Beaching keel adhesive.

Discussion in 'Materials' started by fallguy, Oct 15, 2019.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    B7BD6112-9E31-43CE-9817-B0B68A70FC4D.jpeg I am attaching a sacrificial timber to my beaching keel on a catamaran build. The timber is a 4 piece epoxy thixo laminated stack of ash lumber. The stack is 1.3" high. The designer specified 2", but I am skimping a bit.

    the keel is about 12' long.

    designer specified an unnumbered sikaflex, but I was gonna use 4200

    any argument for 5200???

    I just don't want to lose the keel and there are no mechanical fastenings allowed...desired...planned, etc.

    Here is a picture of the glass portion of the keel; wood gets glued to it...
     

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  2. bajansailor
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    bajansailor Marine Surveyor

    In addition to the adhesive, would it be feasible to overlaminate the keels with a couple of layers of glass going from chine to chine (and maybe wrapping around the chine)?

    Edit - another question - if you don't want to lose it, how 'sacrificial' should it be?
     
    Last edited: Oct 15, 2019
  3. rwatson
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    rwatson Senior Member

    I can't find any info on a Sikiflex 4200.

    Are you sure it's not
    3M™ Marine Adhesive Sealant Fast Cure 4200FC
    you are looking at?

    It doesn't sound suitable "Medium strength marine bonding allows for disassembly"
     
  4. fallguy
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    fallguy Senior Member

    designer specified an unnumbered sikaflex

    I am torn between the 3M 4200 and 3M 5200.

    giving up on silaflex

    I think you sort of tell the story...

    We could probably rope saw the thing off with the 5200 if we ever had to replace the sacrificial timber.

    I wanted something halfway between 4200 and 5200.

    too bad they don't make a 4700 eh?
     
  5. fallguy
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    fallguy Senior Member

    That would be bad. The wood is sacrificial. Glassing it on would make it permanent.
     
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  6. rwatson
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    rwatson Senior Member

    I don't understand why you can't just use thickened epoxy. It will break before your hull, but be plenty strong enough.
     
  7. fallguy
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    fallguy Senior Member

    if the timber wears off; I would have to grind it off to put on a new timber

    that said, if the timber wears off in one area; it could be repaired with thixo
     

  8. Rumars
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    Rumars Senior Member

    Sacrificial keel strip usually means abrasion not "detach on impact". The designer probably expected a wood like oak or other hard exotic and specified sika as it glues difficult woods better then epoxy. Any structural adhesive worth it's name will have the wood breaking and not the glueline. Sika makes exactly one structural marine adhesive rated for wood, 291i.

    Another option is to screw a piece of metal (stainless, bronze) or UHMW PE to the wood to offer aditional protection.
     
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