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Old 09-11-2012, 17:44   #31
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Re: Following Seas Dangers?

I have raced and cruised a few thousand miles downwind in heavy air. One thing that I rarely hear from people is not having enough sail going down wind. I have been in that position.

When sailing in big seas there are periods of time when the lower part of your sails are essentially blocked by waves. the sails recieve far less wind thaen is seen on the anenometer. This cause a problem with steering in my opinion. The boat is moving with the waves and has a good pace over the ground; but the boat is not moving thru the water very quickly. This cuts down on the ability to steer b/c no water is moving past the rudder.

When I steer down wind I learned that it is better to bring the boat up in the lulls and down in the puffs. On a race boat this means that you try to keep a consistent apparent wind angle. It also propels the boat thru the water allowing for good steering.

It is also important to balance the sail that you have up. some sail on port and some on starboard. Without this the boat has a tendency to wallow. It rolls from side to side and is very uncomfortable. I suppose that the shape of the stern makes a big difference too. A wide stern with lots of floatation tends to catch waves easier and to float above the waves. The narrower sterns have a harder time with this.

In heavy air while racing down the coast of Mexico we learned to "reef" the spinnaker. The general rule of thumb is to pull the pole back when running deep. When you do this you have a big sail on one side and a smaller sail on the other. When the Spin gets to full it drags the boat over to one side and you get the death rolls ending in a spectacular unplanned gybe. What we would do in big gusts is bring the pole closer to the head stay and then pull in tight on the sheet choking the spin. The spin was reefed behind the main. As the wind eased we would work the pole back.

After driving a Farr 40 hard like that all thru the night the owner came on deck and pulled the pole back. We asked him not to but he did. It was his boat. Within a few seconds the Spin overpowered the rudder and we were on our side with a shreaded spin. A $4k lesson. While we repaired the "storm" Spin I had the owner break out the binocs. I directed his view at the other boats and explained to him that they were boats that should have been miles ahead of us. They were 3 to 5 feet longer. After that he liked the idea of reefing the spin.
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Old 09-11-2012, 18:41   #32
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pirate Re: Following Seas Dangers?

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Originally Posted by msponer View Post
Totally, but I prefer a deeply reefed main downwind than no main. .... it just feels more flexible to have the ....I have a bit of an 'ick' feeling when the main is completely down....
I think I know what you mean, sailing without anything aft of the mast feels to me a bit like coasting up to an intersection in neutral rather than in gear.

You mentioned there are exceptional circumstances. For me, one of those rare exceptions happens when there's enough wind to be able to sail hard on the wind nicely balanced with just the jib. Then the feeling goes away.
Except there's an even more rare and exceptional possibility, which most people will probably never encounter.

It probably doesn't belong in this thread because the thread is about sailing downwind, but I bring it up because when sailing in fiords and sounds it's often necessary to come up with a sail configuration which works on all point of sail, occasionally under very adverse weather conditions.


We are encouraged to think of helm balance as having to do solely with moving the sailplan fore and aft (or, more specifically, moving the centre of effort - which may simply involve changing tensions at the corners, altering mast bend, forestay sag etc)

In my experience this can be relied on only when the boat is toddling along in light winds, sitting relatively upright.

Once you get significant heel, the heel angle becomes the primary variable for balance. However there's a limit to what can be achieved here by reefing, trim and restowing: once you've stood the boat up as much as forward progress permits, if you still have more heel-induced weather helm than is desirable, you may have to relocate all sail area to be forward of the mast.

I suggest care, though, if there's a possibility of wind going off the scale in a situation where you need to sail a close reach ... There's a topic I posted recently in the "Brainteasers" area on this forum called "Paradoxical Lee Helm", which I've discovered can happen to tender boats with tall rigs. The discussion went entirely off track, so anyone who is interested in this syndrome should skip to the end for the conclusions.

My vector diagrams suggest that this effect is due to parasitic drag on the topmast and top rigging. This acts directly downwind, and if the windspeed increases past a (very high) threshold, the long lever arm due to heel combined with the direction can cause sudden-onset major lee helm when close reaching. This tipping point happens if the moment becomes sufficient to overcome the usually predominant weather helm, which arises due to the sail area acting out to leeward.

When you have such large forces, it doesn't take much swing in a direction vector for lots of weather helm to suddenly become lots of lee helm.

