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Old 16-02-2015, 13:33   #1
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I Guess Catamarans do Sink

I sail a catamaran the the manufacturer states is unsinkable.
I have owned it for 5 years and sailed it in the ocean for 2 years prior to buying a liferaft.
Until one of my monohull racing mates insisted that I buy a life raft would he accompany me on a trip from St. Lucia to Los Roques Venezuela did I begrudgingly purchase one.
Have spoken to many cat sailors who do not carry one however the reoccurring thought of a fire convinced me otherwise.
Now we are not only looking for an Alfa but now a Gunboat which may very well be at the bottom of the ocean.
So......how many of you actually know of a modern Catamaran sinking?
Also I must ask how many of you who sail cats do not carry a liferaft?
Sounds like they may not sink like their lead-belly monohull brethren's but esthetically slowly drift down to Davy Jones's Locker.
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Old 16-02-2015, 14:59   #2
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Re: I Guess Catamarans do Sink

I always find it hard to believe that a catamaran absolutely won't sink. I don't think fiberglass floats so it seems that if all (or maybe even most) compartments of a catamaran filled with water it would sink. I think what manufactures mean is a catamaran won't sink if capsized or from a single collision where only one area of the hull is damages.

Actually, I am pretty sure that the catamaran that the Silverwoods were on and ran aground on an atoll in the South Pacific did end up being washed into the ocean and sinking. Of course it took quite a beating on the reef, but technically it did sink.

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Old 16-02-2015, 15:17   #3
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Re: I Guess Catamarans do Sink

I depends on the total weight of the vessel and machinery verses the bouyancy of the materials used in the construction.

The majority of australian designed catamarans use all foam/balsa construction (Schonning, Grainger, Seawind etc) and the bouyancy of the foam/balsa core used in the construction is greater than the weight of the vessel so they will float/not sink regardless of filling all compartments with water. Heavier vessels will float lower in the water.

Simply comes back to Archimedes' principle which indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.

If the weight of the water displaced is less than the weight of the object, the object will sink otherwise the object will float, with the weight of the water displaced equal to the weight of the object.
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Old 16-02-2015, 15:17   #4
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Re: I Guess Catamarans do Sink

I'll bet a beer that Gunboat won't sink all the way.
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Old 16-02-2015, 15:19   #5
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Re: I Guess Catamarans do Sink

Quote:
Originally Posted by capnmatt View Post
I always find it hard to believe that a catamaran absolutely won't sink. I don't think fiberglass floats so it seems that if all (or maybe even most) compartments of a catamaran filled with water it would sink. I think what manufactures mean is a catamaran won't sink if capsized or from a single collision where only one area of the hull is damages.

Actually, I am pretty sure that the catamaran that the Silverwoods were on and ran aground on an atoll in the South Pacific did end up being washed into the ocean and sinking. Of course it took quite a beating on the reef, but technically it did sink.

Matt
What type of catamaran?? A solid fibreglass cat could sink. Depends on the amount of foam/balsa core used in the construction.
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Old 16-02-2015, 16:17   #6
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Re: I Guess Catamarans do Sink

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Now we are not only looking for an Alfa but now a Gunboat which may very well be at the bottom of the ocean.
Wait, your thread title made me think you were aware of a sinking. This looks like pure speculation. Is there info you have that I don't?
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Old 16-02-2015, 16:38   #7
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Re: I Guess Catamarans do Sink

It is pure speculation but being a catamaran owner I am concerned.
The Alfa has been missing for a long time and obviously the Gunboat not so long.
It does however make me question how many out there know of a cat actually sinking?
You do see pictures of multhulls lying upside down and to me that is somewhat reassuring.
Maybe no modern day catamaran has ever sunk.
I will give them a little more time to find Rainmaker before I assume it is lying at the bottom of the ocean but you have to admit the Alfa was left in an area of heavy traffic yet has never been found.
Then again it is the Bermuda Triangle
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Old 16-02-2015, 16:42   #8
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Re: I Guess Catamarans do Sink

I'm gonna title my next post. I've won the lottery. I'm sure some one has..:what:

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Old 16-02-2015, 16:54   #9
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Re: I Guess Catamarans do Sink

Regarding your own vessel a Voyage 440 you could do the sums if you found out how much core is used in its construction.

For instance if only 7 cubic meters of core was used (displacing 7 tons of water) and the vessel weighs 10 tons it could sink unless several tons of sealed bouyancy chambers are built in.

The above figures are closely approx as I have not allowed for the weight of the core and the slight differences between salt and fresh water. Its simple Archimedes' principle.

Find out from the builders how much core is used in the construction. If it has solid hulls below the water thats not positive bouyancy.
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Old 16-02-2015, 16:56   #10
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Re: I Guess Catamarans do Sink

Mine sinks all the time. When it's not flipping over that is. Oh yeah, it breaks up a few million times a day too. Pretty routine catamaran stuff really.
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Old 16-02-2015, 16:59   #11
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Re: I Guess Catamarans do Sink

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Mine sinks all the time. When it's not flipping over that is. Oh yeah, it breaks up a few million times a day too. Pretty routine catamaran stuff really.
Yep I seen your photos of it sitting on the bottom at Fraser Island.
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Old 16-02-2015, 16:59   #12
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Re: I Guess Catamarans do Sink

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Regarding your own vessel a Voyage 440 you could do the sums if you found out how much core is used in its construction.

For instance if only 7 cubic meters of core was used (displacing 7 tons of water) and the vessel weighs 10 tons it could sink unless several tons of sealed bouyancy chambers are built in.

The above figures are closely approx as I have not allowed for the weight of the core and the slight differences between salt and fresh water. Its simple Archimedes' principle.

Find out from the builders how much core is used in the construction. If it has solid hulls below the water thats not positive bouyancy.
Not just the volume of the core though. You need to include the volume of everything, even the solid glass, the mast, batteries, engines etc. They all displace water.

If the total volume in m3 is more than the total weight in tonnes it will float. (Unless it's a catamaran.)
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Old 16-02-2015, 17:01   #13
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Re: I Guess Catamarans do Sink

About 3 months ago ! Enough said !
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Old 16-02-2015, 17:01   #14
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Re: I Guess Catamarans do Sink

When cats were popular with home builders, I remember seeing stories every few years about one found upside down, sometimes with survivors. A raft is good life insurance and easier to spot than than a water logged boat. In the navy and as a fisherman, I've been involved in rescues, searches and giving aid. Even when you've found the debris field, with dozens of lookouts, finding survivors can take hours.
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Old 16-02-2015, 17:11   #15
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Re: I Guess Catamarans do Sink

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Originally Posted by 44'cruisingcat View Post
Not just the volume of the core though. You need to include the volume of everything, even the solid glass, the mast, batteries, engines etc. They all displace water.

If the total volume in m3 is more than the total weight in tonnes it will float. (Unless it's a catamaran.)
Don't forget sealed compartments as well. You'd have to knock all four corners of our boat in to get most of them.
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