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Old 06-02-2008, 06:36   #1
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Catamarans for Circumnavigating-Why not stock?

A current thread asks what a circumnavigating catamaran should have as its ideal characteristics. The thread's initiator makes it clear that he is looking for advice about what cookie-cutter factory-made boat to buy. Well, many fine voyages have been made in such boats, but IMHO no factory set out to make catamarans primarily for ocean voyaging, and their characteristics reflect this. Factory boats are made primarily for weekend and vacation use, and of course, factory catamarans are also made -perhaps primarily- for vacation chartering in places like the Caribbean and the Whitsundays. In my analysis, I'll compare my 65' catamaran with your standard 45' French or South African cruising palace-because they have about the same weight and accommodations. (Here I exempt the cream of the crop, the Outremers and Gunboats of the world. Yes, I include you, FastCat435, but I would confuse people if I said, African cats but not Africancats.) ************************************************** ************************************************** *************** Floatation: Many times I have read that catamarans are unsinkable because of their core material. Well, I have done the math, and it isn't true. This isn't that hard to do-check the core thickness, figure the cubic volume by making an estimate of the cored surface and core thickness, and see if it exceeds the boat's loaded displacement or not. For my 65' design, there are about 5,000 square feet of area, counting the deck between the hulls as double, because it has a top and bottom that are cored. My core material is one inch thick. 5000 x 1"=5000. Divide 5000 by 12=417 cubic feet. 417 cubic feet x 64 pounds (the weight of seawater) = 26,667 pounds of floatation. Obviously, a 65' catamaran in ocean voyaging trim weighs a lot more than that. You say, but what about the area displaced by fiberglass? Well that weighs about 100 pounds a cubic foot. If I have 16,000 pounds of fiberglass, that equals 160 cubic feet, or another 10,240 pounds of displacement. You say wait, what about your tankage? Well, I have designed a lot of tankage in my BigCat-about a thousand gallons worth. This equals another 125 cubic feet, or another 8000 pounds worth. So, add 417 + 160 + 125 = 702 cubic feet = 45,000 pounds. For an ocean voyaging 65' catamaran, I'd say we are still looking, at best, at neutral buoyancy. (I know what you are thinking, but remember, nobody is going to make you put a thousand gallons of diesel and water in your boat, if you don't want to.) ************************************************** ************************************************** *************** So, where can we get more floatation? I'd say, under the bridgedeck, and inside the connector beams if the design has any connector beams. Many designs have aft connector beams but use the house on the bridgedeck to form a beam-like structure for the forward part of the boat. In my design, I put 45,000 pounds worth of unicellular polyurethane foam inside the connector beams and under the deck connecting the hulls. My tween-hulls deck is one foot thick, so you get about 600 cubic feet from the deck thickness, and 120 cubic feet from the connector beams. So, roughly 90,000 pounds of floatation between all the sources of floatation. ************************************************** ************************************************** *************** Yes, floatation does add to the weight of the boat. Even floatation foam at a 2 pound per cubic foot density adds up if you install 600 cubic feet of it-2x 600=1,200 pounds. Balsa weights 4 times as much, so there is about 1 1/2 tons, yes, tons, of balsa. Foam core wouldn't be any lighter, if you specified a foam as strong as balsa. If you used lighter foam, you'd have to use thicker skins, and so would gain nothing, weight wise. Or have a more fragile boat. Who wants to circumnavigate in a rinky boat? I''ll leave sleepless nights thinking about hitting flotsam and jetsam to those who think that its worth a knot and a half of boat speed potential-an extra increment of speed which will just make it even easier to hole their boats if they "find" a cargo container floating awash at sea. ************************************************** ************************************************** *************** How much floatation there is isn't the only question to ask, but also ask, "Where is it?" Remember, if you are counting the displacement volume, of say, the deck over your hulls, it doesn't provide floatation until it is under the water. Since staying above the water is the goal, this theoretical number has to be taken with a grain of salt. So the question becomes, how much floatation is there under the water? Obviously, the sole of the deck between the hulls is going to be awash if your boat is right side up, and that is where your floataion is. Likewise, your situation will be the same if the boat is upside down. ************************************************** ************************************************** *************** Watertight compartments: It is all very well to assume that having a few of these makes you safer, but once again, you have to do the math. If your watertight compartment is forward of the accommodation, say, the first seven feet of the boat, what is its volume? Probably something on the order of 7' long x 3' wide x 6' high. That is about 150 cubic feet, or say 9600 pounds of displacement. If that is where the water is coming in, well and good. If not, it doesn't supply all that much buoyancy. Multiply by two, because it is a catamaran, after all, and we are still rather shy of what's needed. If you have two similar compartments astern, you are probably getting a useful amount of buoyancy from your 5 compartment boat. I say five, because every stock catamaran I can think of has the two center compartments connected by the