Dufour catamaran

[Valiente]

Originally Posted by BigBeakie

And yes, I seriously think they will sink if they are too heavy. That's just simple physics. Some condomarans have sunk when flooded.


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Even some ships regarded as unsinkable have suffered same fate!

[tuskie]

Originally Posted by Factor

Time to fill those mini keels with lead then

Most of the catamaran designs which require increased stability have dagger boards.

[catmancan2]

Originally Posted by tuskie

Most of the catamaran designs which require increased stability have dagger boards.

A) The stability of a multihull has nothing to do with whether it has keels or boards. Stability is a function of overall waterline beam which in turn determines sail area.

B) A catamaran with daggerboards (raised) is less likely to trip in high storm driven beam seas as opposed to a catamaran with keels.

C) A properly built multihull with sufficient watertight bulkheads will not sink, and a requirement for CE certification.

[tuskie]

Originally Posted by catmancan2

A) The stability of a multihull has nothing to do with whether it has keels or boards. Stability is a function of overall waterline beam which in turn determines sail area.

B) A catamaran with daggerboards (raised) is less likely to trip in high storm driven beam seas as opposed to a catamaran with keels.

C) A properly built multihull with sufficient watertight bulkheads will not sink, and a requirement for CE certification.

A. Is relevant, B and C are off topic.

Stability is a function of beam, yes AND weight too. More beam, more stability. More weight, more stability. Its been done to death in many threads, including this one:

http://www.cruisersforum.com/forums/...ed-175996.html

What I said was "all other aspects ( design, weight distribution,,etc) being equal, a heavier catamaran will be more stable, ie. resistant to flipping."

Note that I said, all other design aspects being equal.

Factor replied, suggesting that mini keels (ie. those fitting to non-performance catamarans or "condomarans" as they are frequently referred to) should be filled with lead. My response was to allude to the point that most lightweight catamarans (they ones that tend to flip, such as the Atlantic 57) are in fact usually fitted with dagger boards. So the point is more related to WEIGHT rather than the type of keel. Most mini keeled, "non-performance" cruising catamarans, such as the Dufour being discussed have plenty of weight already, so adding extra in the form of lead filled mini keels would be quite unnecessary and quite silly. I think Factor might know this.

[surf_sail]

Originally Posted by rom

In some interview I heard the boss say they will never do that. Maybe with with another brand, like catana did with Bali.

I don't know why Outremer would do that. They seem to have found themselves a really nice niche. Long backlog, higher prices, and I'd bet better margins than a lot of other cat manufacturers...

The more interesting question to me is why are the late comers (Dufour, Jeanneau) following a me-too strategy of going into the condomaran market? Nothing wrong with a condomaran, but it's got a lot of competition. Personally if I wanted a condomaran, I'd need a pretty good reason not to go for a Lagoon who with their high production volume hopefully have more scale and (hopefully) worked out more of the kinks from the design.

Alternatively, I'd think a real competitor to Outremer could be an interesting play.

[catmancan2]

Originally Posted by tuskie

A. Is relevant, B and C are off topic.

Stability is a function of beam, yes AND weight too. More beam, more stability. More weight, more stability. Its been done to death in many threads, including this one:

http://www.cruisersforum.com/forums/...ed-175996.html

What I said was "all other aspects ( design, weight distribution,,etc) being equal, a heavier catamaran will be more stable, ie. resistant to flipping."

Note that I said, all other design aspects being equal.

Factor replied, suggesting that mini keels (ie. those fitting to non-performance catamarans or "condomarans" as they are frequently referred to) should be filled with lead. My response was to allude to the point that most lightweight catamarans (they ones that tend to flip, such as the Atlantic 57) are in fact usually fitted with dagger boards. So the point is more related to WEIGHT rather than the type of keel. Most mini keeled, "non-performance" cruising catamarans, such as the Dufour being discussed have plenty of weight already, so adding extra in the form of lead filled mini keels would be quite unnecessary and quite silly. I think Factor might know this.

What naval architect provided you with your info? Or is this simply your assumption based on the Atlantic 57 thread? Not trying to be an arse, but I've never heard or read where more weight improved the safety of a multihull.

[tp12]

And it's an extremely long bow to draw saying that two, very well understood, capsizes means that a particular design tends to flip.

It's simply not enough data to draw any conclusions from, statistically.

[tuskie]

QUOTE=catmancan2;2552817]What naval architect provided you with your info? Or is this simply your assumption based on the Atlantic 57 thread? Not trying to be an arse, but I've never heard or read where more weight improved the safety of a multihull. [/QUOTE]

As I said, it's been done to death and I have no intention to discuss the pro, cons and relative dangers of Chris White Atlantics.

[yeloya]

Originally Posted by surf_sail

I don't know why Outremer would do that. They seem to have found themselves a really nice niche. Long backlog, higher prices, and I'd bet better margins than a lot of other cat manufacturers...

The more interesting question to me is why are the late comers (Dufour, Jeanneau) following a me-too strategy of going into the condomaran market? Nothing wrong with a condomaran, but it's got a lot of competition. Personally if I wanted a condomaran, I'd need a pretty good reason not to go for a Lagoon who with their high production volume hopefully have more scale and (hopefully) worked out more of the kinks from the design.

Alternatively, I'd think a real competitor to Outremer could be an interesting play.

