Canting Keel Monos vs Multihulls

Alternative discussion at SA

There is now an interesting thread over at the Forums section of Sailing Anarchy about mechanical failures on big fast racing sailboats, especially those with canting keels. Below you will see the opening posting from the Editor in which he poses the coupled questions for the thread...

The recent keel failure, capsize and abandonment of Alex Thomson's Open 60 is simply the latest in a long list of structural failures of these large, canting keel extreme shorthanded machines. The question, in two parts, is this: Are incidents like this simply what can happen when the envelope is pushed with boats like this; and if so is this acceptable? And if it is not, what should be done to prevent boats like this from ending up how they often do - upside down?

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You can go directly to the thread with this link:
http://www.sailinganarchy.com/forums/index.php?showtopic=44699

Picture below of Golding's new mast configuration after his went blewey for an unknown reason. Photo from Golding's personal website:
http://www.mikegolding.com/

jehardiman said:

While it depends on the particular hull, all the studies I've seen and conducted, show that water on deck/slamming is a greater problem with multis than monos...becuase the waterplanes are selected to minimize motions and accelerations. You see, you can't have it both ways. Either the waterplane is so small the hull doesn't rise to the wave and you get wet depending on cross deck effects, or the waterplane is large and the hull profiles the wave causing large motions and accelerations.

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Well, if you pick one, it seems to disprove one of your contentions. You say that multihull motion is worse and that decks are wetter. Since "you can't have it both ways," which is it?

By the way, if you'd like to say "Both are true," then to be fair, you should say the same of monohulls, with the added disadvantage of rhythmic roll. The idea that the monohull has a more comfortable motion depends on not "profiling the wave," to some extent, correct? So it must logically also include the idea that solid water is more likely to hit the deck, as you mention above.

Do you have a cite for your contention re solid water on multihull decks, and one for your contention that this is the major cause of man overboard? I'd be interested.

I agree with your idea that multihull decks will be wetter, because the boat will often be going faster, thus creating more spray. Spray isn't very dangerous, however-- it's green water that does the damage. The multihull is lighter and with boards up, more raftlike. In general a breaking crest will be more likely to accelerate the boat away from danger, whereas a monohull with a deep keel will be more likely to take green water on the decks, because that keel is down in more stable water, and is more likely to hold the boat in place to take the blow from the breaking crest.

jehardiman said:

The choice of the Hadler paper is interesting (I have seen it, but today we use other criteria for motions) because that paper is not generally applied today due to the atmosphere it was written in (i.e. the lab was pushing an agenda.

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So your position is that roll is not a major factor in crew fatigue? Okay, but I'll have to see a good cite for that position before I take it seriously. Most folks who've sailed extensively on both multis and monos find the lack of roll an enormous advantage in comfort, even if for other reasons they prefer monos. In the Kretschmer piece Vega quoted above, he contrasts the motion of the Venezia with the motion of his steel monohull in 25 knots of wind offshore. On the cat, his coffee cup is still sitting undisturbed on a fiddle-less table and his crew are still asleep in their cabins. On his monohull, of which he is very fond, he'd be rolling 30 degrees.

Hey, as I said above, there are many legitimate reasons to like monohulls better than multihulls. It's my opinion that safety is not one of them, though the capsize vs. sinking conundrum has good arguments on both sides. But when it comes to comfort, I think it's pretty hard to make a legitimate argument that the monohull is the winner there. If there's one theme that attends the grounding and loss of yachts (much more frequent than either capsize or sinking) it's the crew fatigue factor. The boat that takes better care of the crew has an enormous safety advantage when it comes time to make the sort of decisions that can lead to shipwreck.

rayaldridge said:

Furthermore, the judgement he made was of a specific cat design-- apparently one in which bridgedeck clearance was too low. Would it be fair to judge seakeeping ability for monohulls using a poorly designed monohull?

....In the Kretschmer piece Vega quoted above, he contrasts the motion of the Venezia with the motion of his steel monohull in 25 knots of wind offshore. On the cat, his coffee cup is still sitting undisturbed on a fiddle-less table and his crew are still asleep in their cabins. On his monohull, of which he is very fond, he'd be rolling 30 degrees.

