Bieker 53 - Exciting high performance cruiser

[44'cruisingcat]

And why do you think trimarans can have greater beam than catamarans?

[Polux]

That's a good question. I know that they can because designers, even on pure racing sailboats give them more beam than to cats but I am afraid not knowing enough of multi-hull design to answer that for sure.

But I would say that has to do with trimarans sailing, even on moderate conditions, with an ama out of the water. That makes the effective beam much smaller.

Most modern top racing trimarans even when not sailing have one ama on the air, that means that the beam that counts for drag, the one that is on the water, is smaller than on a cat.

https://www.youtube.com/watch?v=9xM2W3Bje8c

[Polux]

Originally Posted by estarzinger

^^ I will comment that the specific case of this capsize - it was a double user error . . . . they should have been full well aware they would get a gust as they came out from behind the island, and they should have been fully able to dump the sheets (and other reactions) instantly (during the whole racing period).

I would not place any 'blame' on this design, except that almost by definition it requires a knowledgeable and alert crew.

Yes I agree with you.

There is a TS 42 making the racing IRC circuit on the main races in Europe and on the Caribbean too. They sail incredibly fast beating much bigger cats and I confess that due to the TS 42 characteristics (small for a performance cat and very light) and because they sail it really on the limit I was afraid that they would capsize on one of the races.

But so far so good and they had made a lot of races including the last ARC with flying colors. They were the fastest cat by far beating an Outremer 5x by 5 days, an Outremer 64 light by 7 hours a Catana 62 by 2 days and 7 hours and several other bigger performance cats.

Curiously the boat has not a professional skipper but one of the good French racing amateurs the CEO of Guyader Gastronomie, (Christian Guyader) a sailor with lots of past victories.

He is going to make the "Route du Rhum" solo on that cat and that is HUGE. I hope he manages to finish it (quite a challenge on that boat) but he deserves already a big Chapeau.

The TS42 is a cat that I like a lot, kind of a POGO cat (fast and relatively inexpensive). I made some years ago a post about it on my blog. Of course, not a cat for the inexperienced or for the ones without a very sportive posture. I think that sailing it solo on a transat is quite a challenge.

https://www.facebook.com/TS42-1627241777543635/

[Just Another Sa]

Originally Posted by Polux

If we consider a modern typical cruiser racer like the Sunfast 3600 the Max RM will be 17.5t-ft, hugely superior to the one considered and with the modification of the monohull stability curve according with that value no way the surface under the stability curve of the cat would be 150% bigger. Maybe just a little bit bigger

Originally Posted by Polux

You did not read the thread or the article?

This graphic was posted by catsketcher and what the graphic says (and the article) is that a 35ft performance cat has 150% of the overall stability of a 35ft performance monohull.


Considerations for Seaworthiness

I did read both the article and your false claim.
Your mutually exclusive contradicting statements quoted in bold type and underlined above show that you were wrong.
3 is only 50% greater number than 2. Not 150% greater unlike 5 would be.
3 is 150% of 2 and therefore a greater number than 2.

[44'cruisingcat]

Originally Posted by Polux

That's a good question. I know that they can because designers, even on pure racing sailboats give them more beam than to cats but I am afraid not knowing enough of multi-hull design to answer that for sure.

But I would say that has to do with trimarans sailing, even on moderate conditions, with an ama out of the water. That makes the effective beam much smaller.

Most modern top racing trimarans even when not sailing have one ama on the air, that means that the beam that counts for drag, the one that is on the water, is smaller than on a cat.

"The beam that counts for drag"? Now you're just making things up.

Put simply, tri's are beamier than cat's because they can be. Greater beam provides more righting moment, which allows more sail to be carried. Do you think racing catamaran designers don't know this? The centre hull provides rigidity that would be impossible to engineer in a cat without a bridgedeck.

As materials and structures improve, it's possible extreme beam cats, possibly with a central accomodation "pod" may come to the fore again.

