Tunnel Section Lost Buoyancy

Discussion in 'Stability' started by Abhilash Satheesan, Feb 15, 2018.

  1. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I think Abhilash Satheesan will hallucinate seeing where his innocent question has come from. I still advise him to forget tunnels. Some other opinions ?. It would be interesting to know what they think, or how they work, other members of the forum.
     
    Raffaele Frontera likes this.
  2. vv3k4i
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    vv3k4i Junior Member

    Let's be honest, we do have 21st century and as mentioned before, there is absolutely no problem to add those surfaces and simply do the calculations on proper shape. Tansl, the problem is not about the 2%, the issue is, that on each stage you increase your calculation error. Mass calculations contains its error, hydrostatics add some % on top of this, than several more places where you can increase your contingency, and the role of designer is to decrease calculation error as much as possible. We don't know what the calculations are for, but the good practice is to do everything as accurately as possible.
     
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  3. TANSL
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    TANSL Senior Member

    @vv3k4i, Okay, I will be totally honest in expressing my opinion that it is the following: it is totally useless to worry about the volume of those tunnels. I am a fervent defender of accuracy in calculations and accuracy in all, absolutely all, jobs, but I am also a fervent defender of giving each thing the value it has and not to waste time in giblets. The errors introduced by not considering tunnels in calculations are silly compared to those that are going to be committed in the rest of the construction process. And, perform the calculations with more or less precision, will not diminish, at all, those errors.
    Again, being very, very honest, my advice is, if the OP has a problem with the tunnels, no matter how small that problem is, forget about them.
     
    Last edited: Feb 19, 2018
  4. Raffaele Frontera
    Joined: Feb 2018
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    Location: Amsterdam, The Netherlands

    Raffaele Frontera Naval Architect

    I fully agree with VV3k4i, we are talking only about hydrostatic, but what about the tank plan then? also the WB presents where there is the tunnel will not match with the exactly volume and geometry giving a contribute on the global stability error..and again I say, for inland waterway having right shape of the tunnel it is important having for damage criteria the distance from the margine line of 0.10 m ADN 2015.

    Regards

    RF
     
  5. TANSL
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    TANSL Senior Member

    Frankly, I do not understand you. And I'm not just talking about hydrostatics, I'm talking about all the calculations of naval architecture.
    What does the plan tanks have to do with the tunnels? I do not see any relationship.
    What is the WB?
    What is global stability and how is it calculated? Why can the tunnels alter it ?.
    What damage criteria do you mean?
    What does the margin line have to do with the tunnels? Absolutely nothing.

    I'm sorry to ask so many questions but it's because I do not understand anything. Probably because of my poor English.
     
  6. Raffaele Frontera
    Joined: Feb 2018
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    Raffaele Frontera Naval Architect

    Tank plan: of there often there are WB or other tanks in their area so some tanks can be off in the tank plan.
    Global stability (sorry, not accurate to say that of course) I used to say intact stability (error hydro + error for geometry of some tanks) + damage stability ( change the calc of the FSM of the tanks involved where there is the tunnel) which the most critical criteria is the distance of emergency exit and if you have the buoyancy of the tunnel of course can make some difference for some openings. I really start to think I am sorry to say but you don’t have the feeling of the accuracy for the inland waterway. I have as experience more then 50 stability booklet approved for inland waterway by LR, DNV GL and BV and I never saw one booklet with 2015 ADN without the definition of the tunnel, sea chest and bowthrustet as you are saying...
    I am sorry but if you don’t have the right tools in 2018 to delete a 3 or 4% of a simply stability calculations is your problem not a suggestion that you can give to someone else.

    I am not interesting in your reply being your last message not professional with provocative comment and questions (not the first time).

    Regards
    RF
     
  7. Raffaele Frontera
    Joined: Feb 2018
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    Location: Amsterdam, The Netherlands

    Raffaele Frontera Naval Architect

    P.s. for naval architect WB is a water ballast of course
     

  8. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I have not wanted to bother you, at any time, I just do not understand some things that you say.
    For dealing with only one of the topics you have talked about, it is very likely that, if there is a tank above the tunnels, which I doubt very much, its volume is so small that there is no need to make the correction for its free surfaces. Therefore the FSM method does not need to be applied (in the tunnel tank). I'm talking about the boat the OP showed in post #1.
    I have no experience, you are right, in boats for inland waterways but there are more than 200 work boats sailing around the world, built with my projects, and in all of them I had to carry out the inclining test and the stability booklet (with 2015 ADN) . That also gives me the right to have my opinion on how the calculations can be made and their accuracy.
    Modestly I repeat that I did not want to bother you at any time. If you want us to continue discussing some issue of naval architecture, I will be happy to do so. Although in some way I do not agree with you, which is logical and natural, the exchange of ideas is always enriching and, of course, you deserve all my respect as a professional, even if I do not agree with you and I let you know.
    Thanks, now I know.
     
    Last edited: Feb 22, 2018
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