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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #21  
Old 07-30-2008
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Johnshasteen. Well, here's the interesting bit that hadn't realised before about the risk or othwerwise of being pooped. To quote from Jordan's site:

"In addition to a feeling of helplessness, there is another irrational attitude that countered our obtaining a solution to the capsize problem. The shape and motion of storm waves when viewed from the deck of a yacht are such that it can lead to optical illusions which confuse the skipper. A large storm wave approaching the boat appears to be a dangerous wall of water and the skippers instinctively tend to head up or run off to avoid being pooped. Actually the water in the wave is not moving towards the boat and will lift the boat harmlessly"

Jordan then goes no to say:

"Another optical illusion is that it is possible in a survival storm to reduce the hazard by running off before the waves and, by skillful seamanship, to out maneuver a dangerous wave. This is a particularly unfortunate choice. The waves are moving faster than the boat can go. A 40 ft .breaking wave will be moving at a speed of approximate 23 knots. The breaking wave is completely random. Furthermore, by far the most important concern is that, if the boat is moving through the water, the chance of being caught by the wave and surfing to a dangerously high speed is greatly augmented".

And finally:

"A final misconception is the belief that a breaking wave "strikes" the boat and that the moving water in the crest does the damage. Actually, the boat is lifted by the forward face of the wave with no impact. When it reaches the breaking crest the boat velocity is close to the wave velocity. The crest water is aerated and has little damage potential. Damage to the boat is incurred when the boat is thrown ahead of the wave and impacts the green water in the trough. The leeward side and the deck are struck. A careful reading of "Fastnet Force Ten" and "Fatal Storm" will confirm this conclusion".

It maybe we're talking about two differnet things here: a survival storm versus something not quite so life threatening. But the wave mechanics can't be too different.

I've not yet had the "pleasure" of running before a storm but I did spend a very uncomfortable night bashing head on into a Force 9. It was OK for 8 hours or so but I can't imagine how a shorthanded crew could do it for days on end. Even in conditions less than a survival storm I'd be tempted to put the drogue out and go below for a kip.
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Last edited by GrahamCownie; 07-30-2008 at 04:45 PM.
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  #22  
Old 07-30-2008
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Much of Jordan's work was done because of the Fastnet disaster. That was what prompted Jordan to design the series drogue in the first place. He also worked very closely with the USCG in the development and testing of the JSD. While the USCG doesn't approve the JSD, it certainly seems, from the document on Jordan's site, to advocate the use of them.

If you read the USCG report, the report's abstract says:

Quote:
Model and full-scale tests were conducted to investigate the use of drogues to prevent breaking wave capsizing of sailing yachts. A mathematical model was developed which simulates the motion of a boat and drogue in regular waves and in a breaking wave strike. A series drogue is recommended for optimum performance based on the results of this study. Design information for both series and conventional drogues is presented.
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  #23  
Old 07-30-2008
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Quote:
Originally Posted by GrahamCownie View Post
Johnshasteen. Well, here's the interesting bit that hadn't realised before about the risk or othwerwise of being pooped. To quote from Jordan's site:

"In addition to a feeling of helplessness, there is another irrational attitude that countered our obtaining a solution to the capsize problem. The shape and motion of storm waves when viewed from the deck of a yacht are such that it can lead to optical illusions which confuse the skipper. A large storm wave approaching the boat appears to be a dangerous wall of water and the skippers instinctively tend to head up or run off to avoid being pooped. Actually the water in the wave is not moving towards the boat and will lift the boat harmlessly"

Jordan then goes no to say:

"Another optical illusion is that it is possible in a survival storm to reduce the hazard by running off before the waves and, by skillful seamanship, to out maneuver a dangerous wave. This is a particularly unfortunate choice. The waves are moving faster than the boat can go. A 40 ft .breaking wave will be moving at a speed of approximate 23 knots. The breaking wave is completely random. Furthermore, by far the most important concern is that, if the boat is moving through the water, the chance of being caught by the wave and surfing to a dangerously high speed is greatly augmented".

And finally:

"A final misconception is the belief that a breaking wave "strikes" the boat and that the moving water in the crest does the damage. Actually, the boat is lifted by the forward face of the wave with no impact. When it reaches the breaking crest the boat velocity is close to the wave velocity. The crest water is aerated and has little damage potential. Damage to the boat is incurred when the boat is thrown ahead of the wave and impacts the green water in the trough. The leeward side and the deck are struck. A careful reading of "Fastnet Force Ten" and "Fatal Storm" will confirm this conclusion".

It maybe we're talking about two differnet things here: a survival storm versus something not quite so life threatening. But the wave mechanics can't be too different.

