Bulkhead repair

Discussion in 'Materials' started by East Coast Tolly, Feb 7, 2022.

  1. East Coast Tolly
    Joined: Feb 2022
    Posts: 2
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    Location: Connecticut

    East Coast Tolly New Member

    I am working on replacing a section of my 40 Tollycraft aft bulkhead. The beam is 14’8” and only a section has some rot I would like to replace. I do not believe I would be able to replace the entire bulkhead in one section, so a seam is inevitable. What are options for the joint?

    I made a trial of joining two ¾” pieces of Marine plywood together using the following process

    1) Make a Rabbet cut ¾ deep on each piece leaving half the thickness of the ply.
    2) Use polyester fiberglass structural putty to mate the two sections together.
    3) Use a 3 inch planner to make a 1/16 pass above the joint.
    4) Lay 3 inches of CSM into the groove, and use polyester resin to lay it in place to improve adhesion.
    5) Use a 9 inch strip of biaxial 1708 over the CSM and joint.
    6) Repeat on the opposite side.

    Your thoughts about this joint or others would be greatly appreciated. Thank you.
     

    Attached Files:

  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Tolly.
    We shall look forward to seeing your photos - as the saying goes, 'a picture is worth a thousand words'.
    I think you have to post a certain number of posts before you can then post photos (?)

    In the meantime, how large is the area / section that you plan to replace?
    For example 12'' square, or bigger, or......

    Re how 'a seam is inevitable', what sort of finish do you intend to have on the bulkhead?

    Re your laminate process described above, I think it would be much easier / stronger / simpler if you used epoxy rather than polyester resin to glue in the new section, and then apply a layer of cloth with epoxy over it.
     
    Last edited: Feb 8, 2022
  3. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Welcome to the forum.

    Unfortunately that is a recipe for a weak joint.

    Better options
    -Increase width of the 1/2 lap to 8 times the plywood thicknesses.
    -Use epoxy.
    -Forget about the CSM

    Good luck
     
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  4. Rumars
    Joined: Mar 2013
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    Location: Germany

    Rumars Senior Member

    Try a plain scarf, if you work tidy the glue joint will be almost invisible, no glass is needed. It is difficult to cut the scarf in place you need to practice on a vertical piece of ply. For a stepped scarf make more larger steps to increase glue area.
    Whatever method you use, only use epoxy, saturate both sides with neat, then clamp with thickened.
     
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  5. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    3x - don't bother with poly

    you can use an oscillating tool with a better quality carbide and follow Rumars advise and make a nice scarf joint on some scraps; a dull cutter or too fast a cut will burn and blacken the wood forever

    thicken the epoxy with fumed silica; this is a simple repair done right

    if you don't have cutter tool distance for all the scarfs; do your best or combine the half lap and scarf using the oscillating tool and a chisel. An open joint is best because the thickened epoxy will fill any errors with too big a cut.
     
  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

  7. East Coast Tolly
    Joined: Feb 2022
    Posts: 2
    Likes: 0, Points: 1
    Location: Connecticut

    East Coast Tolly New Member

    Thank you for the feedback. We just purchased the boat, and it is in Ohio, and I am in Connecticut. The Survey revealed the bulkhead issue, but bit the extent, so there are some unknowns... I am going out next week to make the repair, and will be able to send some more photos of what it looks like once I get out there and teardown the insulation. The scarf joint looks like the best option so far...
     

  8. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The scarf joint looks neater. However, you can butt block the repair if one side is hidden.
     
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