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RE: [PSUBS-MAILIST] Steel Pipe Hull



Hi Doug,
 
I think we need Cliff Redus to comment.
 
I checked your spreadsheet and compared it to mine, and the difference was the center to center spacing of stiffeners.  I left mine at the default value of 10 inches and you had changed yours to the length of the pipe (I assume) which is 60 inches.  The output doesn't make sense to me either since I assumed a .0001 stiffener and web was essentially equal to not having a stiffener.  The center to center spacing of stiffeners shouldn't be a factor in that case.  I'm guessing there are some assumptions built into the formula's behind the spreadsheet geared towards a reasonably sized hull and it may not be applicable to pre-manufactured small diameter pipes without stiffeners.
 
Hopefully Cliff will see this message and take a look himself.
 
Jon
 
-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org]On Behalf Of djackson99@aol.com
Sent: Monday, January 29, 2007 12:12 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Steel Pipe Hull

Jon

Your right about the stiffeners, but there must be other problems.  Now I get 8 psi :)  What are you using for "Center to center spacing of stiffeners"?  When I change it the outcome changes, and that does not make any sense.  Your calculation can not be right either;  57 psi for a 1/4" think 10 inch pipe?  No Way! I get 57 psi out of a garden hose and I've used 10" steel pipes for temporary colverts and had concrete trucks drive over them.  There is just no way they would not perform to anything less than 1500 feet.

You can download my sheet from here: http://www.submarineboat.com/sub/BOB2_Hull_Calculation.xls to have a look if needed.

I really do appreciate this exercise I hope the outcome is a simpler and more full proof approach.

--Doug J