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Old 17-06-2010, 07:20   #1
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On the Verge of Flipping-Over a Cruising Cat...

39 feet well known brand and make cat, my wife + two guests with me on board, 25-27 knts just at 90 degree (apparent) on my starboard, boat speed on water 10,5-10,7 knots, almost flat water (2 max 3 ft swells from the wind direction) no reef and everything seems to be under conrol with the exception of the rudder that is pulling strongly towards the wind. At certain point, the cat suddenly swang towards the wind and almost simultaneously the starboard hull took off. We were heeled for about 5-7 sec up to 25-30 degree. I steered immediately further to the wind (nothing to do with seamanship just an instinct..) which fortunately worked well and the cat stabilized, we took down the sails immediately and came back to marina just 2 nm away. The people that has seen us from the marina confirmed that one hull was completely out of water for a while. Not to mention that I was dead scared and still cannot believe that we could recover form the situation without being fliiped over. (from what I know, contrary to mıonohulls, the cats are very tough to be heeled but once they reach 7-10 degree, they go down easily)

I must have mde many mistake to fall into this position. Nevertheless, to my knowledge whatever you do, a well designed cruising the cat would never and ever run into this kind of trouble.. (remember almost flat water, the true wind not exceeding 25 knots and from behind, boat speed around 11 knots..)
Meanwhile I must say that I am not an experienced sailors as much as most of you guys in this forum. But I have sailed many times in much tougher conditions various cats (and even some monos) and I didn't even come close to anything like this.
I am ruling out the possibility of serious design error as the make is well established and proven. We checked out the boat and there was nothing wrong with the riggins or mechanics.

So what must have gone wrong, any thoughts ?? How this could have happened ?

Cheers

Yeloya
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Old 17-06-2010, 07:24   #2
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I think that in 27 knots under full sail you had gone beyond the point of needing to shorten sail.
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Old 17-06-2010, 07:36   #3
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Every treatise I have ever read has said you ALWAYS reef based upon your instruments, not on feel in a catamaran. The challenge with a cat is you don't get that visceral feed back that you're coming close to an incidence. The general rule is you take your first reef at 25 knots of wind.

I think most theory suggest that once you achieve a certain heeling angle, your righting moment starts decreasing. This is as opposed to a mono-hull whose righting moment is steadily increasing with healing angle. Fortunately, the same principle of "spilling air" as you heel helped to keep you out of trouble here. Live, and learn!
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Old 17-06-2010, 08:19   #4
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Quote:
Originally Posted by yeloya View Post
... 25-27 knts just at 90 degree (apparent) on my starboard, boat speed on water 10,5-10,7 knots, almost flat water (2 max 3 ft swells from the wind direction) no reef and everything seems to be under conrol with the exception of the rudder that is pulling strongly towards the wind...
Yeloya
I think your story tells it all. I have no idea about reefing your sails at this point, probably you should have, but I don't think it has anything to do with what happened.
Just apon what you described, I think your sails where not balanced, and your main sail was pulled in way to much. I seen it happen allot on mono hulls.
Basically, your center of rotation is between the main sail and the head sail/ genoa.
Your main will try to pull the boat in to the wind (what sounds like happen to you) and your head sail will try to pull the boat away from the wind.

A well balanced sailing boat should have the rudder in the middle, with the sails steering the boat and keeping her on course.

When the boat heads in to the wind, 2 things happen, the amount of wind pressure on the sails increases, and the rotation it self creates pressure on the sails, so combined the two forces got the hull closest to the wind got out of the water.

I would recommend that you take the boat out on a nice day, get only the main up, see how the boat reacts. pull only the genoa out and find how the boat reacts. find the balance points for your sails in all sail directions relevant to the apparent and true wind, and enjoy your boat.

My best advise is be a lazy sailor, if you have to fight the boat than something is wrong.
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Old 17-06-2010, 08:36   #5
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Should have taken a reef! Way too much sail for the wind conditions unless you're on a 39' Hobbie Cat. Never minded pushing those cats into never-never land!

Chuck
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Old 17-06-2010, 09:07   #6
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I am surprised that a 39' cat (Privilege I assume?) would lift a hull under those conditions. I would expect the static stability of a boat like this to be closer to 50 knots, although some boats are designed with less. In 25-27 knots gusts of 35 knots would be common and 40 knots not unheard of. Were you in an area where you may have been affected by katabatic winds? Does this mean that Privilege will be adding hiking straps to their boats?

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Old 17-06-2010, 09:08   #7
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If you tried to turn a car that sharply. it might get up on two wheels, too!
Weather helm (the tendancy for a boat to turn into the wind) is a safety valve. A little is a good thing. Too much, and the rudders can stall. The result will be just what you experienced. Weather helm can result from over-trimming the main sail, or under trimming the jib or genoa. If you only have one set of sail-tails on the headsail, you might miss a clue that the headsail is out of trim. That can happen if your genoa sheet cars are too far aft or forward. Three sets of sailtails will tell you if you should change the sheeting angle.

