My rear window on my 01 Boxster S was yellowed and finally cracked pretty badly. With summer thundershowers just around the corner I needed to solve the problem.
Things are still a bit tight around here financially so I decided to go the sew-it-yourself route.
After looking at many different suppliers I bought the Kal GLas .40 Mil plastic from Sailright in Indiana. It was only $39!!! with shipping it came to $48... perfect for the eternally cheap like me.
http://www.sailrite.com/Kal-Glas-40-Gauge-Vinyl-Window-Material-29-x-68
The window material is DOT approved and quite thick, it is good to unroll it and let it relax overnight before trying to work with it.
I decided to remove the top with the frame rather than attempt to do the work "in situ". This was a good idea and I highly recommend doing this rather than visiting the chiropractor.
http://www.renntech.org/forums/index.php/topic/18782-oh-man-someone-cut-the-plastic-on-my-top/
You will need black outdoor UV treated polyester thread, a pack of large needles as well as two thimbles, tweezers, a pack of razor blades, a glue gun and some straight pins, a big towel, some scissors and a few folding chairs and a work light. I got black silicon sealer for the waterproofing.
I used the razor to cut the old window out of the top. Pulled the threads out with the tweezers. Flipped the top upside down on the table with a towel under the window cut out to keep the new window from being scratched.
DO NOT CUT THE NEW MATERIAL TO THE SIZE OF THE OLD WINDOW, I did this and it made the job a lot harder than it had to be. Leave at least two inches of extra material all the way around the size of the old window.
You can pin or as I did hot glue a few points around the window to get it to stay in the proper position for sewing.
I did check with two local upholstery shops to see if they couls sew the window in fro me and the price would have been around $100 for the service but neither of them had a sewing machine with a long enough arm to clear the rear frame of the top and sew the top of the window.
After the window is pinned or glued in place flip the top over using three chairs and a forth for you to sit on at the rear of the window.
I started sewing along the bottom edge of the window, the material is very thick and you have to push hard on the needle to get it to go through. Make sure you get large thimbles because the ones I got were a bit too small and they started to really hurt after a while.
You will poke yourself and curse for the first ten minutes but then you should start to get the hang of it.
It took me about two and a half hours to go all the way around.
Trim the extra window material from the inside of the window after you have finished sewing.
Seal the threads on the inside with black silicon, this also keeps the threads from unraveling. Also I ran a very thin bead of black silicon around the edge where the top meets the window on the top side. This keeps water from running down the window and collecting at the seam and then running into the car through the threads. It also makes the seam neater to the eye in case your stitches are not perfect.
Replace the top and the window should be a bit tight because it will relax and stretch a bit once it is on the car for a while.
I am rather pleased with being able to see out of my rear view mirror for less than fifty bucks.
Given my "druthers" I would replace the top but this is a good stop gap method and if you didn't know that I had done the job you will not notice the minor imperfections in the sewing because of the black thread.
So...a new top is better but this works just fine if you are patient and don't mind pricking your fingers a few times.