bridgedeck through the deck house-giving you one compartment between them. If you want a lot of reasonably sized watertight compartments, you end up with a Wharram type of configuration, where you have either no or a small cabin on the deck, and access to each compartment is via the deck that connects the hulls. ************************************************** ************************************************** *************** So far, I'd say we have eliminated 100% of the stock boats based on a requirement to have multiple watertight compartments of a useful size, and floatation. This is not their fault, as they were designed, after all, to give people a nice vacation where they anchor or tie up every night, and barbecue dinner or zoom ashore to eat out. ************************************************** ************************************************** *************** Rig redundancy: Well, obviously it should be, like the rest of the boat, bulletproof. I read a lot about how one of the great things about catamarans is that they have (usually, in the ocean voyaging size, anyway) two completely separated engines, fuel tanks, and systems for total redundancy in case of trouble. If this redundancy business is good for engines, to give you a spare, why is it so unusual to insist on the same for rigs? No stock catamaran has this. With any unstayed biplane rig, you have 100% redundancy. Sloop rigs obviously don't have this. It is almost impossible to get this in the standard ketch rig, as the two masts are almost always stayed together, in order to get a reasonable angle on the backstay of the main and the forestay of the mizzen. Also, the mizzen isn't much compared to the mainsail in terms of area or mast height, so a ketch rig isn't 100% redundancy. ************************************************** ************************************************** *************** Rig reliability: Well, I don't think any rig that depends on a minimum of 9 turnbuckles with thier 18 swedgings, 9 toggles, 9 wires, 9 tangs, 7 chainplates, 2 spreader assemblies, etc. all of which are subject to the combination of fatigue and corrosion called stress corrosion, can be called inherently reliable. See Catalina Direct: SeaLube Turnbuckle Lubricant for photos of what goes into just one shroud or stay assembly. On the other hand, if you design an unstayed mast with adequate scantlings, and make it out of a material that won't rot, there is nothing to go wrong. This won't work for aluminum masts, by the way. Aluminum is prone to fatigue through bending, and will suddenly fail once it has undergone enough cycles of bending. Aluminum masts must be stayed. Unstayed masts should be wood, steel, or composites. Steel is too heavy. So wood, if you protect it well against rot, or composites (carbon plus glass with a high strength resin-either epoxy or vinylester.) You could eliminate some of the stainless by going with vectran for all but the forestay. You'd even be thought quite progressive for replacing your turnbuckles and wires with lanyards and deadeyes. I love the irony of that. ************************************************** ************************************************** *************** Rig economy: Well, if you eliminate $50,000 to $100,000 dollars woth of rig stuff, you can save an awful lot of money. Eliminate the following--mainsail assembly (traveler, traveler car, sheet winch track, slides mast gooseneck,) the standing rigging described above, jib stuff ( sheets, their cars, two sheet winches, roller furling,) factory mast, sail loft made sails (main and jib, at a minimum.) Now if we are talking about a standard 44' -four cabin or one master and two guest cabin cruising catamaran, you probably need all of that stuff to be the best-everything with ball bearings, and so on. Harken or Frederickson-neither is cheap. Maybe even a few electric winches. If you plan on having a boat that goes fast downwind, add a spinnaker and all its stuff. At least catamarans don't need a spinnaker pole. Get a marine catalog, price this stuff, and I think you'll whistle at the bottom line. Your sails and standing rigging is going to have to be replaced after one circumnavigation or its equal in miles-maybe 30,000 miles. Ouch! there goes $20,000 or so. ************************************************** ************************************************** *************** Rig ease of handling: Well you can conquer the inherently hostile nature of the Marconi rig if you throw enough tens of thousands of dollars at it, and buy enough gear with stainless steel ball bearings and electric motors. Or you can go with a rig that doesn't require expensive and chancy taming. Your call. See 'Rig economy' above. ************************************************** ************************************************** *************** So, we have now eliminated the usual stock boats based on floatation, watertight compartments, rig redundancy, rig reliability, and rig economy. At least, I have. Most yachtsmen cling stubbornly to all of those vulnerable little bits of metal, never stopping to think that a flagpole, a skyscraper, an apartment balcony, or a jet's wing are all structurally the same engineering principle at work as the unstayed mast-the cantilever. The fundamental problem here is "group think," but popularity in characteristics developed for daysailing and brief vacations is the basis of popularity in yachting-not suitability in voyaging. If 98% of yachts had been designed and built for ocean voyaging and only 2% had been designed and built for brief recreation, and these characteristics had been evolving since Nathaniel Herreshoff designed the first catamaran yacht, the Amaryllis, I think very different characteristics would be popular, and therefore common wisdom. ************************************************** ************************************************** *************** Conventional wisdom sank the catamaran idea for a hundred years after the Amaryllis was banned from racing. Perhaps in another 100 