Tempered Glass is Insanely Expensive - Any Good Sources?

[Montanan]

Glass is cut to the desired shape and size and then is tempered. That is why there is a leadtime and indeed it cost moderately more, say $5 per square foot.

Once tempered glass can not be readily cut to size.

Tempered glass cannot be cut using the same methods as you’d use to cut ordinary, untempered glass. If you must cut through a pane of tempered glass, you’ll need to heat it to nearly 1,000 °F (538 °C), then slowly cool it. This process is called annealing, and it will effectively undo the tempering process, weakening the glass to the point that you can cut it. Once it’s cooled, the glass will be in a state in which it can be cut. Anneal the glass if you have access to a kiln.

Essentially any glass shop can get the tempered glass you desire, nothing unique, just requires lead time.

[captlloyd]

Originally Posted by cyfishburn

You might look at laminated glass. This is used in cars, makes all those little cuboid bits you see on the road after an accident. Laminated glass is quite strong, don't know how it compares to tempered glass. You can buy it many places without waiting for the tempering process, you can cut it yourself.

I believe you have this backwards. Tempered glass is the glass that explodes when broken, think driver side door. Laminated glass would be windshield glass.

[Chotu]

I think my wording was off on the first post.

When I said “my cuts”. I probably should have said “the necessary cuts”

I’m not making cuts in glass at all.

[Montanan]

https://www.procurveglass.com/lamina...in%20a%20storm.

LAMINATED GLASS IN THE MARINE INDUSTRY
Posted December 12, 2019 by procurveglass-admin

Laminated glass can be some of the strongest and most durable types of glass around. It’s made by taking two or more pieces of glass and bonding them together with an interlayer in between them. This provides laminated glass with its strength and prevents it from shattering in the event that it’s ever broken.

Post-Break Performance vs Tempered Glass

When tempered glass breaks, it leaves a hole in the side of the boat, while the plastic inside the laminated glass holds it together and helps maintain the boats water integrity, which is important if it breaks in a storm. It performs so well, that the class societies will allow us to design a laminated glass window that does not require storm shutters.

Thanks to its strength, laminated glass has become popular in a range of different industries. It’s been used to build cars for more than 80 years now. Windshields are laminated glass products that are specifically designed to keep both drivers and passengers safe in the event of an automobile accident. Laminated glass has also been used early and often by architects, builders, and designers putting together plans for structures. Outside of the fact that laminated glass can keep these structures more secure, it can also be used to reflect UV rays from the sun, which can make buildings more comfortable and reduce energy costs.

Additionally, laminated glass has found a home in the marine industry in the form of high performance marine laminated chemically strengthened glass.

[Americanrancher]

I replaced all of the glass in my port lights with laminated safety glass. One of the 2 layers was lightly tinted. I am super happy with the result, no worry about crazing or water intrusion in a breakage situation. The tinting was great as well, if I were to do it again I would tint both layers instead of just one. If it delaminates in 40 years that is ok with me as I will be in heaven long before that! When using it as with all glass you must be careful of any sharp metal points contacting the glass as it will cause a crack. I did break a piece when installing it by not allowing enough space between the bronze frame and glass and tightening it too much. A new piece and some spacers solved that problem. If you are interested in my source PM me for details, they ship worldwide. Prices are very reasonable. Ben S/V DAWN

[johnn33]

Hallo Chotu

This thread on storm boards might be useful
https://www.cruisersforum.com/forums...ws-189928.html
This is one solution
https://www.seastream.co.uk/advice/storm-boards/
John

[shearerc]

Acrylic and Polycarbonate are both half the weight of a comparably sized piece of glass and yet both plastics are much stronger than glass providing much greater impact resistance. Polycarbonate is stronger than acrylic. That aside, both are very strong.
If you are comparing to glass, acrylic has 10 times the impact resistance of glass. Polycarbonate has 250 times the impact resistance of glass.

[Chotu]

Originally Posted by shearerc

Acrylic and Polycarbonate are both half the weight of a comparably sized piece of glass and yet both plastics are much stronger than glass providing much greater impact resistance. Polycarbonate is stronger than acrylic. That aside, both are very strong.
If you are comparing to glass, acrylic has 10 times the impact resistance of glass. Polycarbonate has 250 times the impact resistance of glass.

