On the Verge of Flipping-Over a Cruising Cat...

[yeloya]

The comments so far are focusing in 3 basic points:

-should have been reefed earlier, even some have suggested that I should be putting the reef when I was about to or already flying a hull and instructing how to do it with details. (Thx a lot) If one should reef at 8-12 kn which was the average wind until 2 min before the accident, then something is clearly wrong. Yes, I've seen the gust coming (I could have missed it if it was dark..) and expected it to be around 25 kn. One option was to start the engines, turn around, reef the main and continue. I didn't because I was pretty sure that the boat could easily handle these conditions (which proved wrong) .

-some suggested the wind could be much higher than measured. I too never fully trust instruments, but the wind was close to one I have seen on the anemometer and definately below 30 kn mark. (the difference beetween 25 and 30 + kn is noticeable even by a beginner)

-the issue of trim has been mentioned. We were not perfectly trimmed for sure but not too far off either. My theory is that even if you leave the boat alone or in whatever trim you like, you cannot rollover the cat under these conditions.

Here are some other experiences with similar size of cats from the same manufacturer: (all with full sails, with professional staff pushing the limits..) I didn't include Orona and Salina as they are significantly bigger and heavier:

-Fidji 39 ft, built 92, very narrow hulls, light and early generation cruisin cat. 29-30 kn from 100 app. 14.5 kn (max speed and for couple of minutes) of boat speed, perfectly flat water. I felt we were really on limits, the boat slightly heeled (3-5 degrees max or I felt so..) but boat seemed fully under control. After a shortwhile we eased the main sail and slowed down. This was clearly not a sustainable situation in a long run but the boat felt perfectly safe.
-Athena 38 ft, built in 02, initally the wind was 20-25 kn from 40-45 degree, stabilized later at 28-29 kn with 8-10 ft swells in the direction of the true wind, we could maintain easily 9-9,5 kn for an hour or so. No heeling, wheather helm whatsoever. We later reefed as we thought the wind could further increase. It didn't and with a reef we were back to 8-8.2 kn and we had much more comfortable ride..
-Lipari 39 ft, built in 2010, almost flat water, 25 kn app from 90, 10,5 knots of boat speed. Stalling rudder, lost of control, flying hull ..
Take all the measurements exagerated by 10-20%, so boat speed 12-13 kn (not 10,5) , the wind 30 app (not 25 kn), the heeling only 20-25 degrees (not 30-35)
Add to this scenario extremely poor seamanship and an idiot on the helm !! Does all this justify what has happened ?? That's the only point I want to make.

Happy sailing

Yeloya

[Joli]

Sorry that happened Yeloya. Now in the back your mind resides the "what if" niggling thought. What if your below when the gust goes through, what if your sailing at night and don't see the next gust, what if your off watch and your wife is driving.......... I think that bothers you more then anything else.

Here is the discussion link to the Prescott that went over. Flipped Cat in Airlie - Sailing Anarchy Forums. I think Y-Bar said it best in the thread. "It's a soul destroying event for the owner".

[Southern Star]

Yes, very disconcerting indeed. I am embarrassed to admit that on a couple of occasions while pushing the envelope, I have been hit by a gust in excess of 30 Knots without a reef, yet came nowhere near lifting a hull. Yes, my boat has a rudders aft of the saildrives, a lower SA/displacement ratio and a relatively low CE for the sailplan (it is a cutter rig), but still, it strikes me that no cruising cat should lift a hull in the conditions described by Yeloya. Furthermore, the fact is that there are very few reports of cruising cats being capsized by wind alone (microbursts aside), which tends to confirm that in fact, very few would lift a hulll in those conditions.

As to the cat that capsized out of Airlie Beach, the reports say the owner/skipper had previously "just missed out on the record for round the Whitsundays by a few minutes", so it strikes me that he is hardly your typical cruiser. In any event, I am unfamiliar with the boat in question and have not yet read any reports regarding the wind/sea state, but assuming it is really a cruising oriented boat (a big assumption), I would be suprised if it was caused by a gust of 25 knots on relatively flat seas.

Brad

[Event_Horizon]

Originally Posted by Joli

Sorry that happened Yeloya. Now in the back your mind resides the "what if" niggling thought. What if your below when the gust goes through, what if your sailing at night and don't see the next gust, what if your off watch and your wife is driving.......... I think that bothers you more then anything else.

Cute typo

I'd like to point out that while Yeloya's experience what sudden and an adrenaline rush to be sure. He was probably in no danger of capsizing.

As I understand it, the story goes like this:

-Boat sailing on a beam reach in 25 kts of wind
-Boat suddenly begins a turn--simultaneously, boat begins to fly a hull
-Boat turns further into wind, settles...everyones wishes they wore diapers that day.


