Saturated deck core

Discussion in 'Fiberglass and Composite Boat Building' started by Nick.K, Jun 22, 2015.

  1. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    Is there any way to dry a saturated balsa core?

    I'm working on a refit of a 20m sail yacht. The yacht had a new Teak overlay deck fitted about seven years ago. Whatever genius fitted it used a screw every 20cm on every strake seam to secure the strakes while the adhesive cured. Later the screws were taken out and the seams caulked. Unfortunately, they were economical with the bedding mastic creating voids under the teak which are now water filled and the water is saturating the core through the screw holes. The core isn't rotten and there seems to be no delamination.

    I used a hole cutter to cut away the interior laminate and look at the core in places where we could see water dripping.

    Any suggestions (apart from those on the theme of a Viking funeral..)

    I've read about vacuum drying in osmosis treatment, would this work?
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    In seven years, the core has deteriorated. Drying it is not enough. You need to replace the core. There isn't a quick or cheap repair, unfortunately.
     
  3. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    Thanks Gonzo
    It looks that way to me too; but have to say, in the places where I pulled off the inner laminate there was good adhesion and the core is solid...just very wet. The deck still feels stiff to walk and jump on.
    Nick
     
  4. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Could you cut a series of strips out of the inner laminate say 1/2 inch wide then seal off the general area for heat loss and put 2 - 100 watt bulbs in there for a month would that work?


    repair with epoxy putty and paint over.
     
  5. snowbirder

    snowbirder Previous Member

    Circular saw to cut the glass off, scoop out the balsa. Replace with balsa or foam, re glass.
     
  6. Nick.K
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    Nick.K Senior Member

    We were considering cutting disks of say 55mm out of the inner laminate on a grid, dehumidifying the interior, monitoring the drying and then laminating over...
    but difficult to imagine that the core would really dry that way.
     
  7. snowbirder

    snowbirder Previous Member

    Faster and easier to just do it the right way.
     
  8. rasorinc
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    rasorinc Senior Member

    Aim a couple of fans at the area and you can dry most anything, i t just takes time. and power.
     
  9. Nick.K
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    Nick.K Senior Member

    Not much power either with a bit of dehumidification. I've seen this used in flood damage situations very effectively.
     
  10. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    I'm with Gonzo and anyone else who says replace the balsa.
    To try to get it dry you need to remove one skin, exposing the balsa completely.
    Then you could try to dry the balsa by using a heater and an airconditioner (takes out the moisture).
    But when will you ever decide the other side of the balsa is dry?
    Since you have the skin off you might as well replace the balsa, cause you will never be able to tell if the balsa has started to rot and what strength is left.

    Sorry, but you should consider the new teak just a casualty and build the deck properly.

    Short cuts just cost too much.
     
  11. rwatson
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    rwatson Senior Member

  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Drying out a core isn't usually practical, except in very localized areas, where it can be fully accessed and opened. Fans, blowers, A/C units and even dehumidifiers are a waste of time, unless you can completely seal the boat, less the entry point for circulating air. Don't get me wrong, technically, it's possible, but it'll take many months, not days to dry a soaked core, with few guarantees it's really dry and still adhered.

    I have had success with chemical drying on localized areas, but this would be very dangerous on large areas, not to mention costly. This is why the cores are usually just yanked out and replaced.
     
  13. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    Yes, that's the only practical way to dry it. It got to be a vacuumed to about 0,01 bar thou it depends also a lot of the temperature.
    But that doesn't fix the leaking deck..
     

  14. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    Thanks everyone for the replies.

    The boat came to us for an interior refit, but as I couldn't see any sense in starting without fixing the deck leaks I begun exploring. Real shame to see the damage created by shoddy and lazy work on the deck (although it looks good). It's not my call to say what will or won't be done but as pointed out above, whatever is done with the core won't fix the leaks so the teak will have to come off anyhow if the issue is to be fixed.

    Thanks for the link to the article on microwave drying, interesting!
    Nick
     
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