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Lexan Windshield PDF Print E-mail
Written by Peter   
Wednesday, 23 January 2008

When life hands you lemons...   

As cool as Hood Pins are, don't forget to latch them! I forgot, and my hood flew up and shattered the windshield!

As with anything on this project though, it's just an opportunity to improve.




Pictures of the destruction and resulting removal of the windsheild. It was amazing the quantity of very small sharp shards of glass that were left behind. It took about 40 minutes with the shop vac before the car was mostly free of glass.

To remove the glass, I used some windshield wire that I purchased from a local body shop supply store. I also used a chissle, and after a lot of frustration I decided that it was already shattered, so I used a jigsaw to make access easier. Eventually, the windsheild was gone!


Next, I had to figure out how to attach a new windsheild. Here are some R&D pics of other Lexan installations that I took while at a track event


I decided to go with 3/16" thick Lexan. The NASA GTS rules did not specify a thickness, but the American Iron rules specified 3/16" with 1 center support, so I used those requirements as my guidelines.

A big problem that many have with using Lexan is that is scratches very easily. Many racers I spoke with said that I would most likely change it once every 1-2 years. While it is possible to buff it out, the thought of having yet another maintance item on the car was not attractive.

As a solution, I am trying Speedglass from Percys High Performance. This product is still Lexan (by GE) but it has a propritary coating on it that is advertised to be very scratch resistant. I tried some sand paper on a scrap piece and it was indeed pretty impressive (for Lexan).

Naturally there was not a preformed windsheild for the XR4Ti, so I got ahold of a 3'x5' piece of flat Lexan and made my own windsheild.

Here's a rough outline of what I did:

1. Welded in a center support
2. Made a cardboard template
3. Transferred the template to the Lexan
4. Cut the Lexan
5. Painted the stripe around the parameter
6. Installed new moulding
7. Predrilled all screw holes
8. Installed Windsheild Adhesive
9. Installed new windshield!

1. Welded in a center support

Big thanks to Chad for helping with this part of the project. For this, we used a piece of 3/4" angle iron. We cut one side of it in the middle, and then split the differences again so that we had 3 slits equally spaced. We then bent the angle iron very slightly, and once we had a good bend, I welded the slits back together. There was a lot of test fitting in this process, so take your time should you decide to do this. Once we had the curve right, we welded the support to the car, ground down the welds, and painted it.

The center support had two purposes - the first being to physically support the windsheild. Lexan is not as ridged as glass, so at 140mph it would bow in and most likely collapse into the car. The second purpose of the center support is to help us get the factory compound curve. This way, we can bow the Lexan both horizontally and vertically.

2. Make a cardboard template.

With the center support in place, Chad held a large piece of cardboard in place while I traced around the inside of the windshield frame. I then drew a line on the template about 3/4" out from my line so that the template would fit in the frame. A little fine tuning with a sharp utility knife and we had a good template.

3. Transferred the template to the Lexan.

Be sure to leave the protective film on the Lexan throughtout the entire process. I used a dry erase marker for the first round, and then once it was perfect I traced it with a sharpy.

4. Cut the Lexan

To cut the Lexan I used a high quality, brand new, and very sharp DeWalt course Jigsaw blade. Note, I said course, as in "fast cut - wood." Logic would first tell you to use a metal blade - however this would cause too much heat buildup. Lexan is not like Polycarbonate, it doesn't brake, it bends. This sharp blade was awesome, and it did a wonderful job of cutting the material. If I would have had access to a nice band saw I bet it would have worked better, but I'm fine with the end result.

5. Paint a stripe around the parameter

Once I test fit and fine tuned the fit of the lexan, I painted a black strip around the parameter, just like factory windsheilds on any car out there. My stripe is 3.5" at the top, and 1.75" on the sides and bottom. I masked it off first. Then becasue of the coating I had to sand the area to be painted. I used 300 grit and then 600 grit sand paper for this. Next, once cleaned, I used a plastic-specific spray paint from the hardware store. It took 7 coats to finally be imperable to direct sunlight.

6. Install new moulding

To add to the quality of the job I went to a local auto glass shop and bought some 1" moulding for the parameter of the Lexan. I highly reccomend this, it made a tremendous difference in the finish of the project.

From here forward, thanks to Dan for his help!
7. Predrilled all screw holes

To attach the windsheild, I first used some 8-32x3/4" Stainless allen head screws, washers, and ny-lock nuts. I started by securing the four corners. Then, I speaced the corners at 3" and put two more screws. Then, we split the difference on the rest of the sides. Once each hole was drilled, we removed the windsheild again and cleaned up the holes in both the lexan and the metal frame.

8. Lay adhesive

I should have used windshield ahesive for this, but instaed I used some black silicon caulking. ($3 vs $15). I put a thick bead around the center of the metal frame, a smaller bead around the outer edge of the frame, and then a dot in each screw hole.

9. Install windshield!

Lastly (and this is definately a two person job), we installed the windsheild for the final time. I was in the car starting the nuts while Dan was on the outside tightening everything down. The purpose of the ny-lock nuts was so that we did not have to tighten everythign down completely. This woudl have distorted the lexan. The Ny-locks allowed us to fine tune the tension all the way around the windshield so that it was smooth.

We removed the protective film and enjoyed our result!:



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