Re: [PSUBS-MAILIST] Re: Welcome, apologies and multi-hulls.

["Adam Lawrence" <adteleka@in-tch.com>]

The sum of the forces has to equal zero. The sum of the forces or the
strength of the hull has to be equal to or greater then the sum of the
external forces exerted by the water on the hull. So hull strength is a
function of material properties in conjunction with the geometery. As the
diameter of the hull increases, reinforcement has to increase (ie. plate
thickness). If engineering calls for 1/2 plate at a 36 in. diameter, but you
want to use thinner material and propose a double hulled design, that's a
plausible idea, but you are still dealing with, let's say 300 psi.
In order for the sub to remain static, the forces will be transfered through
each layer until they go to zero. The amount of material used in the hull
might be decreased (steel is cheap though), but fabrication will be a lot
more complicated and costly while the pressure has stayed the same. A single
walled cylindrical hull with reinforcing rings is the most economical
design, besides one that is spherical.
A "honeycomb" structure is very strong and is similar to a double hull
structure. While this design might someday be the next best thing, the
barrier comes when trying to come up with a fabrication method that is
economical. Kind of like the idea that you can make gold out of lead. You
can make gold but after you're done, you've spent more on the process and
it's radioactive. Again it's economics.

I'm interested in the ideas of using other materials, but the conversation
should be based on developing ecconomical fabrication methods.
Adam
----- Original Message -----
From: <emm03@mirapoint.uow.edu.au>
To: <personal_submersibles@psubs.org>
Sent: Tuesday, January 28, 2003 3:55 PM
Subject: Re: [PSUBS-MAILIST] Re: Welcome, apologies and multi-hulls.


> Hi People.
> In an attempt to make up for my embarrasing, unhelpful, and
> narrowminded comments I made earlier. I would propose some
> more discussion on this idea of 'compartmentalising'.
> (please excuse any spelling mistakes, I dont possess the
> apparent intellectual capacity of some giants on this list)
>
> Is there any merit in using a multi-layer hull?
>
> For a single layer hull for an ambient machine, the pressure
> differential is at a maximum. If we were to use TWO layers
> (or more) in the pressure hull, and partially pressurise the
> layers in between, then is it not possible to sustain a
> greater TOTAL pressure differential?
>
> I am now going to attempt to draw an ascii illustration..ahem.
>
> The traditional method:
>
>        |
> Inside | Outside
>    @   |    @
>   1atm |  4 atm
>        |
>
>
> pressure differential = 3 atm.
> Depth ~30m
>
>
> A multilayer hull:
>
>         |           |
> inside  | Intermed. | Outside
>   @     |   @       |  @
>  1 atm  |  4 atm    |  7 atm
>         |           |
>
> Pressure differential per layer is still at 3 atm.
> Outside depth ~ 70m
>
>  If I have this right..I think I have it vaguely correct,
> compartmentalising might be a really good way to get to
> greater depths. I know this sort of thing has been discussed
> before, but I am too lazy to look up the archives..
> My apologies for any spelling mistakes Herve, I hope you can
> overlook them just this once.
> If I have overlooked any fundamental physics of hydrodynamics
> and hydrostatics, please be nice!
>
> Thanks!
> EM.
>
>
>
>
>
> ---- Original message ----
> >Date: Tue, 28 Jan 2003 16:21:43 EST
> >From: BauWauHausDesign@aol.com
> >Subject: Re: [PSUBS-MAILIST] Re: Welcome to the
> Personal_Submersibles_Disc ussion
> >To: personal_submersibles@psubs.org
> >
> >   In a message dated 1/27/03 5:56:13 PM Pacific
> >   Standard Time, dub@linuxmail.org writes:
> >
> >     Even if it increased to ambient, or even half of
> >     ambient, you would not
> >     be able to withstand the bodily strain at the
> >     depths in question.
> >
> >     Warren.
> >
> >   provided that the pressure is ambiant. what if you
> >   were able to stratify pressure zones without a
> >   structural membrane (ie cockpit, pressure suit...)?
> >   to say it is not possible is to deny many example in
> >   nature that rely on non-compartmentalized stratified
> >   pressure zones to exist.
> >
> >   jeffrey