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Old 23-08-2010, 13:00   #271
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Quote:
Originally Posted by estarzinger View Post
One question for you large multi-hull sailors - can you reef while sailing downwind?
Not sure if my boat counts as "large" but yes, IMO this is a critically important feature on all cruising multis and yes we can and do reef on all points of sail. I have my reefs set-up with a simple single line system and I grind them in using a winch when sailing downwind with large amounts of apparent wind. For shaking them out the single line system allows me to control the twist as the sail goes up so the battens don't get hung up on the shrouds. Obviously reefs go in and out faster and easier with the wind forward of the beam and there is less that I can do to de-power the main with the wind aft so I use less main and bigger sails forward of the mast when sailing down wind. DDW with full main in big conditions on a multi is just asking for trouble. Also might be worth considering that a "fused" main would not be helpful when running, indeed if the fuse on a reef line blew while tucking it in it would be "bad"...

Gavin LeSueur's Multihull Seamanship has a nice section on reefing and is a useful and amusingly illustrated read IMO.

Tom
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Old 23-08-2010, 13:58   #272
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Thanks for the photo, Estarzinger - and you are correct, that is a pretty deep reef. One of the issues that makes it difficult to answer your question precisely is that cats, like monohulls, have different balance: they can have weather-helm, be relatively neutral, or have lee helm. Frankly, I don't know if they were suddenly on a beam reach because of lee-helm, or whether the winds shifted aft, or both. If due to lee helm (a dangerous tendancy, IMO, on any boat), then they may well have been better to bear off as that is the natural tendancy of the boat (and it would take much longer to head up from a beam reach on a boat with lee helm ). On the other hand if it was from the winds shifting aft, it could have (and as you pointed out, should have) been dealt with by setting the autopilot to wind angle rather than compass course.

When on a true beam reach (wind absolutely perpendicular to the hulls), the situation is more complicated and one could technically do either - again, depending upon the boat and conditions. If the prevailing winds were in fact, typically slightly forward of 90 degrees, then it would be better to head up, unless: a) your boat has significant lee helm (as discussed - and, by the way, a condition which I would have attempted to correct before going offshore in any boat), and/or b) you will also be turning the sides of the boat towards large waves.

As indicated, each boat behaves differently, but the important thing is to have a plan of action ready for your boat in any conditions that may arise. My boat has slight weather-helm and hence, my preference is to head up if the true wind is abeam (and that is, afterall, also the natural tendancy of the boat); only if by heading up into the wind I would also be bearing off large seas (and hence now taking them from the side), would I have a different plan of action when beam reaching.

Of course, part of the problem is that for safety, I wouldn't be beam reaching in heavy and changeable conditions. Why? Because you will typically be taking the greatest forces of wind/waves directly off the beam, thereby increasing the risk of capsize. In those conditions I prefer to bear off to a broad reach or run (the most comfortable for most cats, expecially in heavy seas, as you don't run the risk of broaching). Alternatively, I could have been close reaching as the seas were apparently not very large. In those circumstances, a powerful below-deck, hydraulic autopilot like mine would certainly be able to quickly and effectively keep the boat at the correct angle to the wind for the existing sail trim. No, you wouldn't end up with the additional safety provided by luffing (or letting out the sails), but at least you would not end up with the additional heeling forces generated when the boat is turned off the wind with sails that are sheeted in too taut for the new course.

Sorry if the above sounds very complicated - it really isn't. First, get to know how your own boat responds. My doesn't have lee helm, so that is a factor I do not have to consider. On a beam reach (or forward of the same), I would head up unless in doing so I would also be bearing off of large seas - a pretty rare situation.

When on a course below a pure beam reach, or on a broad reach, I would typically bear off. And in heavy/changeable conditions with squalls in the area, I tend to avoid beam reaches for all of the reasons indicated.

