Viewport Seats for Concrete pressure hulls

[DaveIrons@aol.com]

My goal is to build an undersea habitat/submersible that is large
enough to be comfortable.  Safety is another reason for building a
large structure.  A large structure would allow: water tight
compartments, a diver lock out and extended reserve air.  

Most of the engineering problems for building large concrete
habitats have been resolved.  Stachiw has even recommended that
concrete may be a good material for a submarine oil tanker.  

The viewports are easily the most expensive components.
The viewport seats in "Seacon" and "Concrete Pressure Hulls" are
massive steel structures.  The design rational for overbuilding the
viewport seat was to make the viewport stiffer than the than the
concrete hull so that the hull was "unaware of the large hole."

Stachiw used 316 stainless in his scale model design for a habitat. 
The cost of the viewport seat alone would be $10,000.00, for a
large viewport, about a meter in diameter .   In addition steel, even
stainless steel, has the potential to corrode.  The viewport seats
must be polished to allow the acrylic viewports to slide in and out
with pressure changes.  Even tiny flaws would damage the
viewports.  Plastic may be a better material than steel for viewport
seats. 

Concrete has sufficient rigidity to provide a viewport seat.  If more
strength is needed, concrete can be mixed with acrylic polymers. 
Polymer/concrete mixture will effectively double the compressive
strength of concrete. (about 20,000 psi)  The baring surface for the
viewport seat could be a thin acrylic film molded to the dimensions
of the viewport seat.  Acrylic seems like the logical choice. 
Acrylic could be used as the polymer/concrete mixture.  Therefore,
the bond between the hull and the baring seat would be easily
formed.  

I have considered other methods of constructing a viewport seat
including:  Installing a thin stainless steel viewport seat cast into
the concrete hull.  Epoxy or other high strength polymers such as
glass reinforced plastic may be a good alternative to steel viewport
seats.  

Has anyone seen any of these materials used as viewport seats?

What problems should I anticipate using these materials?

Perhaps a scale model can be built and tested?

My goal is to create a cost effective and safe design for
submersibles or habitats.  Most of the same design principles apply
to both submarines and habitats.  

The ideal method of undersea exploration may well be a self
sufficient mobile habitat.  At some point the distinction between a
habitat and a submersible may becomes blurred.  A habitat with
thrusters and a ballast system would be a submarine.  

I am interested in any thoughts other members may have.  

I am especially interested in innovative methods of manufacturing
cost effective submersibles.  

David Irons