Box shape Barge resistance

Discussion in 'Boat Design' started by Hisham, May 14, 2006.

  1. Hisham
    Joined: Oct 2005
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    Hisham Marine engineer

    for any type of ship total resistance = 1/2 ( density * v * A * Ct)

    Ct -----> Total resistance coefficient (including wave making resistance)

    the common known methods for predicting Ct can't be used for box shape barge

    Ct for box shape Barges should be constant since the shape is constant

    can any one give me a range for this coefficient?
    or where can i fiend a good document about this?
     
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Ct is not constant for a box barge. It is a function of B and T. It can also vary by -50% depending on bilge radius. And rake adds a whole different issue.
     
  3. SamSam
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    Location: Coastal Georgia

    SamSam Senior Member

    Are you talking about the chine radius? If I built a scow type hull, rounded chines would have less resistance than a 90 degree angle chine? Sam
     
  4. jehardiman
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    jehardiman Senior Member

    Yes, the radius needs to be ~ 10% or more of B to get the maximum restiance per ton reduction (after about that tonnage starts going down faster than the resistance). Noticable improvenents are seen with the radius as little as 2% of B. See Hoerner: "Fluid Dynamic Drag".
     
  5. Hisham
    Joined: Oct 2005
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    Hisham Marine engineer

    haaaaaaaaaaaaaaay

    i was asking.. how i can calculate resistance for box shape barge

    need help plz:confused:
     
  6. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Come on, Hisham, this is easy. A second year hydrodynamics question...Just figure out the pressure drag and add the surface drag. Get your pressure coefficients from Hoerner or Blevins.
     
  7. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

    Some info at:
    http://boatdesign.net/forums/showthread.php?p=12081

    A computer program:
    http://www.ds-t.com/software-cd/softwares/hci/navcad/texte/bfts/NC TechSheet.pdf
    http://www.hydrocompinc.com/knowledge/whitepapers/HC120-PredictingPowerITB.pdf

    Also a simple downloadable Propulsion Prediction Program, based in Holthrop. See if your barge is within the range of applicability.
    http://www-personal.engin.umich.edu/~parsons/470web/newpage1.htm
    Cheers.
     

  8. Hisham
    Joined: Oct 2005
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    Location: Egypt

    Hisham Marine engineer

    tahnks...... i am going to check them
     
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