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Old 17-10-2020, 09:59   #1
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What, really, is a rogue wave?

Is this a fair assumption? A rogue wave is not defined by a certain height, but by how different it is from other waves the boat is sailing through. I imagine a boat all adjusted for sailing through certain conditions, and suddenly a wave bigger enough to upset that boat comes along.

But in other conditions if all the waves were that big, it would not be a rogue, and the skipper would have the boat set for those conditions and the same wave would not upset the boat.
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Old 17-10-2020, 10:17   #2
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Re: What, really, is a rogue wave?

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Is this a fair assumption? A rogue wave is not defined by a certain height, but by how different it is from other waves the boat is sailing through. I imagine a boat all adjusted for sailing through certain conditions, and suddenly a wave bigger enough to upset that boat comes along.

But in other conditions if all the waves were that big, it would not be a rogue, and the skipper would have the boat set for those conditions and the same wave would not upset the boat.
Yes that is a reasonable assumption. In my experience rogue waves occur when two different wave patterns 'collide' and run together for a relatively short period of time. So two crests meet and ride along together for a bit - resulting in a crest that is the sum of the two crests. So two 4' waves merge (for a short while as they are on slightly divergent courses) into an 8' wave. I perfect example existed in the recent Trump boat rally when several boats were sunk on a calm stretch of water. The wakes of any one boat would not have sunk any boat, but the aggregation of multiple waves 'in sync' produced multiple rogue waves.
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Old 17-10-2020, 10:20   #3
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Re: What, really, is a rogue wave?

“ rogue” waves happen all the time, ever been sailing and suddenly a wave slaps the side of the boat and your get splashed?
Thats a rogue wave, a tiny one of course, but as it’s markedly different than all the rest, it’s a rogue.
Of course usually by rogue, most are talking about the monsters, thought for ever to a myth, but I believe satellites have photographed many and they aren’t considered to be a myth anymore.
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Old 17-10-2020, 10:29   #4
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Re: What, really, is a rogue wave?

Yes, but some waves are more rogue than others. There is the wave combinations, speed and directions, there is current, there is depth of the sea, it's all really interesting stuff. It can be much more than two different wave sets combining. I don't know, you may have seen this article:
https://www.quantamagazine.org/the-g...aves-20200205/
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Old 17-10-2020, 10:33   #5
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Re: What, really, is a rogue wave?

More discussions:

https://www.cruisersforum.com/forums...es-230153.html

https://www.cruisersforum.com/forums...dy-181348.html

https://www.cruisersforum.com/forums...ave-30191.html

https://www.cruisersforum.com/forums...or-222856.html
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Old 17-10-2020, 11:25   #6
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Re: What, really, is a rogue wave?

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Yes, but some waves are more rogue than others. There is the wave combinations, speed and directions, there is current, there is depth of the sea, it's all really interesting stuff. It can be much more than two different wave sets combining. I don't know, you may have seen this article:
https://www.quantamagazine.org/the-g...aves-20200205/
I did start reading this article but after a page or so I realized that it was way beyond my ability to comprehend.
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Old 17-10-2020, 11:35   #7
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Re: What, really, is a rogue wave?

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Originally Posted by a64pilot View Post
“ rogue” waves happen all the time, ever been sailing and suddenly a wave slaps the side of the boat and your get splashed?
Thats a rogue wave, a tiny one of course, but as it’s markedly different than all the rest, it’s a rogue.
Of course usually by rogue, most are talking about the monsters, thought for ever to a myth, but I believe satellites have photographed many and they aren’t considered to be a myth anymore.
Yep they are real from direct observation in '89 in South China Sea average wave was 20 to 30 ft between 2 typhoons . Suddenly got hit with a 50+ft monster from a different direction than the prevailing waves happened 2 times within an hour . Cost one of my men his life.

Glad I was on the biggest warship on the planet at that moment .

Here is a short video that does a good job on rogues.
https://youtu.be/2ylOpbW1H-I
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Old 17-10-2020, 11:36   #8
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Re: What, really, is a rogue wave?

