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Old 06-02-2008, 21:58   #31
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Originally Posted by Nordic cat View Post
How do you work that out?

First the figures don't add up, secondly, do you have the specific layup information on this boat? Do you know what all the internal furniture will give in the way of bouyancy?

Let's just work with your figures:

11200 lbs/2.2 = 5090 kg. Foam is 80 kg/m3 not 800 kg/m3! 5090/80 = 63.6 m3
This gives a buoyancy of 63,6 x 1025 (salt water density) = 65190 kgs.
From this we subtract the weight of the foam wich is 63,6 x 80 = 5090 kg
Difference is: 65190 - 5090 = 60100 kgs

Your result was "9000 lbs of lifting force" or around 4090 kgs. So 60100/4090=14.7 times off the mark!

Diesel is lighter than salt water, so will also give buoyancy.

I would suggest a more cautious approach to knocking other peoples designs would be more beneficial for all involved.

Alan
You need to do your calculations again
We use foam with a density of 80 , that is 80 kilo,s per cubic meter
one cubic meter contains 1000 liters or 1000 kilo,s of lifting force .after splitting the foam into slices of 20 mm and adding resin to it the actual weight has gone up to around 200 kilo per cube or a lifting force of 800 kilo,s per cubic meter is left ,
According to your math one cubic meter of air has 10000 kilo,s of uplift force.
Where do I get these meters

Back to the calculator ( or school) is a good idea.

P.S a layup is not necessary it all boils down to total weight versus buoyancy

Only if foam is used in the internal furniture can it be used for buoyancy calculations and if that is the case it is minimal compared with the foam used in the structure , it is thinner has a higher absorbtion per cubic meter and very little is used.

I do not knock any design , never do only work with facts , not one design was mentioned or knocked get your glasses out.

Warm Greetings

Gideon
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Old 06-02-2008, 22:06   #32
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David, this is a voyaging scenario-you may be floating around for months. You want to live on 6-12 ounce cans of water and a couple of candy bars for months? What if you're cold? If your extra sweater and socks are at the bottom of Davey Jones' locker, you'll just have to shiver. You want all your stuff for the same reason you took that stuff in the first place--because you need it. And yes, being inside an upside down catamaran would not be nice. I don't see why you would have diesel or oil inside your accommodation's cabins. My boat is designed to USCG commercial passenger vessel standards for carrying 149 paying passengers, so the air vents for fuel tanks vent onto the bridgedeck, and the engine rooms are completely sealed from the other compartments. I don't see much reason to get into the engine rooms if the boat is upside down. The upside down hulls wouldn't lack air space-there would be about 3' above the water level. There would be water sloshing around, and it would be pretty miserable, but you wouldn't drown. If you cut a hatchway into the bottom of your hull, you'd have good ventilation. You can certainly take planning for life upside down farther than I have. I read a really good illustrated article about this in Multihull magazine, and that author took it farther than I have. Also, I repeat, read Chris White's book, pages 215 and subsequent.
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Old 06-02-2008, 23:48   #33
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, but there is a book about a catamaran which capsized somewhere in the pacific, and remained afloat and habitable for months (3 or 4 months? I cant remember) . The crew (of 3 I think) lived in and on the upturned boat until it drifted ashore. .
The boat was the ROSE NOELLE and skipper and author was John Glennie (I think) and I think they were capsized for 150 odd days (apparently 119 - see below). CAnt remember the design of the boat but it was an early trimaran, I think made from Ply. I have read the book and it says a lot about strength of character in these circumstances, I got the feeling that John Glennie was a bit of a cantankerous bugger but when the chips were down held the crew together. But that is just my interpretation of his writings which of course were from his perspective.

A check on the web reveals the following

Rose Noelle capsized in a storm east of Napier on June 4, 1989, and drifted upside-down for 119 days before washing up on Great Barrier Island in Auckland'Rose Noelle capsized in a storm east of Napier on June 4, 1989, and drifted upside-down for 119 days before washing up on Great Barrier Island in Auckland's Hauraki Gulf.
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Old 07-02-2008, 00:35   #34
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I'm off to the hospital for a few days. I am getting a 2nd surgery for a colovesical fistula, which is something no one would want to hear about at dinnertime. I'll check on the thread in about a week, I would think.
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Old 07-02-2008, 01:17   #35
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I wish you good luck in the operation and years of happy sailing afterwoulds

Gideon Goudsmit
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Old 07-02-2008, 02:48   #36
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I/we have a new Fontaine Pajot, 40ft cat, Lavezzi, that we intend sailing fm NZ to Tonga, Vanuatu, Fiji and then Australia.
It says it is rated to category 8 (Beaufort scale)..
It's our first experience on a cat (have monohull in Canada); would be interested to hear some opinions re seaworthiness etc. We have watermaker, solar cells, yellow bottom...Should we have generator? Is this boat suitable for our intentions?
ta
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Old 07-02-2008, 02:50   #37
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Hi Troutbridge, just curious on your last boat, what was it? I do some sailing on a Schionning Radical Bay 8000 cat with a carbon-fibre bi-rig, have been out in +30kts of wind without problems.
A Freedom 39 pilothouse. I also went out in 30+kts, no real problem but on the Atlantic crossing the main mast creaked and groaned the whole way across, leaving me speculating on what the mast would take out if it gave way. Interesting, Freedom yachts gave a lifetime guarantee to the first owner (I was the second) so they obviously had confidence in the build. I suppose on a cat unstayed mast(s) would be a good idea as they would flex and spill some wind in a gust.
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Old 07-02-2008, 03:12   #38
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fontaine pajot cat

