sabo
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    Joe sabo Junior Member

    Interesting. The boat is upside down and I repainted the bilges will I have to right the boat back up and irrigate it with sprinklers and just caulk her with it upside right. was it a bad decision to do the CPES on the bottom? the seams on the topsides are much thinner than on the bottom and the seam between the keel and the Garboard plank is twice as wide what do I fill that with cotton also or oakum. the keel section in the aft where the prop shaft comes out has large gaps also should I use oakum on those as well?
     
  13. Joe sabo
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    Joe sabo Junior Member

    Thanks for the videos they were informative I have the proper mallet and the thin caulking Iron Id love to go to the school but thats not possible
     
  14. BATAAN
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    BATAAN Senior Member

    No reason to right the boat as it's much easier to caulk upside down.
    CPES is questionable but it's too late now.
    It does prevent the soak water from being as effective as it could be, but a sprinkler or soaker hose used at a low level for a few days should wet the hull as much as you are going to get until it's launched, and probably enough.
    When caulking, the first step is tapping in loops of material.
    The size of, and distance between, those loops governs how much cotton goes in the seam.
    Small seam, tight loops far apart-
    Big seam, big loops close together.
    When you work this into the seam you wind up with the right amount.
    If you overfill a seam just pull it out and do again.
    Start with the butts, then the tightest seam on the boat, as the caulking will tend to open it by moving the plank over into the adjacent, uncaulked seam's space.
    Do the largest seam last.
    Then the stem and garboard.
    Be careful not to pound the iron into the wood or caulk so tight it breaks off the inside edge of the plank.
    The exposed oak keel aft/stern timber may need a spline instead of caulking.
    Post some pictures so we can see better what the keel problem is.
    Check the garboard fastenings and make sure the plank is not adrift. Whaleboats are usually caulked with all cotton with oil/white lead putty over.
    Oakum in general is for plank over 1", and then over cotton usually, though in Europe (Denmark I know for sure at least) caulking is all oakum and they are horrified at caulking with cotton saying it holds moisture and rots the planks....
    Sometimes a caulker must will twist two or more strands together to make a 'superstrand' to caulk a particularly large seam, or sometimes split a strand to make a thin one for a particularly tight place.
    Overlap all ends at least an inch every time you start or stop a strand.
    At any point on the hull an old caulker's trick is to put your fingertips on a caulked seam, then tap smartly on the planks on both sides of your fingers. If you feel any movement something is amiss with the fasteners and/or caulking.
    This is an especially important check of all butts and hood ends and is part of any knowledgeable surveyor's kit of tricks.
    When a proper job of caulking is finished, the former bundle of loosely associated lumber becomes a rigid and quite rugged structure known as a boat.
     
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  15. BATAAN
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    BATAAN Senior Member

    If you are unsure, a 'practice caulking wall' of 3/4" x 5" x 48" pine planks, say 6 of them, planed with a beveled caulking seam (tight on the inside, 1/8"-3/16" on the outside) and nailed to 2 x 4 'frames' on about 10" centers, gives a cheap way to learn the job without screwing up any of your nice planks on the boat.
    The seam can be made on one edge of each plank only and makes no difference, so long as it's tight inside and has about the right bevel.
    This is the usual tool for teaching caulking in a boatbuilding school.
    Caulk it up, reef it out and do it again.
    Then tackle the boat with more confidence and skill and do a fine job.
     
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