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Thread: leak in our folkboat just got worse?

  1. #1
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    Default leak in our folkboat just got worse?

    We have a 63 year old clinker built nordic folkboat - copper nailed mahogany on oak. She's always leaked a bit but never more than a litre or so in 24 hours. She was overwintered afloat in a local marina, checked regularly until a week ago when we moved her to her summer swinging mooring. It was a 5 hour journey much of it motoring into a headwind and steep chop. Halfway through the trip I realised that every time she slammed down into a wave trough a small plume of water would appear in the bow. Not enough to get the automatic bilge pump running but just enough to worry about.
    We made it to the summer mooring, pumped her dry with the manual bilge pump, covered the cockpit to keep out rainwater (cockpit drains into the bilges) and left her there. We've been back to check every few days and the water levels in the bilge are much higher than they used to be.
    Could the slamming into the waves have caused some of the planking to become loose?

    We're about to dry her out on the scrubbing posts for annual maintenance, painting and antifouling. Is there anything I should be looking for?

  2. #2
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    Default Re: leak in our folkboat just got worse?

    I don't know that this could be true in your damper climate but here in New England a boat left in the water keeps her bottom nice and tight but the topsides can dry out. It's not unusual for it to take a week on the hook, more dynamic, for the topsides to fully swell up.

    This might not be the case for you. It's less of an issue in our Pacific Northwest with a climate not unlike yours. Also if she's leaking on the mooring, the chances are that it's not just dried out topsides.

    My old schooner Goblin (Alden 43' built in the 1920's) worked a great deal when sailed, especially if sailed hard to weather. On a hard beat the main mast pushed the coach roof and hull so hard that cabin doors could not be closed if open and not be opened if closed. And she'd go from her normal leakage of 50 gallons or so per day to ten times that or more, then taking a few days to a week to settle back.

    My impression is that carvel construction can settle back to nominal leaking more readily than clinker. So you might or might not tough it out this summer but may need a bit of tightening up within a year. I doubt that inspection will show anything you don't know, like the obvious sprung plank or bit or rot or breakage. Rather, you make the call based on leakeyness.

    Get a really powerful 1-1/2" minimum, better 2", hand operated diaphragm pump. The Edsons of this type can remove 30 - 55 gallons per minute. As Tristan Jones put it, woodenboats so seldom sink because they carry great pumps.

    If you're copper riveted, tightening is tedious but not hard. Given the thousands of rivets, a pneumatic tool will make things much easier. Still a two person pain as one must go inside with a bucking iron to push against the rivet being tapped down.

    G'luck

  3. #3
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    Default Re: leak in our folkboat just got worse?

    If she seems to be taking on water even when on her mooring I would first suggest a bucket and large sponge. Pump her as dry as you can then start working with the sponge and simple follow the flow to its source. Then you will have an idea of what you are dealing with.

  4. #4
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    Default Re: leak in our folkboat just got worse?

    If you have a counter on an automatic bilge pump you can readily log all leakage and correlate that to conditions and activities. The pump will take out a fairly consistent quantity each time the float cycles it on and then off again and a bucket under the outflow once will give you a volume per cycle. Or just count cycles.

    If you don't have a counter, get one.

    I have no electric pumps so I have bounced between counting pump strokes - very zen feeling - or keeping track of how many minutes it takes to pump.

    And log it.

    This will provide the data as to whether you should actually worry or just enjoy old boat ownership.

  5. #5
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    Default Re: leak in our folkboat just got worse?

    When at the scrubbing posts look at the hood ends, plank ends, at stem and transom, as well as the garboard seam, these are not riveted but screwed or nailed. All the copper riveted joints should be good, but Ned's suggestion should be tried first to see what you are dealing with.

  6. #6
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    Default Re: leak in our folkboat just got worse?

    This worked well as a 'temporary' solution that lasted all summer. A motor launch.

    First the boat was pumped and sponged so that we could see about where on the inside water was emerging. On the assumption that water can travel in a seam - that the location of inflow might not be the location of the leak outside - we used that as a guide but worked six or more feet fore and aft.

    Both fine sawdust and ultra fine sanding dust were collected. The tool was a plastic cup nailed to the end of a stick. Took a bit to get the hang of filling, inverting as the cup is slammed into the water so the dust does not fall out in the air or float out prematurely in the water. Once under about the right place the cup was turned right side up and some of the dust would float into the leak, swell, and plug it. The saw/sanding dust was labeled "Mill Pond Mix."


  7. #7
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    Default Re: leak in our folkboat just got worse?

    Before you go alongside the scrubbing posts do as NedL (#3) says to try to establish where the leak is located – you know it is up forward somewhere because that is where the water was squirting in.

