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Old 27-05-2016, 15:36   #16
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Re: Trimaran wit "equal" hulls

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And the single inboard Perkins. Hate to try turning that hard in a marina
Not my cup of tea, even if I didn't have to go broke to afford it.
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Old 27-05-2016, 15:44   #17
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Re: Trimaran wit "equal" hulls

Most trimarans have single engine, mostly because side hulls are small and not made to accommodate big and heavy items like engines. While this design (with equal hulls) will allow to install two engines, as I understand, most folks here say that its performance is no good.
BTW, Neel 45 and Neel 65 also have single engine, but at least Neel 65 has bow thruster to deal with tight places.
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Old 27-05-2016, 16:31   #18
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Re: Trimaran wit "equal" hulls

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Definitely speed and sea worthiness due to the center of gravity. But to each his own. Interior space generally stinks, finding a slip or haul out is a bitch.
if anyone can find it there was a definitive paper by James Wharram named Unsafe in Any Sea. The paper was published in Yachting World, Yachting Monthly or one of those periodicals in the 80s

Wharram suggested that tris are advantaged up to 30ft, after which catamaran advantages become clearer. And yes its about how hulls are designed to be consumed as accommodation.

Wharrams main beef was that multihulls in general were becoming too overpowered, and he gave a deft mathematical examination of the causes of capsize. Which generated a fairly convincing view of capsize due to wave action especially with large sail areas, and where the lesser buoyancy of a tris sponsons made them easier to submerge, roll under, and indeed trip the boat over.

If we think about the high structural accommodations on cat bridgedecks chasing the need for standing headroom and at the same time maintain a suitable clearance to prevent bridgedeck slamming; the commensurate effect those combined purposes have on the height of the boats designed CG, and how this also contributes to the capsize factor.

So I guess it comes down to heavy high bridgedecks on smaller cruising cats vs the lower buoyancy of trimaran ama's. Addressing these issues means larger tri sponsons and plainly larger cats where bridgedeck accommodations are required. And we should note that cruising cat designs in and around the the once popular 30ft or so sizes have largely been excised from the production boat market since the 80s.

Or alternately the comparison becomes cats without large bridgedecks vs the accommodations of trimarans the same size, where tris doubtlessly have some considerable advantage.
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Old 27-05-2016, 17:46   #19
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Re: Trimaran wit "equal" hulls

Our Trimaran was hard to turn in a marina until we added a Yacht Thruster external bow thruster and we can now turn in out own length. See web site-

side-power.com/kategori/1831/ex-serien/
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Old 27-05-2016, 18:56   #20
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Re: Trimaran wit "equal" hulls

There are a lot of generalized statements in this (so far) short thread. If you paint with a broad brush it gets messy.

1) There's no reason a tri is any more difficult to turn or maneuver than any other single engined boat. Deep fin centerboard or daggerboard and high aspect rudder along with bow thruster and judicious use of prop walk allow one to pivot nearly in its own length, and good maneuvering in reverse. OTOH a low aspect keel/skeg-hung rudder will be a challenge to maneuver.

2) Capsize resistance: Trimaran ama buoyancy of 3x displacment or more (not unusual in more modern tri design) along with typically wider beam/length ratio compared with a cat translates to great capsize resistance. Note I didn't write "greater" because that's not a rule and other factors are to be considered in any comparison. One must get specific about comparisons.

3) Performance: weight, length, narrowness of hulls, shape of hulls, SA/D, sail design and rig design. Lots of factors. Whether 2 hulls or 3 matters less than these other things. However it's easier to design light with 2 hulls.

Nobody has yet mentioned joy of sailing. The better "feel" of a tri comes from the fact that it has some heel so it's easier to "read" how hard you're pushing the rig, and tune in with your senses as monohull sailors know (but at higher performance in most cases). The boat the OP showed is more like a cat with exaggerated nacelle, not like most tris. It may be technically a tri because it has 3 hulls but I would expect it to sail more like a bloated cruising cat because most of its displacment is in its amas.
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Old 27-05-2016, 18:58   #21
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Re: Trimaran wit "equal" hulls

It kinda looks like the catamaran version of a macgregor. It would suit the person who just wants a floating motor home with sails.
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Old 27-05-2016, 22:35   #22
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Re: Trimaran wit "equal" hulls

Actually, the purpose of this thread was to "analyze" this unusual "equal" hulls design vs "classic" tri vs catamaran. It seems discussion went in a little different direction
See, some bigger modern tris have bigger side hulls with usable space in them (Neel 45, Neel 65). But side hulls still much smaller than main hull. Both Neel 45 and Neel 65 positioned as "performance luxury" boats (at least, in advertising).
My vision is that such design (tri with usable side hulls) creates more usable space per same length. So I'm trying to figure out, how these tris with heavy side hulls sail comparing to tris with light hulls (which, probably, sails better if properly designed) and comparing to properly designed cat, which has two heavy hulls by definition.
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Old 27-05-2016, 22:50   #23
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Re: Trimaran wit "equal" hulls