... But when it comes to comfort, I think it's pretty hard to make a legitimate argument that the monohull is the winner there. .
.

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You are being very partial. Or do you really find it comfortable to sleep in a cabin that makes you “felt like you were inside a kettledrum”.

Fact is that he says that cruising cats have a lot more motion that monohulls.

What he says is that while there is no waves of significant size (6ft), the cat is more comfortable than a mono. He says also that in a storm the boat is very noisy and I guess that it is here that they “have a lot more motion than monohulls”.

Curiously he says that a cruising cat is not faster than a monohull of the same syze and he says that they have an “appalling leeway” when trying to stay close to the wind in a storm. Not a big storm, we are talking of 50K of wind.

You had given the idea that this is not a good cruising cat, but that is not true. The Fountaine- Pajot are among the best.

You can agree, or not with Kretschmer, but it is just unfair to give a wrong impression of what he says:


"I was on the dawn watch thinking I had a read on the apparent wind. So I was surprised to find out in scanning the instruments that the true wind had actually increased to a steady 25 knots. When did that happen?
My cup of coffee on the fiddle-free cockpit table was just where I had placed it minutes ago, and my three crew members remained sound asleep in their separate staterooms. The Autohelm 7000 plugged along in automaton-helmsman style. And in general, this Fountaine-Pajot Venezia 42 maintained poise as she tracked over the Atlantic, easily coping with the six to eight-foot seas rushing between her hulls. It was easy to get lulled into a contentment.
.....
.... These cats in general have a lot more motion than a monohull. Also, as designers create more interior volume in the saloon, they lose wing clearance, or bridgedeck freeboard, between the hulls. This can result in a great deal of pounding and slamming underneath, especially when sailing upwind in big seas. During a Force-9 gale ... and in the aft cabins you felt like you were inside a kettledrum.....

I was surprised at the amount of slamming and slapping that the after-hull sections took. We had a scare when the latch supports of the emergency hatches in both heads broke. Suddenly we had open hatches four inches above the water with no way to secure them. The storm reached its peak that night, climbing to a steady 50 knots, .... ...

To maintain our heading, we sailed close to the wind, but the GPS revealed that we were making appalling leeway. Although we were sailing nearly 50 degrees off the apparent wind, our track over the bottom was closer to 80 degrees.

Ironically, my initial anxiety about being caught out in a cat gave way to frustration. We were unable to make much progress during the blow. I decided to accept Neptune's fate and shortened sail further, reducing our forward speed to around three knots. This reduced the slamming beneath the bridgedeck and along the inside of each hull."

We all appreciate the wanderment of going slightly off-topic for awhile. It looks like you guys (Vega and Ray) have seriously locked horns on one of those never-to-be-determined topics that has run for centuries and will likely continue to do so.

Please don't get me wrong. I'm not one to criticize anyone for directly engaging another group member on a particular topic. Done enough of that in my time and will probably do it some more, so it isn't about that. In fact, I rather like the interplay you've shown in the process.

Is there anyway you guys could re-engage the canting keel/multi argument... or perhaps start a new thread?

There's a wealth of very current info on canting keel performance boats right now and that should provide more than enough data for the grist mill of discussion.

Vega: Have you had a chance to look at any balanced reportage on capsized monohulls that sink rather than jump right back on their feet? This data would be useful in the overall determination in the argument as to survivability once capsized compared to a floating multihull. I'd especially like to know of any hard numbers as they pertain to canters.

Something tells me that there have not been many multihull sinkings when compared to monohull sinkings. Feel free to apply the relationship to cruisers or racers as is appropriate on a like for like basis.

Chris

Chris Ostlind said:

Vega: Have you had a chance to look at any balanced reportage on capsized monohulls that sink rather than jump right back on their feet? This data would be useful in the overall determination in the argument as to survivability once capsized compared to a floating multihull. I'd especially like to know of any hard numbers as they pertain to canters.

Something tells me that there have not been many multihull sinkings when compared to monohull sinkings. Feel free to apply the relationship to cruisers or racers as is appropriate on a like for like basis.

