# can anyone suggest, how to calculate volume of forepeak tank

Discussion in 'Boat Design' started by appusree888, Dec 18, 2014.

1. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

can anyone suggest, how to calculate volume of forepeak tank as it is triangle in shape. 1/2 BxH or Lx Bx H can we use any of this equation

2. Joined: Dec 2014
Posts: 6
Likes: 0, Points: 0, Legacy Rep: 10
Location: Temperance

### doug9694Small Engine Mechanic

Calculate tank size

There will be a double triangle. One looking down from the top, another from the side. So the volume will be only 1/4 what it would be if rectangular. Providing there is no flat on the bottom. equation would be 1/4 HxLxW.
You may want to consider a bladder tank.

3. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

thanks douge. But which value we will take as width..is it the width at aft end of forepeak tank

4. Joined: Dec 2014
Posts: 6
Likes: 0, Points: 0, Legacy Rep: 10
Location: Temperance

### doug9694Small Engine Mechanic

re-1: Calculate tank size

Yes, it would be the widest "aft" dimension.

5. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

but we cannot take this equation.because the forepeak tank shape is a tetrahedron shape so the equation may change

6. Joined: Dec 2014
Posts: 6
Likes: 0, Points: 0, Legacy Rep: 10
Location: Temperance

### doug9694Small Engine Mechanic

re-2: Calculate tank size

A tetrahedron is a four sided solid pyramid. Is that what you have? The pyramids in
Egypt are not tetrahedrons because they have 5 sides.

http://en.wikipedia.org/wiki/Tetrahedron#Formulas_for_a_regular_tetrahedron
Volume

The volume of a tetrahedron is given by the pyramid volume formula:

V =1\3 x A x h

where A is the area of the base and h the height from the base to the apex. This applies for each of the four choices of the base, so the distances from the apexes to the opposite faces are inversely proportional to the areas of these faces.

If your tank or the space is a different shape then I need the dimensions.

Last edited: Dec 18, 2014
7. Joined: Dec 2014
Posts: 6
Likes: 0, Points: 0, Legacy Rep: 10
Location: Temperance

### doug9694Small Engine Mechanic

re-2: Calculate tank size

I messed some where and sent a duplicate. So just delete this.

Last edited: Dec 18, 2014
8. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

acube / 6 x root two is the equation for tetrahedron and it have only four side ..L x B x H / is the equation for pyramid and have five side so both are different.so which one we will accept

And area of collision bulkhead surface is 4.49 side shell surface is 7.65 and deck surface area is 10.29

9. Joined: Sep 2011
Posts: 6,471
Likes: 385, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

You can draw several sections of the tank and integrated by the method of Simpson, trapezoids, ...

10. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

Thank you tansl

11. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

can you suggest which frame we can take as lcg where we can take tcg in this particular shape of No.6 F.O. Tank

#### Attached Files:

• ###### Tank Plan-Model_001.jpg
File size:
89.6 KB
Views:
415
12. Joined: Sep 2011
Posts: 6,471
Likes: 385, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

Similarly to calculate the volume, integrating the areas of the sections, you can integrate values which are each sectional area multiplied by its distance from a certain point. The ratio of the value of the integral and the total tank volume will give the position of its center of gravity relative to the chosen point.

13. Joined: Jul 2014
Posts: 21
Likes: 0, Points: 1, Legacy Rep: 10
Location: Dubai

### appusree888Sreenath

Can you explain it as simple...i didnt understand that.its my fault not yours. and i think it will be 29th frame when we taking it from profile view.right?

14. Joined: Sep 2011
Posts: 6,471
Likes: 385, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

Now, to calculate the volume, you calculate the areas of several sections and, for example with Simpson's method, you calculate the total volume.
To calculate the center of gravity, rather than the area of each section, you have to calculate the value of the area multiplied by its distance to, eg the AP. These values (areas moments), integrated with Simpson, will give a certain value, divided by the total tank's volume, will result in the distance of the tank's cog to the AP. If instead the distance to the AP you take the center line distance or the distance to the base line, you'll get the coordinate of the cog in relation to these planes.
Sorry, I can not explain better. Maybe someone with more mastery of the language than me could explain it more clearly.

15. Joined: Mar 2014
Posts: 247
Likes: 8, Points: 18, Legacy Rep: 50
Location: Bulgaria

### RabahSenior Member

Hi appusree 888,
Whether have you a computer model in 3D, on what program and whether location of a forepeak bulkhead is fixed?

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.