A 40 ft Lavezzi'. Is it up to the task of a crossing fm NZ to Oz?
Want to know all the pros and cons, and given we already own the boat, what should we be doing/concerned about?
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Old 07-02-2008, 07:00   #39
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Same goes for you Andreas, if you have any experience, tell us about it.
Hi BigCat. I know it's easy to insult people you feel better than, but belittling them, only shows your own ignorance. I've sailed across the Atlantic twice and lived on a 40 foot sailboat for a year, sailing solo in the Med. That might not count much in your book, but at least I know what blue water sailing feels like. Good luck with your BigCat ... Hopefully it will make you happy!
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Old 07-02-2008, 08:24   #40
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Lee,

Does your Lavezzi have Cat 1 cert? If so, then it's up to the task according to NZ gov't. Seriously though, I don't know much about it, but it looks like a fine boat - if it's outfitted right and sailed within its limits then you shouldn't have any problems. Are you going with a para-anchor or series drogue?


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Old 07-02-2008, 08:38   #41
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And Lodesman, there is very little floatation value in fresh water and not much more in diesel.
BC,

The comment was a somewhat tongue-in-cheek counter to Gideon's statement that water and diesel tankage would ultimately contribute to sinking a vessel. That is not the case; regardless of the flotation value of fw or diesel, it is buoyant. Of course in an inverted cat, those full tanks would be deadweight (hopefully) as they should be out of the water. But once they're immersed they will help the boat float, not sink it - Archimedes proved that.

BTW, best wishes for your surgery.

Kevin
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Old 07-02-2008, 09:03   #42
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A 40 ft Lavezzi'. Is it up to the task of a crossing fm NZ to Oz?
Agreeing with Kevin, assuming your boat is properly fitted out and in good condition, it should be capable of the passage you describe, if - and this may be the most important IF - if YOU are capable as a skipper, you have a capable crew, and you make the right decisions as to when to go.

Because you're asking rather broad questions about making long passages, it suggests you may not have all the knowledge you should. I'm sticking my neck out guessing here - but it's for your own safety. At a minimum, please consider taking on experienced crew or hiring an experienced skipper.

Dave
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Old 07-02-2008, 10:03   #43
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Originally Posted by 44'cruisingcat View Post
You don't right the boat, you live on and in it upside-down. What most people call "escape hatches" are actually more likely to be used as re-entry hatches.

No doubt, the interior of an upturned boat will be a mess - and possibly contaminated with diesel (although it shouldn't be if the diesel tank placement has been thought about) BUT, in any kind of sea, it would still be more comfortable and safer than a liferaft. It should also likely have plenty of fresh water still in the tanks, and will make a much more visible "target" for rescue. With some forward planning you can ensure that an upside-down cat would be a perfectly livable in a survival situation.
Don't you think there would be a big rush of air going out and a subsequent lowering of the hull further into the water when the emergency hatch is opened?

For one thing, how do you get fresh oxygen into the hull? How do you collect fresh water? What about exposure and hypothermia living in the water for days on end? Are you going to eat food that has been saturated by salt water? How do you deal with the crankcase oil at the surface from the genset and the engine?

Please, give me the dry life raft with the day-glow orange canopy that is recognized as a life raft internationally. Give me the raft with the EPIRB, sat phone, GPS, water, water collection device, food, flares, signal mirror, medical kit, fishing line, etc. Give me something that is dry that does not rob body heat and reserve energy like the water does. A good ditch bag will have everything you need for letting the world know of your situation. Its technologically not necessary to float around the ocean for months with the inability to get help untill you get lucky and someone spots you.
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Old 07-02-2008, 13:44   #44
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I'm really having trouble believing this debate is actually taking place.

Bullimore, Autissier, the crew of the Rose Noelle, and many others I'm sure, survived by staying with their upturned boats. Many crewmembers in the Fastnet storm died because they left their boats and took to liferafts.

If you think the interior of a liferaft is going to be either dry or comfortable in bad weather you're seriously misguided. I suggest you take a liferaft course - just getting INTO a liferaft is a lot harder than you might think - in a swimming pool! And even in the calm of a swimming pool you take a lot of water in with you. I've done liferaft courses, and that was enough to convince me that an unsinkable boat was a better way to go.

Surely you've heard the adage "Only use the liferaft when you have to step UP into it." With a properly designed multihull, with well placed bouyancy, the only likely reason you would abandon the boat is fire.

most production builders don't do it, but I will paint the underside of my bridgedeck bright orange - it will also be non-skid. There will obviously be EPIRBS, handheld VHF, emergency water and food on board. And of course some of the "normal" food would be ruined in a capsize - but some of it would be fine - canned food, bottled drinks, most plastic packaging.
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Old 07-02-2008, 13:46   #45
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I absolutely agree that a non-capsized boat is magnitudes safer than a life raft. I thought the debate was about a turtled catamaran versus getting in a life raft?

I have been in a liferaft in a pool as part of getting my merchant marine officers license, and in a liferaft at sea (intentionally). Liferafts are miserable...its not much different than sitting on a water bed that is sloshing around with a bad leak. I have also been in the water and know that you are much better out of the water than in the water as you would be inside a turtled catamaran or grasping to the hull outside of a turtled catamaran. Being in a life raft your butt and legs are most likely to be wet, but inside of a capsized cat you are going to be wet from the neck down. Which really is better? Being out of the water is magnitudes better than being in the water. I do not understand how you can disagree with that?

So my point is, who cares if a capsized catamaran sinks or floats...you don't want to be inside of one or grasping to one if you have the option of "stepping up" into a life raft or your dinghy.

Still unanswered, how does a large turtled catamaran right itself without external help?..other than a freak very large wave that does exactly the right thing to right the boat or drifting ashore?
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