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Old 28-12-2014, 21:55   #31
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Re: Tri's or Cat's?

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Originally Posted by weavis View Post
Twitchy bobble?
I think that is as accurate a description as any for a catamaran's motion underway. Maybe not so much for downwind.

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Old 29-12-2014, 00:32   #32
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Re: Tri's or Cat's?

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Originally Posted by Ann T. Cate View Post
newt,

If you can wangle it, try going out in about 20-25 knots in both, and see how you react to the motion on all points of sail. My concern is that as an experienced monohull sailor, you may not like the twitchy bobble you may encounter with both the tri's and the cats, although, to be honest, the tri's bobble more at anchor than cats. If you have no problems with the motion, then you're good to go.

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Great suggestion. I did and loved the cat! Especially sailing in the teens, where on our mono it would be 7 knots, maybe.

I could go below and make coffee, which on or mono would have had me vomiting in no time.

But further to your suggestion, try a couple of nights in a rolly anchorage too... then go sailing.
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Old 29-12-2014, 01:38   #33
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Re: Tri's or Cat's?

Dont forget to try 3 days at sea deep downwind in a mono, doing the death rolls. It was precisely that trip which finally sent me toward the path of enlightenment.
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Old 29-12-2014, 03:38   #34
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Re: Tri's or Cat's?

If you are into flying hulls, Even a cruising Tri will please. I personally prefer the stability of a Catamaran but a Tri is exciting.

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Old 29-12-2014, 05:59   #35
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Re: Tri's or Cat's?

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Originally Posted by weavis View Post
Twitchy bobble?

Spluttering coffee here. Thanks for the laugh.
Twitchy Bobble? I think we might have gone out together a few times...
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Old 29-12-2014, 07:54   #36
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Re: Tri's or Cat's?

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I am not sure if I understand what you mean. They say this :"The width of NEEL trimarans is an important factor for safety on the high seas because it is a guarantee of stability" on the Neel site because their boats, as generically trimarans, size by size, have more beam then Catamarans. For instance a Lagoon 450 has of beam 7.84m a Neel 45 8.53m, a FP Helia 44 7.40m, a Catana 47 7.64m, a Leopard 44 7.25m, an Outremer 45 7.1m.

An increased beam gives more stability to a multihull, all other things being equal.
The problem is all things are never equal and there is no such thing as a "guarantee".

Tri's generally need more beam as the outer hulls tend to have less bouyancy, so they need a longer arm to avoid burying the hull and tripping over it (an issue catamarans are far less likely to experience).

The beams ratios are different for a reason not because one is better or worse.

The tri will generally outperform the cat in sailing ability but it's not even close with the cat being far more comfortable in port. Since 95% of cruising is spent in port as long as the cat is capable, my choice is obvious.
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Old 29-12-2014, 08:00   #37
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Re: Tri's or Cat's?

FWIW, since I own the cat the OP wants to compare, in lengthy conversations with factory engineers when the model was first released, they concluded the rigging would break before the wind would capsize the boat. I have to believe that to be true on flat seas, but get it sideways on a 10m breaking wave and all bets are off.
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Old 29-12-2014, 08:25   #38
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Re: Tri's or Cat's?

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The problem is all things are never equal and there is no such thing as a "guarantee".

Tri's generally need more beam as the outer hulls tend to have less bouyancy, so they need a longer arm to avoid burying the hull and tripping over it (an issue catamarans are far less likely to experience).

The beams ratios are different for a reason not because one is better or worse.

...
Off course, warranty is not my words but theirs. It is however true that beam on a multihull increase stability and that has nothing to do with amas buoyancy that would be the same being the boat more or less beamier. In fact a more beamier boat will give more stability, will allow more sail area and will demand amas with a bigger buoyancy, not less.

In what regards the correct buoyancy of the amas to make a trimaran safe, they can be more or less well designed. There are trimarans that can take all weight of a boat on one amas without submerging it. It all depends on the design.
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Old 29-12-2014, 09:48   #39
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Re: Tri's or Cat's?

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There are trimarans that can take all weight of a boat on one amas without submerging it. It all depends on the design.
I can't view the video, but from the still picture, I think that tri has foiling daggerboards - which provide a lot of lift to the ama, some to 70% lift. In this case, the ama is not designed will full static floatation ability with the boat riding on it - the foil takes care of it.

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Old 29-12-2014, 10:17   #40
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Re: Tri's or Cat's?

