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BoatyardBoy 03-26-2014 11:21 AM

Lexan/polycarbonate vs acrylic
 
3 Attachment(s)
I have two long fixed port lights on my boat. They were leaving so I removed them to reseal. Well one was already cracked so I'm deciding to replace them. Which should I use since they are so long and aren't being walked on? Also, they had screws about every 6 inches, should I have those redrilled or only half of them redrilled?

Attachment 25450Attachment 25458Attachment 25466

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BoatyardBoy 03-26-2014 11:23 AM

Re: Lexan/polycarbonate vs acrylic
 
Only reason I ask, is because I read that lexan has a higher expansion rate which could be a problem since the size..

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jrd22 03-26-2014 11:35 AM

Re: Lexan/polycarbonate vs acrylic
 
You could use either polycarb or acrylic. The poly will be stronger but will scratch easier, the acrylic will stay clear and is more resistant to scratches. The problem I see is how they are attached with just screws and no stainless or aluminum trim piece to evenly apply pressure around the entire perimeter, but if you use a good sealant like Dow Corning 795 and overdrill the screw holes (the plastic expands and contracts so if you tighten the screws you will have cracks) and use washers with flexible gaskets you should be OK.

krisscross 03-26-2014 12:22 PM

Re: Lexan/polycarbonate vs acrylic
 
You could make the replacement in 2 pieces, inserting a piece of trim between them. That would reduce the stress on the parts - both from thermal changes and from mechanical stress.

mitiempo 03-26-2014 05:32 PM

Re: Lexan/polycarbonate vs acrylic
 
I'd use acrylic. True polycarbonate is stronger but acrylic is strong enough. What thickness?

As far as attachment holes and fasteners aren't needed. Dow 795 and 3M VHB tape is all that is required. The combination will hold through incredibly well and without holes cracks from stress are eliminated. I agree with smaller sections of glazing to reduce expansion problems.

This explains the method.

http://i1314.photobucket.com/albums/...ps5aefbac4.jpg

http://i1314.photobucket.com/albums/...ps8e7ebd38.jpg

http://i1314.photobucket.com/albums/...ps8fe594f6.jpg

BoatyardBoy 03-27-2014 09:59 AM

Re: Lexan/polycarbonate vs acrylic
 
Thanks yall, I am leaning to acrylic now.. It's half inch is what came off the boat. I just don't want it to look old and scratched in a few years, so I'm not doing lexan.

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mitiempo 03-27-2014 10:29 AM

Re: Lexan/polycarbonate vs acrylic
 
The fastener holes can lead to cracks over time. If you can avoid using fasteners the results will both look better and last longer. I don't know of a manufacturer using fasteners.

Irunbird 03-27-2014 10:31 AM

Re: Lexan/polycarbonate vs acrylic
 
Quote:

Originally Posted by mitiempo (Post 1670314)
I'd use acrylic. True polycarbonate is stronger but acrylic is strong enough. What thickness?

As far as attachment holes and fasteners aren't needed. Dow 795 and 3M VHB tape is all that is required. The combination will hold through incredibly well and without holes cracks from stress are eliminated. I agree with smaller sections of glazing to reduce expansion problems.

I'm thinking of doing something similar (although my windows are considerably smaller and thinner). Is it really safe/effective to just use adhesives and not screw the windows down like they were originally? All of my leaks are from screw holes, but I'd hate to lose a window some day out sailing...

Ray

mitiempo 03-27-2014 10:34 AM

Re: Lexan/polycarbonate vs acrylic
 
Yes it is safe if done correctly.

zz4gta 03-27-2014 10:45 AM

Re: Lexan/polycarbonate vs acrylic
 
acrylic all the way.


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