Dan, it's not Lexan -- Lexan is a brand of polycarbonate and Superlite doesn't use it. I know at some point Superlite switched to a superior hard-coated polycarbonate which is more scratch resistant. I'm not sure when they made that switch or if it would have any effect on yellowing.
Hi Guys, I cut even curved polycarbonate with 36-teeth-per-inch fine metal cutting blades in my saber saw. I use Bosch brand, which are available in packs of 4-5 from Lowes. The edges come out almost polished with no roughness or "heat boogers" (technical term). When you're done you just run your fingers along the edges and all is clean. The keys are: (1) the very fine tooth blade and (2) cover the foot of the saw with some tape and just glide the saw over the plastic without pressing down so as not to scratch or mar the plastic. Also, keep the protective film on to keep from scratching the plastic.
Also never use flathead screws/bolts. They cause hoop stress and will eventually crack the polycarbonate. Use a bolt that puts the material in compression like a pan head bolt. Drill oversized holes and use washers to distribute and cushion localized stress and compensate for expansion and contraction of the polycarbonate as the temperature changes.
Last but not least never ever ever ever use thread locker on the bolts. They are not compatible with polycarbonate and will eventually craze and crack the material.
When making cuts always try to leave a radius (even a 0.020" radius is a big help) on all inside corners. polycarbonate is very notch sensitive and always use good support along the edges.
Hmm. I countersunk all my windows 8/32 in the rear clam, doors and windshield. I've not seen a single crack in any of them in 14k miles. I think the trick is Fran recommended using black nylon screws. A huge amount of give. My last track event we ran counterclockwise on Eagles Canyon. The front was getting airbourne on bad pavement in turn 8 for four sessions x 8-10 laps. Still no cracks... no yellowing either since 2009.
Has anyone ever tried using standard windshield butyl glue to set the Windows? It's flexible, water tight, and if you ever remove the "lexan" it should come off with a standard windshield removal tool.
Just a thought - If you're planning to do any open track events, many of the organizations require the windows to be rolled down so you can waive people by. On an SLC that means either removing the windows or having a hole in the window to stick your arm through. Windows held on with screws are easy to remove for the track.