Yes. I know. I chose polycarbonate last time.

It’s the superior material, until it:

A) is destroyed by mold while you are away from the boat

B) rips off the adhesive, channels or whatever is holding it in place

C) gets scratched by something dragging along it by mistake

For these reasons and my unwillingness to keep doing windows over and over and over, it’s glass this time.

Laminated glass (unless also tempered) is not a good choice on a boat. You know when a pebble destroys your windshield? Yep, that’s regular laminated glass. Tempered is the choice because with a little luck, an impact might not break it, while with regular laminated glass, it will.

All the talk of the laminated glass staying put after it breaks is not even an advantage it has over tempered. A Ballistic film on the tempered (please read the thread and see the video) is the best of both worlds and superior on every front.

Other than polycarbonate which is the best choice, until it isn’t.

This is an area where materials science is really failing us. There is no ideal material for this application

[BillKny]

I don't mean to be a spoil sport here... but how do you KNOW that 1/4" glass (tempered or laminated) in a 4 X 8 foot span (or close to that) is anywhere NEAR strong enough to withstand a wave strike? What calculations have you done? What authority can you quote? That's pretty thin stuff. Tempered glass is also VERY susceptibly to sudden failure from minor scratches or dings to the edge, even without significant loads.

That thickness seems minimally suitable for a house window, but a boat at sea? Nowhere NEAR! I'd also worry about it being able to withstand the movement of the hull. Do you have any idea how much twist and flex you expect in the hull? Will the glass and mounting system accommodate that? Numbers please? Or are you just hoping it will work?

Now to be fair, I am responding with the seat of my pants here, and maybe your butt is way more calibrated than mine. But if it was MY boat, I'd be running numbers, or finding someone who could.

There are places where engineering by the seat of your pants is OK, this seems to me to be a place where real engineering NUMBERS ARE KEY!

Other issues: You know that much tempered glass is not optically flat, but contains significant distortions? Also, it presents significant opacity when viewed in polarized light (i.e., with sunglasses). That's not normally an issue looking out from the inside of a building, but it might matter onboard a boat.

[Chotu]

Originally Posted by BillKny

I don't mean to be a spoil sport here... but how do you KNOW that 1/4" glass (tempered or laminated) in a 4 X 8 foot span (or close to that) is anywhere NEAR strong enough to withstand a wave strike? What calculations have you done? What authority can you quote? That's pretty thin stuff. Tempered glass is also VERY susceptibly to sudden failure from minor scratches or dings to the edge, even without significant loads.

That thickness seems minimally suitable for a house window, but a boat at sea? Nowhere NEAR! I'd also worry about it being able to withstand the movement of the hull. Do you have any idea how much twist and flex you expect in the hull? Will the glass and mounting system accommodate that? Numbers please? Or are you just hoping it will work?

Now to be fair, I am responding with the seat of my pants here, and maybe your butt is way more calibrated than mine. But if it was MY boat, I'd be running numbers, or finding someone who could.

There are places where engineering by the seat of your pants is OK, this seems to me to be a place where real engineering NUMBERS ARE KEY!

Other issues: You know that much tempered glass is not optically flat, but contains significant distortions? Also, it presents significant opacity when viewed in polarized light (i.e., with sunglasses). That's not normally an issue looking out from the inside of a building, but it might matter onboard a boat.

Actually, you’re right on the money. You’re completely correct.

1/4” is to keep weight down and is not viewed as adequate thickness. Ballistic film is to keep it safe in worst case scenarios. So no worries about impacts. If it’s an impact strong enough to crack the tempered glass, it’s still waterproof and very VERY hard to get leaking.

My boat doesn’t flex. AT ALL. It’s insanely stiff. I got a good deal on 1” core when the plans called for 3/4”. So I used the 1”. The stiffness of the boat is just crazy. It’s a rock. Still has all the same scantlings as a 3/4” core boat. Same bulkhead placements, same everything. It’s just way, WAY more stiff.

The last part of your post is definitely a big concern.

All I can say is “what the actual f^)k?” At this point.

If tempered glass can’t be seen though, polycarbonate won’t stay on or last, acrylic won’t stay on or last and laminate glass is fragile and gets water between the laminates then what the actual f^(k????