Chris

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Chris, I have some difficulty in understandig that point of yours regarding the floating multihull. What matters is whether people live or die. In that recent accident I was referring to, the cruising cat floated inverted, but several persons have died.

Chris Ostlind said:

Vega,
Perhaps, in the interest of fairness, you could provide a data supported, as well as an anecdotal, set of references as to monohull sinkings once knocked-down? I have a sneaking feeling that the process would more than qualify as "tragic"

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About this, I am afraid I can’t. A modern monosailboat would not sink during a Knock-down. The downflooding angle is superior to 100º and a modern boat still has a lot of positive RM at 90º, so it would right itself up.

But as Ypster has suggested, I like fast boats, and that includes cats and tris and I don’t think that a big cruising oceangoing cat is dangerous; Just different from the mono.

You have been asking the wrong questions

rayaldridge said:

Wind-only capsizes are pretty rare. Most capsizes occur from wave action or from a combination of wave and wind. It's my opinion that a multi has a couple advantages in the conditions most likely to produce capsizes; big wind-induced waves with minimal or no canvas up.

A monohull with a keel is more vulnerable to wave-induced rollover, I think, because the keel is down in denser more stable water when a boat is hit by a fast-moving aerated breaker and provides a lever over which the boat can trip. Multihulls, and particularly cats with boards up, are more raftlike. They tend to surf sideways in a breaking wave, a phenomenon I can personally report to be true.

Consider, for example, a keelboat spilling sideways down the face of a big steep wave-- a scenario that has damaged and sunk several yachts. The keel will dig in and attempt to flip the boat upside down. At best, the rig will be driven masthead first into the trough, and few rigs will survive such treatment.

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I agree with Ray here, even if I consider that most of the Cat capsizes have to do mostly with wind pressure. But that's because Cats are a lot better than monos regarding waves.

Even if it is possible to capsize a cat just with wind, and impossible to do the same with a monohull (and that was what I was discussing), regarding breaking waves, cats are a lot more difficult to roll. Ray has explained why.

When a mono is rolled, a lot of things can happen. Some are rolled with the main hatch open and downflooding occurs preventing them to return to the upright position, some boats are just too weak and can breake and others, if sailed properly (hatches closed) will have no problem in rolling, except, probably losing the mast.

So each boat has its strong points and its weaknesses, and the main big weakness of the cat (for me) is price and costs at the marina (double).

Finally, about canting-keel boats, I consider them to be yet at experimental stage. I give you that they are not yet reliably in what concerns stress problems in very long races (around the world). It is natural and it is not a reason to stop development. With time I am quite sure that we will have reliable canters.

Now, one thing is mechanical problems, that have to do with the youth of the concept and with finding the proper materials and scantlings to deal with the new stresses. Other is the improvement in the sailing characteristics of the boat. Regarding those, it is a giant step in performance and safety.

But the boat will continue to be a monohull and its stability curve is still a monohull curve, just better, and as so, completely different from a cat’s stability curve.

In the future we will have better, safer and faster monohulls, but unfortunately, I am afraid, as expensive as cats, if not more. At least regarding marina prices, they will be cheaper.

Vega said:

You are being very partial. Or do you really find it comfortable to sleep in a cabin that makes you “felt like you were inside a kettledrum”.

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Have you ever been in a storm in a poorly-insulated steel monohull? There's a whole band banging away. Also, he ascribes this noise to the aft cabins-- which are usually the funkiest places to sleep on any big boat.

Vega said:

Fact is that he says that cruising cats have a lot more motion that monohulls.

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Fact is, he doesn't say that this is more tiring than rolling 30 degrees in his own steel monohull. Which would you personally prefer?


(snip)

Vega said:

Curiously he says that a cruising cat is not faster than a monohull of the same syze and he says that they have an “appalling leeway” when trying to stay close to the wind in a storm. Not a big storm, we are talking of 50K of wind.

You had given the idea that this is not a good cruising cat, but that is not true. The Fountaine- Pajot are among the best.

