Discussion in 'Multihulls' started by rkpshenoy, Jun 15, 2007.

1. Joined: Apr 2007
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rkpshenoystudent

Hey there is one problem i faced lately while calculating volume of tanks required by capacity plan with the help of bonjeans.
As bonjeans are positioned at the stations which may not
necessarily be at the location of bulkheads or frames,i have been unable to calculate the volume of tanks.

Also is there any scheme to position bulkheads to divide the ship ( i mean is there any standard spacing between them?)

Thanx

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jehardimanSenior Member

As long as there are no extreme changes in section or knuckles, you can use the Bonjeans to work up longitudinal curves of volume at different heights. You can then slice them anywhere you want for preliminary design estimates. Normaly, however, real tank capacity curves are worked up individually and directly from the finished arrangement/structural plans.

Bulkheads are placed based upon many factors, such as floodable length and volume, secondary structural loading, and cargo factors. If you are designing to a set of society rules (Lloyds, ABS, DNV, etc), they will have something to say about where the bulkheads go and how many you have to have.

Last edited: Jun 15, 2007
3. Joined: Apr 2007
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rkpshenoystudent

I am presently designing a catamaran with a transverse framing system so im not considering any tanks positioned to the portside or starboard side. instead i am spacing the transverse blkheads longitudinally to divide the tanks. In such case,in the capacity plan i am largely having to divide the demihull into a number of holds.
can i use the bonjeans in that case and how given bulkheads are not exactly where the bonjeans are?

Oh ok i am going by IRS rules and it doesnt give bulkhead spacing.since you are saying its coming under floodability calculations i thnik i can take this from ABS.

Thanx

4. Joined: Aug 2004
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jehardimanSenior Member

Are you sure you understand how Bonjeans work? You can use the Bonjeans (curves of area at the stations) to develop a curve of volume along the length of the hull at any height (the sectional area curve, i.e. axis is length, ordinate is sectional area at the station, and the area under the curve is volume). You can then directly measure the approximate volume of any hold space between any two points along the length of the hull. This is basic naval architecture.

Last edited: Jun 15, 2007
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jehardimanSenior Member

Here is an example of what I mean.

Attached Files:

• Tank.gif
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6. Joined: Apr 2007
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rkpshenoystudent

oh ok got your point. but i was talking about the numerical integration part (simpsons rule). notice that in the picture you have shown the tank is not starting or ending exactly at stations. also the shaded area cannot be obtained by applying simpsons rule.

Thanx
tripod

7. Joined: Aug 2004
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jehardimanSenior Member

Sigh.... ....I should always rember the saying...
It is not that pigs can't be taught, but rather they will not learn. So never try and teach a pig to sing, it wastes your time and annoys the pig.

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rkpshenoystudent

Very funny. I appreciate your sense of humour but this is not the place to use it.

Thanx

9. Joined: Aug 2004
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jehardimanSenior Member

Ok, I'll stop trying humor.

Based upon this and your other posts, it sems that you are either a student looking for a project to copy, or a builder looking for a vessel to copy (Edit, oh looking further I see that you are a student). Your poor knowledge of even the most basic of marine calculations and requirements is disturbing if you are actually trying to design and build a vessel for service. In either case, it is most likely a diservice to your country and fellow citizens to allow this to go forward as enough people die in poorly designed vessels over there.

But setting your worth and motives aside......and dropping back in to teacher mode....

Query to the student: Why can't you use Simpsons 1st rule, or 2nd, or one of Tchebycheff's, or one of the arbitarily spaced ordinate rules to determine the volume of the tank?

Last edited: Jun 16, 2007

10. Joined: Apr 2007
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rkpshenoystudent

Thanx for all the concern. But i guess instead of involving yourself in some interactive discussion you are spying on me.why do you have to look at all my posts. If you want to continue this discussion ill give you my mail id instead dont spoil the forum space. rkpshenoy@gmail.com

Thanx again for all the compliments jehardiman

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