hull draining and closed cell foam draining

Discussion in 'Fiberglass and Composite Boat Building' started by gtflash, Aug 21, 2014.

  1. gtflash
    Joined: Jun 2006
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    Location: uk

    gtflash Senior Member

    My boat has twin step hull. The most forward step creates a low pointin the hull forward. If my water ballast (furthest forward and slightly higher 150litres) arrangement ever went wrong Id have no way to shift the water stuck in the low point. Should all compartments drain aft? And in my situation, as it wont drain uphill. should I put a bilge pump in?

    2nd question. I have removed almost all the original foam stringers and replaced with new foam and laminated in epoxy. Also replaced 3 bulkheads. They were all water logged due to poor repairs. But it has me thinking if they should actually be sealed or allowed to weep. In theory there will never be water in them.... BUT if there ever was, it couldnt escape.

    Any opinions appreciated please GT
     
  2. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Couple of questions - I have no idea how big the boat is - maybe 150 kilos is nothing. Also, a small boat probably only gets low use, a big boat will be out in the weather and water a lot more.

    Also, you dont say what type of foam you used for the ribs, or what sort of foam was in there.

    As a general rule, I wouldnt rely on a bilge pump. In a small boat, who need the pain of pumping, and on a big boat, its just one more electrical thing to go wrong. Ifs its possible to drain it somewhere, thats preferable.

    If you have used high density foam in the stringers, I would just cover it up.

    Weep holes in lo density foam ( like the ones you mix and pour yourself), can be a problem. Weep holes might allow water to enter under pressure ( like 6 inches of rainwater etc )

    I would be content to cover up lo-density foam, but check it regularly. I would do that by drilling holes and inserting screw in inspection plugs at strategic places.

    If it is low density foam, I wouldnt be averse to drilling really long holes into the stringers, so any moisture would weep out into them, making it easy to drain.

    In fact, if its low density foam, and the stringers are enough structure, you could pour petrol or turps into the stringers, and melt out the basically unneeded foam. That would make it easy to drain.

    Quite a few variables in this question.
     
  3. gtflash
    Joined: Jun 2006
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    gtflash Senior Member

    thankyou for reply... each in turn

    Boat is just over 8m long. 150kg isnt excessive, it did have a tank about 5x the size when it was used for racing, but it was beyond repair. It is a decnet sea boat, (rib), the hull has several offshore records, including round britian, cowes monte carlo. It wont need much ballast upfront, only on rare occasions, as they run very level naturally. I had a 7m version without stepped hull before and she had a 3m front locker that had no facility to drain aft. It was watertight, with quality lewmar hatches. Its only the water upfront that offers a potential flooding if a hose would split, or pickup break.

    The foam is Divinycell HCP low density foam. NOt pourable, but I suppose just a form for the laminate. It would probably break my heart to disolve it after the money invested in it, but i see your point. maybe a screw drain is the compromise.
     
  4. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Divinycell is not a problem. It is a manufactured, closed cell foam that should be fine to assume is virtually waterproof. I would just cover it up, and not dissolve it at all.

    Its your decision on the forward compartment. I don't
    have enough information to form an opinion
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Why not just put a bilge pump(s) into the area(s) that constitute "traps" ? Seems like the obvious solution. And you don't need to worry about Divinycell soaking up water to any degree.
     

  6. gtflash
    Joined: Jun 2006
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    Location: uk

    gtflash Senior Member

    Thankyou. confirms my thinking. A pump it is.

    So leave bulkheads sealed and dont make them draining?
     
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