Frank Boettcher wrote:

Can you comment on its ability to resist
differential expansion cracking and crazing? For instance, if you use
it in an application where a portion of it (border for instance) sees
less temperature change than the balance, does it tend to crack at the
boundry between the two temperatures from cyclic differential
expansion.

I'm pretty sure it would be fine. It is just Acrylic with the surface
layers treated to harden them. The 3/8 Acrylic in my boat lasted 26 years.
It developed a consistent pattern of small carzing cracks that were a visual
obstruction only but nothing structural. I'm going to go with the Polycast
SAR and increase the thickness to 1/2 inch. The 3/8 x 21" x 21" panels
bowed when anyone stepped on them (I can often yell quickly enough) which
may have also been a factor in the crazing. the 33% increase in thickness
should nearly double the strength and stiffness.

The hatch frame spigott is exactly 1/2 inch so the thicker glazing will
stick up above the frame by the amount of the bedding. I'm going to put a
slight bevel on the edge and use minimum bedding on the flange with careful
filling in around the edge. I may make the new lens slightly smaller to
make it easier to get a good, bubble free, application of compound between
the edge of the plastic and the aluminum. An applicator spout small enough
to reach the bottom of the slot so the compound is working in from the
bottom up is essential to a solid seal.

--
Roger Long