Favorite rough weather technique

Discussion in 'Sailboats' started by gonzo, Nov 10, 2009.

  1. gonzo
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    gonzo Senior Member

    A fin keel 4 to 6 times less area? Are you serious? Fin keels have more area and that is why they are more efficient upwind. Don't throw stupid numbers around to try to win an invalid argument.
     
  2. TeddyDiver
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    TeddyDiver Gollywobbler

    You better to check your facts too... ;) Thou Vimes exaggerated some..
     
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  3. gonzo
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    gonzo Senior Member

    Measure the actual lateral area of a long versus a fin keel
     
  4. MikeJohns
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    MikeJohns Senior Member

    Without specifying the vessel and the ‘fin’ and the ‘full‘ you can’t put numbers on it.

    Generally and for most of the vessels I can think of the lateral plane area is lower for the fin keel version.

    The dual role of the sail-boat keel as the ballast carrier usually dictates the span (depth) and for the same beam and same righting moments this will result in a full (or ¾) keel with significantly more lateral plane area, perhaps cut-away creatively fore and aft to reduce wetted surface a little or to shift the CLR. The fin shaped foil will not usually be deeper than required for the righting moment and will have a smaller lateral plane projection.

    Fin keels have a better lift to drag ratio but they stall more easily. When stalled they are not as good at damping or entraining mass as a keel with a longer chord.
     
  5. BeauVrolyk
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    BeauVrolyk Sailor

    While the keel's lateral area certainly inhibits rolling around the horizontal fore/aft axis, in large waves that are attempting to knock the boat down (which is what we were discussing) it actually works the other way. Consider the action of the wave on the boat.

    First the boat is sitting relatively upright. Second, a wave smashes into the beam of the boat attempting to hurl it down the wave front. Third, the keel (providing lateral resistance) resists moving sideways through the water. This causes the boat to heel much more than a boat with little or no keel.

    The greater the lateral resistance to the water, when trying to move the boat sideways down a wave, the more the boat will heel.

    This is precisely why I used to pull the centerboard up in really bad weather in my big ketch. I could actually observe a wake from the boat streaming off to windward as the waves and wind pushed the boat sideways down wind. Saga heeled much less and was far easier to ride upon. It is also why a dingy will be much easier to keep upright going down wind with the board up a bit than all the way down. Try this in a Laser or 5O5.

    The effect is precisely opposite to rolling induced by waves that are smaller than the depth of the keel, such as those found when out for a sunday sail in fine weather. There, the long keel helps keep the boat stable and the bigger the better, as you've correctly noted. But, when the waves get really big the big keel works against you. It is a bit like imagining a sea anchor attached to the bottom of the keel as the boat is being tossed down a wave; the lateral pull of the sea anchor would make the boat heel more not less.

    BV
     
  6. TollyWally
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    TollyWally Senior Member

    BV,
    That is an interesting concept that I had never thought of before. This bears careful consideration.
     
  7. gonzo
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    gonzo Senior Member

    Bringing the centerboard up in really rough weather lessens the rolling. However, a bit of board down helps. Got to find the right spot.
     
  8. TeddyDiver
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    TeddyDiver Gollywobbler

    But but... what are you doing having board up.. I mean running of perhaps bare poles or storm sails, hove-to, lying-a-hull :confused:
    The most weird storm tactics I've ever heard of..
     
  9. gonzo
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    gonzo Senior Member

    If you are beating and heeling too much, it will reduce heeling.
     
  10. BeauVrolyk
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    BeauVrolyk Sailor

    TW,

    Perhaps I should give a few more details on what happens with a "board up" vs "down" and also the difference between a dagger board, like in a Laser, and a centerboard, like in a 5O5.

    The daggerboard lift vertically, which is good from the point of view of keeping the center of lateral resistance closer to its original position. However, there are times when a boat tends to develop weather helm. This can be for a number of reasons. The advantage of a centerboard is that one can start to raise it; and because the board rotates around a pin at the head end, the bottom of the centerboard moves aft. This moves the center of lateral resistance aft and helps counterbalance the weather helm. In old long keel designs these sorts of centerboards are evident on boats like the J class, some of which had two centerboards (one in front of the other) and the crew would balance the helm by raising and lowering the boards.

