Thread: deck hatches
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Roger Derby
 
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Default deck hatches -- glass

Terms here in the colonies are somewhat different.

Plate glass is made by flowing the molten glass onto a (preheated) iron
slab. It is the truest, flattest, available; but hasn't been made for
decades. What one gets now is "float glass" made by flowing the glass onto
a (shallow) puddle of mercury. It's almost as flat, but not optical grade.

The heat treated and pre-stressed stuff for automobiles is "tempered" glass.
The idea is to avoid the great shards that are generated when plate glass is
broken. (My 1933 Ford had plate glass. I'm glad no one was seated in the
back seat when I rolled it.)

Anyone interested in glass should visit the Corning museum in Corning, NY.
Besides duplicates of the various presidential gifts made over the years,
they have ALL species of glass on display.

Roger

http://home.earthlink.net/~derbyrm

"Steve Lusardi" wrote in message
...
Nigel,
Houdini sells these with polycarbonate as well, but they are junk. If all
you want to do is stay tied up, they are probably OK. I dropped 1500
pounds Sterling on 2 companionway hatches a while back. These were
sliders. No matter how I installed them, they stuck and would never slide
well. They scratched and they leaked. I threw them away in the end and
designed and built my own out of stainless and armor glass.

Please do not confuse the different categories of glass. There are many
and they go by different names in different countries. Automotive glass in
the UK is called toughened glass. This glass is heat treated and cooled
quickly. This leaves the glass very hard and highly stressed. This is the
wrong stuff to use as hatches. It is also called plate glass. In the UK
the glass you need is armor glass. This glass is also heat treated but the
process used causes the glass to be stress relieved and it is delivered in
an annealed state. It is most commonly laminated with plastic in between
panes of glass for bullet proofing. It can be found up to 12mm thick. I
use it 10mm thick unlaminated. It is very scratch resistant. It doesn't
fade and you can literally beat on it with a hammer and bow it under
severe load and it doesn't break. It is the best, but it isn't cheap.

One responder mentioned Gebo Hatches. Even though they are made in France,
they are very good. I have 13 in use. They do not leak and parts are
readily available.
Steve


"Nigel" wrote in message
...
I need to buy a new deck hatch. The choice seems to be either a Lewmar 60
or a Houdini super 50 foredeck hatch. They are both the same size
(they're both the same size) The Lewmar has Perspex (12mm I think) and the
Houdini 6mm toughen glass. Houdini are a lot cheaper and I quite like the
idea of toughened glass, but is toughened glass likely to shatter into
little squares if it's walloped by a clew or similar object