[PSUBS-MAILIST] ABS Hull Calc

[Sean T. Stevenson via Personal_Submersibles]

Per the ABS rules, different equations are provided for unstiffened cylinders, primarily because the absence of stiffeners which meet the "heavy stiffener" criteria means that the overall length of the section considered for the  overall buckling calculation is increased to encompass the length of the cylinder in question, the length of any adjoining conical sections and subsequent cylindrical sections (up to the first instance of a "heavy" stiffener), and 40% of the inside length of adjoining heads. Thus, you must know this total effective length to properly evaluate the proposed section.

Sean


On April 23, 2014 6:34:27 PM MDT, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>You have to put in some kind of value and as I recall, very small 
>numbers can come up with some weird results.  If you use 36" OD, 72" 
>length, and .25" thickness for the shell, and then enter .1" for the 
>stiffeners, you'll see that the bottom line calculation (line 92) is a 
>max depth of 1 foot.  However, if you look at line 51 which is the 
>maximum Pa for inter-stiffener strength you'll note that it is 61.2 psi
>
>which matches the results of the unstiffened online calculator.  Note 
>that both of these results correspond to a "n" of .8 which you can 
>manipulate in the excel spreadsheet but is hard-wired in the
>unstiffened 
>calculator.
>
>So I think the answer is that you have to use very small number for 
>lines 18 through 21 (try .001) but ignore line 92 and find the lowest
>Pa 
>between lines 51, 56, 63, and 71 to determine the maximum allowable 
>operating pressure.
>
>Jon
>
>
>
>
>On 4/23/2014 7:02 PM, Pete Niedermayr via Personal_Submersibles wrote:
>> What do I enter if I don't want to have hull stiffners. I want to
>compare results with the Psubs online calculator
>>
>> Thanks Pete
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