Hatch rebuild - replace wired glass?

[Han]

The midships hatch on our new-to-us boat is leaking, so we've pulled it off and taken it apart (see pic below). It's a faux-butterfly hatch (i.e. it looks like a butterfly hatch, but the whole thing lifts up at the front like a regular hatch).

The glass in it is wired safety glass and we're wondering if we should replace this with something else. We plan to sail offshore and are concerned about impact (waves, winch handles, etc) cracking the glass.

What are people's thoughts on actual glass in hatches as opposed to acrylic or lexan? the span is ~1ft x 3ft, can lexan or acrylic span that distance?

Thanks!

[coopec43]

If you use toughened glass you will probably find the hatch will brake before the glass.

The strength of tempered glass means it can stand up to impacts, blows, scratches, strong winds and other weather events. Because of the resistance of tempered glass, it's often used in high-rise buildings and commercial settings where it can withstand higher forces.Nov 20, 2017

http://www.pleasantonglass.com/7-advantages-tempered-glass/

[GordMay]

Traditional wired glass is not impact resistant.
Wired glass breaks easily when impacted; because the embedded wires act as a discontinuity, actually making the glazing weaker than plain glass of the same thickness. Wired glass is about half as strong as the same glass without wire.

[a64pilot]

Don’t use tempered glass in a place where if it breaks it’s going to be a problem, main reason for tempered glass isn’t to make it stronger, it’s so that when it breaks it busts into tiny pieces and won’t hurt you, as opposed to two big pierces that could cut you in half.
This is why shower doors for example are tempered glass, The gravel like pieces it breaks into are pretty harmless.

However if you want the glass to stay in one piece even if broken, but want it to be clear, you need laminated glass like a cars windshield.
Lexan is tough, but soft and flexible and scratches easily. But it’s also a lot lighter than glass and some can be had that has a scratch resistant coating, but it’s still not going to last as long as glass.

[Han]

Originally Posted by GordMay

Traditional wired glass is not impact resistant.
Wired glass breaks easily when impacted; because the embedded wires act as a discontinuity, actually making the glazing weaker than plain glass of the same thickness. Wired glass is about half as strong as the same glass without wire.

Very interesting, after your post and some research on wired glass, we will certainly be replacing these!

[Han]

Originally Posted by a64pilot

Don’t use tempered glass in a place where if it breaks it’s going to be a problem, main reason for tempered glass isn’t to make it stronger, it’s so that when it breaks it busts into tiny pieces and won’t hurt you, as opposed to two big pierces that could cut you in half.
This is why shower doors for example are tempered glass, The gravel like pieces it breaks into are pretty harmless.

However if you want the glass to stay in one piece even if broken, but want it to be clear, you need laminated glass like a cars windshield.
Lexan is tough, but soft and flexible and scratches easily. But it’s also a lot lighter than glass and some can be had that has a scratch resistant coating, but it’s still not going to last as long as glass.

Thanks for the info, laminated glass looks interesting. I think we'll probably go with acrylic or lexan (I won't reignite the debate between the two here ) due to cost and weight, but I'll look into UV protected and scratch resistant types.

[Cheechako]

I like glass. Laminated would be great in that place. I don't know if it's stronger or weaker though...? It just breaks safely. Plastic breaks readily also when impacted. Seen it racing sailboats.

[AndyEss]

Originally Posted by Han

The midships hatch on our new-to-us boat is leaking, so we've pulled it off and taken it apart (see pic below). It's a faux-butterfly hatch (i.e. it looks like a butterfly hatch, but the whole thing lifts up at the front like a regular hatch).

The glass in it is wired safety glass and we're wondering if we should replace this with something else. We plan to sail offshore and are concerned about impact (waves, winch handles, etc) cracking the glass.

What are people's thoughts on actual glass in hatches as opposed to acrylic or lexan? the span is ~1ft x 3ft, can lexan or acrylic span that distance?

Thanks!

Your "span" is 1 ft while the width is 3 ft. An adequate thickness of lexan or acrylic will easily span 12".
I'd definitely go with plastic (smoked to cut down insolation) and live with scratches.
It's not as if we have to walk far to the cockpit to have a good view of the sky.

[chowdan]

If your looking for laminated glass, contact a local glass and glazing shop. There is a franchise company called "the glass guru" who would be able to source the glass for you. If you gave them your pieces they could easily have their supplies cut to shape to be an exact match.

