Clear or smoke lexan (polycarbonate) and Plexiglass (acrylic) are
available from AIN, Farco and a lot of other plastics houses.

Polycarbonates are more flexable than acrylics but more shatter proof.
THey are also a LOT harder to thermoform. They absorb moisture and will
bubble when heated to froming temperatures so you have to bake them
carefully at about 200ºF for several hours before forming to drive out
the moisture.

Acrylics come in two basic grades, extruded and cell cast. They don't
absorb moisture so they don't have to be baked. For optical clarity
after forming you want cell cast. Slump forming still requires very
even heating to keep the optical clarity. IT is fairly easy to slump a
shallow dome but it is very hard to get a full hemisphere to come out
right. For a 21 cm diameter dome you need 1/4" thick material at a
minimum and preferably 3/8".

Personally I would look for a pre-made security or aquarium dome like
this: http://www.aliendecor.com/acrylic_domes.htm. By the time you
screw up a half sheet of 3/8" acrylic you could have paid for a real one.

Jan Møller wrote:
Looking for a source of Lexan or similar material that the supplier can form
into a dome to be used as a lookout on my Open 40' singlehander. Radius is
21 cm.
Have tried various places and Google but to no avail.
Thanks in advance for any help and hints
Regards
Jan




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

You might also check one of the homebuilt aircraft suppliers like Wicks or
Aircraft Spruce & Specialty to see if there's a pre-fabbed bubble you can adapt
to your needs.
Greg sefton