This is how a problem could develop: Your genoa car is too far aft which lets the top of the sail open out, spilling air. The sailtails at the middle of the luff could still be looking right, but the main is doing more of the work, increasing weather helm. An extra puff is all it takes to overpower the rudders, and the boat heads up very quickly. Then car dynamics take over and you are flying a hull. Fortunately the new heading is too high for the sail to work, unloading the weatherhelm and giving you back control.

Solution: Someone has a hand on the mainsheet or the traveller; Letting it out a little bit fixes the problem immediately, the rudders don't stall, and you remain in control, sailing even faster!

So add this to you sailing routine: when sailing fast, be ready to ease the main at any moment.

The above applies to cruising cats: the dynamics of very high performance cats can require you to actually turn down wind to maintain control in gusts!

Another point: taking a reef in the main before you get to this point is not only prudent; it could actually improve your VMG by reducing your slip angle! You could be going FASTER!!!
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Old 17-06-2010, 09:17   #8
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In addition to too much sail area and an over-sheeted, over-traveled main, you must have gotten a gust.

Quote:
At certain point, the cat suddenly swang towards the wind...
In those conditions, without having a reef in, I would have had someone first ease the main sheet (to get the tell tales flying properly) and then the traveler to ease the weather helm.

Glad you are here to talk about it with the cat still upright.

Fair Winds,
Mike
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Old 17-06-2010, 09:21   #9
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It seems that the rudder lost it's bite, in part because it was over loaded by having too much main up, in part because many cruising cats have undersize foils, and perhaps in part as a wiave pulled the foil out of the water (only 1 rudder working).

When the helm gets heavy, the main needs to get smaller. Often sailors reduce the jib first (or set a small working jib) because this is easier, but it is quite unbalanced on many boats. The heavy helm was a clue.

My personal opinion () is that the best way to learn to sail big cats is to start on beach cats. But--there is always a but--the reaction time of a big cat is much slower. Sandy suggested that bearing off my be a solution (it is often a good answer on beach cats and the Stilettos that Sandy and I both used to drive) but since your rudder was cavitating, I doubt you could have turned quickly. It is a good answer if the boat is balanced.
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Old 17-06-2010, 09:34   #10
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Sheet out the main. Always have somebody on the main sheet if sailing full up in heavier winds on a cat. If weather helm shows up, sheet out and head down to unload, especially on a beam reach. If sheeting out doesn't work, reef.
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Old 17-06-2010, 09:34   #11
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thinwater,

In that much wind, a cruising cat with rudders a bit too small and an over-trimmed main would be unable to turn downwind.

Fair Winds,
Mike
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Old 17-06-2010, 10:00   #12
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Turning down in a gust is ONLY appropriate in ultra-high performance multis sailing below a beam reach, where their boat speed adds a considerable amount to the apparent wind. It is not appropriate for any cruiser. I'm not sure where the trade-off occurs, but I think its limited to boats that fly a hull as a matter of routine, and that doesn't even include Outremer Ultra lights! For our PDQs and Catanas and FP's et al, heading up is the answer for a gust from any point of sail above a run. Easing the sheets should be the immediate response, always!
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Old 17-06-2010, 10:17   #13
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On a sailing vessel (wind surfer, hobie cat, beneteau 49) if it is hard to do you are doing it the wrong way, the easy way is the right way! Thanks to Penny Whititng of NZ for that line!

In this case:
1. reefed main
2. drop/ease the main sheet
3. i hear drop the traveler a lot but wonder if a combo of taking on the traveler to windward and simultaneously dropping the main sheet is not a better way to open up the top of the big roachy mains. More twist at the top is a good thing in the stiffer breezes since the heavier air is alway higher off the water. Not sure here just thinking out loud...I am sure the boom vang could use some more or less tension to optimize the twist at the top too?

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Old 17-06-2010, 10:19   #14
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Doctrine for a Manta 42 is 1st reef at 20kts. I'll bet that the boat was shuddering a bit as you sailed on that beam reach. That's the clue to reef. Another clue is the higher rudder angle required to maintain heading. Less sail = less rudder = higher SOG anyway.

I think what saved you was only the air spilling out the top of the sail when you heeled over; then your turn to windward. You had to have caught a gust.

Cheap lesson learned - glad everyone is safe.
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Old 17-06-2010, 11:35   #15
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My Endeavourcat uses the same basic rig as the Manta and also has a recommended first reef at 20 knots. The Endeavourcat has fairly small rudders for a 43.5 foot boat and at 10 knots (boat speed) or above I notice they start to loose their effectiveness and it's time to reef. This point also happens to correspond well to the 20 knot wind speed rule. I find that I usually loose less than a knot of speed but controlability is greatly improved and the weatherhelm disappears, at least up to the point where I have to put in the second reef.
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