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Thread: Repairing glued lapstrakes

  1. #1
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    Default Repairing glued lapstrakes

    I offered to help a friend repair her 10ft Acorn dinghy. Of course, I did that before I got a look at it! Anyhow, the situation seems to be that it was used as a tender to sailboat and there was probably undue forces put on the laps from getting in/out & standing on the inside of the laps. The boat was an amateur build (her father) and looks as though it was built to the plans although the fit & finish is not great. Besides the wood being wet due to being stored outside in ME uncovered under trees (!) what I have seen so far is 3 glued laps now unglued specifically amidships and aft, no rot or ply delamination. Given that this will not be a total rebuild but rather a repair to useable condition, what would be the best strategy for repair?

    Thanks for the help!

    PS. That's a putty knife poking thru the lap joint.

    Anita's Acorn 1.jpgAnita's Acorn 2.jpgAnita's Acorn 3.jpgAnita's Acorn 4.jpg

  2. #2
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    Default Re: Repairing glued lapstrakes

    I would be inclined to dry & clean everything well, and work a bit of thickened epoxy in and fasten those sections of laps with small copper clench nails (which will hold the seams tight while the epoxy cures as well as giving a bit of a belt and suspenders approach afterwards).

  3. #3
    Join Date
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    Default Re: Repairing glued lapstrakes

    ^ Just so. Or if you are single handed and cannot clench through fastenings, short bronze screws would hold until the glue sets up
    It really is quite difficult to build an ugly wooden boat.

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  4. #4
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    Default Re: Repairing glued lapstrakes

    The tough part is cleaning weathered wood and failed glue out of the joints. A multi-tool or sandpaper glued to a putty knife might be effective. Use a syringe to get thickened epoxy into the joints. If you remove them after the glue has set, you could hold joints with steel screws.

  5. #5
    Join Date
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    Default Re: Repairing glued lapstrakes

    Run a hacksaw blade through the open joint to clean the wood edges. No need to be real aggressive, nice and smooth a few times.

  6. #6
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    Default Re: Repairing glued lapstrakes

    If some have failed then surely more will. I'd do my best to locate any weak joints and clean them out too, then the epoxy, and I'd copper clinch nail the entire hull.

    Once that's been done I'd put a small fillet on both the inside and outside of each lap, full length, then re-paint.

    You may be able to cut a narrow strip from a belt sander belt, feed it thru the joint and use it to clean out the crud. I haven't tried that, just an idea.

    Get your friend to help, it's going to be a fair bit of work.

  7. #7
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    Default Re: Repairing glued lapstrakes

    Thanks for all the input. Pretty much as I had figured it - dry, ream out old glue, sand or somehow “freshen” up the wood, then re-glue. That good but I am concerned about putting back what has already failed once & in much less favorable wood condition. Note in the pics there are battens on the first two laps both sides of the keel. Although the glue has failed on one of those battens, the batten has also broken. It was very poorly repaired, screw heads sticking up, short scarf joints, etc. obviously this piece needs to be replaced. What do you all think about adding battens to the next 2-3 lap joints to add more rigidity with the intent to prevent bottom flex when being stepped on? Epoxy isn’t very flexible & re-glueing old wood isn’t optimal. Thoughts?

  8. #8
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    Default Re: Repairing glued lapstrakes

    The epoxy should be stronger than the ply. I would suggest that the hull had been dropped on a hard corner to crack seams and break that batten. For the batten to snap the bilge was pushed in from outside, not flexed outward by weight on the inside.
    Properly built as designed will be OK.
    As an illustration I visited a couple of young boat builders starting out when epoxy was young. They were working in a loft workshop. Their prototype pram dinghy was built without frames. As they were taking it out of the shop it slipped from their hands on the stairs. It bounced down the entire flight without any harm.
    Do the repairs as well as you can, including re-scarfing in that broken batten and you will be OK.
    It really is quite difficult to build an ugly wooden boat.

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  9. #9
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    Default Re: Repairing glued lapstrakes

    I own a Tom Hill ultralight canoe which has been damaged twice. The first time was sailing in a stiff breeze and hiking out. The boat was not designed to sail, but had a rig when I bought it. The mast levered at least one lap open. I was away from home and my tools. I put epoxy in the lap and "clamped" it with weights over plastic sheet. That worked well. The second injury was caused by me hopping into the boat in waist deep water, splitting the keel lengthwise and separating the garboards. That was repaired with epoxy from a syringe, and reinforced with fg tape on the bottom.
    You can inject epoxy or putty knife it into the open laps. If any clamping is required, weights may do, or copper nails or staples. Either of those can be pulled later. Unless the lap is wide open, you won't need clamps. Good luck, forge ahead and keep us posted.

  10. #10
    Join Date
    Aug 2017
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    Default Re: Repairing glued lapstrakes

    Ok, consensus it is! Clean up & a re-glue it will be. Probably a couple weeks to dry out so in the meantime I’ll fire up my heat gun & get some paint stripped. Dehumidifier running in the basement should help the drying process. Thanks for the advice & stay tuned.

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