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Old 19-02-2016, 10:07   #76
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Re: Following Seas and Cockpit Height

I read here, over and over, about "sliding glass doors" and am curious if anyone actually has a "glass" door? Mine is just under 3/4" thick poly carbonate I've seen some acrylic of the same thickness on other cats. Is there any of the muti hull owners here who have a glass door? Have any of the multi hull owners here ever seen their door, heard of any door or ever came close to their door exploding from a following wave?
As this is on the multihull post and to keep the previous argumentative tone of the post at bay I would request input from multi owners not opinions of those without any knowledge or ownership of a cat.
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Old 19-02-2016, 10:48   #77
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Re: Following Seas and Cockpit Height

Yes, glass is often used (Model 1730 - 1736, Sliding, Top-Hung, Single Leaf & Bi-Parting Automatic Doors. Freeman Marine Equipment, Inc. provides the finest marine and specialty closures available. Custom fabricated doors, hatches, portlights and windows. just for example). Polycarbonate is lighter and resists point loading better, but glass lasts longer and is stiffer (thus resists area loading better). Usually acrylic is viewed as a better material than polycarbonate - as it is stiffer and longer lasting.

Also, with either, aluminum frames and channels might well be weaker that the actual glass/plastic.

It is certainly possible to enginner all this to withstand any given wave. There are specific engineering guidelines in most class codes. But there are also occasional rare waves that will break most things - very strong ship Windows 100' above sea level get broken occasionally.

And no, damage does not happen very often. You need to be in true breaking waves, which are very rare to start with, and ever rarer with this sort of boat (eg there are not many people cruising the southern ocean with "glass walls").

As to breakages - I know of two second hand (when we were in chile). In neither case did the "glass" shatter. In both cases the structure supporting the glass deformed. My understanding is that similar happened to the entire saloon window structure on the alpha 42 - it deformed due to wave impact, casing massive leaks, which shorted out the entire boat.

And remember it is not only waves that can break things - whitness the rainmaker incident. Where the boat was basically entirely shorted out (and down flooded) when a broken rig cracked the saloon Windows.

Look . . . I think most of us agree this is a low risk, especially given how most of these boats are used. But denying it is a risk is just denying engineering. But it is clearly a risk many are willing to take given the great benefits. I personally just think you need to have thought thru what will happen if the bad happens, and minimize the consequences (perhaps make your main/core systems more water proof even if inside the saloon) - that's just seaman like with any risk.
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Old 19-02-2016, 11:10   #78
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Re: Following Seas and Cockpit Height

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Yes, glass is often used (Model 1730 - 1736, Sliding, Top-Hung, Single Leaf & Bi-Parting Automatic Doors. Freeman Marine Equipment, Inc. provides the finest marine and specialty closures available. Custom fabricated doors, hatches, portlights and windows. just for example). Polycarbonate is lighter and resists point loading better, but glass lasts longer and is stiffer (thus resists area loading better). Usually acrylic is viewed as a better material than polycarbonate - as it is stiffer and longer lasting.

Also, with either, aluminum frames and channels might well be weaker that the actual glass/plastic.

It is certainly possible to enginner all this to withstand any given wave. There are specific engineering guidelines in most class codes. But there are also occasional rare waves that will break most things - very strong ship Windows 100' above sea level get broken occasionally.

And no, damage does not happen very often. You need to be in true breaking waves, which are very rare to start with, and ever rarer with this sort of boat (eg there are not many people cruising the southern ocean with "glass walls").

As to breakages - I know of two second hand (when we were in chile). In neither case did the "glass" shatter. In both cases the structure supporting the glass deformed. My understanding is that similar happened to the entire saloon window structure on the alpha 42 - it deformed due to wave impact, casing massive leaks, which shorted out the entire boat.

And no remember it is not only waves that can break things - whitness the rainmaker incident. Where the boat was basically entirely shorted out when a broken rig cracked the saloon Windows.

Look . . . I think most of us agree this is a low risk, especially given how most of these boats are used. But it is a risk. But a risk many are willing to take given the great benefits.
Thanks for your input,

I spoke with Paul at Freeman and he shared they do sell glass when naval architecture and replacement windows are required. He shared that in aft facing sliding doors on catamarans Lexan and Poly carbonate are used with less chance of breakage. He declined any knowledge of catamaran doors exploding from following waves. Were the two you "heard of" in Chile catamaran sliding doors?
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Old 19-02-2016, 11:15   #79
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Re: Following Seas and Cockpit Height

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Were the two you "heard of" in Chile catamaran sliding doors?
Don't remember. I saw the boats in question, talked with the skippers. But it was a while ago now and at the time I was not really interested in the details. I was dealing with my own issues and we were just commiserating together.
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Old 19-02-2016, 12:30   #80
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Re: Following Seas and Cockpit Height

I guess I think it is probably time to hang up this thread. Not sure even what the debate is about any more.

I believe we agree it would take pretty serious breaking wave situation to damage a forward cockpit 'glass wall'. And factually those situations are quite rare. I doubt many here have actually seen them.

And we should agree that it is possible to break a glass wall. That's sort of a tautology - it is in fact possible to break almost anything. To be a bit more specific, we will agree that glass walls can be engineered as strongly as desired. But that a 'glass wall' is fundamentally more challenging to build equal strength than a continuous fiberglass wall. And that typically they are not (yes, that is a generalization) - with quite a wide range between the strongest and the weakest.

