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#1
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On Mon, 30 Jun 2003 22:53:08 +0100, "Jan Møller"
(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 |
#2
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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 http://members.aol.com/SailDesign/pr...cbweb/home.htm |
#3
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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" wrote: It strikes me that it would be difficult to maintain optical clarity while forming a dome in this manner -- any thoughts? |
#4
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"Jan Møller" (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 Brooke) http://www.jasmine.org.uk/~simon/ to err is human, to lisp divine ;; attributed to Kim Philby, oddly enough. |
#5
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"Jan Møller" (fjern xx) wrote in message . 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 |
#6
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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" (fjern xx) wrote in message k... 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 |
#7
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look into building a vacuum form out of wood...
"Brian Whatcott" wrote in message ... 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" wrote: It strikes me that it would be difficult to maintain optical clarity while forming a dome in this manner -- any thoughts? |
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