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Old 11-01-2018, 03:15   #76
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Re: Dufour catamaran

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Originally Posted by BigBeakie View Post
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.
Are you a lawyer trying to play word games to imply things without technically saying them?

Yeah, if you fill most boats with water they sink (at least to the water line if foam filled). A broken thru hull flooding is bad on any boat. The lagoon issue doesn't appear to be related to being "obese" but a failed thru hull.
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Old 11-01-2018, 03:28   #77
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Re: Dufour catamaran

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Originally Posted by surf_sail View Post
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).
Yes the shorter the water length the more the cat is prone to hobby horsing. However, the distribution of weight is even more important and decent boats can be made at 35-38 ft range. I remember FP Tobago 35 which sailed pretty well. After all, anyone who wants to buy a brand new boat at around 200 k, could accept some tradeoffs..

Concerning Catana, I know that not all of them are light enough to be considered "performance oriented". Mine is though..

Cheers

Yeloya
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Old 11-01-2018, 12:36   #78
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Re: Dufour catamaran

I am truly amazed that we have reached a point where some think that more weight in a multihull is a good thing, truly amazed.
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Old 11-01-2018, 13:07   #79
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Re: Dufour catamaran

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Originally Posted by valhalla360 View Post
Are you a lawyer trying to play word games to imply things without technically saying them?

Yeah, if you fill most boats with water they sink (at least to the water line if foam filled). A broken thru hull flooding is bad on any boat. The lagoon issue doesn't appear to be related to being "obese" but a failed thru hull.
No, not a lawyer. Which part of the common English word sink, don't you understand? Sink; as in proceed directly to the bottom of the ocean, glug glug, deep six, etc. NOT float at the waterline....

Once upon a time, one of the advantages of cruising cats was that if holed at sea, at least you could survive in the still FLOATING cat, because it would not SINK.

Now, things have eventuated where some think heavy cats are an advantage, and to the point where SOME of these "cruising"cats will actually sink.

That's not the kind of cat I'd want my family on if crossing oceans. But for chartering close to shore, sure.
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Old 11-01-2018, 16:38   #80
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Re: Dufour catamaran

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Originally Posted by Factor View Post
I am truly amazed that we have reached a point where some think that more weight in a multihull is a good thing, truly amazed.
Like most things, there are advantages and disadvantages. I won't apologize for discussing either.

Air trapped in water tight compartments is the thing that keeps most holed multihulls afloat. If a catamaran has more weight it's design would incorporate more internal volume and this needs to be partitoned into watertight compartments.
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Old 11-01-2018, 17:11   #81
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Re: Dufour catamaran

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Originally Posted by Factor View Post
I am truly amazed that we have reached a point where some think that more weight in a multihull is a good thing, truly amazed.
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Old 11-01-2018, 18:02   #82
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Re: Dufour catamaran

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Originally Posted by yeloya View Post
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

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Hmm, dynamic stability is just various cases of static stability using various sets of parameters. Hence, design for the worse case, e.g. 50kt winds and 10m seas on the beam (or whatever you want) and you have covered all lesser cases. The school mechanic drawing is still pertinent.
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Old 11-01-2018, 22:01   #83
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Re: Dufour catamaran

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Hmm, dynamic stability is just various cases of static stability using various sets of parameters.
Yes, but Yeloya is correct in stating that dynamic stability introduces a series of extra factors.

For example, if a lightweight performance catamaran is overloaded it's static stability will be increased ie. it will require more force to blow it over, standing still. It's dynamic stability, however will probably be adversely compromised in that the increased mass may cause it to wallow, be pooped or bury it's bows. This extra weight will also slow it down and may cause structural loadings which the designers did not allow for, resulting in breakages. For this reason, good designers stipulate a maximum displacement or payload. However, this information, if available at all may not be found on the website or the brochure!

If weight, per se, is such a bad thing, one wonders how the world's top multihull designers, such as VPLP, Morrelli and Melvin and Berret - Raccoupeau could possibly design stable, safe and servicable cruising cats ("porkers") yet still incorporate considerable weight into each Lagoon, Leopard and FP model. Perhaps they know a thing or two about catamaran design?
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Old 12-01-2018, 00:13   #84
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Re: Dufour catamaran

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I am truly amazed that we have reached a point where some think that more weight in a multihull is a good thing, truly amazed.
Hmm. Let's see them adding ballast.

If anyone really thinks heavier is better, go ahead, buy some lead shot, some polyester resin, and fill your bilges!

I'll even come and do it for you.
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Old 12-01-2018, 00:38   #85
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Re: Dufour catamaran

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Originally Posted by arsenelupiga View Post
i give you 10 kn and performance cat where you can use as much sail as physically possible and have daggerboards as long as you want.

And will put you in confused seas say 1m which is nice average around east coast australia.

And you will motor or look like struggling cat doing 2 knots and ripping sails apart and make monohullers laugh
You really don't have a clue, do you?
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Old 13-01-2018, 01:29   #86
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Re: Dufour catamaran

Oh dear, what a tread because of telling, that Dufour is building cats again. Will recommand Yeloya for repair and service, if you need it in the Med!
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Old 13-01-2018, 02:58   #87
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Re: Dufour catamaran

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Originally Posted by 44'cruisingcat View Post
You really don't have a clue, do you?

I base my statements on evidence. Have seen performance cats struggling badly in 10 kn.

It appears, you have never experienced such seas sailing in protection of GBR?

oh dear
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Old 13-01-2018, 12:16   #88
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Re: Dufour catamaran

O
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Originally Posted by arsenelupiga View Post
I base my statements on evidence. Have seen performance cats struggling badly in 10 kn.

It appears, you have never experienced such seas sailing in protection of GBR?

oh dear
Like your "evidence based" statement that 50% of capsizes are fatal? Only it turned out there was no evidence...

I doubt there would be any evidence to support your sail tearing in 10 knot wind fantasy either.

You could also learn a bit from looking at a map. The Great barrier reef doesn't extend into NSW, nor does it reach out across the coral sea.

So, when are we adding ballast to your lagoon?
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Old 13-01-2018, 12:45   #89
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Re: Dufour catamaran

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Time to fill those mini keels with lead then
no,,, just no
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Old 13-01-2018, 12:53   #90
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Re: Dufour catamaran

OMG,,is this all about pedantics ( sorry I have not read the whole thread ( do ii have the rite to comment) ) .. can I just say , that my half ( ? ) performance ( apparently )orientated ) multihull has got me out of many ( well a few ) tricky situations, ,
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