years, yachtsmen will be surprised to hear that the quaint yachts of a century gone by had been held up with, yes, amazingly enough, corrosion-prone stainless steel wires and metal bits. It is amusing to watch the same process at work in the catamaran revolution-first people started chartering them in the Caribbean because they were huge boats with many cabins, and therefore excellent summer cottages, second they became popular, and third, their adherents became common enough to be recognized as numerous, and subsequently many sailors were astonished that anyone would be foolish enough to go to sea in a boat which could actually sink. Everyone is quite certain that their catamaran can't sink, though no designer or builder has guaranteed this, and no one has done the math on his own boat. Certainly, we have all seen photos of upside down catamarans which didn't sink, but upside down catamarans are almost always racing catamarans, therefore ultra-light catamarans with a minimum of stores on board. ************************************************** ************************************************** *************** Those who can resist this sociological / psychological phenomenon of the unreasoning assumption that the popular must be the best, and instead reason from first principles, are almost outcasts. They are also inventors and the early adopters of new ideas. Certainly, Captain Nat would have gone broke if he had bet his all on catamarans, as being better didn't lead to being more popular for another hundred years. Anyway, back to the point by point analysis- ************************************************** ************************************************** *************** Fireproofness: There are no stock catamarans made out of fireproof resin. None. Yet fire is your greatest hazard, after drowning in a storm, collision or shipwreck on the rocks. Safe navigation is the province of the skipper, but the builder can specify fir- resistant resin. Does it cost more? Of course, that's why stock boats don't use it. Fireproof resin costs an extra fifty cents a pound, which adds up if you use 8,000 pounds of resin. Is it weaker? No. ************************************************** ************************************************** *************** Speed: The characteristic which most influences speed is the square root of the waterline length. Pound for pound and dollar for dollar, nothing else has as big an effect as waterline length. You can design a standard 44' catamaran, stuff it to the gills with berth "shelves" down where the waves will smack them, and even drag in the water if you load your boat down, shove the engine further aft and stick a corrosion-prone sail drive in it to maximize the interior, and you have your standard vacation cottage type catamaran. Or, you can increase your waterline by 20', eliminate the "smacky, draggy" shelves which lower your maximum bridgedeck height, give your engines honest prop shafts, and have a faster boat. The labor of installing a standard shaft drive costs more than those awful sail drives, but it isn't more expensive otherwise, if you are building a custom boat. Plus, if you stretch out your hulls without making them wider, fat piggy little hulls become sleek, slender hulls. Stock vacation type catamarans almost always have the fat, piggy little hulls, and always have smacky, draggy berth shelves. If you are lucky, they are only aft. If not, there are four of them, two forward and two aft. If you step aboard a stock catamaran and your better half oos and aahs about how roomy and airy it is, look for fat, smacky, draggy characteristics. They'll be there. It is really funny when yachtsment buy these boats, and then bolt $30,000 worth of gear to them to make the boats go faster. These boats were designed for the crowd that wants to get to the next anchorage 15 miles away by happy hour, not for voyagers. ************************************************** ************************************************** *************** Of course, your greyhound will cost more to keep in a marina, but those are few and far between for ocean voyagers. If you anchor miles from the nearest bar and restaurant, because you can't afford the marina, take comfort in the fact that a longer catamaran is a wider catamaran, and you can carry a really big inflatable in the davits and by that I mean an 18' inflatable. ************************************************** ************************************************** *************** Seaworthiness: Also, of course, a longer, wider catamaran is a more seaworthy catamaran. It is very widely accepted that bigger is more seaworthy in catamarans. It is just plain harder to capsize or pitchpole a bigger boat. This is yet another characteristic which is of little moment to a weekend and vacation sailor, but very important to the voyager. ************************************************** ************************************************** *************** So, rather like the Christmas carol with the calling birds, turtle doves, and French hens, we have now eliminated stock catamarans for reasons of inadequate floatation, inadequacy of watertight compartments, lack of rig redundancy, lack of rig reliability, lack of rig economy, lack of fire resistance, lesser speed and lesser seaworthiness. Having berth shelves subject to annoying smacking by waves was treated as a mere detail in the subject of speed, the attentive reader will recall. Through this process, I have come to conclusions that most people consider out of the question-a big, unconventional boat which doesn't cost any more to build than the sailing gin palaces currently in vogue, thanks to the charter trade, the BigCat 65, which may be viewed at 65 Foot Sailing Catamaran Design by Tim Dunn .
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Old 06-02-2008, 06:49   #2
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Hi BigCat - I would love to see your boat someday. Seriously. But I think you make numerous mistakes in your analysis. For starters,

