# Which method is better for calculating shear force and bending moment of ship by usi

Discussion in 'Boat Design' started by xichyu, May 18, 2016.

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### gonzoSenior Member

They are point loads to simplify the calculations. You are not understanding basic ship design, or any other engineering calculation where there are forces and reactions.

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### TANSLSenior Member

Well, maybe you can tell me what I do not know about ship design. Tell me now, please, how you simplify to reduce to several loads on several points what in fact is a distribution of forces, continuous, over the whole length of the ship. The OP will also seem interesting, I'm sure, your explanation. Thank you, Professor.

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### gonzoSenior Member

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### TANSLSenior Member

I am not sure that you have understood the post # 2, so I will try to clarify the ideas of the professor. Forgive a humble student so bold as to try to explain things to the professor.
Post # 2 shows an example of load distributions along the length of a hull. It says nothing about how to calculate, with that, BMs and SFs. Do you understand now why it is not enough to read post # 2?
Contrary to what is explained in # 2, you explain (post #12) that you only have to calculate the buoyancy at some very specific points. Why only at them ?. How is this punctual buoyancy calculated?
Given your knowledge of the subject that, apparently, you have, would be very grateful to you to explain how it is done. I think this is the only part missing in your detailed explanation of how to solve the problem. Thank you.

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### gonzoSenior Member

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### TANSLSenior Member

I do not ask for the method set forth in chapter #6 nor any other but the one you seem to use. So forget for a moment chapter #6. Contrary to what is explained in post # 2, you explain (post #12) that you only have to calculate the buoyancy at some very specific points. Why only at them ?. How is this punctual buoyancy calculated?
From there, how do you calculate the values of BM and SF along the length of the boat ?.

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### gonzoSenior Member

Treat is as a beam

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### TANSLSenior Member

Of course, all this calculation was based on the fact that the ship's hull is a beam. But now you are introducing a new variable, how is supported, to what and where, that beam?. Once you know that, you still do not answer the main question, how do you calculate, according to your simplifying hypothesis, the BM and SF at each point ?.
This is what the OP is asking for what he and some of us would be most grateful for you to explain.

Last edited: Aug 30, 2017
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### gonzoSenior Member

Have you read chapter #6? It would allow you to ask intelligent questions. Once more you are hijacking a thread and not allowing the OP to get questions.

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### TANSLSenior Member

I am amazed to see how many efforts you make, how you twist, so as not to answer the main question: how are BM and SF calculated according to your "simplified" method ?. I do not want to read chapter # 6, I just want to know "your method".
I do not think I'm preventing anyone from asking questions. I'm just interested, and I suppose (I suppose, I do not say) that many more people, in knowing your method. That is the initial question of the OP, the best method for calculating BM and SF. There may be several methods, who knows?, but yours, simplified, sounds interesting.

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### latestarterSenior Member

Gonzo, there is no point in answering Tansl's questions. As usual he is pretending ignorance on one thread and giving advice on MaxSurf on another.
@ TANSL
Given you have been designing ships for decades why all the questions?

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### TANSLSenior Member

@latestarter, I do not know why trying to dig deeper into a seemingly new and innovative method, which can greatly simplify a very tedious calculation, can be a bad thing.
Many boat designers, mainly of small boats (I would say most of them), have never had to calculate the BM and SF distribution along the length of their boats. Therefore, in my opinion, one can be a designer and not know how to describe the specific procedure to perform these calculations. Gonzo's simplified method could be of great help to many designers.
I do not pretend to be ignorant at any time but I do not pretend to know more than what I really know, as some others do. Although I can guess the answer, I think I have the right to ask.
As for MaxSurf, should I refrain from advising on what I know about that program? I do not see the reason for not giving advice, am I also doing something inappropriate?

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What is new an innovative here please?

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### TANSLSenior Member

This, for me, is innovative and, if true, greatly simplifies the calculation.
What I would do is calculate the buoyancy at each and every point of the hull, along the waterplane length. What do you think?. Which method would you use?

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