Best material for windows

Discussion in 'Materials' started by mikereed100, Apr 8, 2009.

  1. mikereed100
    Joined: Jan 2007
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    mikereed100 Junior Member

    It's coming up on time to put glazing in my windows but I am having a hard time deciding what to use. I have 12 large windows, most are 60 x 60cm, the largest is 60cm x 85cm. Clarity is of utmost importance to me, as this is a pilothouse cat, so I am leaning towards tempered glass, but I worry about using glass in windows this size. Cast acrylic is an option but I worry about crazing. Polycarbonate alone is not an option as I have never seen a poly window more than a few years old that was not hopelessly clouded. A coated polycarbonate such as Lexan Margard could be an option but I wonder at the longevity (and cost!).

    I would like these windows to last up to 20 years as, once done, I never want to redo them. I guess my question is would glass be strong enough and if not, would coated polycarbonate last long enough?

  2. Landlubber
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    Landlubber Senior Member

    Laminated and tempered glass is used in most commercial applications, it is quite thick and takes plenty of poundings, it certainly would not be a problem if correctly used.
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    FAST FRED Senior Member

    Glass is the ONLY substance that you will be able to see thru in a decade.

    You MUST use plenty of water to clear the salt , as glass can be scratched.

    Happily it can be buffed back fairly clear , but may have some distortions.

    "I would like these windows to last up to 20 years as, once done, I never want to redo them."

    Great concept but most calking is long dead in half that time.

    Build everything to be easily redone.
  4. mikereed100
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    mikereed100 Junior Member

  5. peter radclyffe
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    peter radclyffe Senior Member

    In extreme weather the inside cabin pressure can be greater than outside, so fasten outside a metal or wood flange or strip, or your windows may blow out, for this reason a lot of ali hatches are not seaworthy, dont ever rely on mastic alone , the sun destroys it
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Laminated glass, just like used in car windshields. It's really the only good choice considering your requirements.

  7. Boston

    Boston Previous Member

    tempered glass is best
    but there are some important considerations

    tempered glass as has been mentioned will scratch easier than annealed
    its surface is actually made softer by the tempering process

    there are various tempering processed which produce various levels of strength so be carefull what you buy

    the edges of tempered glass are its Achilles heal, they should be floated above any hard surfaces on glass blocks ( non expanded neoprene is best )
    two blocks on each side placed a few inches in from each corner
    you want two inches of blocking per block for each twenty lbs of glass
    dont go by sq ft as the UBC states because they wrote it for 1/4 and you should go with 3/8 or better

    laminated tempered is best in high risk applications

    use a 3m blast resistant film in really really high risk applications on the interior only as it scratches easily but will prevent flying micro chips in case of a blow out

    you cant really combine the laminates between temp and not temp because the bending characteristics are so different
    which means that if you get hit by a sneaker wave the outer layer of annealed glass would likely crack although the inner temp would remain stable

    the glass should be stopped into place not relying on glue to hold it at any point

    use a steal frame
    it has the closest expansion and contraction characteristics to glass and so when the sun hits it they will move together placing the least resistance on the sealant

    use sealant not a gasket
    there is basically no gasketing system that has yet to be actually waterproof
    the rubber contracts in cold airs and will leave a gap somewhere no mater how well you do the job

    double sided sticky tape works ok
    but EDPM tape is better
    this tape should be applied to the frame in contact with the glass face and the stop
    not the glass
    its structural and wont compress to much and you can bridge over it easily with the sealant

    bridge bead the sealant

    Sikaflex is your best bet on sealant
    takes forever to dry but remains flexible and sticks to just about anything

    sill glaze is a silicone product but also works well
    you cant paint it

    you have to paint Sika

    clean the living crap out of the bare metal surfaces with denatured alcohol before you begin the process and again before you seal it

    if you have oil or grease on the metal and you dont clean it off with some kind of solvent and then clean again with the alcohol you going to have a leak

    the best stop system is one that allows easy repair
    the inside stop should be monolithic to the frame for best strength
    the outside stop should be screwed in with sufficient number of screws to counter act any possibility of a blow out by a factor of 3
    and Ive seen tornado's that will suck the bark off a tree
    so do not underestimate the power of this force

    counter sink all the screw's in the stops and use Philips head screw's
    why people even consider flat head is a mystery to me
    but they sure end up breaking a lot of glass
    square drive is ok but no reason to get silly with the screw's
    just get good solid large diameter screw's made out of the same stuff as the frame
    yes they may rust if you dont treat em right
    so treat em right

    pay em with silicone an cap em with Sika after cleaning the living crap again out of the counter sunk area so the Sika sticks
    Sika doesnt like to stick to silicone or silicone residue so clean it or die

    you need the screw's to expand and contract "breath" with the frame or they will work
    bad sitch
    that will eventually break a window as fast as anything else will
    and when you least expect it

    stops should be square section
    irregular shapes stops can place undue stresses on the glass

    screw's need to be paid in
    but not with a glue like substance or at least to strong a one
    I tend to use any old bar soap or wax when applied in wood but your in metal so you will want something that will prevent water infiltration
    for Christ sakes dont use epoxy or Sika you will never get the dam screw out
    I tend to use silicone as it will break free easily in this application

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