Scroll down to start a new Topic. Subscribe to receive notifications of new Topics and Replies.

This topic contains 2 replies, has 2 voices, and was last updated by  fraser20000 4 months, 3 weeks ago.

  • Author
    Posts
  • #18092

    fraser20000
    Participant

    Hello again

    I am a few days away from digging into the repair of the of Blue jackaroo and noticed some bubbles under the paint of her hull.

    nails

    Nail I picked at

    I am not sure if these are part of the normal hull? or what they are doing at all to be honest. the corrosion looks a little odd to me.

     

    In any event what would be the best way to go about sorting this? I am considering treating them with something to harden the corrosion then epoxying over them but i am a complete novice so i am not sure. the wood looks fine other than the gouging.

     

    The paint is raised on all of them I assume because of the corrosion I just picked away at this one to see what was going on because I feared rot was under each of them.

     

    Any help would be greatly appreciated

    Fraser

  • #18094

    AOA
    Keymaster

    Hi Fraser

    A lot of boats have experienced this problem at some point. Indeed my boat A124 has a few similar looking screws.

    You are looking at dying brass screws, which have ‘de-zincified’. Fairey Marine used these brass screws through the hull above and below the waterline to fasten the internal framing / stringers. Over the years the salt water gets to the screws and starts to corrode them. The corrosion causes the paint to crack off which is useful as a warning sign.
    In many cases he screws become so weak that you are unlikely to be able to unscrew them – the slots and/or heads just break off. The corrosion can also weaken the wood in contact with the screw.

    I would love to hear how other people deal with their corroded screws as I have not yet found a method I am completely happy with.

    I have tried a couple of approaches:

    • Drilling out the screw, priming the hole with unthickened epoxy, filling the hole with thickened epoxy, re-drill, new screw and making good
      • This has worked in some cases for me.
      • The challenge is drilling out the corroded screw without the drill bit diving off the screw and making a large hole beside the screw.
    • Using a small hole saw around the screw to the thickness of the hull, breaking up the plug of wood and rotten screw, removing the outer layer of veneer around the hole to permit a ‘patch’ of veneer to be glued over thickened expoxy in the hole.
      • Takes more time
      • Involves removing more of the hull material, although the epoxy does have clean timber to bond to

    Some people have, I believe, removed the corroded screw and filled the hole and then applied a new screw in a new hole near to the old screw.

    Your question has made me think that we should have a ‘technical paper’ on this topic once we have collated everyone’s responses to your question 😉

    Nick

    • #18118

      fraser20000
      Participant

      Thanks for the great response Nick

      I did a bit more digging and can see they are screws now. i only see them on one side though which confused me.

      Thanks for the great advice. I will have a think and try to document what ever I end up doing. I might have a bash at removing them, cutting a new channel possibly in the head. Drilling them out and going for a bit bigger screw might work alright but as you say the wood under might be compromised.

      I wonder how a metal pin would work epoxied into the hole. that way I would only be drilling the metal out and then inserting a plug back in.

You must be logged in to reply to this topic.