From this scenario I'd say that the biggest danger was the momentum of the boat. Granted, you should have reefed, but the wind in this scenario seems more of an enabler than the primary problem.

As someone mentioned before, your sails were unbalanced and that’s why the rudder was pulling toward the wind. Your mainsail sounds like it was way overpowered, this created the force trying to turn you into the wind…likewise, the rudders were doing their best to maintain you heading.
(For a second here you also want to consider the massive momentum boats have when they get going. There is a LOT of energy there. )
At this point many things can happen; you could have caught a gust. One of the larger swells could have taken some of the load off a rudder. Basically, somehow that fine line you were walking tipped in favor of rotation. Also keep in mind this isn’t a turn, the wind artificially shoved the back end of your boat and that the very moment you start rotating it has less influence over your boat. Like always your leeward hull is carrying a heavier burden, it digs into the ocean as your windward hull rises. By turning into the wind you aided in the boats sharp rotation increasing the centripetal force and bringing the hull higher out of the water. Mercifully, nowhere in this scenario is there a sustainable source of energy that could cause you to flip your cat. This action essentially uses all the stored up momentum, with the winds help, and burns it out. This is the same way people flip automobiles. I suspect that no matter which direction you turned your rudder you’d have been fine because there simply wasn’t enough kinetic energy in the system to flip your cat, even though everything that happened (voluntary or not) is exactly what you’d do if you were making a real attempt to capsize your boat.

If wind/reefing were the major issue he’d have been flying a hull when he was at 90 deg apparent and the winds tipping moment was at its maximum. What about a sudden very VERY hard gust?

I took this from boat designer John Shuttleworth (NES Talk)



This is the righting moment for a 35ft cat which should be considerably less than the righting moment is for Yeloya's boat. Since his boat wan't flying a hull from the start. According to this chart his rigging would have to catch a gust that would impart in excess of 15 Tons-ft of rotational force to cause that kind of heeling. Since he didn't indicate that his boat had been demasted by a freak wind, I'm guessing that this wasn't the case (though I have no clue the amount of force it'd actually take to demast his boat...but a 15 Ton-ft impact seems up to the challenge).

[schoonerdog]

I've heard of FPs flipping, in Hong Kong I think they had two flip in the two months. While the FP has a lot of underwater clearance "in general" under the shelves for the after births the clearance is much less. I've suspected the shelves catch the waves at high speed with a lot of force on their huge mainsail and trip the boat.

They also tend to be frequently chartered by cowboys who want to have under their belt a voyage on a catamaran with speeds in the teens.

Regardless, FPs, like my boat frankly, have high SA/D and therefore need to be treated far more conservatively than say a Prout or Privilege or Lagoon.

[Event_Horizon]

SD/A (Mainsail + Genoa for standard models according to builder website info)

Lagoon 440: 22.3
FP Orana 44: 25.94
Privilege 445: 26.99
St. Francis MK II: 31.96

Prout isn't included because they don't have any 44' boats on their website...and I didn't want to do any calculations...cause I'm lazy. But just eyeing the numbers I'd guess that the SA/D is in the lower twenties.

[tsmwebb]

Originally Posted by Event_Horizon

According to this chart his rigging would have to catch a gust that would impart in excess of 15 Tons-ft of rotational force to cause that kind of heeling. Since he didn't indicate that his boat had been demasted by a freak wind, I'm guessing that this wasn't the case (though I have no clue the amount of force it'd actually take to demast his boat...but a 15 Ton-ft impact seems up to the challenge).

Not sure I follow your argument here. Are you saying that a wind induced capsize is impossible because the rig would have to fail and therefore the hull lifting was caused primarily by rotation? Just because the force needed to capsize the boat is large I don't see any reason to believe that the rig was incapable of supporting it. Designing a rig that will fail when sailing at max RM in flat water but will not fail when sailing in pounding conditions where there is no likelihood of a wind induced capsize strikes me as not at all easy. The problem is analogous to an automatic sheet release system. An idea that is still waiting for a practical solution. I don't think either is achievable by measuring force alone. The problem is made even harder because from the moment of max RM the forces on the sheets and rigging will be decreasing. If the boat has gotten a hull up then how will the rig know if the boat is capsizing or returning upright? Lacking specific guidance from the designer of your rig I would not count on it failing before a wind induced capsize. And, I don't think that having a rig designed to fail is all that good an idea. A falling rig is a very dangerous situation.

Having said all of that you do bring up an interesting point. Cruising cats in general have high centers of gravity. On first though I suspect that higher CG's mean more pronounced outward heel in a turn... So, it does seem plausible that the fast round up contributed to the heeling. I don't have a clue how much the turning contributed in this case. So I can't say if it was significant or not. But, even if it was I don't see how that says anything about the rig's strength nor do I see how you conclude that it could not have resulted in a capsize...

