Compiled by Juli Case
Question: I’ve been asked to do a cover for an all-terrain vehicle. I have to use a Lexan window and attach an awning rail to it. I’m concerned about cracking the Lexan. Any suggestions?
Answer: A Lexan is a brand of polycarbonate. It’s more rigid than some other window products. We asked members of the Marine Fabricators Association for solutions.
Many fabricators suggested drilling the material. Lexan is strong and unlikely to shatter. The drill bit is important. While there is a special bit for Lexan, you can grind a drill bit, which prevents chipping when the drill exits the panel. Use a new bit as small as possible. Use light pressure and expect the drilling to start slow but end fast. Check with your supplier to see the recommended bit size for the thickness you’re using.
Others suggested pre-drilling a small (1/8-inch) pilot hole, then drill with the next-larger size until you get the fastener size.
Several fabricators mentioned using masking tape on Lexan before drilling. Remove the tape as soon as you’re done, otherwise it might stick.
General suggestions for drilling into Lexan were to stay away from edges, and to practice your technique on scrap material.
Most fabricators mentioned the type of fastener you use is important. Several stressed to make sure metal fasteners don’t touch Lexan. Use a rubber insert or a nylon washer as a cushion. Pop rivets and stainless steel machine screws with acorn nuts were also mentioned. Over-tightening can cause cracking. Use fasteners that go through Lexan, rather than thread into it.
Not all fabricators advocated drilling. One fabricator said she makes pockets or finds other points of attachment, such as suction cups, rather than drill the windshield. Another fabricator mentioned putting a metal “border” on Lexan and attaching fasteners to it.
As for the awning rail, several fabricators suggested pre-drilling the rail before attaching it to Lexan. One fabricator mentioned using tape on the rail to stabilize it during the fastening process, as it puts less stress on Lexan.
Should cracks occur, try drilling a tiny hole at the outer end of each crack to prevent spreading.
Not all fabricators were convinced that Lexan was the best material for this job, not just because of the cracking, but because of UV resistance. If UV is a concern, make sure you’re using a coated Lexan. Several mentioned clear vinyl or plexiglass.
One fabricator mentioned an article published by Hot Rod magazine that gives tips for working with Lexan. The project featured is a car window, but some of the techniques would apply to marine work: www.hotrod.com.