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Old 06-05-2013, 07:43   #301
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Re: Storm Sailing Advice

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Originally Posted by noelex 77 View Post
This is a great thread. We have some some very experienced yachtsmen that allow us pick their brains, and gain from their considerable experience.

Lets not let this thread deteriorate into bickering and mindless personal drivel. Posts of this nature have been deleted.



GOOD!!!!
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Old 06-05-2013, 07:51   #302
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Re: Storm Sailing Advice

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Originally Posted by Andrew Troup View Post
Another way of looking at it is that those once-every-15 minute waves are the waves we tend to think of when we describe the conditions.

Which either means that (as I think I might have posted in this very thread)

- when we overestimate wave heights by a factor of two, perhaps it's because we actually focus on the high waves.

(It's a pity the 'significant' waves don't come with a handy label, saying 'Pick Me !')

or

- if we tend to overestimate individual waves by a factor of two (which I think is a natural tendency) then we may overestimate the significant wave height by a factor of up to four !

I think one of the important "take-aways" for me here has been the fact -- read somewhere else too but even more valuable when you hear it first hand from others -- is that the waves won't all be the same height, they won't come at regular intervals, and they won't even all be at the same direcition (i've experience that one in particular). The Pardeys make the point very well in their book (I think it was the Pardeys). "Averages" can be extremely misleading. I appreciate it when others here "get" that I'm not likely to experience this in the Southern Ocean - and certainly not on my boat. But since my boat isn't "blue water" I view her as more vulnterable in what I will now call "very rough weather" and not "storm" since that's a term of precision for some.

So, while many of you would use the strategies you've talked about in more extreme conditions, I might need them before you. I have a much better sense of what to watch for as well as -- hopefully -- how to deal with it. I've caught a lot of heat every time some aspect of "rough weather" comes up but i've sailed my boat and I know I need to know about it.
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Old 06-05-2013, 08:02   #303
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Re: Storm Sailing Advice

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Originally Posted by Snowpetrel View Post
Thanks for this, I for one am very interested.



This is a very good point. And more closely aligns with my real world experience, that 2x waves are a rarer beast than statistics seem to indicate.


Ramble alert!

The first rogue wave I encountered was on trip from NZ to tonga on a 28 foot steel ganley double ender. We were in about 30 knots (force 7) broad reaching with a 3 reefed main and staysail. I was more or less hand steering as the trim tab windvane was struggling. We where pushing her harder than she really liked. The top drop board was out to let some air out and a small amount of spray in below. The sun was shining and life was good...

Suddenly I heard a roar behind me and looked behind to see a 10 foot wall of white water coming at us from about the beam, I really don't know exactly what happened next except I remember the skippers face in the galley as I yelled to him, and the impact of the wave as I tried to turn the stern into it (without any luck). He bravely held a chopping board up in the hatchway! When the water cleared from my eyes and I got a breath of air I found we where somehow perched and about to start surfing down the face of a very steep, and incredibly deep wave face. My guess is 30 or more feet? But who knows. I still reckon it was about three times the height of any of the other waves we had seen. I let her broach rather than risk pitchpoling or a high speed broach. And we where tumbled about for a second time.

We came up facing into the wind, on the opposite gybe, with the preventer bail ripped out of the boom (probably a good thing!). The trim tab was ripped off the rudder, and the two inch SS pipe tube for the windvane was bent, a shelf in the galley was torn off by the force of the water coming down the hatch. The weathercloths around the cockpit were badly torn and the boat had about 8 inches of water over the floorboards, and was wallowing badly.

Amazingly (and fortunately) it was very calm for about 15 minutes after these two waves, the sea had a fizzy feel, as all the trapped air bubbled out. We dropped the main, and slowly sorted out the boat, making it to Tonga about 5 days later having finally got all the bedding dry by hauling it up to the masthead away from the spray. Somehow both sides of the inside of the boat had been underwater, and all the electrics slowly failed.

At no time where the conditions before the "wave" anything other than brisk, fun sailing. And then it all suddenly turned pear shaped!

I should point out that we had safely (but rather uncomfortably) run before a force 8 earlier when bringing the boat up from wellington. The boat was tender but strong and had coped well with just a reefed staysail.

I still do not know if it was two separate waves, or a kind of double wave. it definitely had two crests. We were a few hundred miles west of the kermadecs, and the seabed there is pretty dynamic, maybe that was a cause... Since then I have read what I can find on waves.

WOW -- a PLANNED broach -- you have nerves of steel!
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Old 06-05-2013, 11:12   #304
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Re: Storm Sailing Advice

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Originally Posted by Snowpetrel View Post
A very good point, thanks for the link. I use the one from the now slightly dated van dorn book "seamanship and oceanography". It includes time as a factor as well, which can be useful. I have been meaning to get a copy laminated to post someplace handy on the boat!
Here's a version with the time factor (wind duration) included.
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Old 06-05-2013, 12:55   #305
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Something touched on by Evans is the idea that waves that exceed the mean come in groups.

