Closer Look: Clear One Polycarbonate Windows

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Glass is wonderful stuff. You can make windows, eyeglasses, carafes, coffee tables, and other stuff out of it. You can even use it to carry phone and internet signals across the globe. And of course, glass makes dandy windshields for our vehicles.

When it comes to race car windows, however, glass is not where it’s at. Glass is heavy; what’s worse, it adds weight to the upper part of the car, which is essentially unsprung weight that slows your car down. As we all learned in Power to Weight Ratio 101, it takes valuable horsepower to move heavy things—horsepower that isn’t contributing to reducing ETs or increasing top speed.

Just as important is the safety factor. Glass is a brittle material with relatively low impact resistance. That’s why automotive glass is laminated between layers of plastic—the design helps keep the glass from flying all over the place when it shatters. Even laminated glass has the potential to cause serious injury when debris turns the windshield into little glass projectiles.

Weight and safety are why many racers have replaced their cars’ glass with polycarbonate, better known as Lexan®.  A complete set of polycarbonate windows can weigh up to 70 pounds less than its glass counterparts. If you accept the conventional wisdom that every 100 pounds of weight reduction is worth a tenth of a second in ET, polycarbonate windows can make the difference between winning and losing.

Polycarbonate is also much more impact-resistant than laminated safety glass—up to 10 times more resistant depending on the grade of material used. Both the NHRA and IHRA require shatterproof windows at least 1/8 inch thick for full bodied vehicles, and endorse the use of polycarbonate as a suitable material. It’s a smart choice for cars running 9.90 seconds and quicker; a rock or small piece of debris that is harmless if it hits a slower car can be a dangerous bullet at that level of competition.

The Clear One Advantage
Summit Racing carries polycarbonate windows from Clear One. The Ohio-based company makes its windows from MR10-coated Lexan, which has 10 times the scratch and abrasion resistance of standard, uncoated polycarbonate. This material is so good, Clear One guarantees it for five years against fading, yellowing, and cracking. That’s darn near a lifetime in the race car world.

With over 300 patterns available, Clear One probably has windows to fit your race car. Most of its windows are made from 1/8 inch thick Lexan (per NHRA rules). They are cut oversize from factory specifications so you can trim the windows to fit snugly. The windows are available in the following configurations:
Stock Size: Flat stock that duplicates factory shape, up to 1 inch oversize
Blanks: Flat stock rough cut to factory shape, 2 inches oversize
Formed:  Windows are formed to exact factory glass specifications, up to 1 inch oversize
Universal: Formed to standard glass specifications, up to 1 inch oversize
Clear One also offers 1/8, 3/16, and 1/4 inch thick flat sheets that are ideal for custom applications.

Clear One windows can be installed using OEM-style window trim or with bolts and nuts. Here are some installation tips for both methods:

Replacing OEM Glass (Existing Trim Application)
1. Place the old glass window face-up on a flat surface. Place the Clear One window on top of the glass and clamp the two together. Don’t remove the protective masking from the Lexan.
2. Flip the windows over so the glass window is on top. Trace the outline of the glass onto the Lexan with a permanent marker. Unclamp the windows and trim the Lexan with a jigsaw or router. Sand the edges for a finished look.
3. If you want to add a black border to the new window, do so before installing the window in the car. Use Clear One Black Border Paint or other high-quality paint.

4. When the border paint has cured, you are ready to install. Peel back the masking material approximately 4 inches from the edges, but do not remove the masking entirely. Attach the OEM trim pieces and test fit the window in the car. Trim the window as needed.
5. Apply adhesive and/or gasket to the window channel and set the window in place. Using adhesive alone is not recommended for racing.
6.  Remove the masking and clean the window with Clear One Plexus cleaner.
7. Apply the supplied date sticker to the inside of the window for warranty and contingency purposes.

Replacing Bolt-On Glass
1. Place the old window face-up on a flat surface. Remove any gasket material or hardware left on the window frame. Clean and prep the frame for a new gasket and adhesive. Put the Clear One window over top of the glass and clamp the two together. Don’t remove the protective masking from the Lexan.
2. Flip the windows over and trace the outline of the glass window onto the Lexan with a permanent marker. If the window will sit flush with the car body, you may need to add up to a half-inch around the edge to allow for proper fit. Clear One recommends making a chipboard template of the old window, use it for fitment adjustments, then transfer the final pattern to the new window.
3. Unclamp the windows and trim the Lexan using a jigsaw or router. Sand the edges for a finished look.
4. If you want to add a black border to the new window, do so before installing the window in the car. Use Clear One Black Border Paint or other high-quality paint.

5. Install the solid rubber gasket from the Clear One installation kit around the edge of the window with the supplied adhesive. Allow the adhesive to set for a minimum of one hour.
6.  Once the adhesive and border paint have cured you are ready to install. Peel back the paper masking approximately 4 inches from around the inside edge. Leave the outside masking in place. Mark holes on the outside masking approximately every 4 inches.
7. Place the window in the opening in the car. Starting in the center of the window, drill and countersink the marked holes. Use a bolt and nut every third or fourth hole to keep the window aligned as you drill.

8. With the holes drilled, install the bolts and nuts. Do the final tightening when all bolts are in place. Do not overtighten the bolts; the window should be firmly attached but not concaved around the bolt head.
9.  Remove the masking and clean the window with Clear One Plexus cleaner.
10. Apply the supplied date sticker to the inside of the window for warranty and contingency purposes.

Cutting, Sanding, and Drilling Recommendations
Using the proper tools is critical when working with Lexan to prevent cracking and other damage. Clear One offers the following guidelines:
Band Saw: Cut at 2,500-3,000 feet per minute using an 8-12 tooth per inch blade
Circular Saw: Cut at 6,000-8,000 feet per minute using a 3-5 tooth per inch blade
Router:  Minimum one horsepower with a straight 2-3 blade, carbide-tipped steel bit
Sanding:  Use a standard palm sander with 180 grit paper 
Drilling: Set drill at 1,750 rpm and use a standard steel bit

Summit Racing has Clear One blank window kits in stock for popular GM, Ford, and Chrysler vehicles as well as flat sheet Lexan, window installation kits, border paint, and Plexus cleaner. Of course, Summit Racing can special-order any Clear One window kit you might need—just talk to your sales rep. When you can make your race car safer and lighter at the same time, it’s an opportunity you just have to take advantage of.