Re: [PSUBS-MAILIST] elliptical heads/ Git Kraken

[Jon Wallace <jonw@psubs.org>]

Hi Dan,

Frank can correct any of this.  I believe the heads are 84 inch OD of 
.375 thickness.  His design depth is 150 feet but he was hoping to 
extend to 500 feet by the use of stiffening ribs which now appears to be 
off the table.  Going back to his original design for 150 feet, the hull 
calculator (spreadsheet) shows failure at 355 feet with "n" equal to 1, 
which is well within his original specification.  For reference, I used 
84 OD, 83.25 ID, 23" depth (per www.hansontank.com), and .375 as the 
thickness.

For viewports, using the viewport calculator for 150 foot operating 
depth, I'm getting the following Stachiw specs:
20 inch viewable diameter from inside the sub = 25 inch diameter x 3 
inch thickness
12 inch viewable diameter from inside the sub = 15 inch diameter x 1.8 
inch thickness

Assuming the 12 and 20 inch descriptions provided by Frank are OD, then 
the Stachiw specs are:
20 inch diameter = 16 inch viewable diameter from inside the sub x 2.4 
inch thickness
12 inch diameter = 9.75 inch viewable diameter from inside the sub x 
1.46 inch thickness

With flat viewports it is important to know if the diameter described is 
the OD or viewable diameter since the Do/Di ratio requirement for the 
seat makes a big difference in the calculated results.  The online 
calculator is slightly conservative since the data was interpreted from 
graphs within Stachiw's book.  It would be nice to have access to 
Stachiw's raw data that he used to create the graphs, but I suspect that 
with the correct Conversion Factor, any print bleeding or other small 
printing imperfections within the book caused as part of the 
manufacturing process are negligible.

Jon

Daniel Lance wrote:
> What was the diameter and wall thickness ?  ( 60" or 74"and 
> 3/8" wall thickness ) I think a 500ft depth rating is optimistic




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