This is something every surfer knows, i have surfed for over twentyfive years, and they are known as "set waves" and are basically what you plan for during a session.

They can be 15minutes to an hour apart and match the bell curve that Evans attached. You can also count that in every couple of two hour surf sessions you will see one set that is 2-3 deviations from the mean in terms of height.

IE in 1m surf with a consistent strong swell within a couple sessions you will see a 3m set - and usually get hammered by it by getting caught inside.

Usually they occur in "sets" of 3-10 waves and the size, frequency, quality amd volume are determined by the geographic refraction/reflection interference pattern, period of swell, interference pattern of other swell trains, and interference pattern caused by the speed of motion of center of swell generation.

Physics will clearly illustrate that variations in energy distribution from a reasonably consistent energy source are created through interference patterns.

These patterns may be statistically measurable over large periods of time but will be vastly different for any given system as they are polynomials with numerous variables - only some of which were listed above.

Bottom line - for some weather events a bomber wave may come once every 12 hours, for others once an hour.

There is no real difference when in bluewater - just lack of reference points. If you spend time on deck looking at the swell you can pick up patterns amd see differing swell periods creating reasonably predictable wave heights.

All that said - once the wind really picks up and the swell does as well it becomes a bit academic and one reverts to preparing for what one knows is coming instead of sitting in the cockpit seeing if one can predict the wave heights.

Still all this gives awareness and planning to what to expect and prepare for.
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Old 06-05-2013, 14:28   #306
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Re: Storm Sailing Advice

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Originally Posted by Hud3 View Post
Here's a version with the time factor (wind duration) included.
Thanks for this picture. I found the book it comes from: https://www.wmo.int/pages/prog/amp/m...702/WMO702.pdf

Just what I need in my work!

Alain
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Old 06-05-2013, 14:36   #307
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Re: Storm Sailing Advice

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As an aside, on a comment in my post above . . . one other thing that has changed dramatically in the past 20 years with respect to storm sailing is our on board weather info. One of the reasons people (including us) took the 'passive' approach in 'the old days' was because we usually did not know which way was better to sail to minimize the storm exposure. Today we have quite good (although still occasionally frustratingly wrong) weather info and can plan 3 days in advance where it is best to position the boat. That makes the active techniques much more powerful and valuable.
Can't over-emphasis this point IMHO. On our crossing from Halifax to Oban, 2010, we ended up Crosshaven, Ireland. At one point we were 300 miles off Spain before we could turn north.

If we had stayed on the great circle route to Oban we would have taken direct hits from 4 major lows over the course of the crossing.

The last one was a 970 mbar low with an 800 mile diameter of gale force winds and storm force close to the low. However the most we saw on the entire crossing was a few brief gusts to 40 knots. No big deal. A Hinckley that was 3 days behind us was hove to for 12 hours in the last low. They were unable to sidestep it.

My point here is we had one to two daily GRIB downloads using the Iridium sat phone and could see this stuff 3 to 4 days out. The entire GRIB download process worked flawlessly, no hassle, and took 5 minutes. This information then allowed us to plot a course to step out of the way of the strong sectors of the storm.

Is it guaranteed? No but it worked everytime for us and we were glad for it. The track of these lows seems to be fairly stable. So instead of being punished we had sails up the whole time and at no time did we have to work very hard. It was the difference between a great, memorable crossing and drawn out miserable grind/slog.
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Old 06-05-2013, 15:19   #308
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Re: Storm Sailing Advice

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Originally Posted by Hydra View Post
Thanks for this picture. I found the book it comes from: https://www.wmo.int/pages/prog/amp/m...702/WMO702.pdf

Just what I need in my work!

Alain
Nice. Thanks. I note two things that caught my eye:

1. Regarding breaking waves, it offers this comment: "In extreme cases the crest falls freely into the trough (plunging). In all cases a high-velocity jet of water is at some point injected into the area preceding the crest. This jet creates a submerged whirl and in severe breaking it forces the water up again to generate another wave (often seen as a continuation of the breaking wave). This wave may break again, resulting in an intermittent character of the breaker." This would in part (along with the wave 'sets' mentioned in posts above) explain the common real world experience of getting hit by multiple breakers in a short time period.

2. It confirms that the Rayleigh distribution is still the best overall model for wave height probability, but it does mentioned the additional model that are being looked at to better approximate the tail (the big waves) of the distribution. I will have to play around with them some time.

