Re: [PSUBS-MAILIST] External vs Internal Stiffners

[DJACKSON99@aol.com]

Thanks for the input Ian.  This hull is for an ROV and only 6 to 10 in ID and I'd start with an extruded aluminum pipe section most likely.  It seems like it would have to be somewhat weaker of a design.  The solid weld will not help with any out-of-roundness problems and would subject the stiffner to failure due to stress cracks and weld failure. 

 

By the way, my hat is off to the folks that put together the spread sheet.  I'll have some questions about it when I figure out what to ask. :)  --Doug J

 

In a message dated 10/25/2006 6:08:37 PM Central Daylight Time, irox@ix.netcom.com writes:

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.