Realistically probably cost $200-$400 for laminated glass and would be damn near indestructible. The benefit of laminate is that if something does break it, it's not going to come out unless the framing is damaged

[Spot]

Originally Posted by chowdan

If your looking for laminated glass, contact a local glass and glazing shop. There is a franchise company called "the glass guru" who would be able to source the glass for you. If you gave them your pieces they could easily have their supplies cut to shape to be an exact match.

Realistically probably cost $200-$400 for laminated glass and would be damn near indestructible. The benefit of laminate is that if something does break it, it's not going to come out unless the framing is damaged

I had an old RV windshield redone with laminated glass, 2 flat pieces a little bigger than Han's. I want to say the glass was about 180$ USD and with labor and automotive grade caulking pushed the bill closer to 300$.

[coopec43]

I don't claim to be an expert on glass because there are so many types. But when I had small windows installed I couldn't use frame type windows so I had toughened glass which the marine window specialist said could take a blow from a sledge hammer but its Achilles heel was that if it got hit on the edge with a hard object it would shatter.

I notice Houdini use toughened glass (which is much stronger than laminated glass) This is an edited version of their spiel.

Houdini Marine Windows

Direct Bond Windows
Direct bond windows are stuck into the boat structure without a frame. To protect the bonding material from UV degradation and for aesthetic reasons the edge of the glass must be screen printed with a solid black band which is fired into the surface of the glass.

Toughened Glass
Houdini predominately use toughened glass due to the benefits of strength, scratch & UV resistance.

Plastic Glazing
Acrylics or polycarbonates are available and these are used where there is considerable curvature present or where there is a high chance of the window being subjected to a large impact from something other than water. All plastic glazing is relatively easy to scratch, polycarbonate more so than
https://www.deckhardware.com.au/hatc...arine-windows/

Should You Choose Laminated Glass Or Toughened Glass ...

Toughened glass, also known as tempered glass after its method of production, is a type of safety glass that is five times stronger than annealed and laminated glass of the same size and thickness. ... Whereas laminated glass holds in place when shattered, toughened glass breaks up into hundreds of tiny pieces.

https://www.sterlingbuild.co.uk/info...oughened-glass

[CassidyNZ]

I have 9 Lewmar deck hatches that are now a tad over 30 years old. In my ownership they have seen some tough days at sea. They are crazed, not clear anymore. They sometimes leak under duress, They are glazed with acrylic plastic 10mm thick. I can jump up and down on them and I weigh 120kgs.

If anyone has hatches like these in which they have broken the acrylic, I respectfully suggest that the cause was not sailing related. My hatches are as tough as any marine hatch I have ever seen.

[coopec43]

Originally Posted by CassidyNZ

I have 9 Lewmar deck hatches that are now a tad over 30 years old. In my ownership they have seen some tough days at sea. They are crazed, not clear anymore. They sometimes leak under duress, They are glazed with acrylic plastic 10mm thick. I can jump up and down on them and I weigh 120kgs.

I am sure there would be absolutely nothing wrong with 10mm acrylic or toughened glass. The only thing that puts me off acrylic is the crazing.

[Han]

Thanks everyone for the replies, after some calling around we're going to go with 12mm acrylic.

One more question: would you screw the acrylic down? I know there will be thermal expansion, so a slightly oversized hole might be in order. Or we just rely on the sealant (Dow 795) to hold it ...

[a64pilot]

Originally Posted by coopec43

... Whereas laminated glass holds in place when shattered, toughened glass breaks up into hundreds of tiny pieces.

https://www.sterlingbuild.co.uk/info...oughened-glass

See that’s an issue, it’s not just how tough it is, but what happens if it’s broken, if you can live with that hole the glass was in being completely open in severe weather, then tempered or toughened is fine.
Most likely thing to bust a window isn’t water impact usually, it’s a loose block or something flying around that impacts the window.

Lexan you just about can’t bust, I’ve jumped on helicopter chin bubbles that were removed trying to bust one, to have it literally turn inside out and where the stress was highest it turned white, but it didn’t break. You can shoot it and it will of course have a hole, but it won’t break.
Laminated glass is sort of in between tempered or toughened glass and Lexan, and staying in place is why it’s in automobile windshields, where every other piece of glass in a car is toughened glass, the Windshield is intended to absorb impacts from road debris etc. and still stay intact.
Lexan would likely be tougher, but a windshield wiper would ruin it pretty quick.
Same with a boat, glass has the highest UV resistance, highest weight and greatest scratch resistance.