Caulking planking over plywood bottom

Discussion in 'Wooden Boat Building and Restoration' started by goingjag, May 21, 2016.

  1. goingjag
    Joined: May 2016
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    Location: Higganum, Ct. USA

    goingjag New Member

    I have a 1968 Trojan Sea Skiff (I believe that is the correct model, but not certain) 28'.

    The bottom is plywood with planking over it.

    The second owner must have pulled all the caulking out, as the owner of a plywood only boat before, I did not realize caulking was needed.

    When the yard put the boat in, apparently they did not put enough padding on the sling buckle and without my knowledge it broke through the plywood. When I arrived the evening of July 4th the sump pump was running every 7 minutes. After discovering the problem (the yard owner had left for the holiday hours earlier) I was able to fasten some plywood on the inside and stop the leaking. That got me through an abbreviated season of being a floating cottage, when I hauled her I noticed the missing caulk.

    Unfortunately due to illness I haven't been able to address her for the last 7 seasons other than to put in a more permanent plywood patch now fastened to the outer planks.

    I am now capable of working on her, but not sure what to use on those seams/how to apply it.

    I have read enough before posting to know not to use 3M 5200. I believe PAR recommended 3M 100? in an old thread but that thread left me wondering if that was still the recommended material, and if so how much.

    Thanks for any assistance.
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The caulk is cotton which gets pounded in with a caulking iron. It locks the planks together by friction and makes it a structural panel. This is a job for a professional and is quite physically demanding.
     
  3. goingjag
    Joined: May 2016
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    Location: Higganum, Ct. USA

    goingjag New Member

    Thanks Gonzo. I imagine that would be the right way to do it, especially back in the day. However I'm hoping (mostly because the skill isn't available in my area) that since the first "planking" is plywood, that the cotton caulking is less important here than in an all plank boat, and that I might get away with some form of modern day caulking only.

    Since the outer planks are fastened through the plywood into the ribs, I'm thinking they can't "move" as much as a standard plank and thus hopefully won't require cotton caulking?
     
  4. gonzo
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    gonzo Senior Member

    That is not correct. If you don't use cotton, the forces will be concentrated on the fasteners and eventually will make them fail.
     
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There shouldn't be any traditional caulking (cotton or oakum) in the bottom or topside seams. The garboard to keel seam will have a cotton string laying in the bottom of the rabbit, but that's about it. It depends on the year, equipement and when they made the transition to goo's, which they were reluctant to do. These Trojans had lapstrake topsides, but plywood bottoms. They did use polysulfide in the laps by '68 (I'm pretty sure) and 3M-101 is the usual choice. All the Sea Skiffs and some of the Sea breezes are done like this. The Trojans were well built before Whittaker took over in '69 - '70.

    Can you post pictures?
     
  6. goingjag
    Joined: May 2016
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    Location: Higganum, Ct. USA

    goingjag New Member

    Thanks PAR. I was mistaken in the boat type it's a Sea Voyager. I believe the flying bridge is a tack on, early in it's career.

    Here's a link to how she looks overall now and some pics of the bottom taken today, as well as one pic from before I bought her.

    http://s1184.photobucket.com/user/goingjag/library/Sea Tramp 2016

    When I was taking the pics today I noticed some above the water line putty pops toward the bow (I think you can see them if you look at the image in full size), I'm assuming that's normal for a boat that has been out for 7 seasons.

    Is a wood filler still the material of choice for filling fastener holes? Any recommendations?

    Thanks for your help - it was your 2008 response to someone that led me to this forum.
     
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Okay, a wholly different animal. These boats do need to be caulked, but more importantly, the structure needs to be repaired, before you can caulk. She's seen some haphazard refastening, which has likely broken or cracked some frames. This need to be corrected (repaired frame and restored fastener holes). If the structural repairs aren't made, you can caulk your brains out, but the planking will quickly just spit out all your efforts, because the structure can't hold things together well enough to retain the caulk.

    Is this a "double planked" boat? Your photos suggest its a carvel, but sometimes they drill the fasteners to the frames on a double plank. This is important as the repair approaches are different between the two types. Also is the planking plywood or solid wood?
     

  8. goingjag
    Joined: May 2016
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    Location: Higganum, Ct. USA

    goingjag New Member

    Below the water line she is double planked with the first "plank" being plywood. I'm not sure what the wood is the constitutes the second plank, however it is solid wood.

    Above the waterline it it single plank solid wood. I haven't actually measured the thickness but I would say that the planks below the water line when added to the plywood equal the thickness of the planks above the waterline.
     
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