Just a quick note. More allot of CAD engineers, are stress analysis program use the term FOS (Factor Of Safety) and design parts and assemblies to a customers FOS requirements. In the aerospace industry, I've been told the FOS needs to be 20% above max expected stresses, or in other words a FOS of 1.2 would be required. Weight is a very important factor in the aerospace industry. Submarines are not as picky weight wise.
Regards,
Brent Hartwig
From: "Jay K. Jeffries" <bottomgun@mindspring.com>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: RE: [PSUBS-MAILIST] Re: Mig welding a sub
Date: Wed, 25 Jul 2007 20:17:09 -0400
James,
Safety Factor is a formal submarine term that is first and always a design issue which in all references is never less than 1.5 times operational depth and generally should be at least 2.0 for a personal submersible. The safety factor makes allowances for not having a perfectly formed hull, discontinuities in materials, transients in operations (especially for those of you considering high speed ops), etc. It is first a design issue that carries over into later dive operations.
As far as the level of due diligence necessary for testing a submersible capable of reaching 200 fsw as compared to one that dives to a depth of 1000 fsw, the same level is required. A shallow water sub is designed with materials suitable for that depth while a deeper diving sub uses stronger materials. Both can have similar failure modes�either of the hulls and fittings can rupture. The failures will be relative to depth. So the same level of inspection is necessary for both hulls. I agree that there is more effort required to build the deep diving sub compared to the shallow sub and it is easier to recovery from a shallow water catastrophe.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
A skimmer afloat is but a submarine, so poorly built it will not plunge.