Replacing planks, caulked Carvel Kauri launch

Discussion in 'Boat Design' started by Andrew Miller, Apr 27, 2012.

  1. Andrew Miller
    Joined: Apr 2012
    Posts: 2
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    Location: Auckland, New Zealand

    Andrew Miller New Member

    Hi, just getting into my first planked launch restoration. I have sanded back the paint over the problem areas to expose the rotten planks and let them dry out for inspection. It is obvious that some planks will need replacing and recaulking Going forward i have a few dillemas. Firstely, the only Kauri timber available to me is kiln dried, so how much gap should i leave between the existing planks and the new planks for the uptake (swelling) of water. or should I use green or air dried timber?? Secondly, what profile do I give the planks for installation, square dressed, or a taper towards the outside to chop the cotton in too? Is there an alternative to using the copper nails and shrouds? What about ss316 threaded rod and nuts? Any advice most welcome.
  2. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You can't use "all thread" (threaded rod) on anything that will be under the water, unless you grind the threads off, above the nut and washer, so water can't migrate up the threads. If you don't grind the threads, water pressure will literally force a volume of water up the threads, past the nut, washer, etc. and into the boat or structural element. This is a guarantee of a leak and/or rot.

    You can use the kiln dried stock, but do your best to find quarter sawn or vertical grain stuff, as it's much more dimensionally stable. As to the beveled edge, it depends on the planking thickness, typically only a portion of the edge receives the caulk bevel.
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