Spacers between wood and steel?

Discussion in 'Metal Boat Building' started by Conachair, May 17, 2009.

  1. Conachair
    Joined: Jan 2009
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    Location: Brazil

    Conachair Junior Member

    Everywhere there is wood touching metal I have rust so the wood has got to go, but not all of it, round the cockpit I want to keep some for various reasons. The current plan is to take the teak off, deal with the rust then remount the timber but with nylon spacers between the wood and the steel at each fastener leaving a small air gap between the timber and the steel. So the questions are-

    Has anyone tried this and does it work?

    Is nylon suitable? I know I can get nylon machined here in Brazil cheaply but not so sure about sourcing more exotic materials.

    Any other options?

    Thanks
     
  2. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Coat the faying surfaces of the wood with epoxy prior to assembly. Not a single coat, but several. Then coat the same surfaces with a bedding compound that will have some flexibility. Also overdrill fastener holes in the wood, fill the holes with thickened epoxy, and redrill.
    There may be other things you can do, depending on whether the wood against the steel is also the wood exposed to the cockpit. The main issue is moisture transferring through the wood and the fastener hole as well. By sealing the wood with epoxy and sealing the holes too (and further, using a flexible sealant in the fastener holes), the steel to wood joint should remain dry and trouble-free.
    It is prudent with any coating of wood with epoxy to seal the outer side as well, or to use an intermediate wood backer which serves as a basis for applying the finish wood.
     
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  3. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    To add to Alan's post

    We have had good success over the years. The steel is be primed underneath and well beyond with a zinc rich epoxy followed by a normal epoxy topcoat. The timber is bolted on with a bed of polyurethane sealant around 5mm thick.

    Varnish the timber first and the excess polyurethane can be easily cleaned off with turps or petrol also the fully varnished timber is stable wrt moisture induced dimension changes..

    Doing this also fully supports the timber which can be thinner.

    cheers
     

  4. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Try to avoid mechanical fasteners too, no need usually when bedded in Sika. All my boats have stainless steel 316L under anything that moves or is covered in teak.
     
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