[PSUBS-MAILIST] buoyancy

[Alan James via Personal_Submersibles]

Yes quite a lot involved, thanks.I believe the Deep Worker 2000 has carbon fiber O2 bottles.These would hold  similar pressures to the CNG tanks Hank mentioned. They must have done the maths on external pressure with regard to external pressure over internalpressure increasing as the bottles contents depleted.I just don't want to close the door on Hanks suggestion of using them for buoyancy.Cheers Alan



      From: Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Thursday, November 12, 2015 11:21 AM
 Subject: Re: [PSUBS-MAILIST] buoyancy
   
I didn't mean to imply that composites are necessarily bad for the application, but rather that they are not easily predictable. Composite hulls usually require verification of theoretical results by physical testing.  As for the theory, fiber reinforced matrix composites usually exhibit properties which are weighted averages of the individual component properties in proportion to their volume fractions, but they have failure modes which homogeneous isotropic materials do not, particularly with respect to buckling, delamination, and brittle fracture. Additional variables such as average length of fiber, the order of consecutive principal fiber orientations, layer thickness and so forth all have an effect on the ultimate part performance, making composite failures less predictable.  That said, there have been a number of commercially successful composite pressure hulls, but there is a significant amount of work involved in valid! atingthem.Sean




On November 11, 2015 2:25:41 PM MST, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Sean,I just put it through the Deep Sea Power & Light program whichhas basic geometries & a materials list with epoxy / fiberglass.I had spent a lot of time a couple of years ago, researching the building
of a fiberglass 1atm sub. The E glass / epoxy combination was the best(including price) for compressive strength.Those carbon fiber pressure vessels are wound so a different kettle of fish.Graham Hawke did a carbon fiber wound submarine pressure hull at one stage.They do have carbon fiber masts which are both under compression & tension,so the compressive strength can't be too bad.Alan 
      From: Hugh Fulton via Personal_Submersibles <personal_submersibles at psubs.org>
 To: 'Personal Submersibles General Discussion' <personal_submersibles at psubs.org> 
 Sent: Thursday, November 12, 2015 8:44 AM
 Subject: Re:[PSUBS-MAILIST] buoyancy
   
Sean,
We have a New Zealand developed programme for design that is widely used in
the pacific islands where Kiwis (NZ'ers) are involved. It covers piping,
fabrication, ditch digging, construction of most things.  It is called
"TLAR".  No guarantees go with it.
Hugh 



-----Original Message-----
From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org]
On Behalf Of Sean T. Stevenson via Personal_Submersibles
Sent: Thursday, 12 November 2015 8:26 a.m.
To: Personal Submersi! blesGeneral Discussion
Subject: Re: [PSUBS-MAILIST] buoyancy

Alan, how did you do that calculation?  What layer count, thickness,
component volume fractions and principal fiber orientations did you use?

Sean


On 2015-11-11 12:15, Alan James via Personal_Submersibles wrote:
> Hank,
> I did a quick calc on a sphere of nominal dimensions made of epoxy / 
> fiberglass.
> With external pressure it had a depth of 4347ft, with internal 3785ft. 
> I should have posted the results in psi, but you get the picture.
> The big thing to me would be that if you ruptured it by hitting 
> anything, or so it failed, you would go down like a lead balloon.
> Alan

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