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Actually, the purpose of this thread was to "analyze" this unusual "equal" hulls design vs "classic" tri vs catamaran. It seems discussion went in a little different direction
See, some bigger modern tris have bigger side hulls with usable space in them (Neel 45, Neel 65). But side hulls still much smaller than main hull. Both Neel 45 and Neel 65 positioned as "performance luxury" boats (at least, in advertising).
My vision is that such design (tri with usable side hulls) creates more usable space per same length. So I'm trying to figure out, how these tris with heavy side hulls sail comparing to tris with light hulls (which, probably, sails better if properly designed) and comparing to properly designed cat, which has two heavy hulls by definition.
Threads will do that

Look again at the Neels. They use the wing deck not the ama hulls for crew space. They also have very narrow amas compared with the design in the OP. They're heavier than optimal for sailing, but if you can get over the looks (I'm not a fan) the Neels make some reasonable design compromises to create interior space. If you load them up for cruising they will be slow.

Fact (not opinion): Tris and cats that are optimized for performance sailing are going to suffer in performance if you load them down.

The design in the OP is a dock or anchorage queen, not optimized for sailing. It's likely to slam in a chop and have the performance of a slug.
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Old 27-05-2016, 22:58   #24
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Re: Trimaran wit "equal" hulls

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The design in the OP is a dock or anchorage queen, not optimized for sailing. It's likely to slam in a chop and have the performance of a slug.
From "for sale" listing: "Sesame was originally conceived by a racer for family cruising". Why racer would create such...thing?
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Old 27-05-2016, 23:32   #25
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Re: Trimaran wit "equal" hulls

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2) Capsize resistance: Trimaran ama buoyancy of 3x displacment or more (not unusual in more modern tri design) along with typically wider beam/length ratio compared with a cat translates to great capsize resistance. Note I didn't write "greater" because that's not a rule and other factors are to be considered in any comparison. One must get specific about comparisons.
typically tris are wider this is true, but the moment they work on is beam over 2 (B/2) because the main hull is the weight, the wetted area, carries the rig and is hence the pivot, only half the beam works in its favour.

Whatever way you figure out the sponsons volume its going to be less than a catamaran hull therefore offer less buoyancy and less resistance to capsize.

As boat lengths come down, the catamaran offers less advantage while at the same time offering variations of less, to no accommodation. But such cats have less wetted area, will tend to pull their windward hulls higher than the waterline, have less total wetted area so boat speeds go up.

Aerodynamically it is easier to have a stayless and vastly more aerodynamic rig in a tri because the mast can be supported within the depth of the largest hull. You cannot do the same on a cat without adding weight to the crossbeam structure and likely reducing sail area, both measures are counterproductive.

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Originally Posted by SailFastTri
Nobody has yet mentioned joy of sailing. The better "feel" of a tri comes from the fact that it has some heel so it's easier to "read" how hard you're pushing the rig, and tune in with your senses as monohull sailors know (but at higher performance in most cases). The boat the OP showed is more like a cat with exaggerated nacelle, not like most tris. It may be technically a tri because it has 3 hulls but I would expect it to sail more like a bloated cruising cat because most of its displacment is in its amas.
most often tri designs keep a sponson out of the water, flying a hull makes them faster because they have less wetted area. So underwater we have a version of an atlantic proa where you would expect it to be lighter, and therefore on the same sail area faster.

Since Farrier, it has also been realised that tris are more capable of being folded which is especially useful for trailering. Here a tri doesnt need or have the ballast of a mono, and the package can generally offer good maximum boat length and still be able to afford the full share of stability at modern beam length ratios within its folding mechanism. As we concluded earlier it should also be quicker to rig/de-rig with a stayless mast.

The asset allows them to be launched off the trailer; conveniently and quickly unfolded as needs be within the confines of a busy ramp and still be able to motor away. In these sizes they are very definitely the most all round useful of boats as demonstrated by the current resurgence of competitive trailerable trimaran production boat designs.

The design we are offered in #1 gives considerably more hull volume, but at the expense of a lot more wetted area. I think it as close to a cathedral hull than either a cat or tri and usually best disposed to power craft.

Unless we can see some opposing data pretty much the worst of all worlds.
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Old 27-05-2016, 23:38   #26
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Re: Trimaran wit "equal" hulls

a trimaran did a test sail from Sydney to Hobart with three equal hulls it was made of ply wood / it still has the unofficial record / don't know the length of the hulls but they are still around/ they are under the floating fish shop in Sydney harbour. lol
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Old 30-05-2016, 22:52   #27
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Re: Trimaran wit "equal" hulls

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I know it's hard to compare apples to oranges. What I mean - comparable length boats of same category - cruising boats, for example. not performance or racing.
A traditional trimaran design will be faster but with drastically less accommodations. But really completely different boat with different design goals.

The overstuffed trimaran will get similar accommodations but it will lose performance compared to the cat due to more wetted surface.

Of course these are generalities. As others have suggested, on very small boats (below 30') it's hard to put accommodations on a sailing cat.
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