Re: Acrylic viewing dome

["Marsee Skidmore" <heyred@email.msn.com>]

Ken is correct that Polycarbonate is tougher (higher tensile strength and
impact resistance) than Acrylic. However, it's darn near impossible to
polish once it gets scratched. This may be the optical property that Dave
mentions. Acrylic viewports in deep diving submersibles get polished and
annealed on a regular schedule to combat hazing. Another pesky feature of
Polycarbonate is its relatively poor chemical resistance, or propensity for
stress cracking, which can have very unpleasant consequences in a pressure
vessel. :-o Joe
-----Original Message-----
From: Dave Everett <deverett@idx.com.au>
To: Personal_Submersibles@psubs.org <Personal_Submersibles@psubs.org>
Date: Wednesday, March 11, 1998 5:58 PM
Subject: Re: Acrylic viewing dome


>At 07:13 PM 11-03-98 EST, you wrote:
>>Hello Dave,
>>
>>What you are doing sounds interesting. From what I have seen on the Psubs
>>website, assuming you are building a dry sub, the port may not have enough
>>strength. Gary Boucher may be able to point you in the direction to the
>>strength needed for a Pressure port.
>>
>>My interest is in primarily the port itself. I am building a wet sub and
need
>>a viewing port in the worst way. The port you described in your E-Mail
would
>>fit my sub almost perfectly. Do you have a source for these ports and can
>they
>>be made from polycarbonate instead of acrylic? I believe the polycarbonate
is
>>stronger, certainly it's impact strength. The few vendors I have contacted
>>want thousands and up for a port. That's more than I wish to spend.
>>
>>I would appreciate hearing from you. I would really like to purchase a
port.
>>
>>Thank you,
>>
>>Ken Martindale
>
>Hello Ken,
>
>I now have my dome. It was made in 3 days and cost me $200. I could have
>had it made in 20mm for about $400.
>
>Unfortunately for you I live in Australia, so my sources would not be
>suitable for you. I simply looked in the local yellow pages and called the
>first plastics manufacturer I saw <g>. Most manufacturers can make domes,
>the one I called could make them up to 1.5m in diameter.
>
>As you say, the dome might be too thin, that's the main reason I want to
>run these experiments. I understand that polycarbonate doesn't have the
>same optical qualities as acrylic.
>
>As a guide on thickness, the explorer 1000 uses a 1.65 metre (internal
>diameter) dome of 70mm thickness and is rated for 1000m.
>
>Dave Everett.
>
>