Brad
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Old 23-08-2010, 14:25   #273
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Quote:
Originally Posted by tsmwebb View Post
a "fused" main would not be helpful when running
Yes, pitch poling while running is a whole nother situation. What's the frequency of that? I had assumed (for largish cruising multis) much lower than side capsize but perhaps I am wrong (again).

For the fuse, on an A57 . . . I have just been playing around with some calculation, which suggest the clew load would be about 10,000lbs at 15 degrees of heel. And the hull 'lift off' load would be about 3000lbs. A fuse of four turns (8 legs) of 1/8" spectra would have about 7600lbs of tensile strength - so good safety factor against breaking at normal 'lift off' load but also good safety factor in breaking before capsize.

Interesting that you can reef downwind in strong winds. Do you have lazy jacks? The minute I easy my halyard to start reefing, the leach tension goes off and the sail inverts and the battens bend around everything available (lazy jacks and stays and spreaders). In theory I can crank in down by easing the halyard an inch and then cranking in the clew reef line to re tension the leach and then repeat . . . but that takes way to long in this sort of squall and can (and has) put rips in the sail.
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Old 23-08-2010, 14:43   #274
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Originally Posted by cat man do View Post
Can you access all the sheets and winches for a fast dump of sail power while inside?
Despite the conditions outside, probably the worst thing you can do is sail your boat from inside - I don't think you get the full impact of the conditions when you can't feel the wind and noise. Would you sail blind folded with earplugs in?
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Old 23-08-2010, 14:57   #275
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Intersting comments from the designer here:

"Only 2 weeks ago, as Kate and I sailed Javelin south along the Windward Islands in the Caribbean, a squall of this type hit us hard. There was a tropical wave passing through which was in the process of turning into a tropical storm, and atmospheric conditions were quite unstable with overcast skies and frequent squalls. It had been blowing 18-20 knots and we had a single reef in the main and the full self tacking staysail. We were sailing at a true wind angle of 50 degrees or so at about 9 knots. The squall looked like the others more or less, though I was concerned that its movement seemed different. In any case, a few minutes after the initial wind gust and rain, the wind really cranked up and headed us. Then it increased again and headed us more. There was way too much wind for the sail we carried, so I luffed up enough to depower Javelin, trying to walk the fine line between flogging the sails violently and keeping our boat speed down below 12 kts. It was exciting, too exciting, and when it did not let up after a few minutes we dropped the mainsail entirely. If truth be told, the whole event left me pretty rattled. We experienced an increase from 20 to 45 kts of wind in a fraction of a minute along with a 90 degree wind shift. I did not expect that at all."

You have to wonder if the results of Anna would have been repeated had the breeze lifted rather then headed? It's pretty easy to sail fat when the auto is driving.
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Old 23-08-2010, 15:01   #276
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Again from the designer:

The Autopilot must be turned off!!

We sailors have to physically take control of the boat in a squall. Pilot off, hands on the wheel, ready to respond.

Quote:
Originally Posted by estarzinger View Post
Perhaps I would have to relearn/retrain that reflex, and take a multihull wheel more, but then I am stuck on the wheel and Beth is alone to do all the sail handling. Somehow that does not seem like the right answer when we have a very capable autopilot.
As you said, who tends the sheets?
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Old 23-08-2010, 15:05   #277
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Your number may be low? Our sheet load uwpind in 28 knots with the #3 is about 8 tons. Given the tremendous righting moment of the Atlantic it's gotta be a whole bunch higher then 5 tons?

Quote:
Originally Posted by estarzinger View Post
Yes, pitch poling while running is a whole nother situation. What's the frequency of that? I had assumed (for largish cruising multis) much lower than side capsize but perhaps I am wrong (again).

For the fuse, on an A57 . . . I have just been playing around with some calculation, which suggest the clew load would be about 10,000lbs at 15 degrees of heel. And the hull 'lift off' load would be about 3000lbs. A fuse of four turns (8 legs) of 1/8" spectra would have about 7600lbs of tensile strength - so good safety factor against breaking at normal 'lift off' load but also good safety factor in breaking before capsize.

