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Old 10-03-2008, 18:33   #61
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Originally Posted by dacust View Post
Oh, I'm not argueing with that. I'm only talking about the slick and the claim that it can stop waves from breaking because of the way it disturbs the water.
Apart from the lucid and detailed account given by the Pardey's in their book, the best motivation I have for believing that the slick induced by a hove to boat can stop breaking waves is this simple experiment:

Get in your dinghy in windy/choppy conditions. Row along and watch the behaviour of the vortices (swirls) left by your oar strokes. The vortices stop wavelets and are so stable that often you can count as many as twenty oar strokes receding into the distance behind your dinghy.

That stability and ability to break up waves comes from the momentum of the vortices. It is a smaller scale version of the combined effects of a hove to keel and a large parachute anchor which will induce swirling in the sea, making a nice stable slick/pathway which helps to destabilise breakers and keep your boat safe.
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Old 10-03-2008, 18:39   #62
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I have been thinking .........could a Para Anchor be deployed from the stern? with the boat then held at the 50 degree angle - it would save having to turn the vessel.......of course would need strong points at the stern!
One reason not to point your tail at the wind and waves given by the Pardey's is that your rudder is exposed to the oncoming waves and so more prone to damage.

It also fails to take advantage of the shape of your boat's hull for heaving to.
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Old 10-03-2008, 18:42   #63
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...
I would suspect something similar in the case of the L & L tactic, although it sounds like this may actually have some actually usable effect. But I'd expect it only helps in marginal situations. If the waves become high enough to break big, I bet this wouldn't change that. In other words, I wouldn't think this tactic would really be something to rely on. It may have an effect, but is it enough to really make a difference in survival?
-dan
Dan, while you may be a non-sailor and talking theory, you are reading and contributing and I suspect, also learning - just like the rest of us. We all have different levels of experience, knowledge and ability to reason and learn.
Apart from "collasping or backless" waves, the danger is from breaking waves. There is no reason that I can see why a stationary boat somewhat anchored by a para anchor would not simply rise up and down with the water in a NON-breaking wave. The water itself is simply doing that - going up and down.

The dynamics change radically when the wave train starts to break. First the water tumbles down the front of the wave like a giant whitecap and later starts curling over and fully breaking more like surf. This is dangerous for the boat and can easy overwhelm her.

This is the very situation that L & L suggest can be altered by use of their tactics. They say it has worked for them in the southern ocean and for others. They don't claim it is a new untried tactic, rather it is an old tactic that for various reason (as stated in the book) has fallen off the current yachtsman's "radar". The advent of new materials makes para anchors possible in small boats and they are revisiting old methods and making them work for modern boats. IMHO.
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Old 10-03-2008, 18:45   #64
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Originally Posted by mjt View Post
...
Get in your dinghy in windy/choppy conditions. Row along and watch the behaviour of the vortices (swirls) left by your oar strokes. The vortices stop wavelets and are so stable that often you can count as many as twenty oar strokes receding into the distance behind your dinghy.

That stability and ability to break up waves comes from the momentum of the vortices. It is a smaller scale version of the combined effects of a hove to keel and a large parachute anchor which will induce swirling in the sea, making a nice stable slick/pathway which helps to destabilise breakers and keep your boat safe.
Excellent observation, thanks for the input, it helps to understand the dynamics even if I still don't know the science behind it.
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Old 10-03-2008, 19:04   #65
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Originally Posted by David_Old_Jersey View Post
It occurs to me that it takes a certain type of person to sit in the middle of a gale and say to themselves "lets try something completely new and untried".

I have been thinking .........could a Para Anchor be deployed from the stern? with the boat then held at the 50 degree angle - it would save having to turn the vessel.......of course would need strong points at the stern!

Anyone want to try it out in a Force 10? (just to satisfy my curiosity )
The last time we were out in Force 10-11 conditions we were in too much of a hurry going somewhere to put out a drogue. Besides, I didn't have one at the time. I did, however, heave to in Force 8-9 to straighten the boat out after a massive broach once. She rode nicely and we were able to get her squared away. Mind you, fetch was limited in both of these occurrences so wave height wasn't that significant. I think I would stream the drogue to windward on a bridle arrangement where I could control the angle. IIRC they said to deploy the drogue out far enough to keep it crest to crest or trough to trough from the boat. That was to minimize chafe and the amount of strain on the lines.
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Old 10-03-2008, 22:11   #66
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...Mind you, fetch was limited in both of these occurrences so wave height wasn't that significant. I think I would stream the drogue to windward on a bridle arrangement where I could control the angle. IIRC they said to deploy the drogue out far enough to keep it crest to crest or trough to trough from the boat. That was to minimize chafe and the amount of strain on the lines.
CharlieC, can you describe the seas on this occurence, size, shape, irregular (or not), breaking or not (occasionally? regularly? overhanging???)
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Old 11-03-2008, 05:05   #67
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One reason not to point your tail at the wind and waves given by the Pardey's is that your rudder is exposed to the oncoming waves and so more prone to damage.

