Lapstrake repair ?

Discussion in 'Materials' started by Fisean, Aug 13, 2007.

  1. Fisean
    Joined: Nov 2006
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    Fisean Fishaholic

    I have an older lapstake oak boat. After recently hauling the boat out to redo the bottom paint. I noticed some extensive "wear areas" on the bow near the keel. I was thinking about reinforcing with some fibreglass, but had a bad experience glassing to wood in my younger days (long story). I'm not sure this in the right forum. But does anyone have any suggestions, or products to try w/o replacing the wood? Thanks in advance.
     
  2. USCGRET/E8
    Joined: Jul 2007
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    USCGRET/E8 Senior Chief

    Some pics would be very helpful to make a diagnosis.
    And yes, I don't think a glass patch would be good.
    Are your laps solid wood or plwood?
     
  3. Jratte
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    Jratte Junior Member

    One word of caution: Epoxy does not have a good reputation for adhering well to oak.
     
  4. Fisean
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    Fisean Fishaholic

  5. USCGRET/E8
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    USCGRET/E8 Senior Chief

    It's plywood. Looks like maybe a bit of rot there. Take a sharp pointed tool and poke it good. If it seems soft, the wood will need to be replaced. (For reference, poke where you know the wood is good). A quick patch fix, would be to remove any soft wood and then fill the areas with thickened West Epoxy. Be sure the wood is good and dry before you do though.
     
  6. Fisean
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    Fisean Fishaholic

    Thanks for the replies, great info....on the road to restoration!
     
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The garboard is surely plywood, it goes to reason that the rest of the planking would be as well. I'm not sure what you have there, but the framing is likely oak (probably steam bent). Judging by general size and fastener spacing you have frames molded 3/4" - 7/8" and sided maybe an inch, possible slightly wider (1 1/8") which would be on 7" - 8" centers.

    The garboard has some hardened goo packed into it already (looks like in the photo), possibility a previous repair attempt. You could patch the area, but the problems this hull has, will come right back. The fasteners are popping the putty, which suggests excessive plank movement, which is typically a result of opened lap seams. I also see unfairness in the sweeps which indicate several plank to frame fasteners are no longer doing what they're supposed to or that frames have cracked/broken (also very probable, in this type of hull).

    I fix quite a few lapped hulls and she's in need of new planks, some frame repairs and likely other things as well. You may get by with new garboards and refastening, but honestly, when they get like (the planks) this you can't save them, you just start over, hopefully they'll provide patterns for the new ones. Sistering up a handful of frames and tossing on new bottom planks is a very daunting job for the novice. Clench built boats are about the most difficult repair going on wooden boats. I would seriously consider getting some profession assistance on this project.
     
  8. Joseph Bettis
    Joined: Aug 2007
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    Joseph Bettis New Member

    lapstrake repair leaks

    I have a beautiful lapstrake snekke built in Norway in 1977 but new to me. After haulout no problem with leaks. But underway major leaks above waterline at stem. Will these eventually swell up or should I get more aggressive with say penetrating epoxy on the inside?
     
  9. alan white
    Joined: Mar 2007
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    alan white Senior Member

    Slowly put the epoxy down...
    Give those joints time. You could use a goo that will squeeze out (3M 5200 comes to mind) if the water is a big bother. Epoxy would be a big mistake, possibly actually doing serious damage. If you sealed the wood well inside and out, it will take that much longer for the above-water planks to swell shut. Modern paints and coatings are sometimes a bit too good.

    Alan
     
  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Do not use epoxy of any kind on a lapped hull. Traditional lap hull construction relies on the movement of the planks to keep out the water. Polysulfide below the waterline and polyurethane above, if you plan to goo the seams, but polyurethane (3M 5200) requires pressure or it will release from wet wood. Generally, this means the plank has to come off, the seams buttered up and the plank re-hung and fastened. This isn't a task I recommend for the novice.

    Lapstrake hulls are particularly good at tolerating wet/dry cycling of the planking. If you're getting leaks, that don't close within a few days of launching, you have other issues. These issues likely are fastener related, which possibly have also caused other issues. Lapped hulls are clenched, roved, screwed or bolted tight, the full length of each lap, on closely spaced centers. Clenches are the least capable of holding the lap closed, followed by screws, roves and closely thereafter by through bolts.

    In short if you have leaks in the laps at the stem or the hood ends at the stem, you probably need to call a boat carpenter to work her over. Just removing the fasteners, without doing any major damage is difficult, so strongly consider professional help.
     

  11. keith66
    Joined: Sep 2007
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    keith66 Senior Member

    I fully agree with Par, i have spent many years repairing boats and have done more than my fair share of clinker (lapstrake) repairs. If there is one thing guaranteed to make me despair it is a poor wooden clinker boat that has been either caulked or slathered in epoxy or fibreglass, i have seen many that could have been repaired properly ruined for ever by the application of modern goop.
    Clinker boats can get leaky with age, and it is not a hard job to refasten them or even pull out a split plank and replace it. The only stuff i would recomend for between the planks is a completely non setting oil based mastic such as EVO mastic, this will squeeze out as the planking swells and not cause damage.
    If a clinker boat is getting really old and knackered, fine use a bead of polysulphide along the seams just to get a few more years out of her before the inevitable vikings funeral !
     
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