What glass in our windows?

john_morris_uk

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We are having some of the windows in our Westerley refurbished. The man who is doing them is adamant that the perspex should be replaced with toughened glass. He says he's done lots and never known one to break. My instinct would have been. (assuming one was moving to glass and not perspex/acrylic) to move to laminated glass. I fear dropping a winch handle on the window or having a snatch block or similar hit one and finding the cabin full of shards of glass.

Any experience of replacing window perspex with glass? Toughened or laminate?
 

Rappey

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Toughened glass is extremely strong and breaks into little squares.
Laminated can suffer from water getting into the laminate and then giving a cloudy mist between the two layers.
Glass is great as it stays clear and never dulls. It's also cheap.
 

john_morris_uk

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Toughened glass is extremely strong and breaks into little squares.
Laminated can suffer from water getting into the laminate and then giving a cloudy mist between the two layers.
Glass is great as it stays clear and never dulls. It's also cheap.
I wish it was cheap. The glass toughening businesses know that a lot of places are trying to catch up and so they've put their prices up!
 
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Many yachts have toughened glass in their windows. Rivals are fitted with toughened glass and it is not a reported issue and they are long in the tooth now with many blue water cruising escapades under their belt.

My own experience is replacing 13 windows (an odd number, aft heads window one side, no window wardrobe the other side). I removed the frames with glass (frames leaking) and sent them for refurbishment. I dropped a few, stepped on them and posted them out with just bubble wrap as protection. When handling the spinnaker poles they get whacked with no issues. One area to consider is any curves. I have a slight curve towards the bow that the frame has to be bent round. The glass is about 3mm thick in a 10mm frame channel, hence the frame flexes but not the glass.

I think their toughness and hence brittleness is a weak point, compared to something that is strong and could flex slightly. An extreme example is ships windows and rig windows which have been known to shatter from green waves; obviously a much larger window area compared to your boat. Then again toughened glass is also used as blast resistant glass on the same rigs, at an appropriate thickness. I think the standard window blank that we would carry for long distance sailing addresses that risk compared to the hassle of scratching plastic.
 

Rappey

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Glass will bend to a certain degree. Don't go to a high street glass and mirror shop though, take a template to a double glazing manufacturer as it's a lot cheaper.
The glass will be cut then sent off for heat treatment.
 

Boathook

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I ordered some new windows a few years back and they came as standard with toughened glass. I have also replaced some perspex bits with laminated glass and this then went cloudy as water entered the laminate. This then got changed for toughened. Perspex is good but looks terrible after a few years with scratches that cant really be polished out.
 

C08

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I had a cabin window cracked by a neighbouring boat. This was a laminated glass window and had cracked the outer layer but not the inner glass. In order to remove it from the frame I had to break it up and pick out the bits. It was immensly strong and even after battering with a lump hammer retained its integrity as a sheet although a bit floppy. The piece about 80mmx40mm was around £30 from a local glass supplier cut to the shaped template I supplied. After a conversation with the glass supplier about the pros and cons of laminated versus toughened glass I was convinced that the original laminated glass was the corrct choice as in the event of a large wave or other incident the last thing you want is the window breaking up.
My experience with polycarbonate is not good with two wheelhouse windows. The first was so soft it scratched badly and then went cloudy after around 3 years. The second went cloudy within 2 years, despite being UV protected grade and fitted the correct way around and also had refraction fringes at the edges where the screws distorted it slightly. In contrast my side wheelhouse windows in cast acrylic have been great with no clouding or scratching.
 

Graham376

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I would stick to acrylic and my instinct is the same as the OP's, if using glass, then go for laminated. Toughened is very strong but can easily be shattered by a sharp tap near the edge or corner from a boat hook or pole whereas laminated will crack but remain in place.
 

Iliade

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I managed to put a ladder through the ~45 year old toughened glass of my Westerly! Doh!

Yes the cabin was fun of glass sugar cubes.

I asked an experienced glazier and he advised that laminated is less strong than toughened so I replaced as per the original. It is still there about five years later, matching the now ~fifty year old originals!

Toughened doesn't like contact with metal (i.e. hard) objects on the edge, but the edges should be protected when installed.
 