Interesting that you can reef downwind in strong winds. Do you have lazy jacks? The minute I easy my halyard to start reefing, the leach tension goes off and the sail inverts and the battens bend around everything available (lazy jacks and stays and spreaders). In theory I can crank in down by easing the halyard an inch and then cranking in the clew reef line to re tension the leach and then repeat . . . but that takes way to long in this sort of squall and can (and has) put rips in the sail.
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Old 23-08-2010, 15:52   #278
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Originally Posted by estarzinger View Post
Yes, pitch poling while running is a whole nother situation. What's the frequency of that? I had assumed (for largish cruising multis) much lower than side capsize but perhaps I am wrong (again).
Good question. Wish I knew the answer. I can't cite any purely wind induced picth poles in non-racing multis. Don't know that that means anything. I did hear a rumor of a charter cat pitch poling but a) I never could track down the specifics and b) the rumor suggested breaking waves as a factor. For some tris and very wide cats, particularly if not sufficiently buoyant forward, there is a potential danger at least in a very violent gust. The mechanics are the same as with the racers but a lot more wind would be required. Still, in as much as I can tell it's rarer than conventional capsize, already a rare event. More common, I suspect, is loss of control when running off which can start off a whole series of "bad" things. Multis can broach.

Quote:
Interesting that you can reef downwind in strong winds. Do you have lazy jacks?
We have lazy jacks but we don't have problems with the battens hanging up on them on the way down. We can simply dump the halyard to the mark and grind in any of our reefs even DDW. It is still a slower/harder process than reefing with the wind forward. And, we don't usually do it that way because the battens warp around the shrouds and the pockets chafe -- we have high pressure hydraulic hose on our uppers which is slippery and that helps nevertheless sails ain't cheap... Typically we over-trim the main a bit dump the halyard to the point where the sail is kissing the shrouds and then hump it down and repeat. A process that takes several minutes if running deep so, as always, best to anticipate and be conservative. The battens can get caught up in the shrouds when hoisting making that a slower process.

Tom
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Old 23-08-2010, 18:52   #279
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It's interesting how the earlier generation of multihull designers, builders, and sailors were much more wary of wind-induced capsize. Wharram, Brown, and even Chris White on his early designs had very conservative rigs put on much heavier boats, and they rarely capsized. I wonder why the change in notion of what is acceptable on multis? I don't think the physics have changed. Some will say that we have a better understanding of design compared to those old farts, which is true, but then the designers are admitting that they are piling on the power today until a capsize is definitely within the realm of normal sailing if the crew doesn't carefully watch what they are doing. I wonder if modern sailors feel that they are much more likely to be rescued quickly, or maybe they are confident that with radar and weather forecasting they will avoid bad weather, which can't always be the case? One thing I know is that the folks sailing these boats have lots of money (the boats are so expensive) so losing the boat is not viewed as a financial catastrophe. So, yes the modern multi is definitely faster, but they don't seem to be safer. The same might be said for many modern cruising monos. An interesting regression in some ways.
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Old 23-08-2010, 19:37   #280
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Your number may be low?
I wonder if dragon knows anything about his sheet loads or righting moment on his A55?

They seemed low to me also. I am essentially scaling up some data I had for a much smaller performance cat, so it is possible I am way off. . . . but I notice two things that made it seem possibly in the right ballpark. #1 they roughtly match the size (safe working load) blocks used in the mainsheet system. And #2 Harken has a nice load calculator. It only takes into account the size of the sail and not the platform under the sail. But the 'lift off' load matches what Harken says the loads will be at 20kts, which could possibly be right with full sail up (with 'empty displacement trim').

