[PSUBS-MAILIST] G.L. summary Design Loads

[jimtoddpsub at aol.com]

Jon & Alan,

I have only been familiar with 1.25 test and 2.0 collapse standard, however the stepped requirements per GL make logical sense.  Percentage margins at shallow depths could be a little thin compared to absolute margins as you illustrated, Alan.

Jim


-----Original Message-----
From: Alan <alanlindsayjames at yahoo.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Fri, Dec 6, 2013 10:38 am
Subject: Re: [PSUBS-MAILIST] G.L. summary Design Loads



Hi Jim,
Yes you are right.
I used feet as an illustration, where they use metric pressure
in their table. 
I like their scale system, because if you are building for a
shallow depth, with a thin sectioned hull, then any small margin of
error will have a bigger impact than on a thicker hull.
As a simple illustration, if you were building 3mm thick & ended up
2 mm that's a 33% error, whereas if you built 10mm thick & were out
by the same 1mm, that's only a 10% error.
Alan
Sent from my iPad

On 7/12/2013, at 5:11 AM, Jon Wallace <jonw at psubs.org> wrote:



              

      Jim,
      
      Yes, there's certainly a point in all brackets where it would      behoove the owner to bump up the nominal dive depth (operating      depth) to take advantage of lower ratios.  I believe ABS uses a      static 1.25 ratio for all vessels regardless of operating depth.       GL would appear to be more conservative than ABS in this category.
      
      Jon
      
      
      On 12/6/2013 6:03 AM, jimtoddpsub at aol.com wrote:
    
    
        
Hi Alan,
        
 
        
If I understand the requirements correctly,            then for designed maximum operating depths of 320 feet and            the 340 feet respectively the test depths would be as            follows:
        
320' x 1.4 = 448' test depth
        
340' x 1.25 = 425' test depth
        
 
        
And the            designed collapse depths would be:
        
320' x 2.4 = 768' collapse
        
340' x 2.0 = 680' collapse
        
 
        
Therefore if my designed operating depth is            near the lower limit of a bracket, increasing the stated operating              depth enough to push it into a deeper bracket would              actually lessen the requirements for            test depth and collapse.  Do I understand correctly?
        
 
        
Thanks,
        
Jim
      
    
    
  

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