RE: [PSUBS-MAILIST] Big acrylic dome problem

[<jonw@psubs.org>]

Hi Darek,

Well, that's quite the issue you have.  First, as others have stated it
would probably make sense to redesign (if possible) using dimensions of
readily available dimensions (48inch or smaller).  As you have already found
out, specialty items are going to cost alot of money.

Second, you have an interesting idea regarding using acrylic cement to
create the desired thickness.  However, you still have the same problem with
the stock for the diameter dimension still being a specialty item.  Chemical
bonding is feasible, although having 20 layers of a small thickness may be
overdoing it a bit.  Chapter 16 of Stachiw's book "Handbook of Acrylics" is
devoted to joining acrylic components and I would suggest this be your next
investment before any further work on the sub itself.  The process is not as
simple as gluing two pieces together and you have to account for voids in
adhesive, etc, etc.  Get the book...you'll be glad you did.  Assuming you
laminated the sheets together enough to get the thickness you wanted,
machining is not going to be cheap either.  Not only will you have to find
someone with a lathe that is big enough, and a worker skilled enough to make
a hemi-spereiod shape that holds the thickness dimensions consistently
through the sphere; but you'll also need to do a lot of polishing afterwards
to bring the acrylic to visual clarity.  Stachiw talks about the
requirements for polishing in his book as well.

Regarding loss of strength with bonding, Stachiw claims that bonded joints
retain 50-90% strength of virgin acrylic depending upon the joint and
process used.

Jon





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