Windows, acrylic or polycarbonate (again)

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_Tiny

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I'm planning on replacing the glazing in my coach roof portlights.

From all the various places I've read, cast acrylic seems the favoured material on account of longevity, despite the crazing. However, I like the idea of improved impact resistance, better clarity and all the other stuff that goes with polycarbonate, but I'm worried about it going yellow or milky and scratching. So, I've started looking at coated poly carbonate and came across Axgard (https://www.haldane-fisher.com/fs/doc/building-materials-/Clear-Amber-AXGARD-Technical-Brochure.pdf).

This breaks my rule for buying materials for fixing boats; if you can buy it in builders merchant, don't use it on a boat. I'm tempted to break the rule.

Has anybody used it?
 
I had coated polycarbonate windows on one of ny boats and are now changing then to acrylic as even with the coating the sun still sends the polycarb milky over time
 
JumbleDuck said:
Is toughened glass an option? Most glazing companies can supply it made to measure, and it's only a bit more expensive than plastic.
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Not sure about it for a deck mounted hatch but otherwise glass offers many benefits. My coach roof windows are glass and I recently replaced the perspex winscreens in my motorsailer with made to measure toughened glass. Vision clarity has increased enormously and they do not scratch or craze.
 
I dont think glass is an option, they are all slightly curved. I think I will conclude that poly-carbonate, despite manufacturers assurances, wont last. I suspect the coating comes off in the real world (salt, abrasion, acid rain, etc) where as it doesn't in a lab.

So, acrylic it is then. Just a matter of which one!
 
_Tiny said:
I dont think glass is an option, they are all slightly curved.
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That's not a problem. You can spring a surprising amount of curve (in the case of my Jouster, an inch over two feet) into tempered glass or you can have it made curved in the first place for very little extra.

I'm not proselytising, just suggesting that it might be worth investigating.
 
Just doing all the windows in my Feeling 1090 ... it turns out alumium cap screws onto stainless steel bolts was not a good design choice. Who knew?

Loads of 12mm perspex on order, CNC router all ready to go ... then into the forming oven and on to the boat.
 
_Tiny said:
I dont think glass is an option, they are all slightly curved. I think I will conclude that poly-carbonate, despite manufacturers assurances, wont last. I suspect the coating comes off in the real world (salt, abrasion, acid rain, etc) where as it doesn't in a lab.

So, acrylic it is then. Just a matter of which one!
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Automotive glass is often curved. It should be perfectly possible to order it to shape and curved. You can have it with bolt holes within minor limitations. My glass came from Vehicle Glass Company (VGC) who were very helpful. A phone call should settle it.
 
vyv_cox said:
Automotive glass is often curved. It should be perfectly possible to order it to shape and curved. You can have it with bolt holes within minor limitations. My glass came from Vehicle Glass Company (VGC) who were very helpful. A phone call should settle it.
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I would rather have cracked acrylic or laminated glass keeping the water out rather than a huge hole when a complete piece of tempered glass shatters into thousands of tiny bits.
 
Graham376 said:
Doesn't need much of a knock from say a spinnaker pole end to shatter toughened glass.
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The word "toughened" is fairly important. Have you any evidence that the glass windows fitted, for example, to every classic Westerly, caused problems? As you say, smashing a car window requires a specialised tool to deliver a very powerful blow to a very small area. It's surprisingly hard to break a windscreen with a hammer.
 
Car windscreens are laminated, side windows usually are toughened glass. When I went to replace crazed windows on my last boat with glass it was actually cheaper to have them made in laminated glass than toughened. You would need a sledgehammer to put the laminated glass through.
 
Graham376 said:
I would rather have cracked acrylic or laminated glass keeping the water out rather than a huge hole when a complete piece of tempered glass shatters into thousands of tiny bits.
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My windscreens are exactly the same specification and thickness (4 mm) as the windows in the sliding doors of VW campers. I would suggest that these have a far harder life than the windows in a boat. I have owned VW camper vans for something like 30 years and know many other owners, yet I have never known one to break.
 
JumbleDuck said:
The word "toughened" is fairly important. Have you any evidence that the glass windows fitted, for example, to every classic Westerly, caused problems? As you say, smashing a car window requires a specialised tool to deliver a very powerful blow to a very small area. It's surprisingly hard to break a windscreen with a hammer.
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My wheel house windows are made from 2 sheets of 2 mm thick toughened glass laminated together to prevent the total loss of the window.

During fitting one of then the glass cane up against a hard point in the frame and one sheet shattered completely but the inner one that did not shatter held the glass together.

I would not have only toughened glass as if it shattered the whole window would fall out.

A covering of security film would help to some extent.
 
JumbleDuck said:
The word "toughened" is fairly important. Have you any evidence that the glass windows fitted, for example, to every classic Westerly, caused problems? As you say, smashing a car window requires a specialised tool to deliver a very powerful blow to a very small area. It's surprisingly hard to break a windscreen with a hammer.
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A rubber mallet is often used to hammer car toughened or laminated windscreens into old type rubbers (I did quite a lot in my motor trade days) but only a tiny sharp object such as a stone to shatter one. My personal preference if replacing acrylic with glass, which is unlikely, would be laminated.
 
black mercury said:
Car windscreens are laminated, side windows usually are toughened glass.
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Lots of older windscreens are toughened. Curious trivia fact: Kenneth Horne (of "Round the Horne") was in real life the marketing manager of Triplex Toughened Glass.

When I went to replace crazed windows on my last boat with glass it was actually cheaper to have them made in laminated glass than toughened. You would need a sledgehammer to put the laminated glass through.
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It's very difficult to make a hole in it but much easier than toughened to break in the first place.

Graham376 said:
My personal preference if replacing acrylic with glass, which is unlikely, would be laminated.
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Suit yourself, but I wouldn't want anything so easy to break. Laminated glass is just normal glass with a layer of plastic to hold the bits together.
 
I had a window damaged. It was laminated glass 6.3mm thick and a!though the inner was broken the outer skin was unbroken. When I came to remove the pane from the frame it took a lot of hammering with a big hammer to break through and penetrate the sheet. I was most impressed with the toughness and durability of laminated glass. The glazier also said there was quite a bit of flexibility and ability to withstand knocks, although clearly not the anchor of an adjacent boat!
 
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