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#31 | |
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Registered User
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L & L's book is sitting right in front of me. My friend gave it to me, and I started reading it yesterday. What I liked most was that it not only solidified in me that "yes, being hove to works in anything that the ocean can throw at you [perhaps with a sea anchor to assist]", but it also addresses why people don't do it as much any more.
To be honest, I think this is another reason that "bluewater" boats tend to have full-ish keels. If there's a slam dunk storm tactic that only works well with big keels, you really should be justifying in your head why you have a fin. The other thing that I agree with is the reason why people don't heave to at the right time: bad seamanship. You start by running off, which tricks you into thinking the wind isn't as fast, because you're probably scrubbing 8kt+ off your apparent. That's a sizeable amount of wind. So there you are, on a run, with 30 knots apparent, and *then* you decide to heave to? You're going to come about into 38 knots of wind and get slammed into the water. And if you're on a bare poles run, it's going to be even trickier. Heavy Weather Sailing shows that there are a variety of ways to survive a storm. There are different tactics for different types of boats, and different types of crews. But for my money, I sleep well knowing that with a big keel the only thing I need to work on is my seamanship and maybe a $50 parachute.
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Keep the water on the outside, you on the inside, and the stick in the air. http://rebelheart.squarespace.com |
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#32 | ||
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Quote:
.BTW the their DVD is pretty good also. Not sure if you can get a $50 quality parachute that will be strong enough for a para-anchor. I know that L & L talk about BOURD surplus but I haven't been able to source anything like that in Aussie. Let me know if you can get one in good old USA - I might want to buy it off you .I understand that the full keel is not essential for this tactic to work but it probably won't work with a really narrow fin keel. Irwinsailor - good to hear another first hand experience of the "slick"; thats two now. I know that 40 knots and 12 ft seas are not massive but from that experience, would you now plan to use this tactic in worse conditions or not. I am assuming you were just hove to, no para anchor deployed.
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All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence Last edited by Wotname : 19-02-2008 at 20:12. Reason: spelling |
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#33 | |
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Registered User
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In regards to the parachute pricing, I've seen a few for around $50 or so at our marine swap meets around here, but I'd need to really investigate them to determine quality.
I answered the thud thread! (finally!) Isn't the entire reason for using the sea anchor when hove-to to keep the bow 50 degrees off the wind? It seems like the trough / crest wind differential is what causes the hove-to position to fall apart, since it's two different winds at that point. They make a reference of that in the idea that bigger ships would heave to with their topsails, to negate the trough / crest situation.
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Keep the water on the outside, you on the inside, and the stick in the air. http://rebelheart.squarespace.com |
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#34 | ||
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Everytime I re-read Storm Tactics I find new information. It is cramed with sensible data and argument. IMHO.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence |
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#35 | ||
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It's all about the boat and the seamanship.
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1961 Knutson K-35 Yawl Oh Joy |
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#36 | ||
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Commercial Vendor
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I also agree with RebelHeart on the full keel idea. If you've got a fin (or modified fin like I had on my last boat), you stand more of a chance of tripping over that fin as you slide sideways down the breaking waves. In any case, it's going to push your rail way down toward the water as you fly sideways down a wave. Take away the draft, and you end up more able to just slip down the faces sideways without tripping, staying mostly upright. Well put. |
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#37 | ||
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I think it's correct that Richard Woods didn't have enough rode, I also think (if we're talking about the incident off South America) that reading between the lines he was influenced in his decision to abandon ship by his crew. That's very easy to say sitting here, so it's not a criticism, but I think when the offer of 'rescue' was made there were other factors at work..... not saying that I would have sat it out either.
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Cruising: Boat maintenance in different locations. ![]() see the web diary: http:/blog.mailasail.com/troutbridge |
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#38 | ||
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Paul L |
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#39 | |
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Registered User
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Troutbridge, you make a good point about the difficulty in coming about if the cockpit is being overwhelmed by breaking waves while streaming your series-drogue. And while I am certainly hoping that this is never necessary, I could forsee a situation where it would be. One would have to time their maneuver and have both engines running hard, but to the extent that there are some proponents of lying-ahull in cats, they should be able to safely come about even in dreadful conditions. Indeed, as we know Richard Woods boat, despite being only 32 feet overall, survived after he was rescued and one would imagine it was taking seas off the beam much of the time.
