catamaran vs. trimaran for open ocean racing?

I thought an interesting discussion (that I would probably learn a lot from) is the topic in the title.

The cat vs. tri question is an old one, and it seems that maybe the answer is not the same in every decade, as advances in design and materials drive one vs. the other.

I'm confining my question to ocean racing, meaning fairly long point-to-point races, things like Jules Verne trophy, or TransPac. And also focused on purpose built race boats, down to things like the Gunboat I guess, which I believe took first-to-finish honors in the Transpac a few years back.

Can we say anything more definitive than "it depends". Theoretically (say assuming you had some ultimate material you could shape anyway and it would be strong enough) it seems like the cat is always better than the tri. Given the same length and beam. But, in the real world no one builds cats nearly as wide as tris of a similar LOA. Even commercial performance tri's go to beams that are 80% of Length, cats are still typically under 60%.

On the other hand the faster the tri the more the amas are doing all the work. The volume is going up so that soon their will be three equal sized hulls, and then maybe the middle hull will start to atrophy. You see the Dragonfly 25 now has the rudders on the amas, because it's possible to fly the main hull.

One tends to think of better stability as a tri advantage, but how much does that exist in the world of flying two hulls?

What are your thoughts on the design advantages of cats vs. tri's in the category of blue-water ocean racers?

 
R

Rob Zabukovec

Guest
........On the other hand the faster the tri the more the amas are doing all the work. The volume is going up so that soon their will be three equal sized hulls, and then maybe the middle hull will start to atrophy.......
I reckon the middle hull will atrophy down to a lightweather displacement accommodation module in the future. Less WSA and more leeward hull LWL for a given displacement......

 

Doug Lord

Super Anarchist
11,483
21
Cocoa Beach, FL
Maserati is on the leading edge of ocean going multihulls-flying most of the time:

Maserati flying 7/18/16:

2ntg3tg.jpg

 

zzarganas

Member
162
1
Greece
All the record holders are tri guys. Phaedo, spindrift, bpv, idec, gitana, etc....there is not exist a cat out there to beat this monsters. So simple.

P.s. correct me if im wrong (last decade at least).

 
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jorge

Anarchist
733
21
The last cat to held a record was Orange, although i'm not sure. And I think tris are more ocean going

 
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Derekkelsall

New member
The Background -

When I started racing and designing trimarans, the main hull took the weight and provided the F and A stability. The outriggers kept the rig up. As more power was added more was demanded of the outriggers. At the start of the OSTAR 96, five 60 ft. French tri left as 25 kts. The main hulls dropped in and then came out of the water regularly. No surprise that two capsized.

63ft., VSD was a tri with the main hull above the water. She felt stable even when the windward hull lifted out. Less angle of heel and often we needed to look to be aware that there was very little or no load on the windward hull. VSD lost her rig, which was nothing to do with the basic concept – which was worthy of further development.

I built a demountable 40ft. Race Tri for lake Geneva. All up weight 1,100 kg. A year later I built a 40 ft. cat, with identical scantlings and rig. All up weight 850 kg.

I also agree that the tri has a certain look and feel which pleases.

Happy boating,

Derek.

 

bushsailor

Anarchist
693
193
QLD Australia
Depends on what your goals are as well.

Do you want to visit islands and cruise back in comfort with a few mates? Cat.

Would this be a new state of the art build? As Derek said above, central structure to take loads possibly just touching the water.

Do you want to punt her around the cans in close racing, probably a tri, can tack faster.

Out and out speed puckering as you go, go buy a orma 60 or 70 tri, plenty for sale. No other use other than racing with a switched on crew though and uncomfortable and very physical to sail.

 

Paul Koch

Member
255
387
HCMC Vietnam
Yes this is a blatant plug , but the Rapido 60 is the answer , Trimaran performance, seaworthiness , safety but lots of cruising comfort and storage space ! Easy to sail with minimal crew ! www.rapidotrimarans.com

 

zzarganas

Member
162
1
Greece
I agree with you guys..just one detail...The topic said ...."OCEAN RACING"...not CRUISING..and ocean racing (untill now) has only one winner...TRIMARAN.

 
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Laurent

Super Anarchist
2,304
1,969
Houston
A few questions/remarks on the topic:

How much of the current trimaran dominance for offshore racing is due to class rule definition? There is definitely no rule for Jules Verne Trophy, but what about Multi 50 for instance? Can you show up with a 50 ft catamaran and still fit in the class? Same question for ORMA 60.

How much is due to "group thinking"? There was a time when the French offshore multihull racing (prior to ORMA60) was dominated by catamarans; remember Jet Service V? Elf Aquitaine?

