Lyman lapstrake repair

Discussion in 'Boatbuilding' started by Jumba, Jun 18, 2022.

  1. Jumba
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    Jumba Junior Member

    I have recently acquired an old Lyman lapstrake boat. Honestly, there is a lot to be addressed. The boat has been out of the water, and drying out in a garage for around 15 years. Additionally, the boat was fitted with a Johnson outboard motor that has a skeg that doesn't fit the boat, causing it to easily cavitate. I would appreciate any information that I could get that would allow me to repair this boat to a useable condition. Thank you. I can provide pictures of anything requested, please feel free to ask if you might help me with this.
     
  2. bajansailor
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    bajansailor Marine Surveyor

  3. fallguy
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    fallguy Senior Member

    Need pics. Cavitation is usually caused by the engine being up too high.
     
  4. Jumba
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    Jumba Junior Member

    Here are some pictures, let me know if you need any other angles or focus on some specific area. And yes, the cavitation is definitely because the the prop is too high, but I really wouldn't want to cut down the transom in order to lower it. Already when stopping the boat, the wake already splashes over the top of the transom, and cutting it down would make that issue much worse.

    IMG_20220618_102223.jpg IMG_20220618_102255.jpg IMG_20220618_102311.jpg IMG_20220618_102455.jpg IMG_20220618_102512.jpg IMG_20220618_102520.jpg IMG_20220618_102548.jpg IMG_20220618_102609.jpg IMG_20220618_102712.jpg
     
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  5. fallguy
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    fallguy Senior Member

    The prop is not too high. Have someone take a picture of you holding a 4' level or straightedge off the bottom edge of the stern and show us how that compares to the cav plate.

    When does it cavitate?

    A boat that has been sitting for a long time might have a dried up rubber in the prop. The prop probably needs to be replaced is all.

    The motor looks ideal to me, but need the side view with the straightedge.
     
  6. fallguy
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    fallguy Senior Member

    Probably worn so bad it is spinning.

     
  7. Jumba
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    Jumba Junior Member

    Keep in mind that I'm going off of information from when it used to be used much more frequently. At the moment, the motor will likely need more than a couple parts just to get it running again. That being said, it would start cavitating when it got up to around 3500 RPMs. Here's the picture as requested.

    IMG_20220618_161523.jpg
     
  8. fallguy
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    fallguy Senior Member

    Move to bottom hole.

    F2EBBCCD-A108-48E2-96C2-0C3D8FA4317A.jpeg
     
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  9. fallguy
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    fallguy Senior Member

    Another thing that can cause cavitation is if the prop is too small. Do nothing to that transom!!!
     
  10. Jumba
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    Jumba Junior Member

    My assumption is that the cavitation plate should be as coplanar to the bottom of the hull as possible, so that makes perfect sense. And I will definitely do that. Thank you very much for that input. I do, however, still have to deal with the fact that the boat leaks like a sieve, and as far as I understand, would probably need to have the hull paint stripped/sanded and redone. Is it easier/better to use a paint stripper than to sand the paint off? What are the suggested ways to seal the boat so that it no longer leaks as it does now? Then the are the portions that have been varnished, but have subsequently started to deteriorate. What would be the best way to restore these spots?
     
  11. bajansailor
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    bajansailor Marine Surveyor

    It does not appear to be much of a change, but you could be surprised by how much effect it will have.

    Re how water comes in over the transom when you stop (I presume fairly suddenly), would it be feasible to build a splash well?
    Although it would have to be where your battery box is currently located, but this box could maybe be moved forwards a bit?

    Because she is clinker / lapstrake construction, you do not want to even think about 'caulking' the seams.
    Because she is so 'dry', from being ashore for so long, your best bet might be to launch her in shallow water (so that she cannot sink very much) and let her gradually 'take up' (ie let the planks soak up some water and swell so that the seams are a tight fit). Would a scenario like this be possible?

    Re the hull paint, to me it does not look too bad really - I think I would be inclined to simply sand it and add another coat of paint.
    And it looks like somebody has kept up with the varnish work on the interior?
     
    Last edited: Jun 18, 2022
  12. fallguy
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    fallguy Senior Member

    As for the leaks, what Bajan said is accurate. Take the boat to a shallow shore/landing and monitor it and run a bilge pump in the stern. Any areas leaking super bad for over a long period of time need special attention and or repair.

    Or, if you have specific areas of known soft or rotten wood, take a picture of them and share. Epoxy is a great friend here. You can remove rotten wood; soak the remainder in CPES and fill the area with thickened epoxy and make it take the shape of the area removed.

    When you mount or screw into wood; you always, always, always do what is called overbore and fill. An overbore removes about 2x-3x the diameter of the screw, being careful to not hole the boat. Then you fill it will thickened epoxy, let it cure and redrill the hole in the thickened epoxy and not the wood.
     
  13. Jumba
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    Jumba Junior Member

    I can definitely bring it to a shallow landing, and let it sit there. How much time should I set aside for this task? Is this measured in hours, or in days? But if I might ask, what would constitute "leaking super bad over a long period of time"?

    Additionally, can you expand upon your method of overbore and fill please? What does it mean to "hole the boat"?

    One of the pictures I shared of the bow had a rotted out section. That is the focus of this particular question.
     
  14. fallguy
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    fallguy Senior Member

    So, any hole in a wood boat needs to be modified so the area is not sealed in wood, but sealed in epoxy resin.

    Let's say you want to screw a cable down with a #10 screw 1/2" long. You drill a hole 5/8" deep by 2x3/16" or 3/8" and fill it with epoxy and fumed silica to protect the wood from ever getting a leak. Then you predrill and screw the screw into sealant.

    Leaking super bad would be any leak that doesn't slow after a few hours. Bulldozer
    Work. Fix the real bad stuff first.

    I'll look closer at the pic.
     

  15. fallguy
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    fallguy Senior Member

    Okay, so that rot on the bow could have been from a screw not sealed well.

    You need to remove all the rot. This is essential to wood rot repair. Not rot can remain. After you chisel or cut it all away;
    I recommend the use of cpes
    Or a penetrating epoxy on the edges of what remains.

    That spot is tricky because the rest of the deck looks good, so thowing the entire deck away mighy be a mistake. So. What I might do is embrace the location for a horn or spotlight and cover the hole with a polished metal patch...etc
     
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