[Thalas]

I can't believe this thread has gone on so long as I find the original boat listed ugly as sin and somewhere between a performance cruiser (e.g. gunboat) and a true racing cat... how many people fit that tiny sliver? I know racers. I know cruisers who like to go fast. I know cruisers who love real estate and a sundowner. I can't think of a single person who wants to go fast so bad, they will give up accommodations found on Gunboats and Outremers, but NOT as fast as committed racing cats. But more power to their marketing team for getting 9 pages of discussion here.

Originally Posted by 44'cruisingcat

The centre hull provides rigidity that would be impossible to engineer in a cat without a bridgedeck.

I think you mean expensive, not impossible. If composite airplane wings can be light and handle stresses far exceeding the loads found at sea, that technology can also connect two boat hulls. Again to my earlier point... even on fast cruising cats, the bridgedeck is a feature, not a hindrance.

[BigBeakie]

Catsketcher,

Spot on, mate!👍


Sent from my iPad using Cruisers Sailing Forum

[Polux]

Originally Posted by Just Another Sa

I did read both the article and your false claim.
Your mutually exclusive contradicting statements quoted in bold type and underlined above show that you were wrong.
3 is only 50% greater number than 2. Not 150% greater unlike 5 would be.
3 is 150% of 2 and therefore a greater number than 2.

Ok, I understand that is some confusion here. like it is stated on the drawing the monohull has 100% the cat 150%. That's what I wanted to say and off course on that graphic, as it is clearly visible the cat has about 50% more area under the stability line.



This should be clear since on other post I claimed that if it was considered the stability data from the Jeanneau SF 3600 the difference would be almost nil. It would make no sense at all that the 35ft monohull considered had 150% less stability than the jeanneau SF 3600.

[Polux]

Originally Posted by 44'cruisingcat

"The beam that counts for drag"? Now you're just making things up.

Put simply, tri's are beamier than cat's because they can be. Greater beam provides more righting moment, which allows more sail to be carried. Do you think racing catamaran designers don't know this? The centre hull provides rigidity that would be impossible to engineer in a cat without a bridgedeck.

As materials and structures improve, it's possible extreme beam cats, possibly with a central accomodation "pod" may come to the fore again.

It seems you did not understand. A racing trimaran has full time a ama out of water. This not only diminishes drag as it dynamically it is like the beam of the boat is only the one between the ama on the water and the central hull.

I thought that you knew but there are reasons that have to do with sailing efficiency not to increase the beam over a given ratio regarding the length of the catamaran.

There are no physical or structural reason to increase the beam of a cat as much or more than its length. Designers don't do that because it is not efficient and the cat even if having more stability does not gain efficiency in what regards sailing, quite the opposite.

[44'cruisingcat]

Originally Posted by Polux

It seems you did not understand. A racing trimaran has full time a ama out of water. This not only diminishes drag as it dynamically it is like the beam of the boat is only the one between the ama on the water and the central hull.

I thought that you knew but there are reasons that have to do with sailing efficiency not to increase the beam over a given ratio regarding the length of the catamaran.

There are no physical or structural reason to increase the beam of a cat as much or more than its length. Designers don't do that because it is not efficient and the cat even if having more stability does not gain efficiency in what regards sailing, quite the opposite.

And once again I have to wonder if you actually read what you write. Of course you don't make the beam of a catamaran greater than it's length. But the fact is, big offshore racing cats have beams far less than their length. Often closer to HALF their length.

This isn't because it somehow reduces drag through the water.

[44'cruisingcat]

Originally Posted by Thalas

I think you mean expensive, not impossible. If composite airplane wings can be light and handle stresses far exceeding the loads found at sea, that technology can also connect two boat hulls. Again to my earlier point... even on fast cruising cats, the bridgedeck is a feature, not a hindrance.

Every dollar you spent on making a cat rigid could be spent on a tri with greater results.

And yes, on a cruising cat the bridgedeck is a feature. On a racing cat it's a hindrance.

[Polux]

Originally Posted by 44'cruisingcat

And once again I have to wonder if you actually read what you write. Of course you don't make the beam of a catamaran greater than it's length. But the fact is, big offshore racing cats have beams far less than their length. Often closer to HALF their length.

....

