Join Date: Apr 2006
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Re: Plexiglass replaced in hatch, came unglued.
"Acrylic has every advantage over polycarbonate in boating applications, unless you expect to be shot at."
Not quite. There are literally dozens of grades of polycarbonate, and acrylics, from several major sources. To make blanket comparisons is like saying "I don't want to use metal, the last metal faucet I had rotted out." Really? Plated plastic, high quality stainless, solid bronze, gold flashed nickel-steel....they're all "metal" but all very different.
The same thing goes with glazing plastics. The stuff on the shelf is just intended to be used for napkin holders and drink coasters. The full range in a catalog will include many degrees of UV and scratch resistance--at much higher prices, and higher again because a small store will require you to order in whole 4x8 sheets of them. Even in Lexan, you can buy Lexan MR10, which has a film bonded to one or both sides, and that film tremendously increases the UV and scratch resistance. In Plexi, there are oddities like "unshrunk type G" which used to be specified for underwater camera housings for some technical reason.
Some years ago my friend enlisted me to tear old the old portlights and put new ones in. I asked him if he really was going to just replace the old ones "same same" and he said sure, of course, they're Lexan they're incredibly strong. And since we were going to implode the old ones to remove their glued frames, and I was already leaning against the cabin side with an ordinary hammer in my hand. I just swung my arm out (BLAM!) and said "I don't think they're Lexan."
To me, the question is, when something falls apart and a spinnaker pole or other hefty "missile" shoots back into the glazing, will it penetrate? Or be stopped? If a guy up the mast drops a monkeywrench, will it penetrate? Or be stopped?
Acrylics can have a strength range of well over 10:1 comparing one grade to another. Lexan can be more than 100x more impact resistant than acrylics.
If you read about the damage boats took in "Fastnet, Force 10" and how many needed to rig storm windows, etc? Lexan doesn't begin to sound so bad. Polish it once a year, keep ammonia and petrochemicals off it, not so hard to keep it up.