Best material for windows

[mikereed100]

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?

Thanks,
Mike

[Landlubber]

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.

[FAST FRED]

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.
FF

[mikereed100]

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

I suspected as much.


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.

Point well taken. The windows will be fastened to the outside of the cabin with GM VHB tape and primer then the edges sealed with polysulfide.



Thanks,
Mike

[peter radclyffe]

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

[PAR]

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

[Boston]

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

stops
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
steal
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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