Some questions about ISO 12215-5: 2019

Discussion in 'Class Societies' started by TANSL, May 7, 2021.

  1. Alik
    Joined: Jul 2003
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    Alik Senior Member

    Another question: has anyone tried outboard engine loads from Annex K the ISO12215-5:2019 standard? There are few sources:
    1. Acting ISO12215-5:2019 standard as published
    2. Paper by JB, making corrections in the formula https://www.researchgate.net/public..._12215-5_for_Hull_Construction_and_Scantlings
    3. Unofficial errata dated 2021/12/06 by G.Dolto
    4. VTT guidelines https://cdnmedia.eurofins.com/europ...elines-for-commercial-craft-version-20162.pdf

    So my findings:
    - Authors in #2 and #3 state that formula for COB in #1 is incorrect, referring #4 as proper source of formula.
    - Formula for COB in #2 includes BT^2. This member is not present in #3 and #4.
    - Formula from #3 and #4 if used gives the acceleration levels of (10...20)g. This is ridiculously high for operational loads, no high speed craft structure is designed for such loads. To mention, IMO HSC Code gives 12g as maximum for collision acceleration loads. Lucas in 2010 paper refers (5...8)g for collisions of small boats.
    - Meanwhile, formula in #1 amazingly gives results which are closer to reality, they are about 50% lower compared to #3 and #4.
    - I assume formula in #2 is incorrect due to typo.

    Any thoughts?
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    I don't have 2019 version.
    However, the objective of this COB is a simple strength of the transom issue. Im not sure why this needs a "load case", it should be rather obvious to the designer.
    Having said that, it does indeed seem that the raison d'etre of this latest version of ISO has been truly lost.

    ISO, was for 'small craft' that fell/slipped or otherwise were between a simple home made (or bought blow up day boat) and those of commercial standards - of which was/is increasing - and thus required "some means" to ensure a degree of safety. The EU needed a universal mechanism to achieve this - ISO. This was intended ostensibly for the buyer. The objective being 'simple' and easy to follow rules for such vessels - as that is what they originally started out to be anyway - simple.

    For those that recall, the "old" DNV high-speed craft rules, that lovely orange booklet, was just that. Simple and easy.
    If ISO is modelled itself on this old version of DNV's rules, it would be far more complete and appropriate, and simpler too.

    Yet it seems ISO has gone the route of the newer version of DNV's rules. The more overly complex and prescriptive.
    For commercial and similar type of vessels, that's fine, but not for these simple pleasure type of boats that ISO was originally intended.

    ISO is going beyond those day boats and and simple pleasure craft etc into trying to capture the 'commercial market', with their behemoth of rules.

    Given that ISO rules are now on par with Class rules, in terms of their volume...why on earth would anyone select ISO as their standard of compliance?
    It seems to me, this latest version of ISO, from comments/colleagues and papers I have critiqued and read, spells the nail in the coffin for ISO.
    It is a dead piece of 'standards' walking...

    As noted, at least with Class, it is centralised and there is a "body" in which one can liaise and discuss issues, successfully or otherwise. Not so with ISO.
     

  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I do have ISO 12215-5:2019, I have it, I have read it, I apply it regularly and I am familiar, in my work and territory, with the work with the ISO standards for small boats and the operations with the entities that supervise these projects and their construction.
    I don't know of any CS that has a public service office, "centralized" or not, where anyone can go to ask questions. It is true that there are many technicians in the CS who not only do it but are obliged to answer only to customers. That is to say to those who have previously paid large sums to the CS to obtain the class for their boat. And those answers, "centralized" or not, are not usually obtained with the haste to which, almost always, we are forced. The "agility" of the CS is not to be admired.
    I will not delve into it, because this topic has already been widely commented on, as to whether the CSs give rise to structures that are heavier than desirable for these small boats.
    I will say that, as far as I know, there are official bodies that recommend the use of ISO standards in matters as varied as the calculation of quick-emptying cokpits or the number and size of life rafts. Not to mention what the European regulations on small boats suggest.
    Since I do have the ISO, I have been able to verify that there is no mention in it, not even in the bibliography that appears at the end of the standard, of the new DNV regulations, among other things, I suppose, because that CS, as such, it does not exist any more.
    Perhaps these reasons, or some of them, and I say perhaps because I do not feel qualified to guarantee anything, are the ones that drive designers of small boats to try to avoid dealing with any CS, especially now that ISO standards are available and that, in addition and fortunately, higher levels of quality are being demanded in both projects and constructions.
    I do not advise using or not using the ISO standards, each one to do what seems convenient, but I do say that it can be interesting to analyze with a magnifying glass the advices that, perhaps due to lack of experience, are not on the right track.
     
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