Re: [PSUBS-MAILIST] ACRYLIC DOME SIZE

[Jon Wallace <jon@psubs.org>]

Alan,

I can't address the diameter issue.  I suppose whatever is personally 
comfortable for you, is appropriate.

The underpressure software likely does not take into account remnants of 
free-form blowing such as variable thickness and shape of the "sphere".  
Additionally, if you are planning on using the equatorial flange that is 
a typical remnant of free-form blowing, the dimensions of the flange, 
heel radius, and instep radius must meet specific requirements.  The 
software does not take these factors into account.

It's impossible to attribute any kind of consistency in performance with 
free-form blown acrylic spheres because fabrication results in so many 
variables.  Be sure to perform multiple tests of the dome to whatever 
maximum depth you are looking to achieve (preferably with a safety 
factor), prior to any "manned" dive.

Jon

ALAN JAMES wrote:
> Hi, I'm trying to get an acrylic dome blown locally and need to draw 
> from psubers experience
> as to what the minimum diameter is that I could use and live with 
> comfortably.
> I'm in a sitting position with my head inside the dome. 
> I have a 500 mm thin dome I am using on  a full scale mock up, but the 
> firm I bought it off
> is doubtful that they can blow a 20 mm thick sheet to 500 mm. Another 
> firm is confident
> it can do a 450 mm O/D at 20 mm thick (18 mm at the apex.) This would 
> give me a 410 mm I/D.
> Is this too small? I know condensation could be a problem the closer 
> my face gets to the acrylic.
> I'm doing the pressure calculations on the "Under Pressure 4.5" free 
> program, what a God send
> that is for a psub designer. Heres the link if anyone out theres 
> designing a sub and doesn't
> know about it.
> http://www.deepsea.com/upwindownload/
> Interested to here what your opinion is on dome size
> regards Alan.
>  
>  
>  




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