Re: [PSUBS-MAILIST] acrylic viewport thickness

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

Hey, Guys - the thread on the viewports is great.

Not asking for hard and fast numbers here, but, any opinions on how deep a
properly mounted [six foot diameter, three feet to apex, one inch thick at
base] hemisphere could go?  I'd like to be "pleasantly surprised" [not
killed, however]  "Developing a predictable curve."  Um, Roger on that.
Phil, can you elucidate?

Quote: [snip]

    "If you actually work the numbers for a series of ring
    areas by their increasing thickness as they approach the 1" base, you
will
    be pleasantly surprised at how deep a thin apex/thick based blowing will
    go! You can easily develop a predictable curve for such domes - just as
you
    can work out with a fair degree of accuracy what thickness the apex will
be
    for a given start thickness, diameter, and percentage of 180 degrees.
Just
    another trick of the trade!"


----- Original Message -----
From: "Phil Nuytten" <pnuytten@compuserve.com>
To: <personal_submersibles@psubs.org>
Sent: Monday, February 21, 2005 10:27 PM
Subject: RE: [PSUBS-MAILIST] acrylic viewport thickness


> Hi, Alec:
>         You made the point to Rick L (. . . .Hi,Rick! . .) that it is the
> minimum thickness in a blown dome that counts. That isn't perzacly true.
As
> always, it's a matter of area versus thickness. If you take a 1" thick
> sheet of acrylic - Plexi G - or whatever and blow it through a 24 inch
> opening, it will wind up quite thin at the apex. No suprise, there. Lets
> say, for sake of argument that it comes out at a little less than 1/2" at
> the apex on a full 12" deep hemisphereical dome. You would then run the
> stress analysis for a 24" X say, 7/16ths dome - as you suggest. But - and
> it is a big 'but' - only the very apex is that thin. It's footprint may be
> less than a foot in diameter - much less area than the full dome - and
> supported by thicker material - which is, itself, a small area supported
by
> thicker materail. If you actually work the numbers for a series of ring
> areas by their increasing thickness as they approach the 1" base, you will
> be pleasantly surprised at how deep a thin apex/thick based blowing will
> go! You can easily develop a predictable curve for such domes - just as
you
> can work out with a fair degree of accuracy what thickness the apex will
be
> for a given start thickness, diameter, and percentage of 180 degrees. Just
> another trick of the trade!
> Regards
> Phil Nuytten
>
>
>
>
>
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