I've not yet had the "pleasure" of running before a storm but I did spend a very uncomfortable night bashing head on into a Force 9. It was OK for 8 hours or so but I can't imagine how a shorthanded crew could do it for days on end. Even in conditions less than a survival storm I'd be tempted to put the drogue out and go below for a kip.
Interesting stuff, but our crew (in both storms) three of us, with a combined 100+ years of offshore sailing in the Gulf, Atlantic and Great Lakes, had no optical illusions or misconceptions about either storm (we actually thought the winds in the March storm were around 40-50 and the seas 18-20ish - the conditions were in fact, according to Coast Guard New Orleans, winds 50-60 and gusting higher and seas 30 feet.
When the sustained wind is above 40, you have to change from sailing to surviving. To the amazement of CG New Orleans and CG Corpus Christi, we "survived" the first storm for 48 hours and the second for 36 hours (both felt like an eternity) - the first question they asked when we were back in port and I called them was, "do you have an EPIRB" - I answered yes - then they asked why we hadn't deployed it. So, while I respect Jordon, every storm is different, every boat is different, every crew is more/less capable. The best you can hope for is that you don't ever get caught in a major storm - but if you are so unfortunate as to get caught in one, you have to play the hand that you're dealt at the time.
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  #24  
Old 07-31-2008
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Quote:
Originally Posted by GrahamCownie View Post
Omatako,

I'm really interested in what happened to you. The esteemed Mr Jordan (as in series drogues) states categorically that yachts don't sustain damage from beaking waves falling onto them. Rather it's the forces generated when boat falls off a really steep wave and slams into the trough that does the damage. Is that what happened to you?

Graham
We were all down below when the wave hit the boat so I have to speculate on what happened. There was no sensation that the boat was falling so I don't believe we fell into the trough.

My wife appeared to fly across the cabin but hindsight had us more believing that she more like fell across the width of the cabin as the boat was knocked down. It's difficult to get perspective of up and down at night in a closed environment.

I believe that the wave broke and hit the side of the boat at about the same time so the water that smacked into the hull wasn't aerated but pure blue. The wave washed right over the boat and rolled the boat onto it's side so it was a respectable size. The cabinetry in the forepeak ended up on the bunk. At daybreak a short while later we went on deck and the seas were huge and breaking all around us in 60+ kn winds. It's probably the only time I've been really frightened at sea.

As far as the esteemed Mr Jordan's assessments go, remember that largely he deals with vessels that are stern (or bow) on to the seas and we were beam on. There is an enormous difference between the two when it comes to energy absorption.

Anyway, as I say we never saw anything (and I'm really pleased we weren't on deck at the time) and can only offer opinions as to why we appeared to absorb so much of the energy.

Andre
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Andre, thanks for the explanation - that was what I thought happened. Your adventure is why in both gales Paloma endured, we did everything we could not to get beam to the seas - we were convinced that we would broach if we did.
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Last edited by johnshasteen; 07-31-2008 at 11:55 AM.
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  #26  
Old 07-31-2008
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Andre,

Thanks for the info - its sounds like it was a truly horrendous experience. It also sounds as if Jordan's assertions about wave behaviour might be too simplistic.

It was interesting to read in John Vigor's book "The Seaworthy Offshore Boat" that he envisages starting by running off, then as things get worse trailing a series drogue and then when things get really critical cutting the drogue and using Bernard Moitessier's high speed skudding technique.

Graham
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Old 07-31-2008
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Graham-

When I spoke with Don Jordan a few years ago, he told me that the JSD was really designed to be a safety device much like an ejection seat on a fighter jet. That when all else fails, and you need to survive the situation, deploying the JSD is supposed to be a fire and forget type device—with no need to resort to other tactics afterwards. I think skudding off at high-speed is far more dangerous than lying to a JSD. One requires the crew and captain to be exposed to the storm and to actively steer the boat. The other is a much more passive technique, and allows the, more likely than not, exhausted captain and crew to hunker down and get some rest.
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  #28  
Old 08-01-2008
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Quote:
Originally Posted by sailingdog View Post
I think skudding off at high-speed is far more dangerous than lying to a JSD. One requires the crew and captain to be exposed to the storm and to actively steer the boat. The other is a much more passive technique, and allows the, more likely than not, exhausted captain and crew to hunker down and get some rest.
My problem with skudding off at any speed is that when nightfall comes the weather that caused the need for survival tactics is often not conducive to decent night vision and when your running ahead of a huge following (sometimes breaking) sea, it requires very good judgement of the angle your are running at relative to the wave train. On a dark night this is not easy when there is little ambient light about and seriously dangerous if you get it wrong.

In the daytime however, I have often and will again entrust the management of the boat to my 24-hour crewmember - my faithful and very competent autopilot.

Mottissier was without doubt a better sailor than I am and one thing is for sure: he was really far more courageous

Andre
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Old 08-01-2008
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Quote:
Originally Posted by GrahamCownie View Post
it sounds like it was a truly horrendous experience.
Graham, sure it was scary but it is experiences like that which make one a better sailor (provided of course you survive ) and as Eric Hiscock once said "Anybody that hasn't experienced the effects of true storm cannot speak with any authority on the subject" (or something similar)

Whilst I have no desire to repeat the exercise, I will be a whole lot less frightened next time around.

Andre
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Old 08-19-2008
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You guys should read "Storm Tactics Handbook" by Lin and Larry Purdy (look for it on Amazon, I couldn't find it on SailNet). In this, they describe a method for heaving to, on almost any boat, as a method for riding out storms. They talk about a number of storms that they have survived in this way.

Of course, before heaving to in a large storm, you reduce sail (you probably would have already done that as the wind started to pick up). You would be on a second (or third) reef and the storm jib before doing this. They also recommend dragging a sea anchor from the forward, windward rail (near the bow) to assist.

You are right, that you would need enough sea room to do this. Also, I think that there is no "one size fits all (situations)" method.

Jeff Griglack
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