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

[D&D]

Originally Posted by D&D

pg$yacht, check out Post #71...

Sorry...typo...pg4yacht

[Laidback]

Couple of comments
The Beam at 57% of the L.W.L indicative of the designers input to increase stability.
Presume the figure for air draft should read 57.61' ft, which probably means that the luff on the mast is less than 46ft ?? Plenty of cat designs with much taller rigs ,eg - Lock Crowther's. There is no mention of the boom length -- guess 13<>14 ft
The main sheet's traveler is on the roof of the bimini hard top - hard to see what's happening.
------------------------------------------
LIPARI 41 - SPECIFICATIONS
L.O.A. 11.95 m / 39.21 ft
L.W.L. 11.82 m / 38.78 ft
Beam 6.75 m 22.15 ft
Draft 1.10 m / 3.61 ft
Air draft 17.56 m / 57.61m
Full load displacement 9,800 kg
Main sail area 56 m² / 602 sq ft (approx)
Genoa area 33 m² / 355 sq ft (approx)
Engines 2 x 20 cv / 2 x 14.70 kW
Fuel / Diesel 300 L (approx) / 2 x 79.23 US gallon (approx)
Freshwater 2 x 265 L (approx) / 2 x 70 US gallon (approx)

[Palarran]

D&D
Why would Fountaine Pajot admit a design flaw? Absolutely nothing happened. Nothing broke. The boat was hit by a gust with full sails. It rounded up quickly and picked up a hull. For how long? Who knows. OP said a few seconds. I know when scared time slows so it really could have been 2. But regardless, I see no fault in this due to the manufacturer. The fact that this is being extensively discussed on two other forums shows how slow real sailing news and topic's are right now.

[Captain Bill]

In response to D&D and Dotdun post 123 and 124. A rudder is basically an airfoil just like the wing of a plane but symmetrical. When the angle of attack is 0 degrees the amount of side force is 0 Degrees, no matter what the speed. As the angle of attack increases the amount of side force increases. The amount of side force depends on both the speed and angle of attack. To generate a given amount of side force a rudder must have a higher angle of attack at low speed than at high speed. But at a critical angle of attack the foil stalls. At that point the smooth flow around the rudder breaks down into turbulent flow, and detaches from the back side of the rudder. It so happens that the rudder is generating the maximum side force it can for a given speed just before this stall occurs. In an airplane the wing stops flying and the airplane starts falling. It is quite sudden and known as a stall break. This happens wether or not cavitation takes place (the boiling of the water because the pressure has been reduced) or ventilation (the entrapment of air in the water flow). Because cats don't heel much they don't tend to get the rudder near the surface and ventilation is not much of a problem. It's pretty hard to get cavitation at sailboat speeds. This is usually more of a problem for props.

Weatherhelm is a turning force trying to move the stern to leeward and the bow to windward. To counteract this, a rudder must create a counteracting side force (or you have to take some action to reduce the weatherhem). The hull between the CG and the rudder acts like a lever and the CG the fulcrum. Let’s just use 10 and 20 feet as example distances. Because of the length of lever arm a rudder 20 feet from the CG only has to produce half the amount of side force to counteract a given amount of weather helm. The other way to look at it is that a rudder at 10 feet either has to have twice the surface area or twice the angle of attack to produce the same counteracting force as one at 20 feet. If the surface area of the rudder ahead of the engines has not been increased enough then angle of attack is the only way to apply more force. In the OP example as the boat accelerated he had to counteract the turn to weather by applying more and more rudder. At some point the rudder reaches the critical angle of attack and stalls. At that point the counteracting force being generated by the rudder goes to 0 and the boat turns sharply to weather. A rudder further back has a higher mechanical advantage because of the length of the lever arm and will not require as high of an angle of attack. While it might be possible to stall the rudder located further aft this would happen at a higher speed than with one located further forward.

I am not familiar enough with the design of the FP to know how far forward the rudders are located, so the numbers presented should be read as examples, not definitive. Without the actual numbers for the boat I couldn't say what the actual difference would be between an aft mounted rudder and the actual rudder, just that basic physics suggests that there should be one.

This sudden uncommanded turn to weather experienced by the OP has all the characteristics of a rudder stall. The counteracting force being generated by the rudders suddenly went to 0 and the weatherhelm forces being generated by the sails caused the turn.

