# Capacity Plan Calculation

Discussion in 'Stability' started by Laranjo123, Mar 18, 2012.

1. ### Laranjo123Previous Member

Hello i would like to know how to compute the capacity plan of the ship per tank...

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### TANSLSenior Member

You can, for example, make a 3D solid model of each tank in AutoCAD. With the help of several horizontal plane at various heights, you can:
- with the command "slice" divide the tank into 2 separate solids. "massprop" will give the volume and center of gravity of each part.
- the command "section" will give you the "free surface" of the tank and the command "massprop" now will give the area and moment of inertia of such a surface.

3. ### Laranjo123Previous Member

ahm i'd like to know how to do it manually?..

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### J FeenstraJunior Member

make one hell of an excel sheet, with columns LXBXH, than calculate using the fluid density, you can determent the volume of the ship per tank.

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### TANSLSenior Member

You have to consider each tank as if it were the hull of a ship:
- define the tank through various cross sections.
- calculate the Bonjean values ​​of each section
- calculate the "hydrostatics values" of such a "hull"

6. ### Laranjo123Previous Member

actually i've this thought that Simpson's are very useful to these tanks. i Can calculate them all by using that rule. Of course every naval architect does that. But i keep on experimenting that. I have seen to my prof. He's using the ship lines to produce Capacity plans. Of course i need those. but when i tried to calculate his works ( his samples ). I get the wrong results. tsk...damn...

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### TANSLSenior Member

I mention a few things:
• Simpson integration uses parables, 2nd degree polynomials which pass through a series of points spaced a regular distance.
• Integration with more modern methods uses splines, which are third degree polynomials passing through a series of points that need not to be equal distances apart. So Simpson, represents a simplification and for ships with transom stern, bow bulb or knuckle, this calculations may give large differences (more than 5%) with reality.
• I do not understand how your teacher can use the hull lines to calculate tanks because the outline of these do not usually rely on the hull. Only double bottom tanks and the like. On the other hand, think of the amount of non-structural tanks that may exist. In any case, the hull will form only one, or perhaps two, of the sides of the tank. Therefore this method will serve for a very small part of the ship's tanks.
• Modern programs deal directly with surfaces or solids and, by triangulation, or more sophisticated methods unknown to me, deducted surfaces, volumes and other physical properties of objects.
In my opinion, the modern naval architect MUST know how to calculate things by hand but has not to waste his time in adding and multiplying. His work, thanks to computers that make these routine functions, must be more creative.
Send me some example if you want me to analyze it.
If I can help more, please do not hesitate to contact me.
Best Regards

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