Tom.

[Eleven]

Nice graph, Event Horizon. Doesn't allow for a Cat side slipping through the water as the heel develops, which could be the reason for the automatic bearing up experienced.
A mono at half it's stability angle has a new heel formed by the deck angle and is likely to complete a barrel roll. Barrel being the operative word once rig is removed.
Prout designers engineered this slip factor in with long length, short depth keels. A bit of wave action helps of course.

[Intentional Drifter]

A very interesting thread, and educational, too. I'm not enough of an engineer to comment on the math, so I'll restrict my remarks to a user's perspective.

Yeloya, from seeing your previous posts in a number of places and reading those on this thread, too, I've got to believe that you are both a skilled and responsible sailor. It just doesn't seem to me that you would put yourself and your crew in such a situation if you had even the slightest inkling that such a scary and "on the edge" experience was possible.

Even without a reef, 25 to 27 knots of wind, especially when you're already sailing at a good clip and it isn't hitting you from a dead stop, is not all "that" high! These aren't beach cats, for chrissakes.

We've had a few times when we had fairly long gusts of 25 to 30 hit us unexpectedly, with a full main, in our St F. While we certainly accelerated and I got ready to blow the sheet, it was nothing like what you experienced and we certainly came nowhere close to flying a hull.

For a cruising boat where there will be many times when relatively inexperienced folks are going to be on them, that seems to not give much margin for error. Personally, I'd rather the boat dismast before flipping.

Have you considered reporting your experience to Fountaine-Pajot? Not as a complaint, but as a cautionary tale for them to follow-up?

I'm glad everything turned out OK. You got everybody back, as well as the boat, so good job.

ID

[Event_Horizon]

Originally Posted by tsmwebb

Not sure I follow your argument here. Are you saying that a wind induced capsize is impossible because the rig would have to fail and therefore the hull lifting was caused primarily by rotation? Just because the force needed to capsize the boat is large I don't see any reason to believe that the rig was incapable of supporting it. Designing a rig that will fail when sailing at max RM in flat water but will not fail when sailing in pounding conditions where there is no likelihood of a wind induced capsize strikes me as not at all easy. The problem is analogous to an automatic sheet release system. An idea that is still waiting for a practical solution. I don't think either is achievable by measuring force alone. The problem is made even harder because from the moment of max RM the forces on the sheets and rigging will be decreasing. If the boat has gotten a hull up then how will the rig know if the boat is capsizing or returning upright? Lacking specific guidance from the designer of your rig I would not count on it failing before a wind induced capsize. And, I don't think that having a rig designed to fail is all that good an idea. A falling rig is a very dangerous situation.

Having said all of that you do bring up an interesting point. Cruising cats in general have high centers of gravity. On first though I suspect that higher CG's mean more pronounced outward heel in a turn... So, it does seem plausible that the fast round up contributed to the heeling. I don't have a clue how much the turning contributed in this case. So I can't say if it was significant or not. But, even if it was I don't see how that says anything about the rig's strength nor do I see how you conclude that it could not have resulted in a capsize...

Tom.

I wouldn't be surprised if the rig could support a capsize. My point was that a gust of wind is likely not the culprit. Claiming a rig can support 15 tons and that it can withstand a 15 ton shock loading like it would have in this case are entirely different things.

[Therapy]

Originally Posted by Intentional Drifter

A very interesting thread, and educational, too. I'm not enough of an engineer to comment on the math, so I'll restrict my remarks to a user's perspective.

Yeloya, from seeing your previous posts in a number of places and reading those on this thread, too, I've got to believe that you are both a skilled and responsible sailor. It just doesn't seem to me that you would put yourself and your crew in such a situation if you had even the slightest inkling that such a scary and "on the edge" experience was possible.

Even without a reef, 25 to 27 knots of wind, especially when you're already sailing at a good clip and it isn't hitting you from a dead stop, is not all "that" high! These aren't beach cats, for chrissakes.


ID

That is what I have been thinking.

The other thought I have is why the rudders did not force the boat to turn. I know about main drawing with jib not but I still think the rudders should have "more power" than that.

Yeoloya, Thanks for not making that boat another "statistic".

[Palarran]

In my opinion, Sandy Daugherty answered the question in post 7. Add to that a possible wave pop when turning sharp and you result in a hull lifting. Big deal. I haven't seen where Yeloya said he was riding a hull. Was it scary? I'm sure. Would it make you think in the future? Absolutely. Was the boat ready to turn turtle? No.

