Glass windows?

[Epicurean]

I need to replace curved windows on my aluminium catamaran. The acrylic is 11 years old and it has a lot of microcrazing that makes them pretty opaque. It also has some other scratches and distortions. I'm thinking of going to glass and am interested in experiences others may have had with it, in outcomes, and having it fabricated. I am aware that glass can shatter, as can acrylic under different conditions. Also, glass is heavier and has different thermal expansion properties. I also don't think polycarbonate is what I'm looking for. I'm tired of boats with windows with poor optical properties. Then, too, there are different types of glass; tempered, toughened and laminated.
Of course, a big question is who can do it?

[Matt Johnson]

Originally Posted by Epicurean

I need to replace curved windows on my aluminium catamaran. The acrylic is 11 years old and it has a lot of microcrazing that makes them pretty opaque. It also has some other scratches and distortions. I'm thinking of going to glass and am interested in experiences others may have had with it, in outcomes, and having it fabricated. I am aware that glass can shatter, as can acrylic under different conditions. Also, glass is heavier and has different thermal expansion properties. I also don't think polycarbonate is what I'm looking for. I'm tired of boats with windows with poor optical properties. Then, too, there are different types of glass; tempered, toughened and laminated.

Of course, a big question is who can do it?

We looked into this too. While the thickness of glass can be reduced one step from acrylic (10mm to 8mm in our case), the weight more than doubles for tempered glass.

The other benefit you do get besides clarity is thermal expansion. Glass expands a lot less than acrylic and makes reliably sealing them much easier.

We can't take the weight, so aren't going this route. But it's something I would do if I could.

[CarlF]

If you can stand the weight and cost, glass is far better than acrylic. No superyacht would have plastic windows.

Steve Dashew used glass in his ocean going powerboats. Here’s a discussion

https://setsail.com/glazing/#more-18170

[clockwork orange]

There is no doubt that glass is the superior material for windows on anything. I replaced two windows on my Gemini cat with tempered glass but these are flat ones that drop down into the wall in front of the helm. I agonized over the weight difference and it was indeed twice the weight for the same thickness but i would prefer to save weight elsewhere and i do. There are companies in the US that can do curved glass windows so i would expect there to be down under as well.

[Epicurean]

Originally Posted by Matt Johnson

We looked into this too. While the thickness of glass can be reduced one step from acrylic (10mm to 8mm in our case), the weight more than doubles for tempered glass.

The other benefit you do get besides clarity is thermal expansion. Glass expands a lot less than acrylic and makes reliably sealing them much easier.

We can't take the weight, so aren't going this route. But it's something I would do if I could.

I'm not sure I want the weight either and I have a performance , i.e., lightweight catamaran. I'd like to be able to see. Acrylic windows just seem to loose clarity fast. Also, they often leak because of the expansion problem.

[Epicurean]

Originally Posted by clockwork orange

There is no doubt that glass is the superior material for windows on anything. I replaced two windows on my Gemini cat with tempered glass but these are flat ones that drop down into the wall in front of the helm. I agonized over the weight difference and it was indeed twice the weight for the same thickness but i would prefer to save weight elsewhere and i do. There are companies in the US that can do curved glass windows so i would expect there to be down under as well.

I'll be heading into the Caribbean and could go to the east coast, maybe Europe to get this done. I met a girl who made a mold and had hers cast and tempered. Flat would be easier. I don't have flat. It'd be interesting to hear from someone who did curved.

[Epicurean]

Originally Posted by CarlF

If you can stand the weight and cost, glass is far better than acrylic. No superyacht would have plastic windows.

Steve Dashew used glass in his ocean going powerboats. Here’s a discussion

https://setsail.com/glazing/#more-18170

Thanks. I read that and he had a lot of windows on his boat and went over-thickness.

[Matt Johnson]

Originally Posted by Epicurean

I'm not sure I want the weight either and I have a performance , i.e., lightweight catamaran. I'd like to be able to see. Acrylic windows just seem to loose clarity fast. Also, they often leak because of the expansion problem.

Didn't see what you sail when on the app. The Mumby doesn't have very large windows. I'd be comfortable going the glass route on that boat and lighter something elsewhere.