Tropic cat. I agree that the turn caused the hull to come out of the water, but I believe that the rudder stall was the cause of this uncommanded turn. Do you have another explanation?


Before you technical people start jumping on my case I know that the lift curve for a foil is not linear and I was just using a linear relationship to keep the explanation simple.

[D&D]

Originally Posted by Palarran

Why would Fountaine Pajot admit a design flaw? ...The fact that this is being extensively discussed on two other forums shows how slow real sailing news and topic's are right now.

Palarran, we never suggested there was a design flaw, only that the enquiry to FP would produce nothing of interest to the discussion.

Our only design suggestion, expressed earlier, was that the trend toward larger sail plans to produce better light air performance must inevitably lower the conditions threshold which put those vessels at some risk. We see the design trend as basically moving cruising vessels closer to performance vessels which must also move the cruisers closer to the risks of performance vessels. We also earlier admitted our guilt because we prefer (and in fact insist on) the better light air performance. So we're certainly not going to criticise FP (or others pursuing the same, improved light air performance) for their designs...far from it as we embrace the trend!

If you feel that the prospect of (or the circumstances leading to) flipping over a cruising cat is not real sailing news, that's a matter for you, but clearly many others disagree.

[D&D]

Originally Posted by Captain Bill

In response to D&D...

Captain, thanks very much for that discussion, in language us NON-techincal people could understand! You would make a good teacher...clear thinking; organised and understandable expression; and patience!

[Event_Horizon]

Originally Posted by Captain Bill

[COLOR=black][FONT=Verdana]
Before you technical people start jumping on my case I know that the lift curve for a foil is not linear and I was just using a linear relationship to keep the explanation simple.

Thank you, saved me a post

[Catwarrior]

Hi Yeloya !

Thanks a lot for your comments, which would be very usefull for me, and FP Cat owners, I think.

Thank's god, you're still in life, for telling us your story !

I 'm looking for buying a "brand new Lipari". Since a few months ago, I 'm searching informations or testimonials about this boat and especially near from Owners and skippers.

After having a quick read of your comments on this famous Lipari 41, I was a bit surprise. In this kind of situation, in my opinion, the only solution is to pray for wind coming down; because you can not govern anymore ?

Could you just tell me more precisly:
> Are you sure that the boat was effectively not overpowered ??
> Could you just remind me what was the sail conditions (Wind Knt and swell ft).
>Was the rudder totally out of water ????
> Was it still possible to govern the boat? at least just a bit on the other side ?
> Did you have time to measure the rudder, as you said in your comment ?

I like FP Catamarans, more than Lagoon Cats, and escpecially the Lipari 41. In my view, it's a very good compromise between confort and sailing performances. Moreover, as youi told us before, it's a good value for money, form id price range. That's why, I'd like to be sure of that, in finding the reason of this incident.

Thank you very much for your reply, and explanations.

In your opinion, should I still be looking for buying a Lipari ???

Thank's again

Catwarrior

[Eleven]

Catwarrior, great name by the way, but as to Lipari, Lagoon, FP?
First be sure you have the budget to buy, then equip, then maintain the boat comfortably.
If it's tight then take a really good look at the second hand market, where you save on the 30 per cent depreciation and consider if New is worth it. If this is the boat for your lifetime then what you save can be spent on 'comforts', upgrades (it should already be fully equipped, or left in the bank for a year or so while you decide that this is the right boat but it needs:-. At the end of that first year it will be your boat, your improvements and changes, yours. It's hard, emotionally, to make changes to a brand new boat, so you end up having the same as every one else. And new boats are made to suit most people, not necessarily you. Extra engine power, more water storage, even a different layout, can be done within the new boat purchase price so don't just look at catalogues. There have been threads here on standard factory engine power. Usually it's marina power, not man enough to get you out of tide/wind combinations quickly enough. Half the quoted speed for an f7/8 on the nose, then take off 2kts for an average tide, 4, even 6kts in some places. The result determines how long it will take you to get out of the tide race area without turning back. Fuel tanks size too can seem adequate, but if this is your life cruiser you'll be shopping for cheap fuel (Gibraltar) to last the Med, or get you to the UK.
And then you need the load capacity, half a ton each of tools, water, food, clothes. Add on dinghy, outboard, genny, and other extras and it soon adds up.
Half a ton of water, 500 litres, 5 litres per day per passenger, how many crew, how far?
40 to 50 days needed for some of the RTW legs allowing 50% contingency. 2x5x30=300 litres. Or go without showers, clothes washing and so on. Cruisers choice but if you're looking to buy new I think you'll be expecting to shower daily? Salt water showrer and fresh water rinse off still adds up.
Now you have some idea of load capacity you'll be looking for boat size. And the costs aren't linear, bigger is a good bit heavier and a lot more expensive. It's all a huge balance between costs and expectations. Good luck, it's more fun if you get it right first time.