    Banging into a head sea can indeed cause the planking to start if the fastenings are getting bad in some way. As Thad (#5) says it's most likely to be the hood end fastenings (the screws in the plank ends into the stem) or the garboard fastenings (the screws from the lower edge of the first plank into the rebate in the wood keel). Look also for signs of the caulking and stopping coming loose along the garboard seam and up the hood ends. Also, if a seam is bad it will generally "weep" as the rest of the planking dries off. And a plank that moves under load will often throw off the stopping over the screw heads.

    If you find a suspicious area, test the screws by trying to tighten or loosen them – if they have corroded over the years they will probably break. Use a small screwdriver to work the stopping out of the slot in the head and then a larger screwdriver that fits the screw slot nicely, as near as possible the full width. With the screwdriver properly in the slot, give it a really sharp bang with a heavy hammer and then try to TIGHTEN the screw perhaps ¼ turn, before attempting to undo it.

    It is possible (quite likely in fact) that the garboard and/or hood ends are fastened with rosehead copper spikes rather than screws – and these can become loosened with age and pounding. Sometimes this can be fixed by driving some additional silicon bronze screws.

    Other possibilities are that the joint between the stem/apron and the wood keel may be in trouble; or possibly the stopwater has rotted away.

    It may be more than can be achieved between tides on scrubbing posts – but you should be able to get a handle on the problem at least.

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

    A C Grayling

  8. #8
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    Default Re: leak in our folkboat just got worse?

    Thanks guys for all the advice. Really do appreciate the time everyone has taken.

  9. #9
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    Default Re: leak in our folkboat just got worse?

    well that was interesting. Followed the advice about using a sponge and discovered that the leak is about 4' aft of the forepeak. It's the port garboard seam which is weeping. A small but steady flow. Will try retightening the fixings and/or using silicone bronze screws. There are a few plank seams that are moist in a few places so will try redoing the copper nails.

  10. #10
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    Default Re: leak in our folkboat just got worse?

    Quote Originally Posted by letham View Post
    well that was interesting. Followed the advice about using a sponge and discovered that the leak is about 4' aft of the forepeak. It's the port garboard seam which is weeping. A small but steady flow. Will try retightening the fixings and/or using silicone bronze screws. There are a few plank seams that are moist in a few places so will try redoing the copper nails.
    You might not have to "redo" the seam fastenings apart from just resetting the rove and peening the ends to tighten them. Try that before taking the nails out, but if you do have to be sure to replace them with nails one gauge larger.
    It really is quite difficult to build an ugly wooden boat.

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  11. #11
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    Default Re: leak in our folkboat just got worse?

    I believe that it is highly possible that the garboards are fastened to the keel with brass screws...

    /Mats
    My blog about my time as a boat building student and as a rigger apprentice http://kaptenmohsart.blogspot.se/ in Swedish only, but there are many pictures :-)

  12. #12
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    Default Re: leak in our folkboat just got worse?

    Another traditional fix is simply putting in new rivets between the existing ones. The rivets themselves are usually not leaking, but they might not be strong enough to clinch the boards together enough to keep the hull completely watertight. Instead of all the work of removing and replacing with larger rivets, you can keep the old ones in place. When they are relieved of doing all the work, they become happy rivets again. Its a lot faster to put in new rivets than removing the old ones.

    We've just taken over a boat built before 1900 in the coastal association here in my town. Built with iron rivets and repaired long, long ago with new rivets between the original ones. We are still going over the rivets, checking for faulty ones, but so far it looks good. The originals must have been giving some trouble, but they are still sound.
    Your copper rivets should be even more time-resistant.

    So - if the leak is due to the rivets stretching and re-clinking doesn't serve, I'd sooner add new ones between the old than remove and replace the originals.
    Do not use screws. Rivets are the solution.

  13. #13
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    Default Re: leak in our folkboat just got worse?

    Hi there

    Wooden folkboats are usually leaking from the clinker plank joints. This is usually caused by some of the arcs being rotten/broken which in turn causes the planking to take the load of any force that applies to hull. That is why the riveting starts to let go (rivets stretch or the plank just cracks (usually along line of riveting holes). This usually happens in two places - where the mast is (that is why there are enlarged or double arcs there) or around the cockpit area (because lazy previous owners did not cover it up and it was open to water 24/7).

    You can fix it buy first locating the leak (go out on the bay with a bit of waves if you don't find it in harbor), marking it, then closing the leak. I have seen closing small cracks with polyretan mass (Sikaflex), re-riveting existing rivets, cutting the cracks straight and then closing with eg. 10 mm stretch of same timber + epoxy.