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Well, many fine voyages have been made in such boats, but IMHO no factory set out to make catamarans primarily for ocean voyaging, and their characteristics reflect this.
You are, of course, entitled to your own opinion, but you are not entitled to your own facts. Your statement above is, well, simply absurd.

I won't waste my time to refute your other numerous errors of fact.

Dave
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Old 06-02-2008, 07:15   #3
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Well, 2Hulls, I think you made a terrific voyage, but I don't think much of your arguments. I made some pretty good voyages, too, from Seattle to Auckland to Hong Kong, and may places not really in between, and I have studied yacht design and boat building very intensively. I didn't make up any facts, and I think my logic is sound.
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Old 06-02-2008, 07:17   #4
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A current thread asks what a circumnavigating catamaran should have as its ideal characteristics. The thread's initiator makes it clear that he is looking for advice about what cookie-cutter factory-made boat to buy. Well, many fine voyages have been made in such boats, but IMHO no factory set out to make catamarans primarily for ocean voyaging, and their characteristics reflect this.
I believe I am the "thread's initiator" you're referring to. I find it interesting that you're sure that I'm only looking for a "cookie cutter factory made boat to buy" only because I didn't like your junk rig. Sorry to have hurt your feelings.
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You are, of course, entitled to your own opinion, but you are not entitled to your own facts. Your statement above is, well, simply absurd.

