Re: [PSUBS-MAILIST] endcap/bulkhead question

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

On Tue, 16 Dec 2003 11:14:26 -0700
"Adam Lawrence" <adteleka@in-tch.com> wrote:

> The shear stresses are compounded by a v-notch around the root of the weld.
> Hydrogen will go to the notch tip increasing the joints susceptibility to
> cracking over time from loading and unloading. Reinforcement will help but
> interior space and weight are precious commodities.

You build a sub with as much interior space as you need (make cylindered
longer).  If you invert your endcaps you can to save weight by not have
end-caps so heavy.  Also you save displacement (more weight saving here
as well).

Unless you have hemi-spherical endcaps, they will be the weakest part of
a pressure hull and will need to be much thicker and heavier than the
cylinder skin.

The biggest draw back about using the invert end-cap is that I don't
know of any subs that have tried it.

  Ian.

> ----- Original Message ----- 
> From: "Ian Roxborough" <irox@ix.netcom.com>
> To: <personal_submersibles@psubs.org>
> Sent: Tuesday, December 16, 2003 11:31 AM
> Subject: Re: [PSUBS-MAILIST] endcap/bulkhead question
> 
> 
> > On Tue, 16 Dec 2003 10:16:38 -0800
> > Ian Roxborough <irox@ix.netcom.com> wrote:
> >
> > >
> > > Any additional stress (I'm not sure if there is any), could easy
> > > taken care of by a heavy frame stiffener/re-enforcing ring.
> >
> > Warren you are correct here, where would be extra stress at the
> > joint of the end-cap and cylinder, but nothing that couldn't be
> > off set with a heavy stiffener.
> >
> > Ian.
> >
> > > As for the displacement, it reduces displacement meaning that not
> > > only have you eliminated most of the risk of end cap buckling, but
> > > your sub is now lighter.  And for useful space inside the sub, that
> > > is going to depend on how clever you get packing things in.
> > >
> > > For people wanting to read more about inverting end-caps on submarines,
> > > I would recomend reading "Pressure Vessels, External Pressure
> > > Technology" by Carl T.F. Ross - Chapter 7 "Novel Pressure Hull Design"
> > > (page 280).
> > >
> > >   Ian.
> > >
> > >
> > > On Tue, 16 Dec 2003 09:15:36 -0800 (PST)
> > > Warren Greenway <opensourcesub@yahoo.com> wrote:
> > >
> > > > The junction between the caps and hull "tube" will be
> > > > under tremendous stress. There will be shearing forces
> > > > on the wleds. Also, you are creating less useable
> > > > interior space for a given displacement. I think those
> > > > would be some of the basic reasons. Reference Concepts
> > > > of Submarine Design for more specifics.
> > > >
> > > > Warren.
> > > >
> > > > --- Emile <2stroke@hetnet.nl> wrote:
> > > > > Hello all,
> > > > >
> > > > > For my future psub I consider an inverted endcap or
> > > > > bulkhead
> > > > > See the "drawing"of the pressure part.
> > > > > ______
> > > > > )_____(
> > > > >
> > > > > At this configuration the sphere shelfs only have a
> > > > > tension loading what is preferrable.
> > > > > I lookt at almost every psub design on the site but
> > > > > no other sub has this configuration, exept for the
> > > > > Spurdog.
> > > > > Am I wrong in my toughts and are there high stresses
> > > > > in the sharp transition from the sphere shelf to the
> > > > > circular hull??
> > > > >
> > > > > hope someboy knows,
> > > > >
> > > > > Emile D.L. van Essen
> > > > > www.AiResearch.nl
> > > >
> > > >
> > > > __________________________________
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