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Old Dec 27, 2012, 06:59 PM
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epoxyearl's Avatar
United States, MD, Elkton
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Petg-petk

I can't help you with definitions of chemical make-up,but I can tell you about the workability of the petg.
My order consisted of 8 sheets of .030,12" x 18",clear material.It has a slightly rubbery feel,that I was looking for,and it's the least bit resistant to cutting with scissors,another good bit...I've just today cut a windshield for the 1/4 Scale Cub,and hopefully tomorrow I;ll install it.......I'm looking to avoid those 'spider web'cracks that developed with the unknown material I used last.

Heat forming those side windows will come later.
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Old Dec 28, 2012, 02:23 PM
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Fantastic plastic

Thanks to the guys who suggested the PETG plastic for me to use.
I installed the 1/4 scale cub windshield today,and after securing it in place,I used the heat gun and slowly brought the plastic up to temp.
I had never used this material before,and I had no idea what to expect..I kept waving the heat gun back and forth past the upper corner(s),and as it came to the proper temp,I could see the plastic relax into place.
The windshield had looked fine, before I heated it,but now the stresses are gone
Later ,I'll make the proper fixtures for molding the side windows...I've been warned about the heavy (.030) plastic maybe wanting to resist forming tight corners,but let's give it a shot! -I need those little flanges to glue the windows into place..
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Old Dec 28, 2012, 03:37 PM
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Australia, WA, Kalgoorlie
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Great stuff Earl! Now where are the pictures then?
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Old Dec 28, 2012, 04:00 PM
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Sorry,Wiz---The airplane is undergoing restoration.I'm doing before and after shots .I'll have a compilation soon.Be patient,please....
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Old Dec 30, 2012, 07:39 AM
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United States, KY, Taylorsville
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Interesting stuff! I've always used Vivak for thermomolding. Stress risers occur most frequently with polycarbonate especially if it gets too hot or if cold bend radius too tight. Don't ask me 'how hot' or 'how tight a radius'- I can't answer specifics- I'm too stupid!
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Old Dec 30, 2012, 08:09 AM
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Stoopid ain't it!.I heated the material I made the last one with...(unknown material),and it crazed any way...The PETG was installed,then heated to relieve stress,and a second one ,unheated.
Both are doing just fine,even at .030 ,which is kinda thick.
We just need to listen to the guys who know what they're talking about.

I'm going to be heat forming some PETG soon....I'll have a report.
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Old Dec 30, 2012, 08:27 AM
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East Texas
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A build last winter got a windscreen of the fashion on thirties era open cockpits with a three sided affair. It had two hard bends of about 75 done cold on a brake using .030 PETG and no crazing occurred.

http://pages.suddenlink.net/arlyn/detailing.html
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Old Dec 30, 2012, 11:52 AM
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Good to know....I need those same windscreens on a Great Planes Stearman...
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Old Dec 30, 2012, 12:16 PM
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Earl... I trimmed the windscreen frames using aluminum tape. It requires patience as the adhesive is very sticky and if at any point something goes wrong, the step must be aborted for another go with probably a new piece of tape. Because of that, I masked off the area outside the frame, applied the tape overlapping the masking and then using xacto, slit the aluminum tape where it lapped the masking tape, and finished by removing the masking tape and the overlapped aluminum. The result was good and has been durable with no hint of the aluminum tape peeling.
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Old Dec 30, 2012, 01:29 PM
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