And just to keep this whole topic 'fresh' and 'relevant' . . . I don't know how many of you noticed there was a force 10-11 storm near the Azores last week, and it now appears there may be two boats lost and 2 more 'overdue with no communications from them'. It brings into focus both the weather forecasting and the tactics/preparation.
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Old 06-05-2013, 15:46   #309
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Re: Storm Sailing Advice

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good hot food is also a great morale booster,
YES!! I hate it when everyone else gets seasick and I just get hungry. I don't mind standing an all-night watch if there's some hearty soup, or maybe a Dinty Moore Beef Stew to be had. I don't care if it comes out of a can, just so it's hot.

I once cooked up a manhattan clam chowder at O-dark-thirty, and some slacker complained that the smell was going to make him vomit. This from a guy who'd been throwing up for two days while I stood watch! My compassionate response, while still heating up the clam chowder, was to ask whether he could practice throwing up a bit more quietly.
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Old 06-05-2013, 15:48   #310
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Re: Storm Sailing Advice

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If we had stayed on the great circle route to Oban we would have taken direct hits from 4 major lows over the course of the crossing.
Did you ever make it to Oban? I'm planning a week sailing there this summer.
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Old 06-05-2013, 16:22   #311
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Re: Storm Sailing Advice

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YES!! I hate it when everyone else gets seasick and I just get hungry. I don't mind standing an all-night watch if there's some hearty soup, or maybe a Dinty Moore Beef Stew to be had. I don't care if it comes out of a can, just so it's hot.

I once cooked up a manhattan clam chowder at O-dark-thirty, and some slacker complained that the smell was going to make him vomit. This from a guy who'd been throwing up for two days while I stood watch! My compassionate response, while still heating up the clam chowder, was to ask whether he could practice throwing up a bit more quietly.
It's easy to overlook the importance of plenty of hot food, for sure.

When five people were doing the work of eight on one trip I was on, because the remainder were totally incapacitated, those five people still had to eat as much as eight starving people normally would.

Luckily one of the five was a farmer, who also happened to be a grandmother, a fantastic rough-weather cook, and a natural helmswoman under testing circumstances...

and she was completetely unfazed by people who needed to eat two heaping portions of a full cooked hot dinner every six hours, 24/7 just to function ... and in at least one case still claw my - sorry - their way to the galley at odd moments for a top-up.

... and still lose weight! it burns up a LOT of energy, functioning in bad weather, particularly wintry bad weather, when there's heaps to do.

My stomach's carrying on as if it thinks my throat's been cut, just thinking about it...
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Old 06-05-2013, 16:30   #312
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Re: Storm Sailing Advice

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Usually they occur in "sets" of 3-10 waves and the size, frequency, quality amd volume are determined by the geographic refraction/reflection interference pattern, period of swell, interference pattern of other swell trains, and interference pattern caused by the speed of motion of center of swell generation.

.
There's one other factor you didn't touch on in your otherwise excellent post, FS:

There's one reliable way to indefinitely extend the period before the next killer set, and that's to dig out the Nikonos. Big waves are notoriously camera-shy...

I've tried fooling them by leaving the lens cap on, intending to whip it off at the last instant, but they're not stupid...
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Old 06-05-2013, 16:39   #313
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Re: Storm Sailing Advice

foolish sailor--when ye get to zihuatenejo, the sets are 14 then almost a minute if delay before the next set o f 14. surfers and fishermen there know this as they depend on surf for landings and fun. i got to know this to save having to wear dinghy as a hat.
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Old 06-05-2013, 16:41   #314
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Re: Storm Sailing Advice

Getting back to serious discussion: the way big waves, formed from the addition of multiple wave trains of slightly differing frequencies, travel in packs ...

seems to me to evoke the intermittent resonance you always get from a multi-engine plane from the piston-engine era, like a Lancaster bomber.

And you didn't have to be there: Anyone who's sat through "The Dambusters" can hardly fail to remember the way all four engines would occasionally be temporarily vibrating in the same direction at the same time, just about enough to make the film go blurry....

Big multi-engine fishing vessels with old fashioned, not very smooth engines, were also prone to this.

I guess there's a faint analogy also with the Vernier scale effect...
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Old 06-05-2013, 16:52   #315
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Re: Storm Sailing Advice

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I got nuttin to add to this more or less great discussion except the wish that all the newby circumnavigators each year would be asked to read about heavy weather and spouses would be tied down and force fed
video clips of big waves. The EPIRB market would fold, and the SAR crews wouldn't be out risking their lives for nothing.


I read "Heavy Weather Sailing" and "Fastnet Force 10" before I ever got on a sailboat.

Those books had me become a strong believer in self-reliance. I won't carry an EPIRB.

My decision, my risk, my choice. I don't want someone else, or perhaps several people, giving their lives to bail me out of a situation that I got myself into.

Great discussion!

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