Something like oakum

Discussion in 'Materials' started by fallguy, Oct 12, 2019.

  1. fallguy
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    fallguy Senior Member

    I have a space I need to temporary seal. There is nothing behind it. I was wondering if I ought to pack it with something like ropes.. no idea how/what..
     
  2. Blueknarr
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    Blueknarr Senior Member

    Pictures are worth thousands of words.
    How big a space?
    Surrounding surface profile?
    How strong?
     
  3. jehardiman
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    jehardiman Senior Member

    You would be surprised how much pressure well adhered good quality duct tape will hold.
     
  4. fallguy
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    fallguy Senior Member

    It is a beam socket. Just needs to be sealed and removable sealant.

    35B49B6A-AD9C-4C7B-9FC7-790740849675.jpeg
     

    Attached Files:

  5. Blueknarr
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    Blueknarr Senior Member

    You mean the 3/16 gap between the aluminum extrusions?

    How frequently does it need to be opened up then re-sealed?
    How much flex does the seal have to endure?

    My off the cuff recumendation;
    Self adhesive foam weather stripping from the hardware store applied to the incert 1/4 inch below surface. Top off with favorite flexible nautical sealant from a caulking tube.
     
  6. jehardiman
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    jehardiman Senior Member

    Soft wood wedges with a splash cover is how mast partners have been sealed for centuries. Supports as well as keeping water out. Modern materials are rubber and sealants.
     
  7. fallguy
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    fallguy Senior Member

    Between fiberglass and the extrusion.

    anytime the boat is disassembled for hauling..this is a 15' beam opening with an aluminum mast

    it is a through hole in the boat, but saltwater would cause crevice corrosion if it gets inside the mast
     
  8. rxcomposite
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    rxcomposite Senior Member

    A good quality marine grade sealant will do. Adhesive sealants like Sika works well for long term but difficult to remove as it adheres to the base material.
     
  9. Barry
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    Barry Senior Member

    It appears that there is an aluminum extrusion that is fibre glassed into the plywood. Is this correct?
    If so---------
    It appears that you have created a well which any water coming down the mast will accumulate producing a corrosion environment and you are trying to
    seal the well 100% against any water ingress.

    So if there is the outside aluminum extrusion, I would remove the one that is in place and substitute it for one that would sit into the well and say 6 inches taller
    up the mast. Fibreglass the outside extrusion in place and fill the well slightly proud of the surrounding fibre glassed plywood,

    Your mast would then sit only into the 6 inch protrusion of the outside extrusion to prevent a water retainment area as before. Around the outside extrusion,
    drill several small holes to permit any water that comes down the mast to weep away.

    When you insert the mast, you could use an alternative "compression pump packing" or "rope style packing material" that are available for other applications.
    Google both topics above.
    I suspect that these may provide some permeability in the presence of water so after the "rope" is installed, ( I suspect that you need to provide stability
    for the mast loads) you could then seal only the upper joint above the rope so that its removal would be easier, say a 1/2 inch bead of a Sikaflex product

    As a further barrier to corrosion if then the Sika seal fails would be to paint the outside of the mast and the inside of the mast receptacle
     
  10. fallguy
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    fallguy Senior Member

    nonono

    sorry Barry, this is a powercat

    that is a horizontal beam socket

    my bad; should have been clearer

    see the hole by the paper lists? That hole is in each hull...

    E4825093-60B8-4507-986D-E2FDE447526D.jpeg
     
  11. Blueknarr
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    Blueknarr Senior Member

    I hope I don't have to retract this suggestion when more information arrives.

    It looks like there is raw exposed foam against the aluminum sleeve. If so, the skins could delaminate when the aluminum presses on them.

    I would;
    Enlarge the cut out
    Replace some foam with thixo
    Tie the skins together with a couple of layers of cloth
    While creating a chamber around the out side.

    Seal everything up with silicone. It can be cut away fairly easily.

    The chamfer should be larger than on my drawing. 15710245780551153749212.jpg
     
  12. fallguy
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    fallguy Senior Member

    no raw core exists anywhere on this build except for a few unimportant cleats and there are none here

    the whitish color is solid glass and thixo; the solid glass is a moulded beam insert; there may be cabosil in that seam as well; there is no reason to decore

    the black outline is a sharpie marker line; we cutout the hull for the beam socket moulded off the boat

    the only questionable build concern would be that there is no fiberglass tape between the inside of the socket and the exterior of the hull-after much consideration; we decided the 6 layers of glass or so bonding the hull to the socket inside would suffice; the socket is 3 layers of 1708 itself and the taping is 6 layers; so we have 9 layers of 1708 there where you are looking ...225 ounces of glass

    the trouble with taping the exterior is simply that it interferes with the beam installation; had I planned it a bit better; the socket mould would have had a relief for those tapes

    however, there are a total of 6 beam sockets and a total of 7 exposed exterior joins; the rest are against the hull; should they develop a crack; the solution would be to grind them back and glass and really that is just self critique...the sockets are all bonded to bulkheads...if the boat was in a nasty hurricane; pretty sure the beams and sockets would stay together while the rest blew apart

    if we get cracking related to not taping; delam would be a concern, but we will see it during inspections of the craft
     
  13. rxcomposite
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    rxcomposite Senior Member

    FG- aren't you going to put a fairing on that to make it look nice?
     
  14. fallguy
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    fallguy Senior Member

    the beam goes through the boat and the cabin sits atop it; it is unseen

    the other side of the port hull is holed through and will get a 316 cap over the socket

    I just put a cutoff section in the socket so you all could see the margin
     

  15. Rumars
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    Rumars Senior Member

    Fallguy I would ask the designer, but IMO there should not be any gap there, it should be a tight fit. If the boat is not to be taken apart often I would even go to a similar fit.
     
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