Does this kayak have core rot?

Discussion in 'Boatbuilding' started by billybob3000, Jul 29, 2015.

  1. billybob3000
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    billybob3000 New Member

    I own an older Betsie Bay Valkyrie made in 1993. Although the boat is in generally good shape. The original owner seems to have tried to do some gel coat repair ten plus years ago poorly.

    I am preparing to fix the boat up. Aside from the gel coat repair I noticed a pocket that has developed a perpendicular hole with may allow water to get into the core. I am not sure trying to follow the hole back is a good idea.

    I also noticed that inside the hull there is a sticky brownish maple syrup like thick goop. I don’t feel any soft sports and the hull is not very thick. Could I have water in the core? The core is plywood. See pics

    Thanks

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  2. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Do you think the goop might be uncured polyester resin, uncured epoxy resin, or uncured epoxy hardener? Or do you think it is one of the above or plywood glue reacting with moisture and plywood? Was the repair job done with epoxy or polyester resin. Is the goop close to the repair job? Is the hole close to the hole or the repair job.

    I think I would begin by removing all of the repair job or at least whatever was done poorly. I would remove any gelcoat or polyester or paint and leave nothing but epoxy and plywood. I think I would do it with an orbital sander.

    Even if the suspected core rot is not associated with the repair, I would use a dremel tool to carefully grind away a small 1" diameter circle of glass and leave the plywood under it intact, like an archeaologist might. Then carefully examine the plywood to see if it is wet, and if it is then where the wetness is tracking from. Try and figure out if the plywood is rotting from moisture alone and its own glue, or if it is rotting from some sort of reaction with something else as well.

    If the plywood is not so bad other than some local wetness, I would dry that out, and then replace all the epoxy and glass that has been ground away with some new epoxy and glass, properly feathered in. If some plywood has been removed dry it out and fill it with epoxy and glass and fair it with epoxy and high density filler. Don't leave anything low density behind or even silica that might clump and trap air, and then moisture. Make sure all the epoxy is mixed well and in proper ratio before adding any filler. Seal the faired repair with unfilled epoxy and then replace the surface glass and epoxy feathered at its edges. I would not use any pigment until the very end, where I would use a polyurethane paint to protect the epoxy from UV, or whatever paint is covering the rest of the boat if you know what it is. I would think it is not gelcoat over epoxy, but either pigmented epoxy, or polyurethane paint over epoxy. You can use spray cans if keep it local or brush or roll and tip it on if doing a large area or the entire boat.

    p.s. I understand the original boat weighs about 29 pounds. How much does your weigh in it's current state. I am not sure if this will necessarily indicated anything as you will never know exactly how much your specific boat weighed originally, but 3mm or plywood soaking up say 1mm of water over a square meter would add 2.2 pounds. You could weigh your boat, and then dry it out really well with a hair dryer and the hot sun or a hot room and then weigh it again after 24 hours. If it loses a pound or more there could be a problem. Good thing to do anyway. If you suspect the thin plywood core is wet over an extensive area you could sand off all the surface paint and weight it, dry it, and then weigh it again to get it as light as possible, and then seal it with epoxy and paint with polyurethane. I wouldn't go down through the epoxy glass to the plywood, as it is a very light and thin construction. The epoxy glass should be thin enough that some moisture should be able to get out if it has gotten in. I would do the same on the inside only where it is easy to get to, or where you know for sure moisture may have gotten in. Where you have that bad repair on the outside anyway it really might not hurt and might be very worthwhile to sand the paint off the outside down to the glass, but not through the glass epoxy, and then go from there. If it is unpigmented epoxy which I suspect it is, but could be wrong, then you will be able to see a lot through the epoxy glass. Dark areas would indicate where you have a problem which might well be from the insider. Freeze-thaw action might have been an issue also. Cheers.

    Sorry this was sort of made up as I went along, so read the whole thing and rework it into what makes the most sense, and depending on what you actually have in front of you.
     
  3. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Yes, in hindsight, if the original epoxy glass construction under the paint is unpigmented then I would start by sanding off all the paint from the exterior hull, fairly aggressively down to the glass epoxy but not into the glass. From there you should be able to see everything much better, where the plywood is darker with moisture, and figure out what you need to do.
     
  4. billybob3000
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    billybob3000 New Member

    The goopy stuff seems to have come though the gray paint. It is associated with the center line of the boat. It seems to relatively unassociated with the hole I found. It looks like it could be resin. Can that stuff bleed though paint over many years?
     
  5. FMS
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    FMS Senior Member

    I had a dinghy which developed a bad spot. It was fine for a couple years of light use. I stored it inside. Then one summer I stored it outside. On one of the hot days I noticed a small crack in the paint. It could have been a repair area or a bad mix in the original. Thank goodness it was confined to a 6-8" area. When I sanded the paint off the sand paper loaded up. Underneath was a thin soft layer that had the texture of thick hot bubble gum that I had to scrape and sand off. It took a pack of sand paper to get all the mushy sticky material off.
     
  6. Jamie Kennedy
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    Jamie Kennedy Senior Member

    If resin is seeping through the paint and it is from the centerline I suspect the problem is coming from the center fillet material, whatever it is. If there are air voids, and water sits in the bottom of the boat after a paddle, moisture can over time diffuse through the paint and epoxy and into those air voids. If there is uncured epoxy or excess harder or the filet filler material was mixed in before the epoxy and harder were themselves well mixed then it is easier for the water to react with these chemicals and polymers. But even well cured paint or epoxy or polyester will degrade over time in the presence of moisture, heat, sea water, urine, dead bugs, freeze and thaw cycles, mechanical stress, whatever.

    Now I read some place this boat is put together in some proprietary method, particularly at the fillet joints, so I am not sure exactly what it is composed of. Whatever it is it still involves a mix of polymers, glass, air voids, filler material, and moisture, and so you may get some moisture diffusion and then plastic degradation over time. I think they mentioned phenolic resin.

    Any how I think your first step should be to sand the paint away on the outside along the center seam, down to the epoxy glass but not into the glass. You might then be able to see different shades in the fillet material, indicating moisture problems. Here is the website of the manufacturer...
     
  7. Jamie Kennedy
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    Jamie Kennedy Senior Member

  8. Jamie Kennedy
    Joined: Jun 2015
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    Jamie Kennedy Senior Member

    They look like really well built kayaks by the way. After 20 years you can expect some issues, but if there is a problem with the center fillet or end grain of the plywood in the area of the center fillet I am sure it is repairable. Nice thing about a 27 pound boat is there is not a lot of material to go bad, and if you have to take away a pound of material and put two pounds back it is still a 28 pound boat. :)
     

  9. billybob3000
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    billybob3000 New Member

    Good to know about the fillet construction. I will start by sanding.
     
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