Trimarans are a natural outgrowth of catamarans.
A very traditional catamaran consists of the vaka, aka and amas, or main hull, the boom that ties ties the main hull to tht outrigger -- the aka -- and the outrigger itself, the amas.
The catamaran is an inherently stable design for two reasons:
1. It cover a larger area for its size2. The second hull or outrigger makes it virtually untippable
Taking this a step further, you come to the trimaran which started its rise in sophistication, design and popularity in the 1970s.
The father of the modern trimaran, who built the first two of plywood in the 1950s was a Russian emigre to the United States, Victor Techtchev. He proved the concept and was followed quickly by many other developers.
The original trimaran consisted on a thin central hull and two outriggers or secondary hulls that were linked to the main hull by, for want of a better word, beams.
The trimaran had a number of advantages of over a standard saiboat. For example:
* The trimaran draws very little water and can run quickly before the wind* The trimaran does not need a heavy keel to help it remain stable. The size of its footprint when the outrigger hulls and center hull are taken into consider mean that she is a lightweight craft that can easily run close to the wind. * The trimaran can also mount more sail for a given size. For example, if you have a 12-meter yacht that is flying a standard sale, jib and spinnaker could be flying several hundred square feet of canvas, while thanks to the inherent stablility of the trimaran design, she may be able to mount twice the sail area.
There comes a point, though, that is very similar to what is known in the auto business as the polar moment. On vehicles with high centers of gravity and larger-than-normal wheels, there is a point where the vehicle will tip of its own accord. If you keep things on the right side of this equation then you'll have no problem, however, if you load more and more onto the top area of the vehicle there comes a point where the balance of the vehicle is upset and this balance point is called the polar point and violating it is called defying the polar moment.
Once you've gone past the polar moment -- onto the dark side, as it were -- there nothing you can do about it, except watch as your vehicle rolls.
On the catamaran, the polar point comes when the main mast and torque from the wind combine to make her unsteady. In this case, though, you have an inherently stable design thanks to its very wide stance which means that when the polar moment is reached (the tendency to the torque of the wind on the mainmast to try to work against the motion of the trimaran and tip), the very construction of the trimaran keeps it "feet on the ground," so to speak.
When the polar moment is reached, the outriggers or hulls tend to slam back down on the water and the sailboat remains virtually unsinkable.
There is one problem with a sailboat that is as weatherly as the trimaran and that is known as pitchpole. Because the trimaran can travel as close to the wind as possible, it can sometimes catch up to the wave it is supposed to be following. At this point, you have to choices, radically trimming sail by dropping the mainsail or having breakaway sales.
If you run into a Pitchpole situation, you will find that the trimaran will dig into the wave ahead by its hull and will pitch over and over (pitchpole). As we have seen this is not a good idea so you have to watch your sail allotment and ensure that you hav enough sale out for speed, safety and no more.
Trimarans are also under experimental design contract with the U.S. Navy through General Dyanmics that has already that has already yielded the RV Titan.
Still, for all their advantages trimarans do have some disadvtanges that must be discussed.
* They tend to wander. In other words, when the run before the wind the tend to run and may actually go somewhat sideways and off course. To prevent this, developers have added removale centertboards or daggerboard to help control sidewards movement.
* Because of the amount of acreage their outriggers take up, though the central hull itself may be short, the outriggers have doubled or tripled the side of the trimaran's dockside footprint so they are very large vessels to moor. Some use folding outriggers that come in somewhat and lessen the size.