[yeloya]

Originally Posted by Palarran

D&D
Why would Fountaine Pajot admit a design flaw? Absolutely nothing happened. Nothing broke. The boat was hit by a gust with full sails. It rounded up quickly and picked up a hull. For how long? Who knows. OP said a few seconds. I know when scared time slows so it really could have been 2. But regardless, I see no fault in this due to the manufacturer. The fact that this is being extensively discussed on two other forums shows how slow real sailing news and topic's are right now.

Hi Palarran,

This is interesting.. Actually one may give credit to the boat for surving the flip over risk while the others can blame it for having coming to this situation at all.
To me both is true.. You cannot say that nothing has happened and nothing broke. Unlike monos, cats are supposed to go flat, hence, everything is settled accordingly. Someone could have gone MOB or badly injured, even killed. Moreover, If you look back the stabiliy chart posted here, you see that not going turtle was a miracle. (actually I had seen this chart earlier and when we heeled by 25-30 degrees, in these couple of seconds I clearly recalled the chart and was dead scared.) I could probably jump out safely but my wife and our guest (by the way, she was an 60+ years old american lady owning a 54 ft mono and she couldn't really figure out why we were so scared. After all, this was her first ride on the cat and she thought that heeling 25 degrees under sail was totally a routine procedure )

As none of us is a experienced cat designer, it is impossible to say how close we really were being flipped over. Maybe 0,5 kn of more boat speed or 2-3 kn more of wind or a bit higher swells and I wouldn't be able to post this.. Do you still think that nothing has happened ?

Yeloya

[Eleven]

I'm totally with you on this, Yeloya. You have to have confidence in your boat. It's clear from the many contributions here that freak gusts and freak waves can, have and will break and sink boats. It is FP's responsibility to provide a boat that will withstand conditions that are likely to be met under the Category the are selling under.
Without trolling through the net I would want to be safe on a 'coastal' boat in up to f8 and in the gusts that can include, and also the sudden gusts that might be experienced in lower wind conditions, right down to zero.
HOWEVER I'm happy that your boat rounded up without input from you, thus reducing the side load on the sails and righting itself. As mine did. Just as a mono would tip on/near it's beam ends and spill the side load.
If you'd been running downwind, with a full main, then, like me, you'd experience a loss of accuracy in the steering suggesting (to a wise sailor) that the main should be reduced accordingly, and in fact not fully deployed running downwind.
The number of Cat's that turn over or pitchpole are far less than the mono's that are rolled right over, lost mysteriously, or sunk by losing and loosening their keels. I've learnt, on a very sound boat, that Cats are more sensitive and must be treated as such.
Nearly all of the time it's only the skipper that's actually worried. Discussing things openly, especially among this knowledgeable crowd, is the best way to assess these concerns and address your sailing practices.

[Palarran]

Yeloya, your mind works different then mine. If I was sailing in basically no wind, saw a gust coming over the water, had my boat accelerate to the point my rudders felt huge weather helm, still continued to maintain course, had the wind continue to push me to the point the boat uncontrollably rounded up, and in that moment it lifted a hull 25 to 30 degrees, in those couple of seconds it wouldn't be the stability chart that made me dead scared.



D&D - "..and FP will almost certainly not admit any design fault. " That sure sounds like you are accusing them of having one.

[D&D]

Originally Posted by Palarran

D&D - "..and FP will almost certainly not admit any design fault. " That sure sounds like you are accusing them of having one.

With respect Palarran, your conclusion goes further than the evidence. There is no accusation above, nor was any intended. In fact, if you wanted to check our view of FP vessels, you only needed to read Post #107 in this thread where we said...