    Why this matters in this discussion is that in addition to reducing the lateral resistance of the hull/keel combination, by raising the board, in the case of a centerboard moving the center of lateral resistance (you naval architects must have a name for that) aft also allows the bow of the boat to turn down wind when struck by a wave from abeam. Turning down the front of the wave is exactly what you want to do, IMHO, when faced with a "survival" wave. This is because you are going to go with the wave no matter what you do. If you're bow on to it, you'll simply start to go backwards down the face of a really big wave, which is why some folks want a drogue or sea anchor to try and help keep them from traveling backwards. If you're beam on, you'll be tossed on your beam ends and pushed along on your side. If you're stern to the wave your boat will travel in the direction it was intended to travel and either surf down the wave or fall off it. But, in either event, traveling bow first is usually a good idea.

    Why? Because the bow is most likely the strongest part of the boat and when you hit the green water in the trough you'd like to hit it with the bow and not the side or stern of the boat. Earlier in this thread someone correctly pointed out that many failures in the Fastnet Gale were to the lee side of the boat. This is because the boat was struck by the top of a wave on the windward side, which is mostly foam and is relatively soft, and it fell upon the trough which is not full of foam and is hard to land on when falling 15 or 20 feet. If one is going to land on anything with one's boat, and here we're are really talking about gigantic waves, wouldn't one want to land with the strongest bit of the boat, heading in the direction that the boat was designed to go? The alternatives: The side of the boat, which typically has windows or hatches and is relatively weaker than the ends, doesn't seem a good idea. The stern has the rudder, which would be jammed up by going backwards, and also seems like a poor choice. (I won't even discuss landing on the deck, although it happened to Sorcery in the N. Pacific in the '70s.

    Those of you who have been following this discussion will already know I much prefer going with the waves. The reason that a lifting keel or centerboard is so nice is that if you can move the center of lateral resistance further aft the boat becomes much easier to steer as you are trying to go down waves. A great example of something designed to go down waves is a surf board. Look at where the skeg is: right at the back of the board. Moreover, having driven a mini-sat race boat down big waves I can personally tell you that pulling both foward daggerboards all the way up, setting the keel in the middle and having the drag of the twin rudders way back in the boat makes it much easier to drive safely.

    In conclusion, I'd suggest that the ability to move the center of lateral resistance aft has big advantages in surviving large waves. The reasons are that the boat will naturally tend to turn its bow down the wave and try to surf, even without you steering it; and that once surfing the boat will have far less tendency to "trip" over its forefoot and keel as it travels at speeds that it was never designed to proceed at.

    BV
     
  11. TollyWally
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    TollyWally Senior Member

    I've perused this thread with interest. I've always sailed, but the bulk of my heavy weather experience has been in commercial powerboats. Inevitably when worse comes to worse we jog into it. I have heard of some boats hanging onto their gear which is much the same as lying to a sea anchor.

    Carry on.
     
  12. BeauVrolyk
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    BeauVrolyk Sailor

    TD,

    Let me try to explain. Storm tactics in truly awful weather are typically about avoiding an ugly monster wave. One can read about the occurrence of monster or "rogue" waves all over the place, but I have found that they are typically worst in places that have two (or more) crossing wave trains. Good examples of places where this happens is the coast of Oregon and Washington, where the major low frequency swell is from Alaska, coming in from the NW, and the storm generated waves are typically arriving from the SW as the gale moves in. The same effect occurs in the western Caribbean SW of Jamaica when the long trade wind waves from the E cross with those coming from the N around the west end of Jamaica. The problem is that when these wave trains cross the make either additive peaks/crests or subtractive nulls/troughs. The result is that when sailing in a storm that has a "normal" wave height of 10' from one wave train and 20' from another that is from a different direction, you'll find the occasional 30' wave as the two pile atop each other. (You don't get all of 30' but it sure looks that way.) Similarly, when you find a place where the two troughs intersect it will look as if someone dug a big hole in the ocean. When these two events happen to occur next to each other - additive crests and subtractive troughs - you get a wave that is itching to break and steep as hell. I think that this is what we're all trying to talk about surviving.

    Now, the options (and you've listed a lot of them) are to lay-a-hull, heave-to, run-off, keep-sailing, and maybe a few more if you include that for some of these options you could also ride to a sea anchor or trail a drogue.

    My points about having a centerboard, that is most of the way pulled up, is that it allows you to safely keep-sailing or run-off in much larger waves than other alternatives, because the boat is much easier to control. My favorite is run-off.

    Why? Because the helmsman can typically see these monster waves developing. Hell, my cat saw one just before it hit us. (but, that's a furry sea story for another time.) When sailing fast down wind, one can turn to avoid the big holes and bumps in the ocean. It's as simple as that. When hove-to or laying-a-hull you are entirely at the mercy of the sea and wind.