Do I just leave them open??? Maybe just some eisenglass type soft cockpit enclosure type thing? (A joke)

I give up. What the hell am I supposed to use then??

[chasfgr]

Originally Posted by Chotu

I’m online comparing tempered glass 48x48 sheets and those, even without my cuts to make them a couple inches smaller, are just out of this world expensive.

Does anyone know where to get better pricing on this stuff?

Leaning toward a half inch thick Dow 795 bead and acrylic at this point because

1) my glazier is really good. So good I can’t get a quote for 2 weeks and can’t get glass until hurricane season begins.

2) getting my own sheets of tempered glass seems crazy expensive

Looking to maybe go acrylic myself. Slightly less expansion than polycarbonate and stiffer, though more prone to crazing and brittle. Cheap though.

But if I can find some reasonable pricing on tempered glass, I’ll go with that.

Not a good choice acrylic (Perspex) embrittles quickly in sun, turns yellow and distorts (in anything but UK sunlight).
If you really want to spend money, go for Triplex glass - easily the best but x3 the price of tempered.
Likely you're going through a supplier way down the chain - because getting float, cut-to-size, and then tempered by the manufacturers is, in my experience, by far the cheapest option.
Comparison with window glass, will of course, be totally other-worldly.

[BillKny]

The ballistic film might keep the glass together when it breaks, but I doubt it will do anything at all to increase its strength to the kinds of forces imposed by a wave impact. A bullet impact is very different from hitting with a sledge hammer, even if they carry the same total energy!

I apologize for something that I am sure has been asked before in the endless messages on this, but: Did the designer of the boat specify window design and material? Is this the first hull to this design?

I am not at all convinced that your cat is unique and the first one ever built that doesn't flex AT ALL. I am picturing the port bow on the peak of one wave and the starboard quarter on the peak of another, with the other corners hanging in the air... But that's your call.

I have never seen a 50 foot boat with a continuous flat window of the size you are talking about. It seems a damn big hole...

[Chotu]

Originally Posted by BillKny

The ballistic film might keep the glass together when it breaks, but I doubt it will do anything at all to increase its strength to the kinds of forces imposed by a wave impact. A bullet impact is very different from hitting with a sledge hammer, even if they carry the same total energy!

I apologize for something that I am sure has been asked before in the endless messages on this, but: Did the designer of the boat specify window design and material? Is this the first hull to this design?

I am not at all convinced that your cat is unique and the first one ever built that doesn't flex AT ALL. I am picturing the port bow on the peak of one wave and the starboard quarter on the peak of another, with the other corners hanging in the air... But that's your call.

I have never seen a 50 foot boat with a continuous flat window of the size you are talking about. It seems a damn big hole...

Man, you gotta scroll back. I POSTED pics of a cat with the exact windows I have. You may have heard of them. They’re called Gunboats. Please read the thread before saying ridiculous things like “I’ve never seen a boat with 48x48 deckhouse windows “. I’m sorry you never left your harbor to see boats like mine. Where are you sailing anyway that you don’t have catamarans like mine around?

Try this on for size. Do your thought experiments with my boat ON THE GROUND lifting opposite quarters. Yeah, that was my REAL LIFE test of the boat prior to launch. We also lifted all 4 quarters and abruptly knocked the support out form just one at a time. No flex. 3/8” was the flex over 50ft. None. A rounding error. Does your boat oil can or something? Bad experiences with that? Don’t assume every boat is the same as yours.

Finally, you didn’t watch the video. I can tell because your analysis is about bullets. The video wasn’t about bullets.

Plans call for 1/4” polycarbonate. That’s what I used the first time.

[smj]

I personally like the idea of eisenglass, something like a Maine Cat. Great for tropical cruising but of course the boat has to be designed to handle a wave coming aboard.

[Chotu]

Originally Posted by smj

I personally like the idea of eisenglass, something like a Maine Cat. Great for tropical cruising but of course the boat has to be designed to handle a wave coming aboard.

And it’s definitely, definitely not made for that. I did toy with the idea, but went with settees, appliances, open stairs down to the hulls.

It’s not conducive to water coming in.

So I need to close it up.