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Hmmm. This may be the source of our disagreement, if you really think that. The French have built these subsidized behemoths pricipally for the charter trade. The Fontaine-Pajot cats are probably fine in charter service, but to hold them up as an example of "the best" is a stretch. For example, the leeway prevention system in the boat Kretschmer is describing is, I believe, low aspect ratio fixed keels. Furthermore, Kretschmer himself mentions that the boat was much faster before the owner loaded it down past its design displacement.

Vega said:

You can agree, or not with Kretschmer, but it is just unfair to give a wrong impression of what he says:

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If that's the case, was it unfair of you to trim off the sentences about how in similar conditions, his steel monohull would be rolling through 30 degrees? Is it unfair to assume that the Venezia, with her inefficient keels and enormous windage accurately represents the performance of all multihulls to windward? Is it fair to judge all multihulls by such a boat, with her two heads and 4 queen berth cabins and standing headroom in the pilothouse?

The fact is that no knowledgeable person would put forward the idea that the Venezia represents some pinnacle of multihull design. There are many similarly luxurious cats that have higher bridgedeck clearance, finer hulls, lighter weight, lower windage. Most of them are a lot longer, as you might expect, but there are able boats in smaller sizes as well.

Please understand that even if the Venezia were an example of great design (which it may be, if you're an interior decorator) Kretschmer is relating an opinion based largely upon the kind of boat that absentee owners hire people like John to take south for the winter.

Vega said:

"I was on the dawn watch thinking I had a read on the apparent wind. So I was surprised to find out in scanning the instruments that the true wind had actually increased to a steady 25 knots. When did that happen?
My cup of coffee on the fiddle-free cockpit table was just where I had placed it minutes ago, and my three crew members remained sound asleep in their separate staterooms. The Autohelm 7000 plugged along in automaton-helmsman style. And in general, this Fountaine-Pajot Venezia 42 maintained poise as she tracked over the Atlantic, easily coping with the six to eight-foot seas rushing between her hulls. It was easy to get lulled into a contentment.
.....
.... These cats in general have a lot more motion than a monohull. Also, as designers create more interior volume in the saloon, they lose wing clearance, or bridgedeck freeboard, between the hulls. This can result in a great deal of pounding and slamming underneath, especially when sailing upwind in big seas. During a Force-9 gale ... and in the aft cabins you felt like you were inside a kettledrum.....

I was surprised at the amount of slamming and slapping that the after-hull sections took. We had a scare when the latch supports of the emergency hatches in both heads broke. Suddenly we had open hatches four inches above the water with no way to secure them. The storm reached its peak that night, climbing to a steady 50 knots, .... ...

To maintain our heading, we sailed close to the wind, but the GPS revealed that we were making appalling leeway. Although we were sailing nearly 50 degrees off the apparent wind, our track over the bottom was closer to 80 degrees.

Ironically, my initial anxiety about being caught out in a cat gave way to frustration. We were unable to make much progress during the blow. I decided to accept Neptune's fate and shortened sail further, reducing our forward speed to around three knots. This reduced the slamming beneath the bridgedeck and along the inside of each hull."

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Yes, no doubt many under-rigged 42' monohulls with huge windage and 4' of draft would be making much better progress to windward in 50 knots.

Oh, Brother

Quote from Vega:

"About this, I am afraid I can’t. A modern monosailboat would not sink during a Knock-down."

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Well, OK, then... I suppose the Emporer is always ready for a new set of clothes if he wishes. As they say in court, Vega... this assumes facts not in evidence. Just how does a modern monohull sink after it is knocked-down, then? There are hundreds of reports that they do. Or do all those investigators simply have it all wrong? The boats that sank during the famous Fastnet storm... was it all an illusion that they were first knocked down and subsequently went to the bottom? How about the Sid/Hobart debacle, was that also an illusion?

"You have been asking the wrong questions."

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What a pleasant response, Vega. And here I was thinking all along that it was you who were not giving the correct answers. I understand that you don't like to address that which is not in support of your argument. I see that you regularly do that in your interchange with Ray.

Is there something, really, that you'd like to just say straight away and be done with it? The, "ask me another proper question" thing is rather inefficient, wouldn't you say? Let me guess... are you an engineer?