It was you that asked why an offshore trimaran is faster than a catamaran. I answered to you correctly that was because trimarans can have more beam for a given length and therefore more stability and that means more power.

I explained also to you that a trimaran can have more beam because the beam considered in what regards water dynamics is the beam between the ama on the water and the center hull, while for stability it is all the beam that his considered.

On cats for dynamic purposes and for stability the beam considered is the same, the one measured between the center of the two hulls and therefore cats cannot have has much beam for length as trimarans without losing efficiency.

Explained also to you that contrary to what you were saying multihulls cannot for sail and stability efficiency reasons have more than a given B/L proportion and that has nothing to do with building or structural limitations, rigidity or otherwise. It has to do with the optimal B/L for sailing efficiency that is bigger on a trimaran than on a catamaran.

It was you that asked, meaning you didn't know. I guess that the answer is clear enough. I have more to do, sorry.

Originally Posted by 44'cruisingcat

...
Put simply, tri's are beamier than cat's because they can be. Greater beam provides more righting moment, which allows more sail to be carried. Do you think racing catamaran designers don't know this? The centre hull provides rigidity that would be impossible to engineer in a cat without a bridgedeck.

As materials and structures improve, it's possible extreme beam cats, possibly with a central accomodation "pod" may come to the fore again.

[44'cruisingcat]

I'll say one thing for you, you have quite an imagination!

Now back in the real world, no, I didn't ask any of those questions. I asked rhetorically why trimarans have a greater beam. Which you admitted, you didnt know. Then gave the answer, it's because of structural limitations.

[Polux]

Originally Posted by 44'cruisingcat

I'll say one thing for you, you have quite an imagination!

Now back in the real world, no, I didn't ask any of those questions. I asked rhetorically why trimarans have a greater beam. Which you admitted, you didnt know. Then gave the answer, it's because of structural limitations.

How can a question be made rhetorically if you don't know the answer?

I had a good idea regarding the problem, I suggested to you a hypothesis, the fact of the trimarans having always an amas on the air and therefore the dynamic beam to be much smaller. Later I researched and it proved correct.

See the attached quote at the bottom.
Multihull Dynamics, Inc. - News Article

Regarding why the B/L can not be bigger than a certain limit (much bigger for trimarans because the distance considered is only between the Amas and the center hull) there are several opinions that are more or less convergent but none regarding the impossibility of doing it structurally:

"Wide hulls and a large overall beam will increase the overall righting moment of a catamaran. A word of caution: Excessive beam will reduce the fore and aft stability.....

For a seaworthy cruising multihull it is important maintain the proper ratio between length and beam, which, in turn, balances equal amounts of athwartship with diagonal stability. The goal should be to prevent the possibility of a sudden discrepancy of powers between fore and aft and sideways resistance.....

But there certainly is a limit as to how wide is too wide. Extreme beam can be dangerous. It can lead to instability fore and aft.... The best examples of this phenomenon are racing multihulls, especially Formula 1 trimarans, which have fine hulls for speed and huge sailplans to provide driving power. They are initially extremely stable athwartships (High Beam-to-Length Ratio), but have a tendency to become unstable fore and aft. They will surf down waves and reach a point where the power of the sails, and speed, will exceed the ability to keep the bows out of the water and the boat will pitchpole. This is the reason why catamaran designers usually draw their multihulls with a Beam-to-Length relationship of between 50% and 55%."

https://www.boatbuilding.xyz/catamarans-guide/h.html

What we know for sure is that the best multihull designers in the world that design the fastest offshore multihulls the ones that are involved for years in a battle, that is not only of sailors but also of designers, to hold the circumnavigation sail record, design the fastest multihulls they can and are using top of the range computer simulation virtual performance tests to design the boats.

You can be sure that if a catamaran was faster they would be using catamarans and if trimarans would benefit from a bigger B/L relation they would be designing them that way.

https://www.youtube.com/watch?v=AHl2MFQUcPM

[Factor]

Originally Posted by Polux

the fact of the trimarans having always an amas on the air

Fixed - No they don't just not so, some do and some don't and I have owned a few of each