It's like a manufacturing operation which makes a margin of only $0.05 on a $20.00 item: if they're selling millions of them, they can still make a lot of money. However if costs change slightly or market forces depress the price, so they're now making a $0.05 loss per item, the high volume can switch overnight from friend to enemy: suddenly the more items they make, the more they lose.
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Old 09-11-2012, 18:51   #33
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Re: Following Seas Dangers?

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Originally Posted by Andrew Troup View Post
I think you misunderstand. Raising a swing keel is something vessels do for the duration.
It might take as long as ten minutes to completely retract on a 50 - 60 footer, so it's not something you do on a wave by wave basis, and it's a decision made as conditions deteriorate.
Not often necessary as boats get bigger, but can be worthwhile in survival conditions.

Swinging it aft is quite often done, though, as it helps reduce weather helm and the resulting risk of broaching.

Wherever it is (unless it's fully up): if it's ballasted, it MUST be capable of being locked so firmly that it would stay where it is if you picked the boat up with a crane and dropped it upside down back in the water.

Because of faulty over-reliance on static theory and lack of understanding of dynamic response of a boat in big waves, many people consider retracting a ballasted keel to be dangerous regardless of context.
While there may be designs where it would be ill-advised, I personally this tactic comes in for a lot of unmerited criticism.

Ive never known anyone that I know with a retractable keel on a largest boat to retact in sailing in large waves, There as too many times you need its hydrodynamic effect. In lots of cases its raises the centre of gravity too, not a thing you really want to do. I think this is a lot of theory talking

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Old 09-11-2012, 18:59   #34
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Re: Following Seas Dangers?

My experience, learned in some storms that I never hope to experience again, is that your milage varies and is highly dependant on boat design and crew ability.

Firstly I tend to agree with the headsail only approach, The main ( on modern production boats ) tends to be too much for most boats and can cause broaching, which is the main danger.


With a good driver, a spade rudder , then reasonable speeds and some surfing can be accommodated without it all getting out of hand. However on undermanned cuisers fatigue and mis-judgements play a far larger part in the problem.

Towing wraps and drogues are my pill of choice, been there have teh T-shirt, never want to wear it again thank you.


Quote:
When I steer down wind I learned that it is better to bring the boat up in the lulls and down in the puffs. On a race boat this means that you try to keep a consistent apparent wind angle. It also propels the boat thru the water allowing for good steering.
Yes that may be the case rqcing , but in a cruising boat, you generally have little concern about maximising speed, the key is too avoid getting into a situation that overwhelms the ability of the helmsman. My experience is that very bad weather incidents are nearly always caused by foggy thinking because of fatigue, then in the application of poor techniques in themselves. In practice in heavy downwind weather, keep main tied away , control the boat with the headsail. On a cruising boat a spinaker in these conditions is a disaster. Avoid overspeeding down the backs of waves, bearing away to avoid a plunge to the trough.

If the crew fatigues out, then you may be forced to heave -to ( not great in modern boats) or as Ive done, turn into it, start the engine and Jog/fore reach.

Having good alert drivers downwind is the problem, especially at night

Dave
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Old 09-11-2012, 19:07   #35
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Re: Following Seas Dangers?

[QUOTE=Charlie;1080657]

What we would do in big gusts is bring the pole closer to the head stay and then pull in tight on the sheet choking the spin. The spin was reefed behind the main. As the wind eased we would work the pole back.

QUOTE]


You are absoultely correct. Aslo, whether you are flying an ayso or sym kite in big winds, 'choke' down the spin sheet, hard! with a floating block midships. This stabilizes the kite and stops most of the wallowing. Move weight aft...
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Old 09-11-2012, 22:07   #36
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Re: Following Seas Dangers?

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Originally Posted by goboatingnow View Post
Ive never known anyone that I know with a retractable keel on a largest boat to retact in sailing in large waves, There as too many times you need its hydrodynamic effect. In lots of cases its raises the centre of gravity too, not a thing you really want to do. I think this is a lot of theory talking

Dave
Presumably you know this either from theory although in your post you seem to be disparaging of "theory talking"...

... or practice although in your post you admit you don't know anyone who has tried the idea in practice.

I'm curious about your basis for rejecting this notion.

