THE UNSEAWORTHINESS OF SMALL CATAMARANS
- Thread starter thika
- Start date
Porra Newbie
Senior Member
Seems to me that many have not been fishing much lately with all this "kak praat" 
go :fishncat or mono enjoy
go :fishncat or mono enjoyPorra Newbie wrote:
LOL you got that right, cant wait for April 14 days at Ponta eish!
Seems to me that many have not been fishing much lately with all this "*** praat"
LOL you got that right, cant wait for April 14 days at Ponta eish!
Thika, I am out of town for 1 day and you go and poke the hornets nest.
I want to ask a Honest question ,
1) The Buttcat 760/865/620 is very popular boats but the 490 Not - WHY?
2) Seacat- 510, 565 very popular but the 465 NOT
3)Z-Craft - In the 90's the 146 and 160 Invaders were put out in their droves now the smallest boat is 16,6.
The answer is very obvious , a small cat rides poefie.
I want to ask a Honest question ,
1) The Buttcat 760/865/620 is very popular boats but the 490 Not - WHY?
2) Seacat- 510, 565 very popular but the 465 NOT
3)Z-Craft - In the 90's the 146 and 160 Invaders were put out in their droves now the smallest boat is 16,6.
The answer is very obvious , a small cat rides poefie.
This is due to the great soft ride of the cats. thika;
to me this is a great tread and needs to be understand and discussed more.
i dont think its about unseaworthyness. it's more about, knowing what to avoid and what to do.
i would argue the folowing:
because cats have these sharp sponsons "hoop dis die regte naam", when you get that beam sea, that sharp hull will dig into the water 'finish en klaar' cause it is sharp and has little resistance. now with the digging, and the other side, water has lifted the other side, cause there is more water at that given time.
so we are going sea sawing......
regarding a mono, as the hull would create more resistance at the same time "hull is blunt" and big.
but i think it would depend on the size of the boat. a small mono could also go over as the resistance could be not enough.
knowing how these factors influence any boat, a skipper should stay clear of such 'events"
yes skippers are the ones to blame, but knowing your craft will asist in avoiding it.
to me this is a great tread and needs to be understand and discussed more.
i dont think its about unseaworthyness. it's more about, knowing what to avoid and what to do.
i would argue the folowing:
because cats have these sharp sponsons "hoop dis die regte naam", when you get that beam sea, that sharp hull will dig into the water 'finish en klaar' cause it is sharp and has little resistance. now with the digging, and the other side, water has lifted the other side, cause there is more water at that given time.
so we are going sea sawing......
regarding a mono, as the hull would create more resistance at the same time "hull is blunt" and big.
but i think it would depend on the size of the boat. a small mono could also go over as the resistance could be not enough.
knowing how these factors influence any boat, a skipper should stay clear of such 'events"
yes skippers are the ones to blame, but knowing your craft will asist in avoiding it.
ok, maar gaan lees hier.
eers is dit grieks, tot die grys stof begin werk
http://en.wikipedia.org/wiki/Metacentric_height
eers is dit grieks, tot die grys stof begin werk
http://en.wikipedia.org/wiki/Metacentric_height
confusing but not
this is what i said in my initial post, or tried
http://www.wisegeek.org/what-is-buoyancy.htm
the sharp keels etc would not resist much and therefore dig deeper easier.
so, is there a sollution, and what can it be, other then avoiding the situation.
plainning plates or something like it?
this is what i said in my initial post, or tried
http://www.wisegeek.org/what-is-buoyancy.htm
the sharp keels etc would not resist much and therefore dig deeper easier.
so, is there a sollution, and what can it be, other then avoiding the situation.
plainning plates or something like it?
Bigger cats mean more crew means lower shared expenses, more fish quota.
The smaller boats cannot really fish 4 in comfort, so 16ft is more popular.
I would say 90% of the mono owners, who fish the sea would swop to a good cat if they had choice.
If you want to ski, be macho make screaming turns and go really fast get a mono, if you want to fish, get a cat.
Guys cant find pics of many mono's rolling in the surf as most guys surf launching are fishing and as such have cats.
Mono's are useful in lagoons, estuary's and dams.
I agree with Bennie, thread is stupid, there is no proof, or fact to back up the claims, Just a few pics of skippers getting it wrong? that is not proof of design flaw.
