Multiple Glass Materials Use For Large Pilothouse Windows

Discussion in 'Materials' started by Bahama, Jul 22, 2010.

  1. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    I've read most every thread that I can find on window materials and they discussed pros and cons of the basic materials, but none of them spoke of combining 2 or 3 window materials together to compliment each other.

    For example, it seems like people like the strength of Lexan, but argue how quickly the protective film will errode and allow the window to fog up--my first thought to this was, "Why not install tempered glass as the first layer, and Lexan as the second?"

    Now you can use Windex all you want, and if you add a thin third layer inside the pilothouse you can clean with Windex there as well.

    I would personally rather build in strong enough glass that I don't have to worry about shutters. I'd still have them for safety reasons, but I'd rather build in my shutter design by simply having overly thick glass.

    I'd rather build a strong tempered glass face, and then an even strong Lexan glass protection behind it.

    Does anyone know of a good source to study the various properties of the common window materials? E.g. strenth figures, UV, weight, etc. Names that I keep seeing in discussions are:

    lexan, makrolon, tempered-glass, acrylic, polycarbonate, tuffak, polygal, plexiglass, Lucite, Acrylite, Perspex, and Optix. I'd like to learn about these various materials as I make my decision.


    I also plan put a strong sunroof design on the top of my pilothouse so that I can see the sails and get some extra light into the house--the glass will be tinted of course.

    I'm going to make it so that this sun roof can be removed by unscrewing some bolts should I need to hoist something large in/out of the bilge area entry below my pilothouse.

    Also, how difficult (expensive) is it to get tempered glass and Lexan that is slightly convex (curved)?

    Thanks.
     
  2. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    You may find some good engineering numbers at any of various materials websites, such as MatWeb.com. For my designs, I have relied on Bent Glass Design in Pennsylvania who are pretty expert in laminated glass. Their website is: http://www.bentglassdesign.com/

    Tempered glass is about 5 to 10 times stronger than laminated glass, and many people like the security of that amount of strength. However, when and if it does break, it shatters into tens of thousands of little shards, and there is nothing worse than having sharp little bullets embed themselves in your skin, the fine wood paneling inside the boat, and in the soft goods when the window gets hit by a big wave. Further, there is also left a big open hole where the window was so that hundreds of gallons of water can continue to flood the boat during the storm.

    Laminated glass, although much less strong, at least stays intact as a membrane after it breaks. It is extremely difficult to break all the way through, and this is why it is so desirable on boats. Even shattered, it will keep the opening closed against any ingress of water. Laminated glass to date has proven a sufficiently useful material for the vast majority of marine windows. You can learn a lot more by browsing through the Bent Glass site, and no doubt you will find others to consult.

    I hope that helps.

    Eric
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Is tempered glass the same as what they call "toughened glass"?
     
  4. Eric Sponberg
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    Eric Sponberg Senior Member

    Toughened glass is a generic term and it can apply to both heat treated glass (tempered, or rather, annealed) and chemically strengthened glass.

    Eric
     
  5. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Indeed use laminated glass, but also study the window frame. It needs to hold the glass, to keep things safe!

    The front windshield of your car is laminated glass. It will shatter, but not break, unless you hit a horse or something at high speed. The glass is glued to the body of the car, using a 2K PU glue.
    In the past front windshields were held in rubber profiles, it is still somewhat common on boats. This will not hold the glass when shattered, so is unsafe in the event of a breakage.

    One thing to mention: If you ever find yourself in a car in the water, do not try and break the front windshield, or do not try to push it out. This used to work on old cars, not on newer cars. Safe your energy rolling down a side window, break a side window (safety hammer!!!) or open the door when the car is full of water. Help your childs out, then go out yourself. Try not to panic, although when I was in that situation, the disorientation was enormous. Left became right, up became down, something simple as using your left hand to open the door became a huge brain-teaser.

    On glass again:
    The tempered glass will break in thousands of pieces, but these are not very sharp. There is some sharp shrapnel (the real small pieces might end up being formed as small daggers) but the damage to the skin is negligable. And the vacuum cleaner likes them... No real damage after a good cleaning.
     
  6. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    Thanks for the website. The reason that I like tempered glass is for the outside protection where it's hard as a rock against scratches, it can be windexed, etc. And if it broke, as you say, then the layer behind it, would not allow the glass to hit me, and it offers the stable protection that the tempered could not.

    So in a sense, my "shutter" is simply locked and loaded all the time. This is what I'm think about doing.
     
  7. Bahama
    Joined: Jun 2010
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    Location: Minneapolis

    Bahama Junior Member

    I like the idea of sandwhiching a thick layer of Lexan in between a thick layer of tempered glass on the outside, and a thin layer on the inside. This allows me to use windex (or any other cleaner that I want) without fear of fogging up the lexan, plus the tempered glass is scratch resistent, and should not break... but if it did, then the lexan will save the day... it's like carrying you shutters all the time.
     

  8. lancelots
    Joined: Feb 2009
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    lancelots New Member

    That's all a nice thought........but..............

    The different expansion rates make it impossible to laminate the different materials together or to construct a double glazed window out of different material

    Laminated Annealed glass will be just fine, if the waves are going to break that then you should be looking for your life raft and grab bag.

    If you are really worried, use laminated glass, and carry a set of bolt on thin Lexan storm boards for heavy weather 

    Of course if you want to get really special look into Dyesol’s nice solar cell glass to boost your batteries

    http://www.dyesol.com

    Kindest Regards
     
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