cats vs tri's?

[2Gringos]

I was at a dinner party Saturday night, and one of the couples there are getting ready to sail their self-built trimaran from here to Bermuda. Of course I got into a discussion of sailing with him once he found out I am lusting for a Gemini 105.

He is quite biased toward trimarans, of course, since he spent years building his. And it's a nice one. But to me, a trimaran is basically a shallow draft monohull with outriggers. I don't see that it has the advantages of either a monohull OR a catamaran. Are there any advantages other than shallow draft and outrigger stability? Are they inherently faster, with three hulls in the water?

[chucklesR]

2Gringo's,
We share opinions. Trimarans are mono's without lead mines, and with ama's as outriggers to provide stability. The only multihull is a catamaran. No one has made a boat with two hulls and two ama's yet.

True some large tri's actually have living spaces in their ama's but a ama is a ama is a ama, it is not a hull. Nautical terminology is what it is. It's not a float, pontoon boats have floats. It's a ama. No one calls a anchor a plow just because it looks like one, they still can it a anchor because that is what it it. There is no such thing as a thingamabob on a boat for a good reason.

Tri's are much faster than mono's because they don't have the leadmine to haul around, and are able to plane because the ama's provide more stability, hence they can carry more sail (the same as a catamaran).

There are trade off's in everyboat, and everyone has different opinions - mine however is absolutley correct and you must disregard all others because of I sail a Gemini and am therefore better looking, and smarter than them

Multihulls are better as cruiser boats because of the stability and space; monohulls are better for freaks of nature that like to live at 20 degrees out of kilter for long period and don't mind living in a hole in the water than might sink. Trimarans are good for people that really can't decide what they want but want it now (i.e., faster).

[2Gringos]

Thanks, that pretty much mirrors my own opinions, except for the part about you being better looking. I have pretty much decided that the Gemini is the best all-around choice for what we want to do, and where we want to do it. We want to sail comfortably for weeks at a time from our home base in the TCI as far north as Harbour Island in the Bahamas, and down the Caribbean. With the possibility of trips to Central America and maybe the Gulf Coast in the future. We don't wanna circumnavigate anything bigger than Cuba. I have seen Tierra del Fuego quite enough for one lifetime. Too much, in fact.
We like the shallow draft, and the 14 ft. beam...( hell, we love our panga, so narrow beams is already a good thing where we are concerned) and we like the internal layout of the Gemini. It's kinda a shame it only has one motor, I think a small outboard on each hull would be useful, but that's not a show stopper.

I am still willing to be convinced there might be a better sailboat choice for us, but so far, nobody has pointed it out to my satisfaction.

[sailingdog]

2Gringos-

Of the three boat designs, generally a trimaran will have the least space, the monohull being a bit more spacious and the catamaran having the most space. This is only true of the trimarans that do not have space or accommodations in the akas.

Designs like the older Jim Brown searunner trimarans have a solid wingdeck and accommodations or stowage in them, so will be more spacious than a monohull of the same LOA. However, they have more windage too, and most modern trimaran designs don't follow that practice.

Trimarans tend to have better sailing characteristics than do catamarans, tacking and turning more like monohulls, because they will generally pivot on the main hull and have less windage than catamarans.. They also tend to be faster than catamarans and monohulls of the same LOA.

Trimarans also have the multihull advantage of relatively little heel while under sail. However, trimarans will generally heel a bit more than catamarans, which have a much larger righting moment, since the buoyancy of a catamaran is in the two hulls. A catamaran may heel 5-10˚, and a trimaran 10-15˚, where a monohull may be 20-30˚ of heel under sail or more...as seen in Gui's photos of his fat boat.

IMHO, they have the best sailing characteristics of both monohulls and catamarans... but I may be a bit biased.

[chucklesR]

Dollar for dollar The Gemini is the best available on the market today. The Tomkat isn't bad as a low cost catamaran built for a couple, but it costs more and you actually get less. The Seawind from down under is priced 100k over the Gemini and therefore not in the same market, altho it's the same length.
Older Catamarans (Prout etc) in the size range are good old boats, but they are older, not up to current design standards etc..and suffer in the internal layout because they are based on monohull layouts which don't work in narrow hulls.

as to single motors:

A lot of Gemini owners put a bracket on the port hull and can mount the dinghy motor there. Even a 4hp is enough for 3-4 knots; the average crusier is now using 10-15 hp for dinghies, and that's enough for 6 -7 knots of boat speed (as reported by Gemini owners).