[clockwork orange]

My son and his girlfriend replaced all the windows on their Simpson 42 cat with tempered glass when refitting, the originals were also glass and flat so not difficult. They did save weight elsewhere though such as replacing diesels with outboards, foam cored cabinet doors and honeycomb cored table etc. We all have to evaluate where we take our weight savings because ultimately, we have to accept weight in things like solar and dinghy etc. I can't remember the name of the company that makes the curved glass in the US. I'm sure there is more than one but there has been one place that has advertised for years in Pro Boat magazine, Just found it, Desman Glass

[mvweebles]

The crazing of your current Plexiglas at just 11 years is likely due to it not being properly formed and curved in the first place. It must be heated and bent or the stresses will eventually show. My 1970 Willard 36 has acrylic corner windows that curve 90 degrees over 4-feet and were pretty clear when I replaced them last year - over 50 years old.

Please update on cost for curved tempered custom glass. Cost of building a proper mold will need to be considered.

[Epicurean]

Originally Posted by mvweebles

The crazing of your current Plexiglas at just 11 years is likely due to it not being properly formed and curved in the first place. It must be heated and bent or the stresses will eventually show. My 1970 Willard 36 has acrylic corner windows that curve 90 degrees over 4-feet and were pretty clear when I replaced them last year - over 50 years old.

Please update on cost for curved tempered custom glass. Cost of building a proper mold will need to be considered.

Attachment 269415

Yes, you're right about figuring in the cost - or effort of building - the mold for the glass. 90 deg over 4 ft is pretty sharp. I don't know how acrylic windows are formed but I assume to avoid crazing they need top be heated and over a mold to maintain optical properties. You're probably right about the crazing coming from improper initial forming. Eventually I'll have to find out from someone who's seen this done or a professional.

[Epicurean]

Originally Posted by Matt Johnson

Didn't see what you sail when on the app. The Mumby doesn't have very large windows. I'd be comfortable going the glass route on that boat and lighter something elsewhere.

I'm not at the boat right now so I can't measure the total area, but I don't think the extra weight, even at double, is a deal breaker. A clean bottom is more important.
I see you're building. Fun! I'm not familiar with the Max 44 but it looks like it will be very fast. You're right about more window area. I actually installed inserts to block out the light and heat from my windows. There was phifertex screening on the outside which leaves a pattern on the surface. Most UV/IR screens are made for glass.
With these boats being weight conscious it's not like there's surplus weight that hasn't been taken off already. Carbon fibre tooth brush handles? Anyway, when I want to look out I want good optical quality.

[Epicurean]

Originally Posted by clockwork orange

My son and his girlfriend replaced all the windows on their Simpson 42 cat with tempered glass when refitting, the originals were also glass and flat so not difficult. They did save weight elsewhere though such as replacing diesels with outboards, foam cored cabinet doors and honeycomb cored table etc. We all have to evaluate where we take our weight savings because ultimately, we have to accept weight in things like solar and dinghy etc. I can't remember the name of the company that makes the curved glass in the US. I'm sure there is more than one but there has been one place that has advertised for years in Pro Boat magazine, Just found it, Desman Glass

Thanks for the tip about Desman. They are at least someone knowledgeable to talk to. I don't have any doors. I have to have diesels, although I can sail with less fuel, but that has risks. Extra crew are the easiest weight to avoid. One person with minimal gear is 200 pounds.

[mvweebles]

Originally Posted by Epicurean

Yes, you're right about figuring in the cost - or effort of building - the mold for the glass. 90 deg over 4 ft is pretty sharp. I don't know how acrylic windows are formed but I assume to avoid crazing they need top be heated and over a mold to maintain optical properties. You're probably right about the crazing coming from improper initial forming. Eventually I'll have to find out from someone who's seen this done or a professional.

Ideally, a mold is built and the acrylic is heated in an oven until soft. It is then bent over the mold until set. It will shrink a bit - guess 3% so form it large and trim after

Alternatively, for smaller pieces in low-labor cost locations, it is formed in-place with a few guys with heat guns inside and outside. Results are a bit variable (especially with compound curves) but works okay with experienced labor.

Please update if you get a quote for tempered glass. I'd be very curious to know.

[Epicurean]

Originally Posted by mvweebles

Ideally, a mold is built and the acrylic is heated in an oven until soft. It is then bent over the mold until set. It will shrink a bit - guess 3% so form it large and trim after

Alternatively, for smaller pieces in low-labor cost locations, it is formed in-place with a few guys with heat guns inside and outside. Results are a bit variable (especially with compound curves) but works okay with experienced labor.

Please update if you get a quote for tempered glass. I'd be very curious to know.

The boat's not in a place where I can get glass molded, I suspect. It will have to wait until I get close to the US. I will update after I speak with somebody about a general idea of cost.
I'm fairly sure you're right; the way to maintain optical properties of acrylic involves uniform gradual heat-bending over a mold. Good results using heat guns must be serendipitous. It's expensive to build molds.