Re: [PSUBS-MAILIST] External vs Internal Stiffners

[irox <irox@ix.netcom.com>]

It's been a while since I've done any pressure hull calculations, but as far as
the math goes, there shouldn't be any difference between internal and external
stiffeners.

>From a construction point of view external stiffeners will be a lot harder.  The
weld has to be load bearing (for internal stiffeners, the welds just need to keep
the stiffeners in place).  Also, external stiffeners will not help push the cylinder
"into round" (since they will all come slightly out of round), so any out of roundness
will have to be "fixed" before attaching the stiffeners.  The only benifits you get
are a slight more internal space, and plenty of points to mount external equipment.

Using internal stiffeners appear to be much more simpler, construction wise.

Ian.


-----Original Message-----
>From: DJACKSON99@aol.com
>Sent: Oct 25, 2006 2:43 PM
>To: personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] External vs Internal Stiffners
>
>Thanks Brian.   So who thinks it is ok to use the 
>ABS_Hull_Calculation___Rev_12_17_2004.xls spread sheet without changes but actually place the stifferners 
>on the outside of the hull
>
>--Doug J
>
>
>In a message dated 10/25/2006 10:46:39 AM Central Daylight Time, 
>ojaivalleybeefarm@dslextreme.com writes:
>Doug,
>           I found this one, but his question was never really answerd:
>To: personal_submersibles@psubs.org 
>Subject: External stiffeners, paint, 'exotic' metals? 
>From: Nathanael Henderson <jude@pconline.com> 
>Date: Sun, 28 Mar 1999 10:05:42 -0600 (CST) 
>In-Reply-To: <file:///D:/html/archive/9903/msg00277.html> 
>
>    It appears most subs have internal stiffening T beams, but I see a
>number of references to external ones as well.   External beams certainly
>have their appeal from the standpoint of internal space (and even some
>ease of construction).  BUT, what do you do after putting on external
>stiffeners?   How do you restore the hydrodynamic body shape to escape the
>drag of exposed beams?  Putting on a second thin hull (perhaps with
>internal ballast tanks, etc.) seems like the inevitable thing to do, but
>then how would you maintain/rust proof the inner hull?
>    Along those lines, is there any advice on how to treat the hull?  A
>special type of paint?  Anybody up to hot-dip galvanizing a whole sub? :-)
>
>
>     Materials.  Steel is cheap and easily worked, but what about aluminum
>and titanium?   Aluminum would sacrafice some strength, but for a person
>with money titanium seems like the gold standard for submarine material.
>Besides the strength of titanium, it's almost complete invulnerability to
>corrosion makes it a very appealing material.   Anybody know what
>titanium costs in bulk and if it's unreasonably hard to work?  (The last
>time I saw a price on titanium it was about $30 a pound, but that was for
>wire, not plate/beam.)
>
>
>Brian
>
>
>
>
>
>----- Original Message ----- 
>From: DJACKSON99@aol.com 
>To: personal_submersibles@psubs.org 
>Sent: Tuesday, October 24, 2006 22:19
>Subject: [PSUBS-MAILIST] External vs Internal Stiffners
>
>
>I remember a thread about External Vs Internal Stiffeners but I can't find it 
>in the archive.  Can someone please point me to the date or title of that 
>thread?   Thanks --Doug J 




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