Re: [PSUBS-MAILIST] dual hull??

[emm03@mirapoint.uow.edu.au]

Hmm, I hate to flog a dead horse here...
but this is almost exactly what jeff was proposing in his 
idea of compartmentalising. 
I for one gave some minor harrassment at his ideas, but 
nothing too nasty I think. I apologise to the list for 
possibly being party to the hostile atmosphere that led to 
jeffs self-rejection, somone slap me in the face if I ever do 
it again.
EM


---- Original message ----
>Date: Wed, 29 Jan 2003 17:23:35 -0800
>From: Ian Roxborough <irox@ix.netcom.com>  
>Subject: Re: [PSUBS-MAILIST] dual hull??  
>To: personal_submersibles@psubs.org
>
>
>Hi,
>
>I think Ray gave a good answer to the multi layer pressure 
hull.
>But, uou could always make the spacing bigger and fill it 
with
>concrete...
>
>Something similar that could work: coil high pressure
>piping all the way along the inside of the hull cylinder, 
with
>the pipe coils kind of acting like framing for the cylinder 
but
>bunched up very close (touching even).  Now if you pressuring
>the high pressure piping it will provide support for the 
hull.
>You could even exposed the inside of the piping to external
>pressure.  The idea being that the pressurized piping keeps
>the hull under internal tension (kind of like the hull had 
been
>pressurized).  Carl T.F. Ross's book "Pressure Vessels: 
External
>Pressure Technology" as a couple of paragraphs discussing 
this
>idea/method.
>
>Ian.
>
>On Wed, 29 Jan 2003 17:59:11 -0700
>jbarlow@bjservices.ca wrote:
>
>> I sent to the wrong address before, but I'm still curious.
>> 
>> 
>> ----- Forwarded by James Barlow/BJSCAN/BJSERVICES on 
29/01/2003 05:54 PM
>> -----
>>                                                            
                                                              
              
>>                       James 
Barlow                                                        
                                             
>>                                                To:       
owner-
personal_submersibles@psubs.org                               
          
>>                       29/01/2003 10:31         
cc:                                                           
                          
>>                       AM                       Subject:  
Dual Hull 
Concept                                                       
      
>>                                                            
                                                              
              
>>                                                            
                                                              
              
>> 
>> 
>> 
>> I'm just thinking out loud here..
>> 
>> If you have a 36" [914.40 mm]OD x 0.500" [12.70 mm] WT 
outer hull and put
>> inside a 34" [863.60 mm] OD x 0.500" [12.70 mm] WT inner 
hull. ( leaving an
>> annulus of 0.500" per side) and fill that area with 
hydraulic oil that you
>> pump up to some high pressure.  The pressure is equal 
everywhere but the
>> area on the outer hull is greater, resulting in a net 
force outward.
>> 
>> 36 - 0.5 -0.5 = 35.000" ID  [889.00 mm]
>> 
>> 34 OD of inner hull = [863.60 mm]
>> 
>> If the was 100 psi oil pressure in the annulus area then 
the force out
>> would be:
>> 100 psi x 355/113 (pi) x 35.000" x length = 3500 pi x L 
pounds
>> [7.030696 kg/cm2 x 355/113 x 88.900 cm = 625.029 pi X L ]
>> 
>>  force on inside would be:
>> 100 psi x 355/113 (pi) x 34.000" x L = 3400 pi x L  pounds
>> [7.030696 kg/cm2 x 355/113 x 86.360 cm = 607.171 pi X L]
>> 
>> a direct ratio of diameters. (id outer / OD inner)
>> 
>> 
>> If you are 100 psi deep (6.80 atm (217 feet [66 m])
>> then the outer hull would see 2.8 psi differential.  
(ratio of 36" / 35")
>> (OD/ID of outer hull)
>> 
>> 
>> 
>> Negating yield of outer hull due to increasing inner 
(which you can't do
>> but maybe you would want to fill with a compressible gas 
like nitrogen
>> instead of oil) the inner hull sees the same 100 psi, but 
the outer sees
>> outside pressure less roughly 100 psi.
>> 
>> Did I miss something??
>> 
>> 
>> Of course you essentially have a 33" [838.20 mm] ID Hull 
now...  and one
>> that weighs essentially the same as a 33" ID [838.20 mm] x 
1" WT [12.70 mm]
>> hull.
>> 
>> 
>> The pressure rating of such a hull would be great anyway.  
However perhaps
>> as the inner hull only sees 100 psi and is protected from 
mechanical
>> damage, it could be made from fibreglass or some such 
material to save
>> weight.
>> 
>> 
>> 
>> All the numbers above are only just numbers I threw in for 
illustration.
>> It wouldn't have to be a 1/2" wall thickness hull.
>> 
>> 
>> 
>> Not to start any wars, I'm not advocating the use of dual 
hulls.  Just
>> curious...
>> Comments?
>> 
>> Jay.
>> 
>> 
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