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I can't view the video, but from the still picture, I think that tri has foiling daggerboards - which provide a lot of lift to the ama, some to 70% lift. In this case, the ama is not designed will full static floatation ability with the boat riding on it - the foil takes care of it.

Mark
That's a a 15 old movie with an old ORMA class trimaran. Yes the foils provided some lift but not foiling daggerboards at least what you call them today. The boat had relatively small dagerboards and a big centerboard (non foiling).

That's one of the most incredible sailing duos ever, Alain Gautier and Mich. Desjoyeaux training for the 1999 TJV on Biscay bay. They were decided to win or capsize...bad luck, they capsized shortly after the start.

From that duo and that boat were taken some of the more impressive sailing images I ever saw. When you have decent internet look at them, they deserve to be seen:


Regarding one ama on some modern trimarans to be able to take all the weight you can see it on this unfortunate capsize:

Long after the foils having any effect on the buoyancy all the weight is on the ama and the ama is not submerged.
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Old 29-12-2014, 10:39   #41
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Re: Tri's or Cat's?

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Originally Posted by colemj View Post
I can't view the video, but from the still picture, I think that tri has foiling daggerboards - which provide a lot of lift to the ama, some to 70% lift. In this case, the ama is not designed will full static floatation ability with the boat riding on it - the foil takes care of it.

Mark
Now that appears to be a racing machine with little in common with a cruising boat but if the main hull comes clear while the downwind hull hits a wave front, it appears that it would make a spectacular cartwheel.

Yes, you can design the tri so it has full bouyancy in the outer hulls but that creates other design tradeoffs. The sportier tris generally have smaller (ie: less bouyant) outer hulls that will have more of a tendency to bury.

The cruising tri's with big bouyant hulls tend to be less beamy (likely for a similar reason that cats are less beamy in general)
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Old 29-12-2014, 11:37   #42
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Re: Tri's or Cat's?

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Originally Posted by valhalla360 View Post
Now that appears to be a racing machine with little in common with a cruising boat but if the main hull comes clear while the downwind hull hits a wave front, it appears that it would make a spectacular cartwheel.

Yes, you can design the tri so it has full bouyancy in the outer hulls but that creates other design tradeoffs. The sportier tris generally have smaller (ie: less bouyant) outer hulls that will have more of a tendency to bury.

The cruising tri's with big bouyant hulls tend to be less beamy (likely for a similar reason that cats are less beamy in general)
Even if not obviously racing boats modern trimarans take a lot in what regards design from racing trimarans, the same way monohulls have take a lot from Open boats. Yes they are less beamy but the modern tendency is to have amas with big buoyancy...like the racing ones. normally they are more sportive than most cats because having them very little interior space nobody is interesting to trade that for nothing.









Even on those with an older design you can see that when they bury a ama (min 0.26) they don't cartwheel:

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Old 29-12-2014, 13:29   #43
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Re: Tri's or Cat's?

This thread is once again a great learning experience, and you can bet I am going to try out the twitchy bobble. One of the gems in here is how a DF 32 is certified Class A and the cat is not.
Perhaps I will get a ride on a few of these beasts and go from there.
I can always charter out of the BVI. But that will not tell me how they do up here in the PNW.
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Old 29-12-2014, 13:44   #44
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Re: Tri's or Cat's?

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This thread is once again a great learning experience, and you can bet I am going to try out the twitchy bobble. One of the gems in here is how a DF 32 is certified Class A and the cat is not.
....
A cat of the same size.

A friend that had bought one explained to me that the floaters, beam and weight were not that different from the 35. In fact when the 32 come out to the market the sales of the 35 went down and the 32 up. It is a boat with an amazing interior for the size and that sails remarkably well.
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Old 29-12-2014, 13:50   #45
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Re: Tri's or Cat's?

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Even if not obviously racing boats modern trimarans take a lot in what regards design from racing trimarans, the same way monohulls have take a lot from Open boats. Yes they are less beamy but the modern tendency is to have amas with big buoyancy...like the racing ones. normally they are more sportive than most cats because having them very little interior space nobody is interesting to trade that for nothing.









Even on those with an older design you can see that when they bury a ama (min 0.26) they don't cartwheel:

Only a couple of the videos played but...I didn't see the main hull flying and the downwind ama was almost completely submerged.

That suggests to me that if pushed harder in rough conditions, the ama could submerge. Yes,they try to compensate by making the amas very streamlined and having the arms lift up in a gull wing shape but the videos haven't changed the issue.

These were mostly day sailing examples with someone at the helm ready to react and not really pushing them to the edge like you would find in capsize threat conditions.
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