I won't waste my time to refute your other numerous errors of fact.

Dave
I completely agree and don't wish to waste any more time commenting here either.
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Old 06-02-2008, 07:28   #5
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Sorry, 2Hulls. I confused you with the guy whose avatar is his boat next to some icebergs. He made a terrific voyage. If you have ever stuck your nose out of the Chesapeake, you'll have to tell us about it. Same goes for you Andreas, if you have any experience, tell us about it. I don't think much of your arguments, either. Oh, wait a minute, you both bailed on the debate. I think you have to play if you want to win. Hey, if you can't stand the heat, stay out of the kitchen.
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Old 06-02-2008, 08:49   #6
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I don't think its a matter of people being unable to stand the heat, its your insistence upon making personal insults about the sailing experience of those who do not share your rather 'novel' ideas. In any case, despite your best efforts, heat does not make light.

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Old 06-02-2008, 09:08   #7
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Big Cat,
I'm generally track with what you are saying although you paint with a broad brush. As you can see, some of your 'audience' isn't listening even before you've dialogued about it. You've obviously put a lot of thought and work into developing your design. You might try building a consensus that leads one to seriously consider your work.

All that said, can you possibly put these thoughts into an aesthetically pleasing package??? Make it good, or even great looking, not just technically superior. I just can't even seriously consider dreaming of a boat that doesn't get my juices flowing aesthetically.
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Old 06-02-2008, 10:18   #8
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I don't know about anybody else, but whilst the design characteristics of a 65' cat are interesting, as is the philosophy behind it, my budget simply wouldn't stretch to a boat like that, or anywhere near it. I have a Broadblue 385, haven't gone far in it yet but I have one Atlantic crossing under my belt (not in the BB). Broadblue market the boat as a 'Blue Water Cruiser' rather than aim it at the charter market and in my somewhat limited experience of Blue Water cruising I'd say they're on the right track. So, I guess I'd disagree about no factory making stock boats primarily for ocean voyaging. My last boat had two unstayed carbon-fibre masts and I wasn't one hundred percent happy once I was 1000nm away from anywhere, just a few too many creaks and groans that I hadn't noticed before.
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Old 06-02-2008, 11:58   #9
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Big cat

I absolutely agree with you that most production cats are made for the leisure market and for that reason will not be great bleu water cruisers .
There are a few exceptions of cats that are specially built for owners and there are a few more than just Outremer , Gunboat and ourselves , take for instance the St Francis 50 a perfect Bleu water cruiser.
The buoyancy is another factor , I agree that most cats will sink if punctured or flipped , I think we are the only exception to that rule as far as I know.
We have well over 32000 lbs of buoyancy in board and it is spread over the complete boat
Of this 38 % is in closed cell foam and the rest in airtight chambers spread around from front to rear.
I we start with the bow , we first have a sacrificial nose of 1 foot in lenght followed by a air chamber over the total height and 2 feet in lenght , after that under the storage space another chamber with a lenght of 6 ft
In the rear in the transom we have 2 separated closed chambers each containing
200 gallons of air , than the rudder compartment and under the bunk a third 350 gallon airtight compartment., besides this all stringer inside are air tight and foam filled , the bridgedeck stringers are foam filled.
I am sure if we punctured a hul in the central walkway in one of the huls we could still sail althought with less sail area.
Then we have added the possibility to even out weight by making the water and diesel tanks so that we can pump water from one side to the other.
Very convinient , not only for safety but also for a better balance while sailing and a slightly higher speed
Each water tank is 100 galons in size and it make a real difference in pumping our water to the windward side , we can do the same with the 100 gallon diesel tanks but that has less effect since these are located left and right of the mast foot.
I am one of the unfortunate people that have a hit with a container some 30 years ago and since that time have decided only to sail unsinkable vessels if possible.
Good luck with your Big Cat
Greetings Gideon Goudsmit
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Old 06-02-2008, 12:02   #10
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My last boat had two unstayed carbon-fibre masts and I wasn't one hundred percent happy once I was 1000nm away from anywhere, just a few too many creaks and groans that I hadn't noticed before.
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.
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Old 06-02-2008, 12:29   #11
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I guess it is all realtive to what makes a "good bluewater cruiser". In the 70s and 80s. double-ender bath tub shaped monohulls were all the rage. Most production cats would be a much better way to travel than those, assuming you were staying out of extrememe latitudes.