Come now, take a ride on a butt cat with 4 strokes and you will sell that 660 so quick ur head will spin.
The smaller boats cannot really fish 4 in comfort, so 16ft is more popular.
I would say 90% of the mono owners, who fish the sea would swop to a good cat if they had choice.
If you want to ski, be macho make screaming turns and go really fast get a mono, if you want to fish, get a cat.
Guys cant find pics of many mono's rolling in the surf as most guys surf launching are fishing and as such have cats.
Mono's are useful in lagoons, estuary's and dams.
I agree with Bennie, thread is stupid, there is no proof, or fact to back up the claims, Just a few pics of skippers getting it wrong? that is not proof of design flaw.
Come now, take a ride on a butt cat with 4 strokes and you will sell that 660 so quick ur head will spin.
Hmmmmm....
See you have been busy chaps
Squaring off for a catfight I see
OK, sit on your butts and try to absorb:
Sea Sick,
you come stand here next to me
Proof?:
Archimedes sat in the bath and shouted Eureka
Because he figured out an object will displace an amount of water equal to it's own volume
Futher,
an object will float if it displaces a mass of water greater than it's own mass
So, a cubic meter of iron which weighs say 6 tons will sink as it only displaces 1 ton of water
If you beat it into 6mm steel plate and buid a boat though, it will float and stay floating even if you loaded another 6 tons in it
Now, a smallish cat weighs say 2 tons with motors, fuel, gear and crew
It floats easily in level water as each sponsoon pushes up 1 ton (buoyancy)
(A mono will be pushing up two tons as well but with one hull only, obviously)
The problem comes when the cat heels as in the pics
Now the downside sponsoon all of a sudden has to push up a lot more than one ton
But because it is small and narrow it gets submerged quite deeply...maybe not enough to fall over, but enough for the crew to fall overboard and even take on water over the gunwale
In the pics, the skippers and crew got surprised because of this unexpected behaviour of the boat
In all fairness to them, have a look at how small some of that surf is
Some overseas manufacturers have figured this out and corrected for it...go have a look at the sponsoons on boats built by Noosa Cat, Safehaven Marine and Glacier Bay/Worldcat: they are deep and massive and inspire confidence, and of course they are all big catamarans
So not all cats are bad or dangerous, but the small ones do what they do in the given circumstances
And if you think this thread is stupid, go think again....any of the guys in those pics would have liked to have read this first. Even other owners can learn from it, and certainly anticipate what I think is a very dangerous condition in surf.
See you have been busy chaps
Squaring off for a catfight I see
OK, sit on your butts and try to absorb:
Sea Sick,
you come stand here next to me
Proof?:
Archimedes sat in the bath and shouted Eureka
Because he figured out an object will displace an amount of water equal to it's own volume
Futher,
an object will float if it displaces a mass of water greater than it's own mass
So, a cubic meter of iron which weighs say 6 tons will sink as it only displaces 1 ton of water
If you beat it into 6mm steel plate and buid a boat though, it will float and stay floating even if you loaded another 6 tons in it
Now, a smallish cat weighs say 2 tons with motors, fuel, gear and crew
It floats easily in level water as each sponsoon pushes up 1 ton (buoyancy)
(A mono will be pushing up two tons as well but with one hull only, obviously)
The problem comes when the cat heels as in the pics
Now the downside sponsoon all of a sudden has to push up a lot more than one ton
But because it is small and narrow it gets submerged quite deeply...maybe not enough to fall over, but enough for the crew to fall overboard and even take on water over the gunwale
In the pics, the skippers and crew got surprised because of this unexpected behaviour of the boat
In all fairness to them, have a look at how small some of that surf is
Some overseas manufacturers have figured this out and corrected for it...go have a look at the sponsoons on boats built by Noosa Cat, Safehaven Marine and Glacier Bay/Worldcat: they are deep and massive and inspire confidence, and of course they are all big catamarans
So not all cats are bad or dangerous, but the small ones do what they do in the given circumstances
And if you think this thread is stupid, go think again....any of the guys in those pics would have liked to have read this first. Even other owners can learn from it, and certainly anticipate what I think is a very dangerous condition in surf.
