Source for lexan or similar tranparent material - for tran..

Jan Møller says:

 >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.

Jan,
Good to hear from you. I'll look around and see what I can find.

Steve
Stephen C. Baker - Yacht Designer
<a style='text-decoration: underline;' href="http://members.aol.com/SailDesign/private/scbweb/home.htm" target="_blank">http://members.aol.com/SailDesign/private/scbweb/home.htm</a><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

It strikes me that it would be difficult to maintain optical clarity while
forming a dome in this manner -- any thoughts?

--
Karin Conover-Lewis
klc dot lewis at gte dot net


"Brian Whatcott" <betwys1.RemoveThis@sbcglobal.net> wrote in message
news:3gk1gv0fkpuacbiknhs8n4f8u2vmsnut13@4ax.com...
 > On Mon, 30 Jun 2003 22:53:08 +0100, "Jan Møller"
 > <jan_moller_xx.RemoveThis@hotmail.com(fjern xx)> 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
  > >
 >
 > There is a vigorous cottage industry engaged in forming cockpit
 > transparencies for light aircraft. Homebuilders will often make a ply
 > crate with an internal electric heater to allow a flat to be heated to
 > its spaghetti temperature, whereon they place it gently over a felt
 > covered (even greased) form, and gently press it down in contact.
 > This is not everybody's cup of tea. There is at least one shop that
 > does nothing but transparencies of this kind, and does them
 > perfectly. I have not kept contact details, but I could suggest you
 > readdress the question to rec.aviation.homebuilt where doubtless
 > someone would have the address on file.
 >
 > Brian Whatcott Altus OK
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

 >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.

Don't know about forming, but the last clear lexan I bought I got from a sign
company. You may have to make the bubble yourself.
Greg Sefton<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

Though I am not speaking from personal experience, I know that people
have often taken two even three shots at forming their windshields
free of ripples and other defects. Still, a surprising proportion do
make an optically satisfactory transparency.

Brian

On Tue, 01 Jul 2003 00:43:08 GMT, "Karin Conover-Lewis"
<spamless.RemoveThis@nopam.com> wrote:

 >It strikes me that it would be difficult to maintain optical clarity while
 >forming a dome in this manner -- any thoughts?<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

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: <a style='text-decoration: underline;' href="http://www.aliendecor.com/acrylic_domes.htm." target="_blank">http://www.aliendecor.com/acrylic_domes.htm.</a> 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: <a style='text-decoration: underline;' href="http://www.rutuonline.com" target="_blank">http://www.rutuonline.com</a>
Shameless Commercial Division: <a style='text-decoration: underline;' href="http://www.spade-anchor-us.com" target="_blank">http://www.spade-anchor-us.com</a><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

"Jan Møller" <jan_moller_xx DeleteThis @hotmail.com(fjern xx)> writes:

 > 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

If you get a solution, could you post it back here? Especially if you
find a shop that can custom-make these things.

Thanks.

--
simon DeleteThis @jasmine.org.uk (Simon Brooke) <a style='text-decoration: underline;' href="http://www.jasmine.org.uk/~simon/" target="_blank">http://www.jasmine.org.uk/~simon/</a>

  to err is human, to lisp divine
    ;; attributed to Kim Philby, oddly enough.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

"Jan Møller" <jan_moller_xx RemoveThis @hotmail.com(fjern xx)> wrote in message news:<3f00b140$0$32441$edfadb0f@dread16.news.tele.dk>...
 > 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

I used to work in a plastics forming shop where we did such things.
Polycarbonate (Lexan) has a high deformation temperature and low
scratch resistance. PMMA (commonly called acrylic, Lucite, etc) has
higher optical clarity, scratch resistance, and lower deform temp, so
is preferred for forming. The high impact resistance of polycarbonate
MAY be essential for some applications. In any case, you'll want to
spec a UV resistant grade of material.

For either material, vacuum forming without a mold is the way to go.
The material is held in a rigid frame and heated to a temperature
where it is fairly soft. Then the air on the lower side is evacuated
in a controlled manner until the dome reaches the desired height
(depth?). We used a photoelectric switch to shut off the vacuum valve
when the dome broke its beam. It doesn't require a high quality
vacuum, but you will need to evacuate a volume, so some sort of
reservoir tank is usually needed. The frame material should ideally
be a poor heat conductor and have a polished and radiused edge.

With a little searching, I think that you can probably find a
ready-made source for plastic domes, but it can be fun to try to make
your own.

Paul Mathews<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

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
 >> Stay informed about: Source for lexan or similar tranparent material - for tran.. 

hi
what you need is Macrolon which is avaliable from builders merchants, it
comes in large sheets and many different thicknesses. it is a sandwich of
Lexan ( polycarbonate ) and another plastic. It will not yellow or crack and
is said to be bullet proof. You can also cold fold it with a metal bender
without cracking so has many uses.

richard



"Jan Møller" <jan_moller_xx RemoveThis @hotmail.com(fjern xx)> wrote in message
news:3f00b140$0$32441$edfadb0f@dread16.news.tele.dk...
 > 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
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Source for lexan or similar tranparent material - for tran..