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Old 29-05-2015, 11:48   #16
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Re: Portlight replacement - tempered glass or acrylic

Wow,
Really lots of good info here. to re-iterate
1. Tempered is strong, very strong, but when it breaks it breaks into tiny pieces, I believe this is actually "safety glass", I think the stuff windshields are made from is laminated glass. Also I do not think you can cut tempered glass, I think it is first cut to shape, then tempered. It will shatter if you try to cut it. I think that makes custom shapes quite expensive. Correct me if I'm wrong
2. You can waterjet at least laminated glass, the stuff like car windshields, laminated glass although not as strong does not shatter, the glue tends to hold it together.
It will over time get moisture in it from the edges and begin to look fogged, look at the edges of a really old car windshield. My portlight that the AC blows directly on is beginning to fog a little at the edge, took 27 yrs to do that though, so I'm not worried. Any glass shop can cut me an exact duplicate to replace it.
3. I too would like to replace my hatches with glass, I understand the limitations but am willing to deal with them, if anybody does this, let me know how. I currently keep them covered to keep the crazing down, but it is plastic you know.
4. Lexan is VERY impact resistant, great stuff for safety glasses etc., but it is very soft and scratches easily and I think UV degrades it pretty quick.
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Old 29-05-2015, 11:48   #17
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Re: Portlight replacement - tempered glass or acrylic

We have glass and I like it. No scratches no haze no nothing. If I were to buy / build I would try to get glass again. I believe ours are tempered.

Sunex S2 here, whatever this stands for.

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Old 29-05-2015, 12:36   #18
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Re: Portlight replacement - tempered glass or acrylic

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Originally Posted by a64pilot View Post
3. I too would like to replace my hatches with glass, I understand the limitations but am willing to deal with them, if anybody does this, let me know how. I currently keep them covered to keep the crazing down, but it is plastic you know.
Hatches should be acrylic or polycarb like all manufacturers make them. There is too much of a chance in having something drop on them. Portlights and deadlights on the cabin side are fine for tempered or laminated glass.

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Old 29-05-2015, 13:52   #19
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Re: Portlight replacement - tempered glass or acrylic

Quote:
Originally Posted by a64pilot View Post
Wow,
Really lots of good info here. to re-iterate
1. Tempered is strong, very strong, but when it breaks it breaks into tiny pieces, I believe this is actually "safety glass", I think the stuff windshields are made from is laminated glass. Also I do not think you can cut tempered glass, I think it is first cut to shape, then tempered. It will shatter if you try to cut it. I think that makes custom shapes quite expensive. Correct me if I'm wrong
2. You can waterjet at least laminated glass, the stuff like car windshields, laminated glass although not as strong does not shatter, the glue tends to hold it together.
It will over time get moisture in it from the edges and begin to look fogged, look at the edges of a really old car windshield. My portlight that the AC blows directly on is beginning to fog a little at the edge, took 27 yrs to do that though, so I'm not worried. Any glass shop can cut me an exact duplicate to replace it.
3. I too would like to replace my hatches with glass, I understand the limitations but am willing to deal with them, if anybody does this, let me know how. I currently keep them covered to keep the crazing down, but it is plastic you know.
4. Lexan is VERY impact resistant, great stuff for safety glasses etc., but it is very soft and scratches easily and I think UV degrades it pretty quick.
Hello, and good luck! My wife and I have had a steel Spray 38 since 1995. Great boat. We just replaced the 12 small Acrylic (or lexan- not sure what they were) windows with SS from New Found Metals. They look beautiful, but hold water in them after a rain, giving you a shower when you open them... C'est la vive, as they say. But what I did want to talk about was the big approximately 50" x 8" side windows. I installed tinted 3/8" thick Lexan there sometime around 1998, then took it off in 2005 when the boat was out of the water, and took all the scratches out and re-installed it in 2012 prior to launch. It is again in need of work, which we consider routine maintenance, by using the stuff that clears the Lexan on car headlights. I do not know anything about them shattering; they haven't yet, but I may take a hammer to a small portion to see if the sun really has made them brittle... I live in St Pete, FL, so the windows have had plenty of sun...
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Old 29-05-2015, 15:21   #20
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Re: Portlight replacement - tempered glass or acrylic

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Just discussed this glass vs plastic with local boatshop recently.
Over the years,they tried about every type of "window plastic"-Lexan,plexi,acrylic,etc.
Aside from expected scratchability,they found they all degraded by UV over time-discoloring,cloudiness,etc.
But the scariest finding was,when replacing windows they had installed 5-10 yrs previous,they had become "brittle" to the point that they would crumble or ,if dropped,or otherwise bumped sharply,would split or shatter.
The original plasticity had gone,& they had become hard & brittle.
This shop uses only glass now.They have a local auto glass shop cut & come install it on site,& are very pleased with results.Never thought to ask if they used "tempered",or auto windshield "safety" glass,but I could find out.
Personally,and aquaintances,have had various glass items-table tops,etc-made by auto glass shops at very reasonable cost- FYI

Grand Manan Boats (no affiliation) build mostly commercial fishing boats 30-60ft-which are used year round in N.Atlantic conditions (rough weather),though they have done some good yacht work also.

