View Full Version : glass in deck "butterfly" hatches

08-28-2008, 11:57 AM
We have cloudy lexan that was put in our 3 overhead "butterfly" opening deck hatches. We're looking at replacing it with clear, laminated, glass. The rabbet is 3/8" total depth (assumed for both glass and glazing) and there's no indicator of battens being nailed or screwed over the edges of the glass allowing full 3/8" thickness. Thus, we're thinking it probably had 1/4" glass originally. The six openings are about 9.5" x 24.5". Protecting the openings are the standard bronze/brass bars (3/8"? diameter) with about 2" spacing. The bars are sitting in our storage unit so I can't measure :rolleyes:.

Is 1/4" glass "normal" in this sort of application? We're contemplating going up to 3/8" but then we'll be dealing with probably changing out the little wood "holders" that hold the bars in place so that we can add rabbeted battens over the glass as the glass will sit flush (unbedded) or above (bedded) the rabbeted teak hatch lids.

Appreciate your experiences. Thanks :)

08-28-2008, 04:05 PM
I've had those hatches with both clear and cloudy glass in them. I'll take the cloudy anytime, it keeps prying eyes out of your private spaces. Think about it!

08-28-2008, 09:48 PM
I've had those hatches with both clear and cloudy glass in them. I'll take the cloudy anytime, it keeps prying eyes out of your private spaces. Think about it!

I should be more "clear" in my description :)

Cloudy lexan from sun degradation not "frosted".

Ron Williamson
08-29-2008, 04:59 AM
We call those glass holder strips, "stops".
IMHO, glass well-bedded and smooth would be better than having a stop that would hold water.

The Bigfella
08-29-2008, 05:15 AM
I've used hardened glass in all my windows and on the hatches. The hatches I made with 1/2" toughened glass.

08-29-2008, 11:21 AM
I used lexan on the inside and bonded with epoxy (like optically perfect for prescription diving masks) and automotive glass outside.....

08-29-2008, 01:46 PM
My impulse is to say 3/8 Lexan with thin glass over it for abrasion resistance.

08-29-2008, 02:05 PM
Hey all,

The rabbet is 3/8" thick (max) so that's all I've got to work with. Bedded properly it seems I can only do something that is 1/4" but I can add surface mounted stops/battens with a rabbet in them if we're talking thicker than 1/4"...

I'm very reluctant to use anything which will have long term UV degradation. According to the folks at San Diego Plastics, lexan will start yellowing anywhere from 3 to 10 years from installation. That 3 years is awful short.

I'm also very reluctant to use anything that will scratch.

I don't trust us being able to bond lexan (inside) to glass (outside) w/o something "showing" or moisture getting in after a while.

As such, we've pretty much settled on "glass" rather than plastic.

Its just how thick that glass should be--and what type of glass.

Terminology gets mixed up here.

Laminated glass is regular (annealed) glass laminated together so that when it breaks it holds together. Windshields are laminated glass. You can still see through the broken glass and it doesn't fall out in a million little pieces.

Tempered glass is cut to size, then heat treated. What you get is something that is stronger than regular glass (by 4-5 times according to some references) and breaks into a million little pieces that aren't "sharp" edged like regular glass would be. This type of glass is used in automotive SIDE windows because it allows egress from the vehicle. It is not laminated.

When people talk about "safety glass" or "automotive glass" I'm not sure which glass they're talking about. Overhead skylights in buildings are typically laminated glass though sometimes they are are layer of tempered glass, then air, then laminated glass on the bottom (to protect the folks below from falling bits of the tempered glass if it should break). Plate glass windows (store displays) are typically tempered glass that will shatter and send little bits everywhere.

I'm told by the local glass shops here that if I laminate tempered glass it will still break into a bunch of little pieces and fall--the lamination layer won't keep that from happening with tempered glass. Thus, they don't recommend laminating tempered glass--even though they offer it...???

I don't want little bits everywhere in my bilge :), I'd like the extra strength of tempered glass but at the moment am tending towards laminated glass. If we go with laminated glass, though, we'd have to go thicker to get even half the strength of tempered glass.

decisions decisions...

Andrew Craig-Bennett
08-29-2008, 05:20 PM
Been there, done that thing, but being divided by a common language I had to work out that a butterfly hatch is a skylight!

I removed crazed Lexan (could not have been original - boat is 71 years old!) and fitted 12mm toughened glass.

The important point is that the glass should be slightly proud of the rebate; that way, water will not lie in the corner between glass and surround and work its way through...

Edited to add - don't ask me how I know that!

08-29-2008, 06:28 PM
as I previously posted....I used automotive safety glass which is about 1/4 inch thick, and then used the epoxy and laminated directly to 1/4 inch lexan.....you lay the glass or lexan on a flat surface with a piece of waxed paper beneath it...liberally apply the epoxy (available from optometrists that do prescription diving masks, having the glass cut to the exact size and the edges smoothed, place it in the epoxy, another piece of waxed paper, cover with folded old army blanket, and add a couple of cement blocks....gently...wait overnight....install with glass out....add a small bead of rtv or similar to the raised edge, smooth with popsicle stick......add protective brass/bronze railings.....clean as a whistle over 15 years later....

The Bigfella
08-29-2008, 07:19 PM
One of the windows on Grantala had been replaced with laminated glass - the rest were standard 70 year old glass. Guess which was the only one that broke (easily) as we were removing the windows.

I'd be using 10mm (3/8") tempered glass. Make sure that the template you give them is good (mine were all made from 1/8" thin mdf). You need clearance - and if you don't have it, you can't cut the tempered glass.