Another option, as you mention, is retrieving some of the series drogue in order to increase speed and lessen the impact of the waves. In order to avoid the impact of breaking seas, I suspect that this would require accelerating the boat significantly and hence, the drogue would no longer be a 'passive' defence, but one requiring constant attention to the helm. Brad |
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#40 | |
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Registered User
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One thing that always seems to be missing in the debate as to which device to employ, parra or drouge, is the position of the vessel in relation to the storm. If I was in the quadrant where running off would follow the track of the storm then I would use the anchor. Conversly if in the other quadrants then running off would shorten the dance with the devil so thats the way I would go.
Searoom may alter the decision however. Mike |
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Status: Online |
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#41 | |
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Registered User
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Mike, I would agree that trying to be in the correct quandrant of a storm as it approaches is extremely important. This is imprecise, of course, as storms rarely stay to a constant or predicted course. Furthermore, the required direction of travel (typically to the west in the northern hemishpere, east in the southern) might cause you to head towards shore, reducing available searoom and putting you over a shoaling (or at least shallowing) bottom: this would only worsen your prospects once the storm hits. If you have the sea room, then by all means you should sail away from the most lethal part of the storm.
Having said that, once you are in the storm and are at or approaching survival conditions (what we are talking about here), running off will require constant attention to the helm and increase the risk of pitchpoling. There are many proponents of high-speed scudding, or running with a storm - Dumas and Moitessier being perhaps the first to write about it in the context of a yacht. Due to the requirement for constant and fastidious attention to the helm, Vigor recommends this tactic only if your boat is being overwhelmed streaming drogues, or setting to a sea-anchor. Indeed, even Moitessier attempted the technique only after he had deployed drogues and found that (eventually) the cockpit was being repeatedly barraged by breaking seas. We must also remember that he was obviously in the wrong quadrant as he remained with the storm for a couple of days - an awfully long time for a short-handed crew, even in good conditions. So yes, scudding makes sense if you are in the correct quadrant, have searoom and adequate rested and capable crew. On the other hand, there is good sense in attempting a passive tactic as a first line of defence. This will allow the crew an opportunity to adjust to the violent motion, sounds and yes fear while maintaining their strength should scudding become necessary. Brad |
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#42 | ||
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Commercial Vendor
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I'll try to explain the way I (and I think rebel heart too) are seeing it. By no means have I "been there" and "done that" on any of these boat types you listed in order of trip-ability, so it's only theory. I have not been in conditions sufficient to warrant the use of sea anchors or drogues in any of the 3 types mentioned. Envision the 3 types of boats, sliding sideways down a wave (hopefully you are in control and using drogues and sea anchors instead!!). Now, if you first picture the catamaran with boards up and rudders too, if possible, you have a very flat hull shape that will slide down beam-on waves almost as well as it would going down them bow first. It's basically skipping like a stone, right? Now push the down-wave centerboard down on the cat, while she is skidding sideways down a wave. (if taking a wave from port and skidding down the wave in a starboard direction, lower the starboard centerboard). What happens? The way I see it, is the area presented to the water in the form of the newly lowered centerboard serves to slow the boat's motion, but in doing so, creates more rotational forces that bury the starboard hull and cause the port hull to lift (given sufficient wave heights and steepness). Would you agree with that? In the cast of the cat, it's pretty catastrophic. It would be a bad error in cat handling. Let's move onto the full keel boat. The full keel is typically running the length of the boat, but draws a comparatively small amount of water, right? Now if you picture this hull shape sliding down the wave in the same way the cat did from our last example (save wave orientation, same slide direction, everything the same except the hull shape), what you have is a boat lying to its side due to the "centerboard" or in this case keel, dragging through the water. At its maximum angle of heel due to water pushing on the full keel, the boat will rotate to its starboard side until such a time as the full keel is up out of the water enough to not produce any more of the force that is rotating the boat to starboard in this slide. This angle of heel will be relative to how deep the keel is, because as you rotat the boat to starboard, you will present less and less keel to the oncoming "apparent current" that is pushing on the keel, and tipping you starboard. Kind of like when a boat heels a lot in a puff of wind, and the force produced by the wind is lessened due to that heel. Would