    I can't count the number of times I have chosen to go around a big bump or hole in the ocean. When racing upwind we do it all the time. When racing downwind in modest seas we actually steer to get in front of the biggest waves so we can ride them. But, in survival situations I strongly believe that the best technique is to have one person on the helm and one person looking aft calling the waves. This gives the helmsman warning when something ugly is coming and the boat can be sailed a number of yards to either side to avoid being precisely where the two wave trains cross and the big breaker forms. The reason I recommend that the helmsman not be turning around constantly to look over his/her shoulder for waves is that almost everyone looses a bit of their balance and perspective as they spin their head around; when they turn back to look forward they take a second or two to re-stabilize and that few seconds matter. This is particularly true given that the boat's stern is lifting and the boat is accelerating as the wave comes up on you. Also, if the helmsman doesn't see the really big wave, they won't be as fearful of it and will do a better job steering. Remember, it's all about controlling the boat so that you don't hit holes or fall off bumps.

    Now, to answer your question about what sort of sails, you want to have something up that lets you move along and have good control even when in the lee of the crest, so you'll feel overpowered at the crests and underpowered in the trough. Second, it is easiest for a cruiser to do what my father's sloop did, which is set a storm jib on one side and a small staysail on the other side of the jib stay. If the LP on these sails (overlap) is small, you don't need a whisker pole to hold the sail out (although Dad had two poles - one for each jib), and you can drive all over the ocean without fear. What you do not want is something that is dangerous if you need to gybe. This means getting the mainsail down and setting a storm jib or storm trysail. You want to be able to steer quickly on either side of dead downwind to get out from in front of the wave and avoid being lifted up on top of a big bump. Then, you sail hard, have fun, and shower later - 'cuz you'll be all wet.

    BV
     
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  13. TeddyDiver
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    TeddyDiver Gollywobbler

    Thanks.. answers my question. Not the best option for shorthanded cruiser me thinks..
     
  14. capt vimes
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    capt vimes Senior Member

    very good point...
    i must say that i appreciate your statements to this thread very much...

    ps:
    haven't read yor post 192 when i put my reply on...
    what you are explaining in this post (rougue waves, steering, 'wavewatch' and such) are absolutely in line with my experinces and i doubt that mine are comparable - in terms of amount - to yours...
    nevertheless - i also do think that with modern yachts it is the best way - have personally sailed storms out that way - as you post... but never had the idea or the material to sail 2 stormjibs like your father learned you...
    i will memorize that!

    gonzo:
    4-6 times is a bit too much... sorry
    my apologies!
     

  15. LyndonJ
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    LyndonJ Senior Member

    I thought in extreme circumstances it was more about having a boat that could adopt a passive survival technique.

    Really well manned very fast slippery boats with lots of very experienced operaters on board end up mashed by the sea when the sea conditions get ugly. We've seen that now in several ocean yacht races and how do we account for the fact that it's the beamy light fin keelers that get mashed and the full keel heavier boats generally don't? That's what led to Southampton putting so much time effort and expertise into the question and also what lead to Marchaj writing his tome on seaworthiness. He pointed out that the old full keeled sail boats were almost unknown to capsize over millions of hours of representitive use in the foulest of conditions.

    Surely a boat that can adopt a passive technique is what you should aim for with a shorthanded crew and heavy weather makes you sick and exhausted.
    In 50 knots and over thers's no seeing anything or calling anything, unless you have a wheelhouse. If that goes on for 3 days like the Southern ones that the racers encounter then it's sitting in shelter watching the autopilot. Then it's down to vessel design.

    Many cruisers are very short handed.

    Then there's pretty irrefutable studies that larger area keels are more seaworthy becasue they reduce the sideways surfing and simply roll and present the topsides to the breaker. What you call tripping over the keel. The light beamy skimmer skims sideways tips, digs the deck edge in and catapults over in a very fast inversion. Typically it's "I didn't see it coming and suddenly we were upside down"

    But all this was talked about to death in a couple of other threads too.

    I dont think you can claim superiority for any design without considering the scenario. Have you read Heavy weather sailing ? They are the accounts of survival conditions and the tactics used, very well worth reading.

    I think you really need to do a meta-analysis ( look at all the studies and accounts and draw new conclusions ) not get stuck on one charismatic opinion whoever that may be.

    The best tactic is going to depend on your boats design and how well you can avoid its poorer seaworthiness aspects.

    But I think lightweight racers don't have a scintillating record in rough weather and rescue is a big bussiness from those boats at times.
     
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