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

[Ray Keefer <Ray.Keefer@Sun.COM>]

Hi EM,

Yes, this has been discussed before. 

Yes, you can use a multi hull with a bunch of partial pressure zones
and it would work.

The drawbacks make the idea not worth it. They are:

1. Added complexity in construction and welding. All the joints have to
   be accessible to weld properly.

2. The partial zones all have to be big enough with access hatches
   to allow for welding, inspection and cleaning. Adding cost.
   
3. The material costs adds up to more then what you would of needed
   with a single pressure hull. Three 1/4" plates are more expensive
   the a single 3/4" plate.
   
4. The pressure difference between the interior of the sub and outside
   is still the same. 
   
5. Multiple pressure zones adds to the displacement for the size of
   interior space. So you get a heavier sub with less room inside.
   
6. More weld seams create require more inspection. More joints for
   possible failures.
   
Regards,
Ray
   

> From: emm03@mirapoint.uow.edu.au
> Date: Wed, 29 Jan 2003 08:55:42 +1000
> Subject: Re: [PSUBS-MAILIST] Re: Welcome, apologies and multi-hulls.
> To: personal_submersibles@psubs.org
> Content-Transfer-Encoding: 7bit
> 
> 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
>