Chris Ostlind said:

Quote from Vega:


Well, OK, then... I suppose the Emporer is always ready for a new set of clothes if he wishes. As they say in court, Vega... this assumes facts not in evidence. Just how does a modern monohull sink after it is knocked-down, then? There are hundreds of reports that they do. Or do all those investigators simply have it all wrong? The boats that sank during the famous Fastnet storm... was it all an illusion that they were first knocked down and subsequently went to the bottom? How about the Sid/Hobart debacle, was that also an illusion?

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I think there were only five sinkings among 278 or so entrants in the '79 Fastnet. There was a multi Fastnet going on at the same time. It had one entrant, Bucks Fizz. She capsized. All the crew died.

Obviously this is not a good statistical base. And I can't see why new serious ocean monos that can sink are built (I know a few monos with positive bouyancy that takes up little effective space). But the '79 mono Fastnet's death rate of about 0.5% looks pretty good compared to the '79 multi Fastnet's death rate of 100%.

I'm not sure whether any boat sank as a result of capsize and downflooding in the '98 Hobart. Business Post Naiad may have; I can't remember. Stand Aside was certainly in awfully big trouble, as was a 40 footer from Mooloolaba, after capsizes.

Two deaths did occur as a result of a Farr 1 ton re-righting slowly; one of these guys had a heart attack and may have died anyway. Most of the other deaths came from a 1930s boat falling apart. If we are going to bring 70 year old monos into the calculations, we must also bring in Piver Lodestars and all the other bad or old multis in.

My family and I know several people who have spent time upside down on or in multis. All of them survived (the people I knew who died on multis died for different reasons), but at the cost of a very unpleasant experience of up to three months, and at the cost of being rescued. There is also a lot of room to doubt whether some of the heavier cruising cats will actually float, and the capsize of boats like a 43 footer from one of my favourite designers has recently convinced me there's no such thing as a cruiser/racer multi that won't flip, sometimes in worryingly benign conditions.

I also know, or knew, several people who spent time in the water after monos sank. Not all of them survived.

It's just a personal opinion, but the self-righting and unsinkable boat is so easy to achieve, that arguing over whether it's better to flip or sink is not worth debating.

Chris Ostlind said:

Quote from Vega:

Well, OK, then... I suppose the Emporer is always ready for a new set of clothes if he wishes. As they say in court, Vega... this assumes facts not in evidence. Just how does a modern monohull sink after it is knocked-down, then? There are hundreds of reports that they do. Or do all those investigators simply have it all wrong? The boats that sank during the famous Fastnet storm... was it all an illusion that they were first knocked down and subsequently went to the bottom? How about the Sid/Hobart debacle, was that also an illusion?

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Modern boats are the ones that appeared after that race, in consequence of the studies and questions raised by those accidents. I have said that modern oceangoing sailboats have an AVS of at least 115º and a downflooding angle of more than 100º. Many boats in that race had an AVS in the region of 100º and poor downflooding angles. But anyway most the boats that sank had been rolled several times, not only knock-downed.

Chris Ostlind said:

What a pleasant response, Vega. And here I was thinking all along that it was you who were not giving the correct answers. I understand that you don't like to address that which is not in support of your argument.

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What argument? I don’t have an argument! (I see that sense of humor is not one of your strong points) I was kidding, as that Green animal should have indicated. If you have taken offense, I apologize.

Chris Ostlind said:

Is there something, really, that you'd like to just say straight away and be done with it? … Let me guess... are you an engineer?

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No, I am an architect and probably that’s why I don’t have the faintest idea of what you are talking about .

Actually Vega, I'm really OK with all the humor in this, intended or otherwise. But I suspect you already knew that. I'm an architectural photographer by trade, so I do get the humor in your words.

I certainly wasnt aware that there was demarcation line out there in the design world when modern began and an older design mode ended. Perhaps that would be a good discussion within our craft?

Chris, the issue is not about any ensuing deaths, (and I'm deeeply saddened for any family members who have lost loved ones in this fashion) no matter the design idiom upon which one was floating prior to the event. It's about the fact that monohulls do sink and they sink for a wide variety of reasons.

