ISO 12215-5-2019 questions/issues

Discussion in 'Class Societies' started by Midja, Oct 15, 2022.

  1. Midja
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    Midja Junior Member

    Hi guys!

    I am a naval architect from Croatia with experience in ship design and related rules.

    I was always passionate about small craft design and this is the key moment.
    I have time and will to design planing workboat in my free time, as a hobby.
    Why planing workboat (fishing boat)? Well, some members of my family earn their paycheck by fishing, so I have their feedback and requirements. Planing workboat is a design that could solve most of their problems.


    So, ISO... pretty confusing text. I thought the ship rules were confusing, but this is a new level. And I need help to understand some of those texts and formulas. I spent way too much time reading and analyzing it, we have saying loosely translated, "I am blind with healthy eyes", so there is the possibility that I am missing something obvious.


    1. What semicolon represents the formula in the picture in the attachment?
    2. Regarding the natural stiffener definition; I´ve designed chine (in attachment) that is unusual for ISO, because there is a horizontal part of chine and angles aren`t in 130-150 deg spectrum, could this design be the exception and possibly the natural stiffener?
    3. I don´t completely understand EIb and EIl as stiffness of the panel per unit width in the b and l direction. I would be grateful if someone could describe these terms in some example.


    That would be all at the moment.

    Thank you!
     

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  2. TANSL
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    TANSL Senior Member

    This semicolon means that one or the other of the values on either side of that symbol must be selected. In some cases the minimum of the two values and in other cases the maximum.
    The chine, as you have drawn it, is a perfect natural reinforcement. To be considered as such, you must also study it as a reinforcement and verify that its module is sufficient to withstand the design pressure on it.
    "EIb" means the product of the Young's modulus (E) of the material by the Inertia (Ib) of the cross section with respect to the axis parallel to the direction "b".
     
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  3. Midja
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    Midja Junior Member

    Thanks TANSL for fast response and clarifying those points.
    I hope that I won`t open much more unclear questions afterwards :)
     
  4. TANSL
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    TANSL Senior Member

    @Midja, you're going to find a lot more obscure stuff in ISO 12215-5:2019. In some cases you will have to make assumptions because the standard will not give you a clear solution to several problems that arise when calculating the structure of a hull. This 2019 standard is the worsened version of the previous one.
    If you have more questions, do not hesitate to ask them. Good luck and patience.
     
  5. Midja
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    Midja Junior Member

    @TANSL haha, thanks. I have also 2008 rules, and I agree with you, also I´ve read other posts on this subject so I am aware that quality is low and there are a lot of issues. So experience is most valuable in this case.
     
  6. Midja
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    Midja Junior Member

    Hi guys,
    Just to confirm, it is first time that I`ve encountered this way of formula writing; page 20.
    At first picture, I have to choose maximum value between those three parts of formula? Also, in attachment is formula without my markings.
    Second questions is also regarding formula (third picture in attachment), but this time I have to choose lower value between marked two parts?

    Thanks!
     

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  7. TANSL
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    TANSL Senior Member

  8. Midja
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    Midja Junior Member

    Thank you once again for support in this battle :D
     
  9. TANSL
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    TANSL Senior Member

    You may be interested in taking a look at my software "SCT_MC" for calculating scantlings according to ISO 12215.
     
  10. Midja
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    Midja Junior Member

    Yes, I saw it on the forum; my plan is to try it later, first I like to understand every aspect of the calculation; so I can also evaluate software results.

    And because of my curiosity, I am at dead end with calculation of E for laminate. I am wandering through ISO pages, each time more confused.Well, my assumed laminate for side consists of:
    1. 2 x 300g mat - outer layer
    2. 2 x 300g mat + 1 x 400g mat
    3. 2 x 400g mat + 1 x 600g rowing + 1 x 400g mat - inner layer
    I would be grateful is someone could briefly explain how to reach E for that laminate.

    Thanks in advance!
     
  11. TANSL
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    TANSL Senior Member

    This example can help you. It is not the laminate that you propose but the procedure is exactly the same for any monolithic type laminate.
     

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  12. TANSL
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    TANSL Senior Member

    The following calculations can also help you.
     

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  13. Midja
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    Midja Junior Member

    @TANSL Thank you very much on your PDF, this part of ISO is so much understandable and it shows how much ISO is intricate, with very little logical order for beginners in this field.
    I have tested your composite and I`ve got same results and most importantly I understand the procedure.
    Only one question is still above my head; calculating final properties for composite, I can`t find and get results as you, because I am obviously missing formulae designated as 7, picture in attachment.
     

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  14. TANSL
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    TANSL Senior Member

    Yes you're right, it's my fault. This is a series of articles related to the use and understanding of ISO 12215-5 and I did not realize that in chapter 9 some formulas are mentioned that appear in chapter 7. I attach chapter 7.
     

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  15. Midja
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    Midja Junior Member

    Thank you, now the story regarding composite Young`s modulus is complete, progress is slow but it is exists :)
     
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