Re: Acrylic viewing dome

[Daniel Stuelke <dstuelke@magick.net>]

Ken, 

 Some more notes on polycarb vs acrylic.

 polycarbonate is much more impact resistant than acrylic because it is
a softer plastic which in a pressure hull could cause problems with
seals if it changes shape too much, but as I understand you are building
a wet sub so this would be of no concern to you.

 Polycarbonate is avaliable in a machine grade which is stronger but has
a rather blueish tint to it, it is also available in an optical grade
which in the thickness you are looking for is fairly transparent but not
as clear as acrylic.   
 You can also get it with a scratch resistant coating on one or both
sides but this would only be usefull in flat panels as it can't be
themoformed without destroying the coating.

 Themoforming polycarb itself is rather tricky because of moisture
inside the plastic which tends to bubble up when heated, it must be
heated very slowly and monitered very closely to do it right. It can be
done but it will be harder to find a shop capable of doing it and it
will probably cost more.

 You can get deeper scratches out of polycarbonate but you can't get it
"mirror smooth" like acrylic.
 If you need another source for your veiwport let me know I have some
plastics industry trademags somewhere in my shop I'm sue I can dig up a
supplier for you.

 Stan,

  yes I am designing a 1 atm sub, with thick acrylic, internal bracing,
and complex curves, (eggshell) instead of a cylinder I should be able to
make a very strong hull. It will be very small, kind of like a sailplane
cockpit.

 I live in Grants Pass Oregon.

 Daniel.