Very good point. If we look at the positioning map of the cats, the only gap seems to be in the below 40 ft, affordable catamarans with a price tag of below 200.000 €. I believe there is a lot of potential over there.
Today the smallest and cheaper catamaran from mass manufacturers are 38 ft and there is nothing less than 250.000 €. Lagoon 380 is close to that, FP Lucia 40 (which is not 40 but 38,5 ft) cost well above 300.000 €..

Outremer has a competitor; Catana..They both makes about 10-15 boats a year.

Cheers

Yeloya

[surf_sail]

Originally Posted by yeloya

Very good point. If we look at the positioning map of the cats, the only gap seems to be in the below 40 ft, affordable catamarans with a price tag of below 200.000 €. I believe there is a lot of potential over there.
Today the smallest and cheaper catamaran from mass manufacturers are 38 ft and there is nothing less than 250.000 €. Lagoon 380 is close to that, FP Lucia 40 (which is not 40 but 38,5 ft) cost well above 300.000 €..

Outremer has a competitor; Catana..They both makes about 10-15 boats a year.

Cheers

Yeloya

While I think you're right a sub 200k <40ft cat would be very attractive I assume it's not feasible to do at that price point and going less than 38ft would create too much hobby horsing. Nevertheless it would be great to see more options.

Good point re: Catana, but some have argued aside from the dagger boards the new boats are no longer performance oriented (too heavy).

[smj]

All extra weight does to a catamaran is put a lot more stress on the structure. Multihull's should be light so they can ride over the waves instead of through the waves.

[yeloya]

Tuskie, I think you are confusing static stability with dynamic stability. If the boat is still stand, you are absolutely right.
When the boat starts moving, the wind blows at 50 kts and the boat is subject to 8-9 meters breaking waves from various directions, then we should be talking about dynamic stability and this is far more complicated than the school mechanic drawing you suggested.
In heavy weather conditions light and fast cat are safer for two reasons; firstly they can escape from the weather. These fronts move at around 10 kts an hour and if you are faster than that you are in safer zone. Secondly, in heavy weather the main issue is to dissipate the huge energy accumulating on the boat. Fast boats can easily convert this energy to kinetic one by simply going faster thanks to their better aerodynamic and hydrodynamic properties.

Cheers

Yeloya

[tuskie]

Originally Posted by yeloya

Tuskie, I think you are confusing static stability with dynamic stability. If the boat is still stand, you are absolutely right.
When the boat starts moving, the wind blows at 50 kts and the boat is subject to 8-9 meters breaking waves from various directions, then we should be talking about dynamic stability and this is far more complicated than the school mechanic drawing you suggested.
In heavy weather conditions light and fast cat are safer for two reasons; firstly they can escape from the weather. These fronts move at around 10 kts an hour and if you are faster than that you are in safer zone. Secondly, in heavy weather the main issue is to dissipate the huge energy accumulating on the boat. Fast boats can easily convert this energy to kinetic one by simply going faster thanks to their better aerodynamic and hydrodynamic properties.

Cheers

Yeloya

Thanks Yeloya. You are correct that dynamic stability is far more difficult to model.

I consider that static stability is proportional, but not directly proportional, to dynamic stability.

There is a huge difference between stability (either static or dynamic) and safety. The two are only very loosely related. Overall safety is IMO more related to the skill and seamanship of the crew. Whether the crew of a lighter, faster catamaran use speed to avoid or get into more danger is an example. However, I don't buy the "fast cats get out of harm's way" line. I've seen a number sail fast to worse weather and their peril. I also don't buy the light cat "accelerate rather than break" argument. This effect only works up to the point that the cat is going too fast, then its is in danger of burying the bows and pitchpoling. I far prefer to go slower in heavy weather, under reduced sail.

Adding weight in order to increase stability is usually not discussed, as it is a designer's least preferred option. The increased weight results in greater displacement, hence increased wetted area, hence increased drag, resulting in less speed. Designers have much preferred to increase stability by increasing beam. That way it is possible to maintain speed as well. Beam widths have probably gone as far as practically possible, with most cruising cats now with beams equal to or greater than performance cats. Never the less, the fact remains that increased weight (with caveats about sensible placement to not shift centre of gravity) increases stability.

[valhalla360]

Originally Posted by BigBeakie

And yes, I seriously think they will sink if they are too heavy. That's just simple physics. Some condomarans have sunk when flooded.


Sent from my iPad using Cruisers Sailing Forum

So you are saying this boat is prone to sinking? Seems a pretty big leap from just some marketing pictures.

[BigBeakie]

Originally Posted by valhalla360

So you are saying this boat is prone to sinking? Seems a pretty big leap from just some marketing pictures.

Am I? Is that what I said? I thought I said that if they are too heavy, they will sink. I think that is self evident. If the weight (mass) of the boat is greater than the total buoyancy of the boat, and this depends on the relative densities of everything about the boat, then if the boat is flooded and the flooding is not stopped in time, the catamaran will sink.

Did I say this cat is prone to sinking? No, I did not. I know virtually nothing at all about what she carries, what core is used, how much of it she is built with, weight of engines, tankage, genset, number of cans of soup stored under the floorboards...you get the drift?

But porker cats can and do sink, as happened to a Lagoon 500 off Brisbane: Category: | The Courier Mail

» lagoon 500 | Sailing Anarchy

The insurance investigation found that a through-hull had been installed incorrectly by the manufacturer and siphoned seawater into the sub floor area when a hose failed.

Caveat emptor.