ABS Rules...under 90 meters. Misleading.

Discussion in 'Class Societies' started by Niru, Aug 5, 2010.

  1. Niru
    Joined: Jul 2010
    Posts: 50
    Likes: 1, Points: 0, Legacy Rep: 32
    Location: Philippines

    Niru Mr.

    Good day everyone.

    just recently i downloaded Rules from ABS @eagle.org...etc.

    can someone correct me regarding the SM(Section Modulus) formula for Web Frames

    Note: ABS Rules Vessels under 90 meters

    where SM=7.8chs(l sqr) , about s=???

    s = is equal to frames spacing??? (m), (well the other formula indicate s=spacing of web frames...)

    the prob is either you use formula 1 (sm=7.8chs x l sqr.),
    or formula 2 ( sm=4.74cs x l sqr.(h+bh1/45K) ) the answer should present close value. due to different "s" requirement the value has a big gap.

    thats prob 1. i hope its just a typographical error...

    next is...prob 2

    SM= for side stringer.
    having a hard time to relate can somebody please translate...

    SM=7.8chs x l sqr.

    where "s" = sum of the half lengths, each side of the stringer ??? were the side shell is transversely framed how does this apply...sorry

    i can really be dumb sometimes ^_^ ... thanks!
     
  2. LyndonJ
    Joined: May 2008
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    Location: Australia

    LyndonJ Senior Member

    Just use the 7.8CHSl2 formula and you wont go wrong. It's just simple beam theory/ grillage with some additional factors.

    Look at each member look at the span and the spacing.

    But what size vessel are you designing and what material?

    As a recend grad NA you really should be working with a senior NA or engineer for the first couple of boats at the very least. Sounds like you are in there all by yourself ! There's a lot of traps in the rules so make sure they are checked.
     
  3. Niru
    Joined: Jul 2010
    Posts: 50
    Likes: 1, Points: 0, Legacy Rep: 32
    Location: Philippines

    Niru Mr.

    many thanks sir Lyndon.

    anyway i was just familiarizing myself with the ABS Rules...

    actually its for an 80meter cargo ship, steel material. ^_^

    "There's a lot of traps in the rules so make sure they are checked." - got it !!!

    i better check other class rules for the sake of comparison...anyway thanks again.
     
  4. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    Niru

    Have a look in the spreadsheet file repository here, there was a commercial GL sheet posted for download that might help you compare.

    I sent you a PM too.
     
  5. Niru
    Joined: Jul 2010
    Posts: 50
    Likes: 1, Points: 0, Legacy Rep: 32
    Location: Philippines

    Niru Mr.

    thanks Sir Mike,

    found the website of GL. regarding the spreadsheet still looking for it.

    hmm comparing the GL to ABS, when you save the Rules in pdf..you have to save section by section...thats for GL..( but still its worth the effort ^_^ )
     
  6. MikeJohns
    Joined: Aug 2004
    Posts: 3,176
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    Location: Australia

    MikeJohns Senior Member

    I have emailed you a spreadsheet based on first principles and a link to the spreadsheet repository on this website.

    Cheers
     

  7. Niru
    Joined: Jul 2010
    Posts: 50
    Likes: 1, Points: 0, Legacy Rep: 32
    Location: Philippines

    Niru Mr.

    found it, downloads category...ive almost download all that i can use for comparison. thanks
     
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