    Almost any chemical used in boat repair requires dry and clean surfaces. If you are in hurry, I have used heat-blower to get the glued place dry in minutes temporarily.

  14. #14
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    Default Re: leak in our folkboat just got worse?

    Quote Originally Posted by Ian McColgin View Post
    This worked well as a 'temporary' solution that lasted all summer. A motor launch.

    First the boat was pumped and sponged so that we could see about where on the inside water was emerging. On the assumption that water can travel in a seam - that the location of inflow might not be the location of the leak outside - we used that as a guide but worked six or more feet fore and aft.

    Both fine sawdust and ultra fine sanding dust were collected. The tool was a plastic cup nailed to the end of a stick. Took a bit to get the hang of filling, inverting as the cup is slammed into the water so the dust does not fall out in the air or float out prematurely in the water. Once under about the right place the cup was turned right side up and some of the dust would float into the leak, swell, and plug it. The saw/sanding dust was labeled "Mill Pond Mix."
    This is an old method that I have used for example on one 14th century clinker replica that had spring time issues with leaking. It does work - dry wood dust particles are pulled into the boat with the flow of water to empty hull and get stuck in the cracks, where they swell up. BUT what do you have as a result in a few months- organic rotting matter stuck in between wooden planks that keeps moisture for prolonged periods and harms the planks. In my case it ended up discovering some kind of worms living in the rotten plank seams a few years later. Now with more experience, I always prefer waiting for the boat to dry and filling it with flexible polyretan adhesive mass if it is clean surfaces (all seawater and sun resistant ones are OK) or with industrial roof bitumen mix (eg Soudal roof bitumen in bottles) - heat it a little for application, it goes in and becomes solid in the crack, excess is pushed out and can be cleaned later. These and similar methods have more hygiene

  15. #15
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    Default Re: leak in our folkboat just got worse?

    The Folkboat owners here in Sweden usually route out the seams to ½" or so and epoxy in a batten for a permanent fix. The setup is a skilsaw with two blades and guidepins
    But I'd check the timbers in the bow carefully so there isn't any structural damage.

    The thing with the sawdust is called "anting" in Swedish, apparently you'd get a shovelful of the nearest anthill and push it under the boat, imagine the size of those cracks if that was suppose to work!
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  16. #16
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    Default Re: leak in our folkboat just got worse?

    All those "sawdust" fixes may work if the boat simply needs to take up after drying out. They will never be a fix however if the problem is structural – which yours pretty certainly is.

    If the leak is in the garboard to wood keel seam, then either the fastenings are getting bad (quite likely) or the heels or lower ends of the timbers in that area are decayed and/or broken so the garboard can start to "work" – which is classic pounding into a head sea. Or both. You can easily see broken timbers. If there are some, they need to be fixed either by replacement or (more easily) by sistering them.

    When she is alongside the scrubbing posts you will most likely be able to see the bad area, which will continue to weep after the rest of the planking has dried off.

    Find out how she is fastened – screws or spikes – and then proceed accordingly. Before driving new fastenings or tightening existing fastenings, it is best to rake out the caulk and stopping from the seam area concerned. Then re-caulk carefully and re-stop after re-fastening.

    It is possible that she was fastened with brass screws I suppose – in which case they will be thoroughly de-zincified by now. But boatbuilders wouldn't usually use brass screws in this situation.

    Plank-to-plank fastenings can easily be tightened up if required – but it is a two-person job with some degree of organization. The outside person needs to hold on the head of the nail with a heavy steel "doll" while the inside person peens the nail over a bit more on the rove. You shouldn't overdo this – just lots of light blows with a small ball-pein hammer (like 4oz) to draw the nail tighter. Heavy blows will simply cause the nail to bend inside the planking, which will just leak again under stress.

    Plank-to-plank fastenings may leak under stress but will seldom get much worse over time. Bad garboard and hood end fastenings will however get worse quite quickly and could easily lead to a dangerous leak situation in any sort of seaway.

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

    A C Grayling

  17. #17
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    Default Re: leak in our folkboat just got worse?

    brass screws was used for folkboats and is a known problem

    /mats
    My blog about my time as a boat building student and as a rigger apprentice http://kaptenmohsart.blogspot.se/ in Swedish only, but there are many pictures :-)

  18. #18
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    Default Re: leak in our folkboat just got worse?

    Quote Originally Posted by mohsart View Post
    brass screws was used for folkboats and is a known problem

    /mats
    Right - I didn't know that. Then it's likely that is the problem – they have simply de-zincified and need to be replaced.

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

    A C Grayling

  19. #19
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    Default Re: leak in our folkboat just got worse?

