[PSUBS-MAILIST] New submarine

[swaters]

Awesome Alan! Thanks!
-Scott Waters




Sent from my U.S. Cellular© SmartphoneAlan James <alanlindsayjames at yahoo.com> wrote:Scott,
just did a quick Google & these people make 1.5" segmented hemispheres 6ft in diameter.
http://www.cmforming.com/tankheads-and-accessories.htm
http://www.cmforming.com/pdfs/hemispherical-asme-code-type.pdf
You may have to compromise depth to line up with what's available if there is a stock item
somewhere.
Alan



From: swaters <swaters at waters-ks.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Thursday, April 10, 2014 3:37 PM
Subject: Re: [PSUBS-MAILIST] New submarine

Jon, 
I haven't thought as far as that yet. Mostly still seeing if this project is even feasable still.
Thanks,
Scott Waters




Sent from my U.S. Cellular© Smartphone

Jon Wallace <jonw at psubs.org> wrote:

As far as I'm aware, ABS doesn't deal with crush depth only maximum working pressure which incorporates usage factors (n), in this case of n=.67.  If n=1 could be considered "crush depth", then the calculator shows crush occurring at 2287 psi with 1.5 inch thick hemisphere and max working depth of 1532 psi with a usage factor of n=.67 which is right in the parameters that he is looking for.  The problem with using n=1 as an indicator of crush       depth, I believe, is that there's no way to guarantee it's an accurate representation of when the hull will fail because actual fabrication variables resulting in less than ideal geometric structures can lower the calculated result.  When using ABS/ASME       we should always be solving for max working pressure, not crush depth.

So your observation is correct, and solving for a working depth of ~3000 feet results in a much thinner hemisphere.  I didn't know what Scott was using for a safety factor so just plugged the numbers to get 2578 psi from the ABS calculator, but that obviously is over-built for what Scott's intended use is.  Using a thickness of 1.25 inches, ABS is showing max working pressure of 1268 psi or 2849 feet, just slightly less than his 3000 foot requirement.

Jon


On 4/9/2014 10:08 PM, Alan James wrote:
I'm a bit confused Jon,
Scott was asking for             the thickness for a crush depth of  5709 feet (2543 psi).
You are saying 2.5 for a maximum working pressure of 2578 psi. The working pressure
I thought was the design depth or maximum operating depth.
Alan



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