Anyway, its just an example calculation to show what could be done if Chris W gave the owners the real righting moment curve.
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Old 24-08-2010, 08:00   #281
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Since previous posters have mentioned Gunboats, I copied this from the Gunboat Website:
"Speed = Storm Avoidance
The ultimate safety feature is pure speed. Sail around storms. If a storm is unavoidable, safety is derived from the ability to surf sideways. With daggerboards up, the round bottom hulls will skate sideways along waves, and the long high bows offer tremendous reserve buoyancy. We believe mega catamarans are the safest platform for surviving the worst weather."

The Atlantic Cats have stub keels, and the first picture of it on the reef there was one board obviously down (up), but it also appeared that the Stbd board was also deployed. Kelly's acct. indicated that only the lee board was down.

As noted in many posts, the sea is unforgiving. Couple that with the inherent dangers of high performance catamarans, and there is always the potential for disaster.

Are HP Cats unsafe? Absolutely not. Maybe "unforgiving". I wouldn't want to be on anything else. Returning from FL to Annapolis in June 2 years ago, we spent 2 days watching thunderstorm cells cross our path, mostly on the plotter. Anything that was on a converging course, we watched carefully, and at the first sign of increasing winds, we doused all sail. several times were uncecessay, with winds only increasing to the low 30's, but twice the winds went over 60. Overcautious? Probably. Moreso now, than when I was younger and sailing & racing with larger crews.

IMHO - The problem with release mechanisms and fuses, is that sooner or later murphy's law can come into play. If folks begin to replace good seamanship with "devices", disasters like ANNA will continue to increase. Unfortunately, Cats are as stable upside down as they are rightside up.
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Old 24-08-2010, 08:19   #282
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Nice post Dragonboat.
I am wondering why you feel it's unfortunate that cats are as stable upside down as right side up? Verses what? No boat at all?
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Old 24-08-2010, 08:47   #283
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Nice post Dragonboat.
I am wondering why you feel it's unfortunate that cats are as stable upside down as right side up? Verses what? No boat at all?
Previous posts have beat the drums of monos vs. cats. The "unsinkable" attribute of the HP cats makes "self-righting" virtually impossible. On beach cats, a mast head float prevents a 180. Not practical on a mega-cat.

As I had said - I'd rather be on an unsinkable cat, than a heavily ballasted mono. It's a choice - to be made with eyes open. Know your limits, as well as the limits of your craft.
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Old 24-08-2010, 11:26   #284
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We thought you were too busy drink good red wine and thinking about playing with velvet

The french (open 60's and g class multis) have looked at this problem (actually a slightly different problem . . . their focus is preventing the loads from breaking the boat, not preventing capsize) and concluded fuses were the answer. That does not mean they are right . . . perhaps their engineers are also distracted by red wine and velvet

I don't understand the reluctance to a clew fuse:

1. I am sure in cruising mode you don't want/plan to ever fly a hull, and lets say 5 degrees of flying hull is the most acceptable. If you set the fuse at the 15 degree righting moment you have a 3x safety factor (the righting loads are almost linear at that part of the curve) so, it will 'never' blow in normal conditions but could save you from a capsize.
You're vast experience on a monohull has led you astray. The righting moment on a multihull does not increase linearly between 0-45 degrees. What actually does happen, is that the righting moment increases very rapidly until you begin to fly a hull (usually around 7 degrees-ish) then decreases. What this means is that if you set your fuse to blow at 15 degrees, it will ALWAYS blow in 'normal' conditions (boat is level with both hulls in the water).

In order for a fuse to work as intended it would need to be smarter than spectra rope. Take these two scenarios into consideration:

1) Wind blows hard on boat. Boat begins to fly a hull. Wind continues to push and boats hull raises 30 degrees.

2) Wind blows hard on boat. Boat begins to fly a hull, but at the exact moment the hull starts to leave the water, the wind dies down moderately so the hull is safely in the water but still pushing quite hard on the sail.

If you simply look at the force on the clew for both these cases, there would be no way to distinguish between the two.

I suspect that this is the reason why we don't see "anti-capsize" fuses on cats.
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Old 24-08-2010, 11:36   #285
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