My 310 RIB with a 2.5hp motor tied alongside is sufficient to push my Gemini at 2-3 knots in an emergency. I know based on experience.

[sailingdog]

No bias in your opinion at all, right?? I'd have to agree that PCI does give you a lot of boat for the buck.

Originally Posted by chucklesR

Dollar for dollar The Gemini is the best available on the market today. The Tomkat isn't bad as a low cost catamaran built for a couple, but it costs more and you actually get less. The Seawind from down under is priced 100k over the Gemini and therefore not in the same market, altho it's the same length.
Older Catamarans (Prout etc) in the size range are good old boats, but they are older, not up to current design standards etc..and suffer in the internal layout because they are based on monohull layouts which don't work in narrow hulls.

as to single motors:

A lot of Gemini owners put a bracket on the port hull and can mount the dinghy motor there. Even a 4hp is enough for 3-4 knots; the average crusier is now using 10-15 hp for dinghies, and that's enough for 6 -7 knots of boat speed (as reported by Gemini owners).

My 310 RIB with a 2.5hp motor tied alongside is sufficient to push my Gemini at 2-3 knots in an emergency. I know based on experience.

[danjarch]

Just to put some records strait, and as an unbiased opinon. Neither cats or trim are really designed to plane. They are built with a much narrower bow and mid section and cut through the water rather then pplowing through the water like a mono. As a monohull builds up speed it produces a bow wave. This wave becomes a barrier that the monohull can't breach. Just like a propellor driven plane, where the prop creates a pressure wave in front of it and the plane cannot go any faster.

This is where the narrow beam of the multi hull comes into play. It cuts through the bow wave, allow the vessel to go beyond the traditional hull speed. Trimarans are the faster of the two because of where the effort is placed. A trimaran's leeside ama acts as a lever that pulls first the weatherside ama then begins to lift the main hull out of the water. This lowers the angle of the bow and allows the vessel to penatrate the bow wave easier. This allows trimarans to continue gaining momentum after a cat has hit its top speed.

Some of the other issues that come into play when looking for your personal boat is that tris don't work well below 24 feet. They are also less weight friendly. The reason builders quit build the wing decks has less to do with windage and more to do with weight. You can cary more weight on a cat but alot of people over load those as well.

The only issue with the gemini's design is the spacing between the hulls. At higher speeds, the bow waves from the two hull will meet up in the middle and create a pressure against the hulls that will increase drag. The faster cats have a wider stance that allow the vessel to pass through before the waves meet.

Other then that, I'm not going to comment on which of you is better looking, and would warn you that if you continue this coarse of debate. CD will feel compelled to come over and defend his honor.

[chucklesR]

Dan's actually correct as to planing, but the not the bow waves meeting and drag thing -
My bow waves meet and hit well before 8 knts, and I can and have exceeded that. I spout rooster tails at 6, and have 3 at 8kts, one off each hull and a centerwave starting at 8. The center wave is the bow wave bouncing and rejoining at the stern. At 10 knts it's three clear tails and a butt load of water noise Unfortunately the only picture I have of my wake is my Boatpix overehead shot - I was doing about 6 at the time so it's not showing. I'll have to snap a shot this summer.

Cat's, cruising cat's, don't plane per se.
We exceed the 1.34 @ cube of LWL speed limits because we can carry enough sail (hp) and have a 9:1 or so length - beam ratio. The actuall 'displacement speed' of a cat comes out to about 1.8 @cube of LWL depending on your source. I cite David Gerr, Chris White and Charles Kanter. Mostly Gerr because he gives good numbers.

[sailingdog]

Chuckles-

Can you name a trimaran that has living space in the AMAS??? I can't... Not even the big racing trimarans do that. Some older designs, like the Newicks, Browns and Crosses have a solid wingdeck instead of separate akas (crossbeams) and have living space or stowage in the wingdeck, but none I can think of have berths in the amas.

[2Gringos]

Hmm...actually that all makes sense. If I understand what I think you are saying...then in light air ( which we never really seem to have here for long) the tri loses its potential speed advantage, due to increased drag and the Gemini gains without the bow-induced wake convergence under the bridge deck? Do I have that right, that you need enough wind to really start pushing before the tri starts to shine?

Hey, I wasn't arguing about Chuck's looks. I have seen his previous avatar, and the one he himself considers an improvement. I am definitely not in his class appearance wise.