    Quote Originally Posted by Ryden View Post
    The Folkboat owners here in Sweden usually route out the seams to ½" or so and epoxy in a batten for a permanent fix.

    The thing with the sawdust is called "anting" in Swedish, apparently you'd get a shovelful of the nearest anthill and push it under the boat, imagine the size of those cracks if that was suppose to work!


    I have read that ants are high in Formaldehyde and a good preservative.... I like the "seam-batten" fix.

  20. #20
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    Default Re: leak in our folkboat just got worse?

    Seam batten is great for a carvel planked boat. The OP boat is described as clinker, aka lapstrake in the US.

  21. #21
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    Default Re: leak in our folkboat just got worse?

    Quote Originally Posted by Ian McColgin View Post
    Seam batten is great for a carvel planked boat. The OP boat is described as clinker, aka lapstrake in the US.
    Misunderstood...one of many today.

  22. #22
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    Default Re: leak in our folkboat just got worse?

    Replacing the edge of a plank in a lapstrake boat with a new "batten" seems like a good idea to me.

  23. #23
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    Default Re: leak in our folkboat just got worse?

    Quote Originally Posted by Ian McColgin View Post
    Seam batten is great for a carvel planked boat. The OP boat is described as clinker, aka lapstrake in the US.
    And I even checked the top post to see which one it was, and still got it wrong...
    I blame the anti-histamines
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  24. #24
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    Default Re: leak in our folkboat just got worse?

    Easy in a long thread to lose track.

    I was hoping that the boat had the laps riveted. If it's all little brass screws then seam tightening is much much harder. I suppose one could remove screws and, as one goes along so the boat doesn't just fall apart, replace with rivets. A job for someone with greater courage than I have.

    And a job that should be undertaken after looking at what's up with the plank ends - both those landing on the stem and those on the horn - and with the ends of the frames - if not all frames at least the frames near stem and horn. At the same time, evaluate the stem and horn timber.

    If the stem, horn and at least most frame and plank ends are still sound, it might well be possible to begin incremental repairs, starting with refastening the plank ends to slow the worst leakage. Then start refastening with rivets if screwed, or tightening rivets if you're lucky, a bit each year.

    You'll need to make frame decisions along the way, sometimes in place frame replacement, sometimes laminating in-place a new frame end, and sometimes just sistering.

    If you're lucky, you can sail the boat each season and do another section of repair each winter, rather than drop about the price of a new boat all at once.

    Hope this can be worked out.

  25. #25
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    Default Re: leak in our folkboat just got worse?

    Traditional clinker construction most often has two clench fastenings (square copper boat nails, clenched over roves) between the timbers (steam-bent frames) which are often at about 6" centres or thereabouts, and a single clench though the timber – I doubt the plank laps will be screw fastened. In European yacht construction (carvel and clinker), screws are usually reserved for hood ends and the bottom edge of the garboard – and even so, especially on larger boats, the hood ends were often fastened with copper rosehead spikes.

    Provided the planking itself is sound, the clench fastened laps may weep a bit but seldom leak really badly. And hardening up the clenches carefully usually fixes the problem.

    It sounds from the OP's description as if the garboard seam (to the wood keel rebate) is leaking up towards the bow. This is likely de-zincified fastenings, a degraded garboard plank or some cracked/decayed timbers – or a mixture. One should also check out the mast loads, if the mast is keel stepped. These can open up a garboard seam if the mast load structures are becoming degraded.

    The thing is, do not simply re-caulk and re-stop the offending seam without exploring the condition of the fastenings, timbers etc. This can easily make the problem worse down the line.

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

    A C Grayling

  26. #26
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    Default Re: leak in our folkboat just got worse?

    Yes, screws where the strakes hit the keel and (possibly) stems, otherwise cupper rivets. The frames are sometimes held with screws, but probably not in this boat.

    /Mats
    My blog about my time as a boat building student and as a rigger apprentice http://kaptenmohsart.blogspot.se/ in Swedish only, but there are many pictures :-)

  27. #27
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    Default Re: leak in our folkboat just got worse?

    Check stem and stern knee bolts. Stop water.
    Boats can become "hinges" at the stem grip. Loads that belong in the keel transfer to planking, where they do not belong.

  28. #28
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    Default Re: leak in our folkboat just got worse?

    Copper nails don't last forever. Sitting in wet timber, they corrode - very slowly. But after 63 years, they'll have corroded a little, allowing more water to seep past them, and also accelerating their corrosion. Nick's suggestion, above, to replace any suspect fastenings with larger ones is the best solution, if you find the copper fastenings are beginning to break down. If the roves inside are green then you definitely have a little moisture seeping through to them.

    Rick

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