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 Boat Design Forums Box shape Barge resistance
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#1
05-14-2006, 06:10 PM
 Hisham Marine engineer Join Date: Oct 2005 Rep: 28 Posts: 49 Location: Egypt
Box shape Barge resistance

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
05-15-2006, 10:10 AM
 jehardiman Senior Member Join Date: Aug 2004 Rep: 2040 Posts: 2,134 Location: Port Orchard, Washington, USA
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
05-15-2006, 06:38 PM
 SamSam Senior Member Join Date: Feb 2005 Rep: 932 Posts: 3,187 Location: Coastal Georgia
Quote:
 Originally Posted by jehardiman 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.
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
05-16-2006, 10:49 AM
 jehardiman Senior Member Join Date: Aug 2004 Rep: 2040 Posts: 2,134 Location: Port Orchard, Washington, USA
Quote:
 Originally Posted by SamSam If I built a scow type hull, rounded chines would have less resistance than a 90 degree angle chine?
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
05-16-2006, 07:37 PM
 Hisham Marine engineer Join Date: Oct 2005 Rep: 28 Posts: 49 Location: Egypt
haaaaaaaaaaaaaaay

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

need help plz
#6
05-17-2006, 12:37 PM
 jehardiman Senior Member Join Date: Aug 2004 Rep: 2040 Posts: 2,134 Location: Port Orchard, Washington, USA
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
05-17-2006, 03:20 PM
 Guillermo Ingeniero Naval Join Date: Mar 2005 Rep: 2247 Posts: 3,631 Location: Pontevedra, Spain
Quote:
 Originally Posted by Hisham 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?
Some info at:

A computer program:
http://www.ds-t.com/software-cd/soft...0TechSheet.pdf
http://www.hydrocompinc.com/knowledg...ngPowerITB.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/...b/newpage1.htm
Cheers.

#8
05-17-2006, 08:23 PM
 Hisham Marine engineer Join Date: Oct 2005 Rep: 28 Posts: 49 Location: Egypt
tahnks...... i am going to check them

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