Are the trimaran more forgiving? If you want to get 100% of a catamaran performance, you basically need to have the windward hull juuuuust flying off the water, right? But if you are not exactly in that sweet spot, how much performance are you losing? Furthermore, overshooting that optimum sailing configuration can be catastrophic: the right moment curve of a catamaran is shooting from 0 to maximum at a few degrees of heel, and then it is all downhill from there...

Where for a trimaran, with the right dihedral angle, you will heel a bit first, then righting moment will increase dramatically until main hull is out of the water and then you mimic the righting moment curve of a catamaran. As the maximum righting moment happens at a higher angle of heel, I wonder if that makes the associated performance curve less "peaky".

In other words, is it the fact that for a trimaran, if you are 5 degrees off the optimum heeling angle, you lose 10% of performance, but for a catamaran, if you are 5 degrees below optimum heel angle, you lose 20% of performance, and if you are 5 degrees above optimum heel angle, you are getting really close to "losing it"?

Anecdotal evidence of the above:

During the second attempt (I believe) of the Jules Vernes Trophy for Banque Populaire 5 (the last one skippered by Pascal Bidegorry), they hit something in the Southern Atlantic and damaged their daggerboard.

Before that point, as they were going down the Atlantic and were in the Trade Winds, there was a small video showing Pascal at the helm, being surprised by a puff; the boat accelerates, and start heeling up, up, to the point where the main hull gets out of the water. Everything is brought back under control, no drama. Pascal makes a face that says: "oooops!".

THEN, some one pops his head out of the companion way and ask funnily something like: "what's going on boss? I thought the orders were: do not fly the main hull!!!"

They knew that they could get most of the performance out of the boat, without living on the edge of a capsize all the time. Sailing with the mainhull in the water, the loss of performance was not so big, in the grand scheme of things.

Don't get me wrong, they knew how to sail it on the edge. Actually, when the same boat broke the 24 hr record, 908 miles (!!!), during an Atlantic crossing, I read somewhere that the order was the exact opposite: keep the main hull just above water as long as possible.

But what you can do for 24 hrs cannot be done for 45 days...

 
A few questions/remarks on the topic:

How much of the current trimaran dominance for offshore racing is due to class rule definition? There is definitely no rule for Jules Verne Trophy, but what about Multi 50 for instance? Can you show up with a 50 ft catamaran and still fit in the class? Same question for ORMA 60.

How much is due to "group thinking"? There was a time when the French offshore multihull racing (prior to ORMA60) was dominated by catamarans; remember Jet Service V? Elf Aquitaine?

Are the trimaran more forgiving? If you want to get 100% of a catamaran performance, you basically need to have the windward hull juuuuust flying off the water, right? But if you are not exactly in that sweet spot, how much performance are you losing? Furthermore, overshooting that optimum sailing configuration can be catastrophic: the right moment curve of a catamaran is shooting from 0 to maximum at a few degrees of heel, and then it is all downhill from there...

Where for a trimaran, with the right dihedral angle, you will heel a bit first, then righting moment will increase dramatically until main hull is out of the water and then you mimic the righting moment curve of a catamaran. As the maximum righting moment happens at a higher angle of heel, I wonder if that makes the associated performance curve less "peaky".

In other words, is it the fact that for a trimaran, if you are 5 degrees off the optimum heeling angle, you lose 10% of performance, but for a catamaran, if you are 5 degrees below optimum heel angle, you lose 20% of performance, and if you are 5 degrees above optimum heel angle, you are getting really close to "losing it"?

Anecdotal evidence of the above:

During the second attempt (I believe) of the Jules Vernes Trophy for Banque Populaire 5 (the last one skippered by Pascal Bidegorry), they hit something in the Southern Atlantic and damaged their daggerboard.

Before that point, as they were going down the Atlantic and were in the Trade Winds, there was a small video showing Pascal at the helm, being surprised by a puff; the boat accelerates, and start heeling up, up, to the point where the main hull gets out of the water. Everything is brought back under control, no drama. Pascal makes a face that says: "oooops!".

THEN, some one pops his head out of the companion way and ask funnily something like: "what's going on boss? I thought the orders were: do not fly the main hull!!!"

They knew that they could get most of the performance out of the boat, without living on the edge of a capsize all the time. Sailing with the mainhull in the water, the loss of performance was not so big, in the grand scheme of things.

Don't get me wrong, they knew how to sail it on the edge. Actually, when the same boat broke the 24 hr record, 908 miles (!!!), during an Atlantic crossing, I read somewhere that the order was the exact opposite: keep the main hull just above water as long as possible.

But what you can do for 24 hrs cannot be done for 45 days...
There have been a few Multi50 cats but nothing that's been competitive interestingly enough there is no minimum weight for cats (trimarans must be a minimum of 3 tonne). A few pod cats have been built to suit the rule but none have been able to hang with the nearly square trimarans that the top Multi50 teams have found to be the best overall performers.

 




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