# Calculating Lightweight of a Barge: A Newbie's Guide

• lyranaval18
In summary, the lightweight of the barge can be calculated by using the formula: length * breadth * light draft * block coefficient * density of sea water. The GRT, or internal volume, of the barge is also a factor in determining the displacement and deadweight. The dimensions given for the barge suggest a 3 m height for the barge wall and a freeboard of 1.28 m. More information is needed to accurately determine the correct lightweight for the barge.
lyranaval18
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.

berkeman
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.

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

berkeman
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 ☺

## 1. What is the formula for calculating the lightweight of a barge?

The formula for calculating the lightweight of a barge is: LW = DWT - (C + F + B), where LW represents the lightweight, DWT is the deadweight tonnage, C is the capacity, F is the fuel weight, and B is the ballast weight.

## 2. How do I determine the deadweight tonnage of a barge?

The deadweight tonnage (DWT) of a barge can be determined by adding the weight of all the cargo, passengers, and crew members on board, as well as any other items that will be carried on the barge. This weight should then be converted to metric tons.

## 3. What is the purpose of calculating the lightweight of a barge?

Calculating the lightweight of a barge is important for determining its carrying capacity and ensuring that it is not overloaded. It is also necessary for complying with safety regulations and for accurate invoicing and billing.

## 4. How do I measure the capacity of a barge?

The capacity of a barge can be measured by calculating its volume in cubic feet or cubic meters. This can be done by multiplying the length, width, and depth of the barge. The resulting volume can then be converted to weight using the specific gravity of the cargo.

## 5. What factors can affect the lightweight of a barge?

The lightweight of a barge can be affected by various factors such as the type and weight of cargo being carried, the amount of fuel and ballast on board, and any changes in the weight distribution due to loading or unloading of cargo. Weather conditions and water density can also impact the lightweight of a barge.

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