Multihulls also get tossed on their backs and the experience can be life changing in the wrong conditions

It's good that you bring-up the reality/potential in design for an unsinkable form in the monohull world. I would also lilke to see a multihull with self-righting capacity as a standard. Now, if you guys want to get into that as a discussion thread and leave the cheeky business of arguing over that which is not to be decided, then let's head-on.

Just wondering out loud here, but how many deaths do you suppose could be averted with boats that can be resistant to sinking and others that can get back on their feet if tossed?

Would it be fair to call those designs as "modern"?

Chris

CT249 said:

It's just a personal opinion, but the self-righting and unsinkable boat is so easy to achieve, that arguing over whether it's better to flip or sink is not worth debating.

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I might agree, were that the only issue. For example, I brought up seakindliness, and the greater comfort level to be found on multihulls, which has a bearing on crew exhaustion and consequent decision-making.

I could probably set up a couple of other stalking horses. Consider beaching in heavy surf. This probably happens more frequently than being sunk by whales or capsized by katabatic winds, but the keelboat will often be destroyed and her crew drowned while the multi may well slide right up onto the beach.

Or consider how much easier it is to get a boat with a two foot draft back into the mangroves than a boat with 6 foot draft. This is a significant difference when a hurricane is on the way.

Again, when the vast majority of extant designs fall into either the "will it sink?" or the "will it flip?" category, it's probably still a worthwhile discussion. Like you, I can't imagine why so many monohull sailors feel content to sail in a boat that can go to the bottom if the hull is holed. I suppose the dedicated monohull sailor can't understand why I'm willing to go to sea in a boat that will not self-right from a capsize. Both conditions are deplorable and to be avoided, of course, but the latter seems less terminal.

Vega said:

You had given the idea that this is not a good cruising cat, but that is not true. The Fountaine- Pajot are among the best.

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I take it you also think that Beneteau are among the best cruising monohulls available.

There seems to be a constant assumption that monohulls will actually self right after rolling over. Yet I have seen several photographs of monohulls floating upside-down, some without keels, which is why they at least stayed afloat, and some with keels still attached, which sank after a time. If the rig survives the roll over there is a fair chance the boat will stay inverted, at least untill another large wave rights her.

CT 249, there should be no further cases of sailors floating around in upturned boats for months - I doubt anyone would venture off shore these days without at least one 406 EPIRB on board.

Yep, some monos do stay inverted, but then again some cruising multis are unseaworthy and so loaded down with twin diesels, gen sets, TVs, air conditioning etc that they may well sink if holed or capsized. There's a constant assumption that all capsized multis float and float in a position where they can serve as a haven for their crew, yet I have known people who found out that these assumptions did not apply.

Surely we cannot look at bad designs, whether mono or multi, and assume that their problems are characteristic of all of their type.

Ray, there's probably lots of stalking horses. I can think of many problems for many multis (the poor helming position (in security and visibility) of some cats; the poor manoevrability of some -not all!- multis, etc).

The beaching argument I'm not sure about; even back in the '50s when Adlard Coles wrote "Heavy Weather Sailing" I think he noted that "light displacement" monos could often be beached safely. I know of numerous "fragile" boats like IOR racers that have been beached (albiet generally in mild conditions) with no casualties and no irrepairable damage, while trying to cheat current on coastal races. A while ago I would have said cats are great on the many river bars around me, but a while ago a cat from a well-reputed designer flipped on a fairly mild bar. People have pointed out problems with that design, which gets us back to the same thing - it's hard to isolate problems with a style of boat, from problems with the individual boat.

Fatigue? Maybe it depends on so many factors that it's hard to apply a blanket rule. I know cats that are exhausting to sail in the harbour, and cats that are a breeze to sail offshore.

Seakindliness? Again, there's personal preference. I hate the motion of heavy-displacement monos, but many people love it. I know cats that can have bad motion, cats that have great motion most of the time but roll very badly when they are "bridging" swells.

Hurricanes? Windage may also be a factor to consider, perhaps. And not all monos are deep keelers.

I'm not biased against multis; I've advised everyone from my kid to my mum to sail them offshore, and they have done so (not just 'cause because of what I said, of course; I'm just indicating that I wouldn't have advised them to do so unless I felt multis were safe)..