Thread: C5 gto
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Old 02-08-2018, 08:13 PM
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heinke heinke is offline
MetalShaper of the Month Jan 2018
 
Join Date: Nov 2009
Location: Prescott, AZ
Posts: 487
Post Making rear GTO window

Well the C5 GTO is finally off to the paint shop so I may not be able to provide another progress update for a while. I did want to give an update on one of the last things I did prior to sending the car off. I made a mold, had a rear window made and trimmed it to the opening.

The original GTO had a plastic rear window that I’m told was Lexan (polycarbonate). I decided to use ¼” Plexiglas on this car instead because it will last longer (at least double the life I’m told) and won’t scratch as easy as Lexan. Lexan is a lot more crack resistant than Plexiglas but I didn’t need that given this window will be held in with a rubber gasket around its perimeter and will have no holes in it. The window opening is 27” by 45” and is a compound curve. I don’t have the skills or an oven large enough to thermal form this window so I made the mold and had a plastics shop make the window for me.

Here’s how I went about making the mold. I started with the fiberglass piece I’d cut out from the body. To support that, I made a wooden frame.



With the fiberglass piece held to the frame with clamps, it was then flipped over and glued to the frame with some fiberglass matte and resin.



A 3” border was needed around the edge in order to keep the softened Plexiglas from drooping during the thermal forming process. I bent and curved some aluminum scraps to form the border. These were attached to the frame with drywall screws. I then sanded and polished the fiberglass mold to remove all imperfections that might transfer to the Plexiglas.



I took the mold to a plastics business, wrote a big check, and they made me a window. The window they returned to me was the perfect shape but oversized for the opening. It was covered with adhesive backed masking paper as to minimize scratching during trimming and installation.

I did the trimming in two stages. The first round of trimming was to get the Plexiglas to fit the opening with very little gap.



I then marked it for the final cut and trimmed it to get an even 5/16” gap all the way around the edge. I did a test fit with chunks of window gasket material to make sure it will fit.





I guess you can see why I wanted to get this window to final form prior to paint. I’d have been real nervous doing all this work over a brand new coat of paint.
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