Just passing this along. / Len
Further info-- I just called GM Boats. They use tempered glass where it might be struck by flying gear,etc,because it is stronger-but it breaks in shards ie: can cut you.
They use windshield safety glass in any windows where there would be danger to crew from flying glass,as it cracks or at worst,crumbles into relatively harmless pieces.
Never thought to ask how tempered is cut or it's cost re shatterproof windshield glass.

Our local ferries use very thick glass (1/2 - 1" ). Don't know what type it is.

I get the impression that auto windshield safety glass would be best all around solution for boat "windows". Strong enough to take a pretty hard sea hit,inexpensive,best vis for longest time & crew safe if broken.

Hatches & other horizontal "lites" should probably be tempered glass or "plastic",as both are stronger if hit by flying objects.
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Old 31-05-2015, 05:14   #21
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Re: Portlight replacement - tempered glass or acrylic

Read all the comments and hears something to note.
I would go the acrylic route but alot depends on size of windows as I wouldnt want acrylic in large windows .
Make sure you request "cast" acrylic - not the run of mill stuff.
Also better to get the supplier to drill any holes and any countersinking if required .
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Old 31-05-2015, 08:54   #22
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Re: Portlight replacement - tempered glass or acrylic

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Read all the comments and hears something to note.
I would go the acrylic route but alot depends on size of windows as I wouldnt want acrylic in large windows .
Make sure you request "cast" acrylic - not the run of mill stuff.
Also better to get the supplier to drill any holes and any countersinking if required .
I haven't had a problem drilling acrylic/Lexon. You just need to use low RPMs so the bit doesn't get hot and make goo of the job.
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Old 31-05-2015, 10:47   #23
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Re: Portlight replacement - tempered glass or acrylic

Glass is much better than plastics for boat glazing applications.

Ordinary float glass is not suitable, so there are two broad options.

1. Toughened glass.
This is generally the strongest option by a slight margin. It will remain clear even if the edges are exposed to water. It almost always breaks into blunt coarse fragments that are not likely to injure. The exception is when broken by small high speed particles. Here they can shatter into sharp splinters. This is very unlikely on a boat.

2. Laminated glass.
The main advantage is that this will remain intact when broken. While it may not be completely waterproof when broken it will often not let in large volumes of water even when broken (providing, and this is a big "if" the frame continues to retain the glazing). The drawback is that under normal use water can enter from the edge and reduce the transparency.

The ideal answer is conservatively specified toughened glass with a storm shutter available to use in the unlikely event of breakage.

Why are so few boat hatches available in glass?
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Old 31-05-2015, 11:06   #24
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Re: Portlight replacement - tempered glass or acrylic

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I haven't had a problem drilling acrylic/Lexon. You just need to use low RPMs so the bit doesn't get hot and make goo of the job.
You have never broken an $8,000 acrylic windshield?
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Old 31-05-2015, 11:14   #25
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Re: Portlight replacement - tempered glass or acrylic

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Originally Posted by noelex 77 View Post
Glass is much better than plastics for boat glazing applications.

Ordinary float glass is not suitable, so there are two broad options.

1. Toughened glass.
This is generally the strongest option by a slight margin. It will remain clear even if the edges are exposed to water. It almost always breaks into blunt coarse fragments that are not likely to injure. The exception is when broken by small high speed particles. Here they can shatter into sharp splinters. This is very unlikely on a boat.

2. Laminated glass.
The main advantage is that this will remain intact when broken. While it may not be completely waterproof when broken it will often not let in large volumes of water even when broken (providing, and this is a big "if" the frame continues to retain the glazing). The drawback is that under normal use water can enter from the edge and reduce the transparency.

The ideal answer is conservatively specified toughened glass with a storm shutter available to use in the unlikely event of breakage.

Why are so few boat hatches available in glass?
Good post. When toughened "tempered" glass goes you will never find all the chards. I'd opt for safety glass. I have seen it fog on the edges from water entering the laminate, but seldom unless water can lay at the edge.
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Old 31-05-2015, 11:18   #26
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Re: Portlight replacement - tempered glass or acrylic

Your plastic shop may be oversimplifying a bit. There are literally DOZENS of grades and types of polycarbonate and acrylic, and the ones they keep in stock and make the most money on, will probably not be the expensive ones with high UV and abrasion (salt) resistance. (Or any other special grades and qualities.) But you can look online, send an email inquiry to a couple of different makers, not just retailers, and see what is out there.


There are also plenty of plastics suppliers who will make up laminated "hurricane glass" for you, tempered glass to resist abrasions on the outside, inner layer of polycarbonate for strength, flawlessly laminated together and cut to size. That won't be the corner "towel holder and candy dish" guys.(G)


Having said that...nothing will stay as clear and clean as real glass. The question is whether that's your priority. And how the budget gets to vote.


I had a car windshield crack because of stress from a rust spot in the frame, apparently unpainted or unprimed during a replacement several years before. So your suspicion about stress from a growing rust canker? Certainly could be the problem. "Good" glazing should be installed with enough gasketing to allow all the movement it needs, but also, a good enough seal to prevent leaks. Lots of stuff just isn't done right because, after all, who looks under the trim on a new boat to see how well the ports were glazed?
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