Box shape Barge resistance

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

1. Joined: Oct 2005
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HishamMarine 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?

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jehardimanSenior 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.

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SamSamSenior 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

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jehardimanSenior 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".

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HishamMarine engineer

haaaaaaaaaaaaaaay

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

need help plz

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jehardimanSenior 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.

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GuillermoIngeniero Naval

Some info at:

A computer program:
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.

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HishamMarine engineer

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

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