Thika the center of the boat on a cat is not the center of the keel like on a mono(sponson), you have weight on the other side on a cat so your center is the centre on the boat not the sponson like on a mono, so the weight is distributed between the 2 hulls as your centre on the boat is mid of the the tunnel? give you a wider footprint, less rolling.
Which is why cats are more stable to fish off. and your crew can stand on one side without the boat flipping over!
If you ran a mono on those waves in the same way you would have the same result, not a different result.
a small cat 14 - 15ft is not 2ton, my 21 butt cat is 1.4 ton loaded with fuel. 14 - 15 is about 850kg - 1100 max.
Which is why cats are more stable to fish off. and your crew can stand on one side without the boat flipping over!
If you ran a mono on those waves in the same way you would have the same result, not a different result.
a small cat 14 - 15ft is not 2ton, my 21 butt cat is 1.4 ton loaded with fuel. 14 - 15 is about 850kg - 1100 max.
Thika the center of the boat on a cat is not the center of the keel like on a mono(sponson), you have weight on the other side on a cat so your center is the centre on the boat not the sponson like on a mono, so the weight is distributed between the 2 hulls as your centre on the boat is mid of the the tunnel? give you a wider footprint, less rolling.
Which is why cats are more stable to fish off. and your crew can stand on one side without the boat flipping over!
If you ran a mono on those waves in the same way you would have the same result, not a different result.
a small cat 14 - 15ft is not 2ton, my 21 butt cat is 1.4 ton loaded with fuel. 14 - 15 is about 850kg - 1100 max.
Which is why cats are more stable to fish off. and your crew can stand on one side without the boat flipping over!
If you ran a mono on those waves in the same way you would have the same result, not a different result.
a small cat 14 - 15ft is not 2ton, my 21 butt cat is 1.4 ton loaded with fuel. 14 - 15 is about 850kg - 1100 max.
FishExcutnr
Sealiner
FishExcutnr wrote:
You are going to struggle to garner support for a cat-hull semi-rigid duck .... that is one instance where a mono is most certainly better than a cat.
You are going to struggle to garner support for a cat-hull semi-rigid duck .... that is one instance where a mono is most certainly better than a cat.
Barry,
I have no point to prove here, really.
But OK,
I used the two tons to convey a concept only
A mono's print in the water has a centre also, the boat's centre of buoyancy.(COB)
It changes all the time depending on the aspect of the boat in the water, put it this way, if a mono heels you have the whole 2 tons pushing up trying to get the COB in line with the centre of gravity (COG) of the boat
A catamaran has two prints, so where is the centre of buoyancy?
A mono hull attempts to right itself because the hull attempts to "roll" to a more upright position against an oblique water surface, eg the side of a swell, and it does so with it's full buoyancy. It can do so because the hullshape allows it to.
As opposed to a cat which HAS to follow the water surface with both sponsoons and cannot right itself against the side of a swell. A cat is like a flatbottomed monohull if that makes sense to you.
Be it as it may, a mono cannot be made to lean like that in similar conditions because of the rule of physics, as I tried to explain here above
And if you come on my boat I will demonstrate it to you
But in real bad stuff like a cresting wave on the backline, both designs will capsize if hit broadside on
I should have used another heading though as I see it is getting some people's gat hare taai!
But beware and don't get caught out...that's it
I have no point to prove here, really.
But OK,
I used the two tons to convey a concept only
A mono's print in the water has a centre also, the boat's centre of buoyancy.(COB)
It changes all the time depending on the aspect of the boat in the water, put it this way, if a mono heels you have the whole 2 tons pushing up trying to get the COB in line with the centre of gravity (COG) of the boat
A catamaran has two prints, so where is the centre of buoyancy?
A mono hull attempts to right itself because the hull attempts to "roll" to a more upright position against an oblique water surface, eg the side of a swell, and it does so with it's full buoyancy. It can do so because the hullshape allows it to.
As opposed to a cat which HAS to follow the water surface with both sponsoons and cannot right itself against the side of a swell. A cat is like a flatbottomed monohull if that makes sense to you.
Be it as it may, a mono cannot be made to lean like that in similar conditions because of the rule of physics, as I tried to explain here above
And if you come on my boat I will demonstrate it to you
But in real bad stuff like a cresting wave on the backline, both designs will capsize if hit broadside on
I should have used another heading though as I see it is getting some people's gat hare taai!
But beware and don't get caught out...that's it