It also fails to take advantage of the shape of your boat's hull for heaving to.
A breaking wave tends to be a lot less substantial than the still waer under it. If you are facing into the breaking wave, your rudder is in the still water under and the boat being forced back can damage the rudder. If the stern is to the wave, the rudder is in the still water and a sudden surge means that the boat is facing the right way for the rudder.
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Old 11-03-2008, 06:08   #68
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Robert is correct - the risk of rudder damage is much greater if you are forced backwards by a breaking wave, rather than forwards.

Brad
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Old 11-03-2008, 08:56   #69
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CharlieC, can you describe the seas on this occurence, size, shape, irregular (or not), breaking or not (occasionally? regularly? overhanging???)
Due to the limited fetch they were 10-15' wind waves with short periods and average faces. The tops were getting ripped off above 50 knots and the sea was turning white with lots of flying spray. When we had to turn into the wind to douse, the waves became steep and breaking occasionally and we regularly took green water down the decks, alongside the cockpit with spray that flew the full length of the boat. The Marina we were trying to get into was a lee shore with a huge rock breakwater. At the same time, a Washington ferry was unable to get more than 200' off the dock against this stuff and had to go back. Good thing Oh Joy has that 50HP Perkins cause we needed all of it. The thing that bothered me most was having to have crew on the foredeck in this stuff, trying to douse the Staysail. Looking forward reminded me of scenes from "The Deadliest Catch" when we'd fall off into a trough and throw white water 20' in the air. Considering the forecast was for a max of 30 knots, I'm happy there was only 80 miles of fetch. We saw TWS of 55 with gusts to 68. One thing I learned that day is that the wind WILL sneak up on you when you're running offwind and by the time you notice it, it's too late.
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Old 11-03-2008, 16:14   #70
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Thanks for the description. Interestingly Storm Tactics (and others) mentions the same risk of be unaware of increasing wind when down wind sailing.
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Old 11-03-2008, 16:48   #71
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Robert is correct - the risk of rudder damage is much greater if you are forced backwards by a breaking wave, rather than forwards.
The question I answered was whether the same slick effects due to heaving to (in that case with a sea anchor) would destabilise a breaking wave if the boat was backwards rather than forwards. My answer presupposes no breaking wave for that reason.

I would need a very good reason to turn the stern of my boat to dangerous seas. The front of my boat is more suited to the task of riding waves and dissipating excess energy safely than the stern and I think this would be true of most.
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Old 11-03-2008, 19:27   #72
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Thanks for the description. Interestingly Storm Tactics (and others) mentions the same risk of be unaware of increasing wind when down wind sailing.
For good reason. After running and surfing for hours, ya suddenly realize you have too much canvas aloft and have to figure out a way to come about and shorten without broaching. I our case, a particularly large wave pushed us onto a Beam Reach in 45 knots where we were pinned for a bit on the face of that wave as it marched North while still making 10 knots along the face. Eventually, the wave finally slid under us and I came up hard in the trough while sheeting the Main till it luffed. Twas a wild ride there for a bit. We doused the Mizzen, put a reef in the Main, furled the 135 and rigged the Staysail. Later in the evening it turned out we still had too much sail aloft and we had to come about once again to douse. The same tactics worked except we chose the time and didn't get pinned by a wave. We ended up surfing a wave through the breakwater at Point Hudson at over 9 knots. It took us over 200' to stop in full astern. I learned a few lessons that day. One of them was to trust this boat.
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Old 17-04-2008, 09:15   #73
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Originally Posted by dacust View Post
Oh, I'm not argueing with that. I'm only talking about the slick and the claim that it can stop waves from breaking because of the way it disturbs the water.
Revisiting the thread as the OP was reading L & L's Storm Tactics. Their third edition arrived today and I will have to get off CF and start reading this new updated edition.

The first gem was referring to the "slick" as a Von Karman vortex street (try a google search for more info).
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Old 20-04-2008, 20:43   #74
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We previously had a mono-hull with a Paratech sea anchor, but prior to acquiring our current heavy displacement catamaran sold it in favor of the Jordan Series Drogue after research including all the reports in the Drag Device Data Base and reports on the web. We have reinforced tangs at the corners of both hulls near the strern with plans to lie to the Series Drogue should it ever be a necessity. Its our belief that the larger rear cockpit will not be compromised by following seas, especially in light of the continued forward movement with the vessel in the seas and the research showing more lift in the stern than in the bow of all vessels.

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Old 28-04-2008, 18:17   #75
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Ed,
As you are no doubt aware drogues and sea anchors do different things. A sea anchor is designed to stop you. A drogue will slow you. They are both useful survival tools but should not be confused in function or form. On my Cat I have bridled attachment points on bows and sterns. The bows to park (stop/sleep/tuck in) with on my para-anchors sea anchor. The stern for my variable opening drogue. WHen I need to keep moving downwind but to stop surfing or control speed I run the drogue.
I would have a concern running my sea anchor off the stern. On 'Magic Happens' (Hitchiker 40 cat) and Chaotic Harmony (Catana 42scat ) I have taken a full breaking wave - solid green) over the boat. (two separate out of season cyclones) The exposed stern cockpit would have been very much at risk in these.
Just a thought.
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