Pilot house windows, how thick, what type glass ?

[kulas44]

The boat is a 54 foot Krogen trawler, fiber@#ass hull with wood structure. Kind of a passagemaker type with forward pilothouse. Three large forward windows about 32" x 32" and several smaller side windows. I'm thinking 1/2 inch tempered up front and 3/8's in the sides, and maybe 3/8 down in the 8 saloon windows. Weight up high is always a concern, and thick glass is heavy. I am more concerned about surviving a knockdown or big breaking waves than any other factors, but don't want to go way overkill on this. Any thoughts ? thanks

[P.L.Lenihan]

Perhaps the folks over at Krogen could provide you with the details you require?
Beyond that, I have read elsewhere that applying a framed metal screen on the outside of your windows,about one inch off the surface, will help considerably in "breaking" or frustrating the full force of direct wave impact on a windshield. May be worth looking into if thick glass is deamed too heavy.

Peter

[py]

I had a 52' boat with a wheelhouse with fairly large windows front and sides. maybe 3' by 2', thereabouts. 3 across the front, 2 on each side. They were laminated safety glass, I think about 1/2 inch thick. My experience generally is that you get some pretty strong blasts of water side on, moreso than front on. -although my wheelhouse was about 2/3 aft and on a sail boat. We'd occasionally get a bit of green water up over the bow, but it was fairly well broken up by the time it got to the wheelhouse. But a big wave side on can go splat right against the side of the house with quite a lot of force. So I'd counsel against lighter glass on the sides.

[The Bigfella]

When I pulled all the windows out of Grantala during the rebuild, one was laminated - it was the only one that broke during removal. I also managed to break a laminated car windscreen the other day whilst removing it. They break much, much easier than solid glass. No way would I put it in my boat. I have toughened class in all windows, mostly 10mm, but a couple of 12mm up front.

[Tylerdurden]

Lexan is trick stuff and is made with new coatings that are highly scratch resistant.
Bit pricey though but you can work it yourself.

http://www.modernplastics.com/june05/wdlexan.html

[Ron Williamson]

Tempered glass is very much stronger than regular glass(5x,IIRC)and laminated glass is just regular glass with the plastic laminate in between.

If you want strong and shatter proof you might look into the plastic film that is used on windows for seismic retrofits and apply it onto a tempered pane.
R

[Ian McColgin]

Most of our winter fishing fleet use Lexan - maybe 1/2" or so.

[donald branscom]

A wave breaking over the bow of a boat can exert 77,000 lbs., per square ft.

Lexan is MUCH stronger than glass. It is poly carbonate.
You have to be careful when cleaning it not to scratch it.

I took a large hammer once and tried to break a piece of Lexan 18 inches square and I hit it many times. Finally the hammer bounced back so hard it almost hit me in the head.

If i was going to be in the ocean, Lexan is the ONLY thing i would consider. And no plexiglass either, although it is stronger than glass but it can shatter.

[Ian McColgin]

If you really want the clarity of glass for day to day use, go ahead with regular auto glass and have Lexan shutters to bolt over when going off-shore.

You might save weight by having non-essential windows shuttered with suitable plywood.

Which reminds me, coming back to America a few days before I was to DF on WABC and heard "Light My Fire", we'd been through a sloggy few days and were a bit punchy. I was going off-watch at 0800 and the doctor was coming on. Manila Mike's younger cousing, Dacron Dan, was at the helm as Benny (the Bendix) had packed in and we were both looking at the dull grey in the saloon windows muttering to each other about the air being battleship grey. Couldn't even see the life lines. Wait. We were looking at the painted inside of the storm shutters.

We looked out the companion and, besides that we could see as far as the lifelines, it was about the same color grey.

[kulas44]

My reasoning for thinner glass in the side windows was that they are much smaller and could more easily handle a large wave. I do agree that a beam to "squash" would be much more damaging than a headon wave, especially in this boat, it has a large high bow and can really bust a wave. Then again, if I get green water on the pilothouse windows, from abeam, the salon windows have probably been underwater already. 1/2 inch would probably be better suited down there. Also the weight factor would not be as great, due to being closer to the centerline. I like the thought of lexan, just don't like the "scratchability" of it.

[Uncle Duke]

Donald notes:
A wave breaking over the bow of a boat can exert 77,000 lbs., per square ft.
Donald - can you educate me on how this is calculated or where? Not arguing, just curious - 77,000 (534 psi) is about twice what a 3" firehose needs in order to shoot water 30 stories straight up, which is my only frame of reference. (Unless my calculations are screwy, which is certainly possible!)
Thanks.

[paladin]

If you have the wherewithall.....a piece of tempered glass epoxy laminated to the lexan gives scratch resistance and toughness....use the epoxy formulated for attaching prescription ground lenses to scuba masks....

[Tylerdurden]

My reasoning for thinner glass in the side windows was that they are much smaller and could more easily handle a large wave. I do agree that a beam to "squash" would be much more damaging than a headon wave, especially in this boat, it has a large high bow and can really bust a wave. Then again, if I get green water on the pilothouse windows, from abeam, the salon windows have probably been underwater already. 1/2 inch would probably be better suited down there. Also the weight factor would not be as great, due to being closer to the centerline. I like the thought of lexan, just don't like the "scratchability" of it.

That link I posted is for the lexan with scratch resistant coatings.
Stuff is great and safe too.

[JimD]

If you have the wherewithall.....a piece of tempered glass epoxy laminated to the lexan gives scratch resistance and toughness....use the epoxy formulated for attaching prescription ground lenses to scuba masks....

That is a cool idea! Yet another use for epoxy.

[paladin]

The epoxy in question costs a bit more but is optically transparent.