Alan, The definition for rated depth doesn't include any wording for a 1.25x safety margin. It is nothing more than the depth to which the vessel has been operationally tested. Absent a test chamber, the only way for a home-builder to "rate" their sub is to test dive it to some depth. However, that depth may be significantly less than either the failure depth or predicted maximum operating depth. For illustration, imagine the owner of a K350 who lives in Kansas where the deepest lake is no more than 50 feet. If they go to 30 feet the first time they dive their sub, then that sub is only rated to 30 feet even though it is a K350. If they go to 50 feet the second time they dive the sub, then that sub is now rated for 50 feet. Assuming they never travel out of Kansas that sub will never be rated for more than 50 feet. It doesn't mean the sub can't go to 350 feet, it only means it hasn't. In this specific example I don't think adding a safety margin (1.25x) makes sense, and by definition its not required. See ABS Underwater Vehicles Section 3.5 for a good example of how rated depth is used. As I understand the ABS rules, rated depth is equivalent to saying "What's the maximum depth this sub has been operated at?". Associating design depth with operating depth (maximum or not) doesn't make sense to me, but I guess I'll have to live with it. We then need to include "failure depth" as a definition to our guidelines. Jon On 12/11/2010 12:30 PM, Alan James wrote:
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