# ABS Rules...under 90 meters. Misleading.

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

1. Joined: Jul 2010
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Location: Philippines

### NiruMr.

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. Joined: May 2008
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Location: Australia

### LyndonJSenior 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. Joined: Jul 2010
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### NiruMr.

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. Joined: Aug 2004
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### MikeJohnsSenior 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. Joined: Jul 2010
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### NiruMr.

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. Joined: Aug 2004
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### MikeJohnsSenior Member

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

Cheers

7. Joined: Jul 2010
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### NiruMr.

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

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