Re: Viewports gobbed on with silicon

[protek@shreve.net]

Paul,
    You do not have to go to that kind of extreme.  If you are using flat
plane windows, a neoprene rubber 1/8 inch gasket is usually all you need.
Get Stachiw's book I mentioned earlier in a post, or PVHO standards for
pressure vessels.  I personally do not like Lexan.  It has much higher
impact resistance than Acrylic but weaknesses in other areas.  The data is
out on acrylic.  The windows have already been designed by professional
engineers who have, (UN-like) myself, credentials in those areas.  Several,
but not necessarly all of the things you need to know would be:

  (1) Flatness of window and seat.
  (2) Roughness of machined cut on seat.
  (3) Inside seat diameter vs. outside window diameter.
  (4) Thickness and type of window and gasket.
  (5) Unsupported diameter vs. total seat diameter.
  (6) Minimum force to seat windows.
  (7) Heat treatment of acrylic.
  (8) Glue to use to hold gaskets in place.

    Except for the heat treating, most of these requirements are easy to
meet.  I made my own windows for The Vindicator and enjoyed the experience.
 That is except for the trip to my doctor friend to get the stitches in my
hand where the Xacto knive slipped while cutting an outer compression gasket.
    Do not even think of using some sort of pillow gasket or exotic
measures.  That is like saying "I need a new tire for my car so I am going
to build me one out of fiberglass."  Don't go there.  Use only methods that
have been approved by engineers that know what they are doing.  
    Civil and construction engineers when they want a storm sewer junction
don't usually sit down and engineer it.  They just go to their files and
get the proven design and use it.  No need to reengineer the wheel.  Get a
copy of PVHO or Stachiw's book and follow what they recommend.
    Hope this helps.

Gary Boucher


At 03:55 PM 8/12/99 PDT, you wrote:
>You guys have some really good points. Just a side note, or question. Has 
>anyone ever used or considered using inflatable seals. They use them for 
>large underwater gates, and they seem really reliable. I understand that 
>there would be some downside if you lost air pressure. A long time ago I 
>considered using one on a DPV, but considered it too extravagant. Any 
>opinions or comments???
>Suds
>
>
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