It is possible for a glass wall to get hit by water - especially if there is operator error, but even if there is not in the 80's breaking wave Sydney to Hobart sort of conditions. But again, it is extremely low probability.

I believe if you were to design a cat with an 'any ocean, any season' objective you probably would not put on a glass wall, because it would be very heavy if engineered to the proper strength. And below that you have all degrees of design objectives and engineering of the glass vs structure (span between structure and thicknesses and materials and such), which as I have mentioned twice are pretty well discussed in class scantlings.

And finally, we can agree that the glass walls are very nice for an 'on the water living space'.
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Old 22-02-2016, 09:20   #81
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Re: Following Seas and Cock Pit Height

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Irritating? Many things are irritating, including snarky comments...but why take the bait?

I was, actually, trying to lighten things up a bit. But you gotta admit, some Cat People are quite defensive, and easily baited.

Disclaimer: I have no negative opinions regarding cats or large sliding doors on oceangoing vessels.
And some cat people drink beer and eat pizza...



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Old 22-02-2016, 12:39   #82
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Re: Following Seas and Cock Pit Height

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And some cat people drink beer and eat pizza...



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Of course they do...fun things like beer and pizza relieve the pressure of always being in defensive mode.
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Old 29-02-2016, 00:11   #83
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Re: Following Seas and Cockpit Height

ha ! another cat mono thing.

my experience so far the worst was in pyramid seas. Although motoring, boat managed to stop in certain combination of pyramid waves and water came to cockpit and there was evidence of water coming thru air supply tubes. No height of bridgedeck would help in this scenario.

Long aft section would likely help:
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Old 29-02-2016, 10:03   #84
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Re: Following Seas and Cockpit Height

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ha ! another cat mono thing.

my experience so far the worst was in pyramid seas. Although motoring, boat managed to stop in certain combination of pyramid waves and water came to cockpit and there was evidence of water coming thru air supply tubes. No height of bridgedeck would help in this scenario.

Long aft section would likely help:
You raise an excellent point, and that is that in certain combinations of sea/wind/current ANY small vessel will be at risk.

My question to you is this: having had the experience you describe, do you feel that light displacement [ability to accelerate] gave you any advantage? I have no experience with light displacement boats, and this seems to be a topic of great controversy, so I am curious.
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Old 29-02-2016, 22:41   #85
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Re: Following Seas and Cockpit Height

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You raise an excellent point, and that is that in certain combinations of sea/wind/current ANY small vessel will be at risk.

My question to you is this: having had the experience you describe, do you feel that light displacement [ability to accelerate] gave you any advantage? I have no experience with light displacement boats, and this seems to be a topic of great controversy, so I am curious.
in confused seas nothing works, except AVOID. the only important thing is structural strength if you there. 'lighter' translated = less structural strength. seen some mono guys that thought differently and i am sure highly of mono abilities, like many here, but came back without mast Wrong attitude kills.

Waves just come up or holes just form out of nowhere and no acceleration helps.

This is my limited experience with this type of sea so far.

Avoid wind against current and certain sections of storms where confused seas form.
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Old 01-03-2016, 16:50   #86
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Re: Following Seas and Cockpit Height

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'lighter' translated = less structural strength.

No, not always. You can build a very heavy boat using inferior materials and techniques, and end up with less strength than a much lighter boat.

Also weight feeds on itself. Heavier boats generate higher loads, which need greater strength.....
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Old 01-03-2016, 17:06   #87
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Re: Following Seas and Cockpit Height

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No, not always. You can build a very heavy boat using inferior materials and techniques, and end up with less strength than a much lighter boat.

Also weight feeds on itself. Heavier boats generate higher loads, which need greater strength.....
To say that light weight must equal less strength is not true, as you say. If it is safe to assume [in general] that most cats are fairly light displacement, then would it be safe to also assume that lighter weight will have less resistance to being struck by a large wave? As in a lighter boat will not just sit there and absorb the force of the wave as a heavier boat will do?

I ask the question specifically regarding cats for two reasons, I am curious about that type of boat and you are a person that [apparently] has a lot of experience with them...
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Old 01-03-2016, 19:02   #88
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Re: Following Seas and Cockpit Height

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To say that light weight must equal less strength is not true, as you say. If it is safe to assume [in general] that most cats are fairly light displacement, then would it be safe to also assume that lighter weight will have less resistance to being struck by a large wave? As in a lighter boat will not just sit there and absorb the force of the wave as a heavier boat will do?
I don't think it's safe to assume most cat's are light displacement these days. Some are remarkably, almost incredibly, heavy.
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Old 01-03-2016, 19:21   #89
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Re: Following Seas and Cockpit Height

It's good to have "dogged" doors with water tight seals to keep out water.

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Old 01-03-2016, 22:43   #90
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Re: Following Seas and Cockpit Height

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No, not always. You can build a very heavy boat using inferior materials and techniques, and end up with less strength than a much lighter boat.

Also weight feeds on itself. Heavier boats generate higher loads, which need greater strength.....
not always of course, however I meant to say to check that this is not the case each boat individually.

Possibility is there to sell boat as 'fast', as an excuse to save on material and time. This seem to be more common today in mono world.
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