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MidLandOne · 18-12-2007, 15:08

I agree entirely with the use of glass being the preferred option, but I should add that if laminated glass is used then it should be laminated tempered glass.

All codes/class rules I know of prohibit both plain glass and plain laminated glass for windows and portlights (don't recall for deadlights as have never used those).

Again, very similarly to the beliefs about Lexan

, many assume that laminated is stronger than plain glass whereas it is not stronger. Plain laminated glass is actually generally weaker than the same thickness of plain sheet due to part of the thickness being taken up with the plastic interlayer. Also, again contrary to popular belief, if it is stove right in into pieces then one is confronted with very sharp shards of glass.

Also, again contrary to popular belief, tempered glass is much stronger than plain laminated glass its only disadvantage being susceptability to sharp pointed impacts (see just like acrylic compared with polycarbonate

) and cost.

Generally single ply tempered glass is used for marine glass but laminated tempered is also less frequently so. Standards for marine glass exist in all western countries and when the glass is cut and tempered for the window the standard mark should be fused in one corner (similar to the way the fused standards mark is fused into the corner of automobile glass). My own yacht uses tempered glass in the hard dodger and the marks are so fused into each pane of that.

That all being said plain or plain laminated glass is sometimes found on very old small commercial vessels built when standards did not exist for marine glass. I was once involved in researching, including discussions with a major glass maker, what to do about this problem as these windows (usually front facing wheelhouse ones) were often stove in, sometimes with the loss of the vessel. But it turned out that the only reliable way to test for tempering was to break the window which was obviously counterproductive for those vessels where the glass turned out to be tempered

.

Another indicator is the air blast marks one can see on the glass through a polaroid filter (like when look at tempered auto glass with polaroid sun glasses on) but is not a reliable indicator of the extent of the tempering.

In newer small commercial vessels I know that plain glass (single sheet or laminated) sometimes gets into them as replacement glass, but that will not happen if the statutory or class inspector/surveyor checks for the fused standard mark or certification as to source as he should do but sometimes doesn't, especially if he is not told that the replacement has occurred (as he should be

).

In the end any glass can fail. Recently an around 130 foot fast ferry I had some involvement with the design of, and which was in class and used tempered glass, nose dived into a big wave at speed when it got away surfing down a wave. The big front viewing windows in the passenger compartment were stove in and water swept right through - fortunately it had no passengers on it at the time.

Again, for pleasure vessels one can in most countries use what one likes. If one is unconvinced and prefers plain glass or plain laminated, or Lexan then go to it

.

18-12-2007, 15:08	#20
MidLandOne Registered User Join Date: Sep 2007 Location: New Zealand Posts: 1,058	I agree entirely with the use of glass being the preferred option, but I should add that if laminated glass is used then it should be laminated tempered glass. All codes/class rules I know of prohibit both plain glass and plain laminated glass for windows and portlights (don't recall for deadlights as have never used those). Again, very similarly to the beliefs about Lexan , many assume that laminated is stronger than plain glass whereas it is not stronger. Plain laminated glass is actually generally weaker than the same thickness of plain sheet due to part of the thickness being taken up with the plastic interlayer. Also, again contrary to popular belief, if it is stove right in into pieces then one is confronted with very sharp shards of glass. Also, again contrary to popular belief, tempered glass is much stronger than plain laminated glass its only disadvantage being susceptability to sharp pointed impacts (see just like acrylic compared with polycarbonate ) and cost. Generally single ply tempered glass is used for marine glass but laminated tempered is also less frequently so. Standards for marine glass exist in all western countries and when the glass is cut and tempered for the window the standard mark should be fused in one corner (similar to the way the fused standards mark is fused into the corner of automobile glass). My own yacht uses tempered glass in the hard dodger and the marks are so fused into each pane of that. That all being said plain or plain laminated glass is sometimes found on very old small commercial vessels built when standards did not exist for marine glass. I was once involved in researching, including discussions with a major glass maker, what to do about this problem as these windows (usually front facing wheelhouse ones) were often stove in, sometimes with the loss of the vessel. But it turned out that the only reliable way to test for tempering was to break the window which was obviously counterproductive for those vessels where the glass turned out to be tempered . Another indicator is the air blast marks one can see on the glass through a polaroid filter (like when look at tempered auto glass with polaroid sun glasses on) but is not a reliable indicator of the extent of the tempering. In newer small commercial vessels I know that plain glass (single sheet or laminated) sometimes gets into them as replacement glass, but that will not happen if the statutory or class inspector/surveyor checks for the fused standard mark or certification as to source as he should do but sometimes doesn't, especially if he is not told that the replacement has occurred (as he should be ). In the end any glass can fail. Recently an around 130 foot fast ferry I had some involvement with the design of, and which was in class and used tempered glass, nose dived into a big wave at speed when it got away surfing down a wave. The big front viewing windows in the passenger compartment were stove in and water swept right through - fortunately it had no passengers on it at the time. Again, for pleasure vessels one can in most countries use what one likes. If one is unconvinced and prefers plain glass or plain laminated, or Lexan then go to it .