I own a FP and like them in general. But I'm fairly sure your going to have rig failure before a capsize due to overpowering from the simple fact that the boat isn't built that tough.

[tsmwebb]

Originally Posted by Intentional Drifter

Personally, I'd rather the boat dismast before flipping.

A couple of years ago a boy was killed out here on a cat when the rig came down on him and I know of two serious injuries sustained in different rig failures in medium sized cats. On the other hand, we had a day charter cat capsize with a full load of passengers a fair way offshore without any serious injuries... That's a pretty small sample size I admit but I am far from convinced that dropping the rig is less bad than capsizing as a rule... If something must let go the sails and running rigging seem like a better bet, but designing a fail safe system on that basis seems like a big ask to me too.

And some general thoughts as background and not intended to be specific to the case at hand:

A design can not be all things to all people. Cruising means different things to different folks and they do it in different places. A boat designed for summer weekending in the Chesapeake will need a bigger rig than a boat that sails in the trades in winter. Some folks will be perfectly happy reefing at 15 knots if it means that they can sail fast in 8 and others will resent having to think about reefing in 20 knots (true). But, no matter what, the faster a conventional multihull is sailed the less safe it gets. And buying a couple of knots of reefing at the high end is very costly at the low end. It seems to me that the choice of how powered up a multihull cruiser should be a largely a matter of taste. What worries me is the apparently wide spread assumption that "cruising" catamarans will, as a matter of course, be designed to be immune from wind capsize. That strikes me as a very dangerous.

I believe that there is a good deal of misleading marketing out there. Sadly, if you want a boat that need not be reefed until there is a gale blowing it will be very underpowered most of the time. For instance, last Friday a 40 foot charter style cat sailed in the local "beer can" races which turned out to be a reach out and back in about 15 knots true. Ideal catamaran conditions. We started two minutes behind them in a 25 foot monohull keeler and finished ahead of them. They were comfy and safe but oh so very, very slow. They looked to be having a good time. I'm certainly not dissing their choices. But, at least some of us cruisers like a bit more power and are willing to reef a bit earlier to have it. And, IMO, the important thing is to realize that a choice has to be made and that the label "cruising" doesn't in and of itself say much about how the compromise was resolved.

Tom.

[tsmwebb]

Originally Posted by Event_Horizon

I wouldn't be surprised if the rig could support a capsize. My point was that a gust of wind is likely not the culprit. Claiming a rig can support 15 tons and that it can withstand a 15 ton shock loading like it would have in this case are entirely different things.

You bring up some very interesting points (and I wish I had the information and time to really explore them) but I think that your conclusion is pretty strongly worded. I'd like to see a more specific engineering theory or real wold cases before coming to so positive a conclusion. And, assuming your theory is correct, are you sure it means that the boat was in no danger of capsize? It doesn't much matter how the hull get's past the point of max RM, once it is there it takes less force to capsize it than it did to get it there. If the round up rotated the boat to 80 degrees a bit of wind on the bridge deck might have finished the capsize...

Tom.

[Event_Horizon]

Originally Posted by tsmwebb

You bring up some very interesting points (and I wish I had the information and time to really explore them) but I think that your conclusion is pretty strongly worded. I'd like to see a more specific engineering theory or real wold cases before coming to so positive a conclusion. And, assuming your theory is correct, are you sure it means that the boat was in no danger of capsize? It doesn't much matter how the hull get's past the point of max RM, once it is there it takes less force to capsize it than it did to get it there. If the round up rotated the boat to 80 degrees a bit of wind on the bridge deck might have finished the capsize...

Tom.

You're right, I should put a disclaimer after all my posts, something to the effect of "these figures are based on conjectures, based on speculation, based on flimsy understanding of the situation...acquired second hand".

The basis for my claim mostly an is engineers intuition. While he was sailing stable, his boat was going the fastest (most kinetic energy), and the wind was imparting the most rotational force on the boat. The second he began to turn his boat lost speed and the wind lost influence. Keep in mind he ONLY made it to 30 degrees doing a maneuver that was using every bit of the energy available to flip the boat. Going back to the graph I posted earlier:



The sum of the shaded area under the curve between 0 degrees and 90 degrees represents the minimum total energy needed to capsize the boat on flat seas. While he there is a lot of energy needed to lift a boat to 30 degrees, you can see that there is a considerable amount still necessary to carry it over. I don't have the expression for these curves so I can't integrate the curve to find the exact percent; but it looks like Yeloya only had about 45-55% of what he really needed capsize the boat. That is my basis for saying he was probably never in any real danger of turning turtle.

Though like I said, and Tom pointed out...my understanding is "meh" at best of the boat/conditions/events and this is just my "reasonable guess".