displacemant of a drum

Discussion in 'Boat Design' started by whitepointer23, Feb 9, 2012.

  1. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    In Wisconsin the temperature changes from 38C to -30C. The drums don't have breathers and do fine.
     
  2. tom28571
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    tom28571 Senior Member

    The OP asked about a pontoon barge supported by 200L drums. This is two cylinders and my comments relate to calculation of the displacement of cylindrical pontoons at varying depths of immersion.
     
  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    So Guy-Lussac's and Charles' law do not apply to Wisconsin.
    Interesting!
     
  4. CDK
    Joined: Aug 2007
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    CDK retired engineer

    OK for a temporary solution, less satisfying if this is going to be a long lasting project.
    The drums will really breath due to pressure differences, but since they are partly submerged, the moisture in the air condenses and remains in the lower half of the drum, gradually reducing buoyancy and increasing condensation.

    An anchor buoy, cracked at the top takes about 4 years to sink.
    Mine did, with some help from clams and oysters.
     
  5. whitepointer23

    whitepointer23 Previous Member

    that is a huge temp range, i can't even imagine what -30 is like.
     
  6. whitepointer23

    whitepointer23 Previous Member

    what about a rubber membrane. if you cut out a section of the drum and fit a membrane that would expand and contract so the drum doesn't change shape. you could also use the hole to reach in with a spanner so the drums could be bolted on.
     
  7. Submarine Tom

    Submarine Tom Previous Member

    KISS,

    Keep It Stupid Simple

    (Less offensive than the traditional KISS and it still works...)

    -Tom
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    If the drum is substantially submerged, it is the water temperature that is far more important than external air temperature, as CDK says barometric pressure can vary quite a way, best plan might be seal the drums when the water temp is about the same as air temp, and bar is in the mid-range of expectations.
     
  9. gonzo
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    Location: Milwaukee, WI

    gonzo Senior Member

    The drums shrink a bit in the winter, but they are out of the water then anyway.
     
  10. TrustedShips
    Joined: Feb 2012
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    Location: India

    TrustedShips Mr.

    A breather is a good idea.

    Also agreed that the moisture would condensate and accumulate at the bottom in the long run.

    How about providing a detachable (threaded connection) pipe breather which can be removed in case you need to pump out the condensate. Simply, open it, pass a flexible pipe and pump out the condensate.
     

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  11. Submarine Tom

    Submarine Tom Previous Member

    Or simply run your breather tube to the bottom and they become self bailing through their expansion contraction cycle.
    If you ran them independently then you'd know where and when you had a leak.

    But, I don't think it necessary.

    -Tom
     
  12. gonzo
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    gonzo Senior Member

    It's over-engineering. There are thousands of plastic drums in use with nothing more than the screw on lids on them.
     
  13. buzzlymutt
    Joined: Jul 2008
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    Location: auckland.new zealand

    buzzlymutt Junior Member

    in fixing collapsed drums,I squeeze a Tyre valve into a bung(drill hole)pump it up,to restore shape.I've considered getting Truck,"dual wheel" inner wheel valves.They go from inner wheel to outer wheel,so are quite long.Could be adapted into bung & then to either outside or thru deck or some other accessable place.This is assuming the drums are placed in line.I had a sailing raft & covered the drums from gunnel to gunnel with plastic sheet;to smooth out flow over the gaps between drums.Changing drums is not a big deal!
     
  14. Submarine Tom

    Submarine Tom Previous Member

    So, what do you get, about 1.3 meters height per barrel?

    13 meters LOA is 26 m of barrels, that's about 20 barrels.

    75 kg lift per barrel (60% reserve), that's 1500 kg max load.

    Not much really for a 40' cat.

    My 25' X 10' houseboat is 5500 kg for example.

    -Tom
     

  15. whitepointer23

    whitepointer23 Previous Member

    goodpoint, no use using drums if it gets to complicated.
     
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