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Thread: Question about using Pine Pitch

  1. #1
    Join Date
    Nov 2006
    Location
    rio, brazil
    Posts
    2

    Question Question about using Pine Tar

    I built a small 12 ft.traditional skiff with a cross-planked bottom. It seals by moisture expanding the wooden planks, 1/2 " mahogany. Since I store the boat out of the water, occasionally the bottom dries out too much and it leaks, spoiling a good sail or row.
    My question is: would watertightness be helped by putting pine tar in the seam ( on the underside ). I have some home made pine tar. How long does it take the tar to dry in the seam or is this unimportant? I don't plan to use oakum or such; these seams were built very tight, but now when completely dry out of the water a few open to 1/16" at most. Appreciate any tips.
    Last edited by rickfromrio; 11-20-2006 at 10:52 AM. Reason: my title should have read 'pine tar' , not 'pine pitch'

  2. #2
    Join Date
    Jun 2003
    Location
    Seabeck, WA
    Posts
    9,754

    Default

    If you want a leak free boat, the only way to do it is to remove that bottom, plane caulking seams into the plank edges, and reassemble those planks tightly by adding one more plank to take up the gaps. Use clamps to get the board edges tight as you fasten them to the chines.

    Then caulk the bottom using cotton followed by seam compound. Soaking the edges in thinned linseed oil helps them hold the cotton, then saturate the cotton with red lead or copper bottom paint before applying seam compound. Then paint.



    All you need is caulking cotton, a small caulking iron (Jamestown Distributors) and a wood mallet.



    Image "I" is a cross section of a caulking seam on deck planks much thicker than yours. On half-inch planks, plane a bevel of no more than a 16th of an inch off to a depth of no more than 3/8". Ignore the oakum...cotton does the caulking and oakum is used to fill large gaps you won't have.

    You can also reassemble the cross planks without caulking seams by "drive fitting" tapered planks at 4-foot intervals....but that only works for boats left in the water for long periods.
    Last edited by Bob Smalser; 11-17-2006 at 02:55 PM.

  3. #3
    Join Date
    Nov 2006
    Location
    rio, brazil
    Posts
    2

    Default

    Thanks, Bob. Yep, your picture looks like the bottom of my boat all right!

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