There are now 1000s of reports of happy cruisers that are sailing new and old prodcution cats all over the world. I hesitate to characterize them as "not good for blue water" Designers and builders often are blinded by their own designs or dreams of new designs and forget to realize that the majority of cruisers cruise in boats that are far from state of the art.

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Old 06-02-2008, 12:36   #12
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I agree that most cats will sink if punctured or flipped , I think we are the only exception to that rule as far as I know.
C'mon, Gideon - It's hard for me to believe that you don't know what you're saying is false. All the major production cat builders claim unsinkability. Are you saying they're wrong?

There are several examples of (rare) capsizings of production cats that did not sink. I don't know of any reported capsizings where they DID sink. In fact, I know of one that has flipped twice and didn't sink either time. You clearly do not have a corner on this market.

How did this overturned Voyage 44 get to the beach unless it was floating?

Dave
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Old 06-02-2008, 13:05   #13
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So many people seem to think there is only one right way (THEIR way) of doing something.
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Old 06-02-2008, 13:07   #14
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C'mon, Gideon - It's hard for me to believe that you don't know what you're saying is false. All the major production cat builders claim unsinkability. Are you saying they're wrong?

There are several examples of (rare) capsizings of production cats that did not sink. I don't know of any reported capsizings where they DID sink. In fact, I know of one that has flipped twice and didn't sink either time. You clearly do not have a corner on this market.

How did this overturned Voyage 44 get to the beach unless it was floating?

Dave
Hallo Dave


I am pretty sure I am right , the sample shown by you was dismasted and a completely empty voyage 440 on a delivery trip on the west coast of the states I have seen what delivery skippers take along , we hire them regularly , almost nothing , the weight of the rig alone on the 440 is 600 kilo
If A fully loaded Catana 471 like you own (I find it a very good boat)
is flipped over or in case of a Catana pitchpoles and you have your water and diesel tanks reasonably full she will sink
Just calculate the amount of foam used in the Catana, Noi dont I have done the math already
11200 lbs of floatable foam at a weight of ,8 kilo per liter gives you 9000 lbs of lifting force.
If you add all the floatation build into the 471 you can add another 6000 lbs of buoyancy or a total of 15000.
The actual weight of an empty but ready to sail 471 is around 30000 lbs now ad your goodies outboard watermaker and all the other junk we carry around and the total weight is probably up to 35000.
Now lets say your boat is inverted and there is limited air trapped in the hulls and you cannot count this as safety added buoyancy because in rough weather and with escape hatches open not much will be left.
You will get a very wet submarine.
You have shown me one example and I am sure there are many others that have stayed afloat. many more have unfortunately sunk.
The boat shown was brand new and really empty..

P.S she was barely afloat , the keels where sticking out of the water so you can imagine how much reserve flotation was in there.

Greetings

Gideon
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Old 06-02-2008, 13:12   #15
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Hello cruisingcat 44


I never said other cats are no good , I just believe in redundancy/safety in every possible way.
This is only our way and I like the idea that if one of our cats flips or pitchpoles
That I can still sit on the Bridgedeck above the water ( now painted in 24 hour glow in the dark paint )
and wait for resque.

p.s. chances are not great to flip over , last year it only happened to 6 cats over 12 meters as far as i know but I do not read everything.

Greetings

Gideon
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