Calculating Lightweight of a Barge: A Newbie's Guide

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Discussion Overview

The discussion revolves around calculating the lightweight of a barge, including related concepts such as deadweight and displacement. Participants share their approaches and formulas while seeking clarification on the calculations involved.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about calculating the lightweight of a barge given its dimensions and other parameters.
  • Another participant suggests that the displacement of an unladen vessel is equivalent to its lightweight and provides a formula for calculating displacement based on the barge's dimensions.
  • Some participants question the accuracy of the lightweight calculation, indicating that their results seem too high compared to expectations.
  • A participant explains the significance of the block coefficient (cb) in the calculations and provides a detailed breakdown of the barge's internal and external volumes.
  • There is mention of the Gross Tonnage (GRT) and its relation to the internal volume of the barge, clarifying that GRT is a volume measurement, not a weight.
  • Participants discuss the implications of the calculated lightweight and displacement on the draft and freeboard of the barge.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct lightweight value of the barge. There are multiple competing views and calculations presented, with some participants expressing uncertainty about their results.

Contextual Notes

Some calculations depend on assumptions about the barge's structure and definitions of terms like lightweight and displacement. There are unresolved questions regarding the accuracy of the provided dimensions and the expected lightweight value.

Who May Find This Useful

Individuals interested in marine engineering, naval architecture, or those involved in barge design and calculations may find this discussion relevant.

lyranaval18
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hi I am a newbie here,
from Philippines,

I need you help guys i want to know how to calculate the lightweight of the barge since i only have the length =28 m, breadth=10m, depth=3m, light draft=0.8m,debsity of sea water=1.025t/m3, cb=0.9 and grt=237 tons. I am so confused how to compute since i don't know also the deadweight and displacement of the barge.

Thank you for immediate response.

[Mentor's note: Thread moved from engineering forum to homework forum]
 
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help me also to get the deadweight and the displacement especially light weight of this barge,the barge is box type only. please help me guys.

thank you.
 
Displacement of unladen vessel = lightweight ?
A rectangular box displaces volume = length * beam * draft = 28 * 10 * 0.8 = 224 cubic metres.
Then convert volume to weight. volume * density = 224 * 1.025 = 229.6 tonne.

What is cb=0.9 ?
 
Cb=block coefficient of the barge,
yes I am looking for a lightweight, of the barge.
but, my problem is i already used that formula but still my answer is still big for the light weight of that barge, so I am confused for the correct computation of lightweight of the barge.
 
lyranaval18 said:
but, my problem is i already used that formula but still my answer is still big for the light weight of that barge,
What is the correct lightweight of the barge ?
 
Baluncore said:
What is the correct lightweight of the barge ?
I don't know. only I know my Boss told me the lightweight i give to him is to big for that barge, and he didn't give me any estimated value of lightweight, that's why I am so confused. the exact value of lightweight for that barge. ; (
 
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lyranaval18 said:
i want to know how to calculate the lightweight of the barge since i only have the length =28 m, breadth=10m, depth=3m, light draft=0.8m,debsity of sea water=1.025t/m3, cb=0.9 and grt=237 tons. I am so confused how to compute since i don't know also the deadweight and displacement of the barge.
The empty hull has a lightweight draft of 0.8 m, the total displacement will then be ;
28 * 10 * 0.8 * 0.9 * 1.025 = 206.64 tonne lightweight.
If your Boss thinks that is wrong then ask him to explain why.

The GRT is the internal volume measured in multiples of 100 cubic feet = 2.832 m3.
GRT = 237 means 237 * 2.832 = 671.184 m3 internal volume.
The external dimensions give an external volume of 28 * 10 * 3 * 0.9 = 756 m3
The 85 m3 difference is the volume of the hull structure and the unusable space.
Those figures are consistent, which suggests the 3 m depth is the height of the barge wall, not the fully laden draft.

Remember that GRT is a volume, not a weight.
But if the GRT volume available was loaded with a deadweight of 237 tonne,
then the total mass would be 206.64 + 237 = 443.64 tonne displacement.
The draft would then be 443.64 / (28 * 10 * 0.9 * 1.025) = 1.717 m. There would be 1.28 m freeboard.

Without better defined information we cannot tell anything more about this problem.
 
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Baluncore said:
The empty hull has a lightweight draft of 0.8 m, the total displacement will then be ;
28 * 10 * 0.8 * 0.9 * 1.025 = 206.64 tonne lightweight.
If your Boss thinks that is wrong then ask him to explain why.

The GRT is the internal volume measured in multiples of 100 cubic feet = 2.832 m3.
GRT = 237 means 237 * 2.832 = 671.184 m3 internal volume.
The external dimensions give an external volume of 28 * 10 * 3 * 0.9 = 756 m3
The 85 m3 difference is the volume of the hull structure and the unusable space.
Those figures are consistent, which suggests the 3 m depth is the height of the barge wall, not the fully laden draft.

Remember that GRT is a volume, not a weight.
But if the GRT volume available was loaded with a deadweight of 237 tonne,
then the total mass would be 206.64 + 237 = 443.64 tonne displacement.
The draft would then be 443.64 / (28 * 10 * 0.9 * 1.025) = 1.717 m. There would be 1.28 m freeboard.

Without better defined information we cannot tell anything more about this problem.

Good Morning,

Thank you so much Baluncore, I really appreciate your help for me to solve this problem.

Have a Merry Christmas :-)
God Bless you
 
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  • #10
gneill said:
Take a look at this website:

https://www.tc.gc.ca/eng/marinesafety/tp-tp14609-3-stability-180.htm

It covers the subject of ship displacements and tonnage with examples. It also includes the definition of the block coefficient which, if I understood what I read there, you'll need to use in your calculation.

Good morning,

Thank you also Gneill. Have a Merry Christmas ☺
 

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