"FP are a very professional organisation with a long and successful repuattion for building very seaworthy vessels."

[SailFastTri]

Sorry folks but if anyone built a boat that was "idiot proof" from overpowering it would not be fun to sail, as the performance would be dismal. I have no relationship with FP in any way, but I think it inappropriate that people are questioning the design when there are so many operator-error indications in the story. I don't want to pick on Yeloya, as I make my share of mistakes, but let's "keep it real".

This incident as described, sounded like a series of misjudgments on the part of the skipper, or to be generous -- lack of preparedness or appropriate response to unexpected conditions. Any type of vehicle or vessel is only as safe as the skills and judgment of its operator.

I re-read Yeloya's original post and I suspect it did not happen precisely as he wrote it. For one thing, he starts by describing the following: "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." Then later he writes: "remember almost flat water, the true wind not exceeding 25 knots and from behind, boat speed around 11 knots." It is not possible for both things to be true, and I get the impression his report is imprecise, at best. This is a major discrepancy, and the difference between apparent and true wind with a boat speed above 10 knots is huge.

""25-27 knts just at 90 degree (apparent)" with no reef is a huge misjudgment in any boat I've ever sailed. Most boats are designed to be fully-powered up (able to reach "hull speed") in 10-15 apparent, on a reach. He should have had a reef in the main at that apparent wind speed, and eased the main if he was feeling strong weather helm; so he was over-sheeted and overpowered with clear indications. All it would take is a gust at that point to create a critical situation and apparently that happened. Predictable. (Multihulls should reef for the gusts).

His sail imbalance overpowered the rudders and forced a round-up in the gust -- further increasing apparent wind. If he was doing around 11 knots as stated, and rounded up -- his "25-27 knots" apparent wind jumped to 35+ apparent. With full main and genoa that should put the boat at risk.

Sorry folks, but let's focus on seamanship as the key element of safety. Accidents can happen to anyone, and when it comes to wind we can't always anticipate gusts so we need to allow some margin for error. STUFF HAPPENS if you operate a cruising boat like a racing boat and sail it (poorly) to the edge of it's limits. (Just trying to be objective with no personal attack intended.)

PS - When the wind forced the rounding-up, the weight aloft combined with centrifugal force further added to wind pressure to lift the windward hull in creating a capsize risk. This episode would have been somewhat predictable. We should learn from it.

[sandy daugherty]

I just posted the following in another multihull forum:

In the Cruiser's Forum mentioned above I was rightly corrected that heading up in a gust from below a beam reach is a bad thing. I stand corrected. Here is my revised explanation:

The OP in that article experienced an uncommanded rapid turn into the wind that raised the windward hull out of the water. I think a combination of factors (small wave*, heavy weather helm due to sail trim, gust from a more adverse direction, and more) rendered the windward rudder ineffective. The opposite rudder immediately stalled, and the excessive weather helm spun the boat suddenly into the wind. It's shoal draft keels were suddenly trying to plow a ten foot wide furrow in 4' of water, and the inside hull came up, as seen by witnesses some distance away. The key factor was tripping over the keel.

Does this mean that all cats can do this? The few rabid half-a-maraners lurking on that thread are licking their chops. What needs to be said is:

A monohull in the same situation would have broached.

It is not at all evident that this or any other catamaran would have turtled. Why?

If it were truly likely, there would be a lot more turtled cats to talk about. Perhaps as many as there have been broached monohulls.

The idea of tripping over a keel presupposes that a cat can change direction 90 degree in seconds. In truth, shoal draft cats are highly directional, many people have said they hold their heading as if they are on rails. Centrifugal force presumes a high rate of rotation, but I have no idea what the math is. Let's just agree that a shoal keeled cat can't turn very fast under normal conditions.

Meanwhile, back at jumping-to-conclusions-city, should a cat always turn down-wind in a threatening gust?

No.

In any dangerous gust, slack the sheets.

Above a beam reach, a cruising cat should head up in a gust, otherwise head down.

Thats my story (today) and I'm sticking to it.

Is that moderate, or what?

*small wave: picture a catamaran with enough wind to almost support the boat on one hull. Sail over a 3 foot swell, and the waterline on the windward side drops 3', ventilating the rudder. Freeze frame. She has suddenly lost half her rudder power!