What glass in our windows?

Stemar

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Your reasoning for laminate as it's still there when broken is a very good point
The problem is that it's far more likely to be broken. While it won't break up like float glass, it's nowhere near as resistant to impact as toughened. If there was a good reason to switch from perspex, and I'm not convinced there is, I'd go for toughened. Yes, when it does break, it's a mess, but it'll take more than thumping a relatively small window with a spinnaker pole, unless you really mean it. The above-mentioned scrote's punch is sharp, so a tap is several hundred (thousand?) psi, the pole is round, so far less pressure, even if the total force is more.
 

mjcoon

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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 ?

I'm not convinced that your concept of "supported" is so advantageous. A blow on a supported portion of glass is all turned into shattering energy. Away from support the glass can flex and spread that energy. Coupled with the difficulty of reaching the middle, if I wanted to break a toughened screen from the outside I would do it at the edge.

I am also not convinced by much of the rest of your physics, like a stone breaking the inside glass layer, or the film doing much sound absorption...
 

Rappey

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I am also not convinced by much of the rest of your physics, like a stone breaking the inside glass layer, or the film doing much sound absorption
That's OK. I've just based my opinion on what I know from a previous life with years in the glazing industry but I'm not claiming it to be fact.
Could nearly always tell when someone had bricked their double glazed unit and claimed it was a stone from the lawnmower !
There are lots of recorded instances where toughened glass in parked cars has shattered for no apparent reason at all.
The sound reduction is fact though and it does make a significant difference in the same way a polymeric barrier in a foam sheet of engine insulation makes a difference. They use a special sound deadening film when acoustic values have to be achieved and a bonus is 99% of uv rays being blocked.

Elon musk demonstrated how unsupported glass breaks easier with his cyber truck.
It withstood huge impacts from a steel ball in a test rig where all 4 sides were supported.
On stage with the window slightly open the ball broke the glass each time.
 

mjcoon

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Elon musk demonstrated how unsupported glass breaks easier with his cyber truck.
It withstood huge impacts from a steel ball in a test rig where all 4 sides were supported.
On stage with the window slightly open the ball broke the glass each time.

Ooh, that sounds interesting! Has he joined Mythbusters?
 

Rappey

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Ooh, that sounds interesting! Has he joined Mythbusters?
I was a live demo to show how strong his "clear aluminium" glass is.
Unfortunately the demo did not go to plan and the steel ball they threw at it broke the glass.
 

rogerthebodger

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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?

I fitted glass in my wheel house mainly as both perspex and polycarb will scratch in time.

Mine are laminated with 2 sheets of 6mm toughened glass. I did have one brake when I first tried to fit one in to the steel window frame but found that it was manufactured oversize compared to the template supplied.
 

NormanS

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My deck saloon windows are double glazed toughened glass. As per surveyor's recommendations, for ocean passages, I have easily rigged polycarbonate storm widows for the side windows. Was advised that no storm windows were required for the three forward facing ones.
 

vyv_cox

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The small windows in my Sadler are toughened, replaced about 5 years ago with glass that has some light reflection properties. The much larger windscreens I fitted in my motorsailer are toughened 4 mm glass, same as is used in the sliding doors of VW vans and no doubt many others.
 

Rappey

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I went on a boat that had 50mm thick windscreen to enable a force of up to 5 tons when piercing through a large wave.
 

Rappey

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What's that in whales per cricket pitch?
approximately 1.735 ;) but would depend on being a blue or sperm whale.

If your reffering to the antiquated makes no sense imperial system then 2"
 
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Lucy52

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I hope to redo my fore hatch and am considering using clear toughened glass with a UV film on the inside that would hold all the little pieces together should it shatter, giving me the benefit of a laminated glass with the strength of the toughened glass.
 

Rappey

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I hope to redo my fore hatch
The film is a valid way of creating laminated effect from toughened glass. The Mod used to put a thick film over windows to make them blast proof in the days of the ira bombings.
I presume the hatch would allow the glass to be flush or lower than its retaining frame as mounted on top would expose its edges..
You would need to find a sealant that is compatible with glass and aluminium and creates a strong bond with the use of primer..
Houdini made or still makes hatches with glass but they also have protective bars across.
I would opt for polycarbonate or similar for a hatch ?
 

Rappey

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Being lazy . Auto correct , can't think of any other excuses at the moment ?
English built boat so tons of force, German made glass so mm
 

Lucy52

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I presume the hatch would allow the glass to be flush or lower than its retaining frame as mounted on top would expose its edges..
You would need to find a sealant that is compatible with glass and aluminium and creates a strong bond with the use of primer..
Thanks Rappery, It has a mahogany frame, I intend to remake it and mount the glass flush as the current hatch is set in from the bottom and creates a swimming pool above when it rains. This hasn't done the wood any good where the varnish has given way. I had thought to use a butyl sealant Arbomast BR.
 

Rappey

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The edges of the glass are ground off for toughened and I would be a little concerned about anything hard making contact with the edge.
How about having the glass recessed say around 5mm to protect the edges and then putting two channels in the forward edge of the wood to allow the rain to drain away ?
 

Lucy52

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The glass would be debated flush and bedded in butyl with an edge gap of a few mm filled with butyl, much like double glazing fitted with choc blocks arround the edges. I believe 5mm would make little difference the butyl would form a fillit at the edges. The current hatch has drain holes forward but as the frame is only 5/8 in thick there is little room after the glazing is rebated from below and so they are small and get blocked up. Water sitting on top is a problem waiting to happen.
 

Zing

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Windscreen glass can be both toughened and laminated. I would have thought that was the strongest, safest and the most suitable for a boat?
 
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