you agree so far? Now let's move onto the fin keel. Put that hull shape in the same situation. What happens? The same thing as with the full keel boat. The boat lists to starboard until the rotation is sufficient enough to be presenting none of the keel to the "apparent current" (which is induced by the boat skidding down the wave). So, if a full keel boat draws 3 ft, an angle will be set up which rotates the boat until that 3' is not directly in the current induced by sliding down the wave broadside. Same thing happens in the fin keel boat. It rotates until the keel isn't presenting its area to the induced current, right? Well, if the keel is 6' or 8' or something like that, the boat will have to roll a lot further starboard in order to achieve the balance of skidding its way peacefully down the wave broadside while presenting no keel area (or little keel area) to the current induced by the starboard slide. So what I'm saying is that the fact that a fin keel is longer (has more draft) than a full keel, means that the boat will have to rotate starboard to a greater degree, futher increasing the risk that the boat will trip on its rail and result in a complete knockdown. All theory, but I'm not sure who of us has been out there to test it?? ![]() |
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#43 | |
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Commercial Vendor
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PS: I am envisioning that the boat might be "side surfing" rather than just pleasantly drifting down the face of the wave in the above post. This is why the area presented by the keel would become more important than wetted area in this example.
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#44 | |
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Registered User
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To avoid the problem of what to do if the drogue is in adequate fro the conditions, have a boat that is set up for having the parachute from the rear,
Robert |
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#45 | |
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Registered User
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Paul L & Ssullivan,
I am not sure I can agree with the explanations of what causes a problem with storm created waves. I think we have to distinguish between what happens when a boat is safely hove to and when it is in danger of capsize / broaching / pitch poling etc. Again I am only considering mono's (because I dont know anything about multi's). Hove to (with or without para anchor set): From my understanding of the Pardey's Storm Tactics, the keel is ~ 50 degrees off the wind (and waves) due to being hove to. The water is then flowing sideways around the keel. This causes turbulence to the surface layers of the water in the wave system. As the boat is pushed sideways downwind, the disturbance appears to move to windard (but really is stationary). Before it dissipates, it has sufficent affect on the approaching wave to modify surface flows in the wave to prevent it breaking dangerously. This is the slick they refer to and how it prevents the crest of the approaching sea from breaking in the vinicity of the boat. The reason the keel shape is considered is because different keel shapes will affect how stationary the boat remains relative approaching seas. The boat must stay directly downwind of this slick and not fore reach out of this protective area. A full keel will remain more stationary then a fin keel but most fin keels should be able to be kept stationary with a bit more effort in considering sail area, sail position and tiller position. The para anchor when set off a bridle and kept directly upwind while the boat maintains ~50 off the wind helps to hold the boat stationary w.r.t. the slick. It also creates some disturbance to the surface layers itself and thus assists in modifying the wave crests even further upwind. BTW this won't happen if a para anchor is set directly from the bow. The para anchor will try to pull the boat out of the hove to position thus will present its keel directly into the wave system and not create any turbulence. A fin keel boat will still sail around a bit and be exposed to breaking seas on its fore quater or even its beam - not good. However very different things happen if there is no "protection" from this slick. As I understand storm conditions, the danger comes from large breaking seas overpowering the boat. Not the type of breaking crests where the water is simply flowing down the front of the wave like a giant white cap. Rather large curling or overreaching seas more like large surf breaking on a shoaling shore. These breaking seas will typically fall onto the lee side of the boat (hove to - out of the slick - or lying ahull). The boat is damaged with tons of water falling onto it. The wind has the boat already heeled, the lee deck is pushed further under by the breaking sea, the circular motion of the surface layer of the wave is pushing the keel up to windward and the boat is at least knocked down if not rolled right over. From my reading, most damage occurs to the lee side of the boat. Slighty different mechanics occur if broaching but the end result remains the same. Again different mechanics with pitch poling and even worse outcomes. The above is simply my limited undertsanding of the dymanics of the seas and mono's in storm conditions concluded from reading every account I can of the same and some rather limited sea time in winds over 40 kts. I am very happy to consider other explanations and to be proved wrong in any of my assumptions.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence |
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