I think informed criticism serves a public good.
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Old 09-11-2012, 22:43   #37
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Re: Following Seas Dangers?

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Originally Posted by rebel heart View Post
I've never gotten a chance to sail downwind with a manual windvane, but that might change some of my opinions especially regarding the exhaustion at the helm.
I've done it, it's not a whole lot of fun but I guess it depends on the vane. Mine is an Aries of the lift-up type.

The problem is that downwind the vane doesn't have as much airflow over it as it does upwind. In a light following wind that makes it almost unusable (but then why would you need it?) but in a heavy following wind it's not a whole lot better. Small changes in the wind direction, little gusts as the boat passes over smaller wave crests, etc, can have a much larger effect on the pressure on the vane, which means your steering is magnified by comparison to using the same kit on the wind.

All of which makes the boat screw around a bit, which makes it more dangerous.

Personally I would get the main down well before it's needed, since I have two foresails (cutter rig) I rarely use the main off the wind anyway. Either head directly downwind with just the staysail, and lash the helm, or use the electronic autopilot.

I've had good results with the staysail poled out in a moderate to heavy breeze, not a huge sea running (perhaps peaking at 2-3m) and the helm lashed to center. A friend here says he's tried a similar rig with the helm left free, but I've never tried that.
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Old 10-11-2012, 03:12   #38
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Quote:
Originally Posted by Andrew Troup

Presumably you know this either from theory – although in your post you seem to be disparaging of "theory talking"...

... or practice – although in your post you admit you don't know anyone who has tried the idea in practice.

I'm curious about your basis for rejecting this notion.

I think informed criticism serves a public good.
What I meant was that the very few people I know with retractable keels ( or centreboards etc) never used them in the manner described. , ie lift them in a big downwind storm. I mean what happens if you broach or suddenly need your keel ?

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Old 10-11-2012, 03:37   #39
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Re: Following Seas Dangers?

Apologies if this is a stupid question: Are the chances/dangers of being pooped by a following wave increased if you have a drogue slowing you down too much?
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Old 10-11-2012, 04:49   #40
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Re: Following Seas Dangers?

Ship2210 - no, the drogue doesn't add to the likelihood of this happening, but what it will ensure is that the breaking wave will not hit the boat broadside-on; if the height of the wave is over half of the LWL when hitting broadside then the odds are that the boat will roll whereas if the breaking wave dumps into the cockpit from aft then the boat should remain upright and boat designs for offshore work include adequate cockpt water drainage so that there will be enough bouyancy. Of course that assumes that all the hatches are closed and hold.
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Old 10-11-2012, 04:56   #41
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Re: Following Seas Dangers?

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Originally Posted by Zanshin View Post
Ship2210 - no, the drogue doesn't add to the likelihood of this happening, but what it will ensure is that the breaking wave will not hit the boat broadside-on; if the height of the wave is over half of the LWL when hitting broadside then the odds are that the boat will roll whereas if the breaking wave dumps into the cockpit from aft then the boat should remain upright and boat designs for offshore work include adequate cockpt water drainage so that there will be enough bouyancy. Of course that assumes that all the hatches are closed and hold.
Thanks Zanshin, a good answer that makes sense to me. I guess having the hatches closed in those sort of conditions is in any event the prudent thing to do and the pooping water will drain away and not cause any real headaches other than a wet helmsman lol
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Old 10-11-2012, 05:25   #42
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Re: Following Seas Dangers?

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Ship2210 - no, the drogue doesn't add to the likelihood of this happening, but what it will ensure is that the breaking wave will not hit the boat broadside-on; if the height of the wave is over half of the LWL when hitting broadside then the odds are that the boat will roll whereas if the breaking wave dumps into the cockpit from aft then the boat should remain upright and boat designs for offshore work include adequate cockpt water drainage so that there will be enough bouyancy. Of course that assumes that all the hatches are closed and hold.

It is my *understanding* -- not my experience, but my *understanding* -- that both the drogue and the parachute are for holding one's position in relation to the wave direction. The thing that pokes me in the back of my mind about that is that wave direction isn't always that consistent.

