Re: [PSUBS-MAILIST] acrylic viewport thickness

["Rick and Marcia" <empiricus@telus.net>]

I meant how many dips before it's established that the hull is safe for use
at operating depth?  I realize that operating depth is a function of test
and crush depths, but I forget how many cycles a hull has to go through
before being deemed safe . . .

Rick


----- Original Message -----
> Speaking of perfection, how many dips to test depth is the norm for a
> pressure hull?
>
> It's been a long time since I've read Busby.
>
> Rick
> Vancouver
>
>
>
> ----- Original Message -----
> From: "Phil Nuytten" <pnuytten@compuserve.com>
> To: <personal_submersibles@psubs.org>
> Sent: Tuesday, February 22, 2005 6:37 PM
> Subject: Re: [PSUBS-MAILIST] acrylic viewport thickness
>
>
> > Hullo, Emile:
> >        Forming temp for acrylic ( 'plexi G', 'perspex', etc.,) is
290-320F
> > (142-160C0. A one inch thick hardboard frame works well for dome -
> blowing.
> > Two sheets of hardboard, with one cut- out to  desired diameter and
other
> > with airline, gauge, control valve, vent valve, etc.. Number of
> > quick-acting clamps - or bolts and wingnuts. Heat hard board frame to
> about
> > 180-200F to  minimize stress and distortion from diff. temp. Heat
acrylic
> > sheet ( separately)by ni-chrome wire elements, quartz lamps, or any even
> > heating that will go to about 350F - (need to overheat because of temp
> loss
> > transferring sheet to frame. Use a plastics pyrometer on sheet surface.
> >         Open air valve - make sure you run thru filter if from
> compressor -
> > not required if from clean,dry, scuba air. ( much more common now, than
> > 'bad ol' days'!)Pressure fairly quickly until stretching starts - then
can
> > slow,  but don't stop until depth is achieved (have line suspended from
> two
> > posts at desired height/depth). If you blow to quickly you will induce
> > excessive stresses in material. If too slow, it may not form evenly if
one
> > area is even a few degrees colder than another Best slightly too hot
than
> > too cold.
> >         Perfection is achieved in the same fashion that musicians get to
> > Carnegie Hall: (Practise, practise, practise!)
> > Phil Nuytten
> >
> >
> >
> >
> >
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