No “wave”, rogue or otherwise, is of any danger to a sailing boat until it breaks. It is said that a tsunami that kills a million people ashore will pass under a sailing boat at sea completely unnoticed.

I have had my boat in very large, very steep seas - the boat goes up and then it comes back down in almost the exact same place. Swells do not generate significant horizontal movement no matter how big they get. When they break is when things turn to custard.

At least that’s my opinion, experience and belief. If anyone finds the need to scare the bejeezes out of themselves, read up on “rogue waves”.
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Old 17-10-2020, 11:43   #9
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Re: What, really, is a rogue wave?

You can understand it. AlanT's explanation doeesn't include all the physics, but it's correct. There are also rogue holes in the ocean, which rarely get mentioned, but two negative waves (troughs) can combine just as two positive waves can. The spectacular rogues come when two wave patterns hit head on.

I once saw one in a swimming pool. Several minutes after everyone had left the water, the wave patterns that were gently rocking the surface hit just right near the center, and the vertical wave splashed as if someone had dropped a cannon ball in.
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Old 17-10-2020, 11:44   #10
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Re: What, really, is a rogue wave?

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No “wave”, rogue or otherwise, is of any danger to a sailing boat until it breaks. It is said that a tsunami that kills a million people ashore will pass under a sailing boat at sea completely unnoticed.

I have had my boat in very large, very steep seas - the boat goes up and then it comes back down in almost the exact same place. Swells do not generate significant horizontal movement no matter how big they get. When they break is when things turn to custard.

At least that’s my opinion, experience and belief. If anyone finds the need to scare the bejeezes out of themselves, read up on “rogue waves”.
Not really correct . The sheer steepness of the wave can and will roll or flip a boat over .
There are many examples of that .

A tsunami is a totally different critter they only present as the Continental shelf slopes gently up to the beach head .
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Old 17-10-2020, 11:50   #11
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Re: What, really, is a rogue wave?

Agreed, Cassidy, but you may be combining two different phenomena. A tsunami at sea is only inches or a few feet tall, and spread over a lot of area. It has a bunch of energy in it. When it hits shallow water, all that energy goes into wave height. Rogue waves on the other hand are made of two wave patterns that intersect additively.

Yeah, let's not scare people. For it to really make any difference to a cruiser, as you say, it has to break, and it had to be made of two pretty scary waves to begin with.
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Old 17-10-2020, 12:00   #12
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Re: What, really, is a rogue wave?

nothing scarier than the sound of a breaking wave behind you... my shoulders raise upwards at just the thought
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Old 17-10-2020, 12:03   #13
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Re: What, really, is a rogue wave?

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Not really correct . The sheer steepness of the wave can and will roll or flip a boat over .
There are many examples of that.
Like I said, I’ve never seen that . . . .

The important distinction is “wave” which appears at sea only in serious conditions, any other time they are swells and I simply do not believe that a swell can roll a boat until it starts to break at which point it becomes a wave.

All of the reports that I have read over the years of yachts being damaged by waves include facts like breaking waves, boat surfing, “rollers”, “curling wave” and so on.

If you say there are many examples, please point me to them, at this moment I am not a believer.
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Old 17-10-2020, 12:27   #14
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Re: What, really, is a rogue wave?

i wonder if its possible to collapse a wave at its base using sound or vibration frequencies? we could tow several long warps that vibrate behind the boat and collapse oncoming waves.
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Old 17-10-2020, 12:33   #15
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Re: What, really, is a rogue wave?

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Like I said, I’ve never seen that . . . .

The important distinction is “wave” which appears at sea only in serious conditions, any other time they are swells and I simply do not believe that a swell can roll a boat until it starts to break at which point it becomes a wave.

All of the reports that I have read over the years of yachts being damaged by waves include facts like breaking waves, boat surfing, “rollers”, “curling wave” and so on.

If you say there are many examples, please point me to them, at this moment I am not a believer.
Put it simple here a 20 ft swell on a 15 second period is gentle but put the same swell on a wind driven 5 second period . The sides are steep enough to roll a vessel or pitch pole them as well .

There is an example in an old Sydney Hobart race where almost half the field was severely damaged due to steep non breaking was . ( Don't recall exactly what year)
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