I have enough experience to respect the dangers of a large following sea -- in my first boat, five foot waves were enough to try to broach my little, overcanvassed boat -- and what prompted me to buy both pieces of equipment (at GREAT prices). I've also lost my rudder TWICE now -- first time it was old and compromised, and second time it was just truly unfortunate timing with a shallow bottom and confused waves close together -- my point being that I bought two drogues (cheaply) because they could also aid in steering someday if this is some kind of recurring nightmare ...

The parachute in particular I would not deploy unless things were REALLY rough, but my boat is not heavy, and bow tender, and I think it was a good purchase. I would PLAN on staying with it out for some time and not expect to be able to haul it back in easily while there's still a lot of strain on it.

But I've been in the situation of a following sea trying to broach me in the valleys, and not being able to reef with the wind behind me -- coupled with a crew member who would NOT follow directions to dump the sails, which is all we needed to get it under control, as it just wasn't that bad out there.

She would tell you to this day that I was wrong and she was right. Didn't she SEE and FEEL that ass swinging around??? Where was she????

There are some people you sail with not once but twice. Bad enough when the crew thinks (but doesn't) know more, but when they're OBLIVIOUS to what it would mean for a small boat to be taking those waves broadside ...

it still leaves me scratching my head.

I finally saw my chance with the boat under control and turned her around (she didn't like that call either).

ANYWAY -- having had that experience, and wanting to be well prepared should the next one be worse --

How much would waves from unexpected directions affect the use of a drogue? When it happened to me, the waves were absolutely consistent -- big (for my little boat and my miniscule experience at the time), and very predictable. What we really needed was less canvas but that was't possible. Taking it down and just using the headsail wasn't possible either -- the headsail had jammed and was ripped.

But the bigger following seas shown here don't look as ... consistend (the nerve!)
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Old 10-11-2012, 06:23   #43
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I love the analogy of energy transfer. This is what a drogue or sea anchor does. It transfers force to fittings and then distributes it out over the device and the inherent resistance. Too much you loose steerage. You can add energy by adding sail. Like laying a hull the energy is present. The boat and its surface decides how to dissipate the energy.
Just like good sailing you transfer the energy from the sail to another foil the keel.
Balance all the energy and you do well. Screw the pooch and you roll or swamp pitch pole whatever.
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Old 10-11-2012, 07:01   #44
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Re: Following Seas Dangers?

isnt the following seas that are a problem, but the BREAKING following sea. even quartering seas an poop the cockpit---btdt in moderate seas (less than 8 ft)in gom--being confused seas, gulf of mexico seas can be fun to sail.
pacific coastal seas are bigger than the seas of gom and atlantic, as normal, as pacific has fetch from japan to build them. also has less chop unless you are close to shore or in a storm...is not bad sailing them down hill... bashing uphill is a problem, and very wet. we experienced seas from 0 ft to 30 ft on our trek down here from sd--was not a problem, as the timing was good. we hit no bad weather, pr plan. we did have a sudden gut lasting a few hours of 60+ kts--also common here on west coast. last yer here in la cruz was experienced by the anchored boats, a heavy 90+mph down draft--not uncommon here. not all our winds get to 90+, mostly they range from 15-30 kts daily in afternoons. perfect bay for year round sailing.
i found is easier to sail thru problems than to try to stop an d futz with bs until problems occur. but, then , i prepare well for everything and do not have qualms about a sea of 8 ft in gom. over 8 ft, smart sailors know is impending storm activity in gom. in pacific, is just another day in pair a dice.
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Old 10-11-2012, 07:42   #45
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Quote:
Originally Posted by goboatingnow

What I meant was that the very few people I know with retractable keels ( or centreboards etc) never used them in the manner described. , ie lift them in a big downwind storm. I mean what happens if you broach or suddenly need your keel ?

Dave
I have a lifting keel, actualy two. One is a small trimming keel aft of the main lifting keel.

I have not sailed this boat in "storm" conditions, breaking waves, but i have had her out in steep large waves for long periods of time.

The best case of lifting the keel to keep motion safer was on a south atlantic crossing where we had long period 3m waves coming from the south with building 4m waves from the east from relitively local gales. By lifting the main keel 75% it shited the CE back and then leaving the adt keel fully dropped it dramitically reduced the effects of the southerly gale "knocking the boat off the face" of the waves. Similar to stopping the tripping action.

I would most definitely partially lift my primary keel in heavy conditoons where there were breaking waves and i had a drogue out.
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