Rappey

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Toughened is very strong but can easily be shattered by a sharp tap near the edge or corner from a boat hook or pole
But how would the edge of the glass be exposed in the first place? its always cushoined in a frame.
Laminated 6mm is 6.3mm. Two pieces of 3mm and 0,3mm of plastic film in between .
Laminated is used for glass in banks as its extremely difficult to beat through it even when broken as the film holds it all together.
Some toughened glass is of a poor standard. Impossible to tell until its broken then the smaller the little cubes the better the quality.. toughened always has the sharp edges rounded off
Glass is amazing stuff. always an exact thickness (can see the verniers and micrometers comming out now.. If you cut a say 200mm wide strip into curves it makes a brilliant scraper for removing varnish, reducing plastic etc.
 

wallacebob

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My W Pageant windows are toughened. My Hunter windows are toughened. Laminate is for car windscreens, where head impact or face injury is possible. The flexing of a boat is not a good thing for laminate glass. Stick with what the man is recommending, and stop over thinking.
 

Rappey

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The flexing of a boat is not a good thing for laminate glass
I wouldnt be so sure about that. A car glass windscreen is a strucural part to reduce the twisting and flexing of a cars chassis. I had a lotus with a huge screen which totally became unbonded.. It was incredible how much i could see the car twisting over uneven road surfaces. Once rebonded the car bacame rigid again.
Any double glazed pvc door fully glazed has the loading of the door sash placed close to the corner of the glass . It can take tremendous pressure.
Run a straight edge along the glass of a fishtank and see how much the glass bends.
Yes there are limits where it breaks.
 

JumbleDuck

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Any experience of replacing window perspex with glass? Toughened or laminate?
I had the windows on my Westerly Jouster rebuild (by C&J International, now gone) and was amazed to find that although teh coachroof sides were curved, the toughend glass was flat. They were only about 2' long but took a displacement of around 1" at one end as they were bolted up.

When I refurbished my Hunter 490 I had the manky old perspex in the windows replaced with toughen glass, also by C&J. It was surprisingly cheap - around 50p extra per window, as I recall. The view is very much better!

Although toughened glass shatters much more excitingly than laminated, it takes a long more to break it. Given an either or choice I would go for toughened every time. I believe that it's possible to get toughened and laminated, though the individual sheets woul dbe rather thin which might reduce the effect of the toughening. I wouldn't go for laminated alon - it's basically just plate glass with a safety feature for when it breaks.
 

Graham376

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But how would the edge of the glass be exposed in the first place? its always cushoined in a frame.

I said "near the edge" not on the edge. Car windows are also in a frame and the scrotes usual method is a sharp tap or automatic centre punch NEAR the edge and it shatters instantly, as do windscreens hit by stones, whereas laminated usually just crack the outer layer. I would rather have a cracked boat window than none at all.
 

Rappey

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I said "near the edge" not on the edge
Ahh. Now I understand what you said.
It's the depth of the glass, ie, 6mm where it's weak spot is. The surface is strong.
The sheet of glass is heat treated. Why would close to the edge be any weaker than the middle ? If anything could it actually be stronger near the edge as it's also supported?
A car windscreens edge is not touching anything. It's the inside surface of the glass that is bonded to the frame some 25mm in from the edge.
Advantages of laminate glass can be sound insulation and uv block courtesy of its plastic film. A good advantage for cabin interiors.
It's only down side is the plastic laminate goes cloudy if the edge of the glass gets wet.
Breaking car windows near to the edge could be to reduce impact noise. It's what they have seen done on TV so it must be right as it might not break in the middle?
Those auto punches can be quite loud in some quiet car park ?
If I stone impacted a toughened screen hard enough to break it then it would certainly crack both layers of a laminated screen. The inside being concave may make it difficult to feel the crack.
Your reasoning for laminate as it's still there when broken is a very good point ?
 

john_morris_uk

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I had the windows on my Westerly Jouster rebuild (by C&J International, now gone) and was amazed to find that although teh coachroof sides were curved, the toughend glass was flat. They were only about 2' long but took a displacement of around 1" at one end as they were bolted up.

When I refurbished my Hunter 490 I had the manky old perspex in the windows replaced with toughen glass, also by C&J. It was surprisingly cheap - around 50p extra per window, as I recall. The view is very much better!

Although toughened glass shatters much more excitingly than laminated, it takes a long more to break it. Given an either or choice I would go for toughened every time. I believe that it's possible to get toughened and laminated, though the individual sheets woul dbe rather thin which might reduce the effect of the toughening. I wouldn't go for laminated alon - it's basically just plate glass with a safety feature for when it breaks.

I’m persuaded. Thanks for chewing it over but toughened it is.
(And I’ll do what coded boats do and carry a couple of blanks and strong backs when crossing oceans. )
 
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