Re: [PSUBS-MAILIST] acrylic viewports

[William Alford <walford@dbtech.net>]

At 11:23 AM 2/20/2005 -0800, Dave Banks wrote: 
>
> I remember taking a straight edge and setting it against the view port at
> depth.  At depth it does start to flex inward just a little, and you can
> measure it.


I have contemplated the placing of a piece of steel reinforcement-- a bar on
edge (perhaps 1/2" x 1 1/2") welded securely into the window housing so that it
would just contact flush to the interior surface of the acrylic and cross the
center diameter of the viewport. This would not obstruct viewing much with so
small a footprint on a reasonably sized window and do much to prevent flexing
of the acrylic by the physical reinforcement, perhaps enabling the use of a
larger viewport for the same thickness of acrylic? Properly machined and
annealed, of course. Clever engineering and fabrication might allow it to be
bolted in, giving the option for removal except for deeper dives. Prevention of
any flexing might also extend the lifetime of the acrylic by preventing stress
deterioration?

BTW don't forget the importance of annealing acrylic following any machining
whatsoever.

William Alford



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