How to Spot a Catamaran
Spotting a catamaran is easy. Simply look at the hulls and count them. Catamarans have two hulls side by side and a relatively large gap between them where you can see light on the other end. Catamarans are distinct from trimarans, which have an additional hull between the two outer hulls.
How do Catamarans Work?
The principle behind the catamaran is simple. You can think of catamarans like cars and monohulls like motorcycles. Catamarans distribute their weight between hulls on either side, whereas monohulls utilize only one hull.
Evidently, cars are much more difficult to tip over and can hold much more weight. Additionally, cars are wider, as they have much more contact with the road. Catamarans work in a similar way, as they have a wide stance and contact with the surface on both sides.
Obviously, that isn’t the most precise comparison. But the basic principle is the same, and catamarans have a few notable benefits over monohulls.
Catamaran Vs Monohull
Catamarans are easy to distinguish from monohulls. A monohull is just a regular old boat with a single hull. The vast majority of boats and ships are monohulls. Catamarans have two hulls, which are usually sleek and narrow.
Here are some comparisons of catamarans and monohulls, along with the advantages twin-hull designs have over most single hull types.
Benefits of Catamarans
Catamarans have numerous benefits. The first is speed. Catamarans produce less drag than monohulls and thus can achieve excessive speeds both under sail and power. They don’t need to plane like monohulls to achieve these high speeds, and they use less fuel.
Catamarans are also much more stable than monohulls. They have a wide stance and shallow draft, and many waves and swells can travel between the hulls instead of below them. This effectively reduces an entire axis of movement and prevents catamarans from rolling excessively.
Drawbacks of Catamarans
Catamarans aren’t advantageous in every way, or else we wouldn’t bother building monohulls. The disadvantages of catamarans limit their use to niche commercial applications and high-end yachts. But what are the drawbacks of a twin-hull design?
Sailing catamarans don’t follow many of the traditional boat handling rules and characteristics that sailors pass down for generations. Some, such as hull speed limitations, are good to do away with—while others, such as responsiveness, are not.
Catamarans aren’t as quick to the helm or responsive as monohulls. There are some exceptions to this rule, but for the most part, you’ll get a lot more feedback from a single-hull vessel. Additionally, the large section of deck between the hulls of a catamaran is prone to pounding in rough seas, which is loud and uncomfortable.
Catamarans can sometimes be twice the width of an equivalent monohull sailboat, which can increase mooring fees and limit docking options.
The final major drawback of catamarans is a consequence of their stability. Traditional full-keel monohull sailboats have a very low center of gravity, which makes them roll in heavy seas but ensures a recovery.
Catamarans have a higher center of gravity, and they can’t right themselves after a knockdown. And though catamarans are less likely to roll, a severe list on a multihull is a much more serious concern than on a ballasted monohull.
Catamaran Vs Trimaran
Catamarans and trimarans are often lumped together, but they have very different design and performance specifications. Trimarans have three hulls, whereas catamarans have two.
Trimarans look a lot like catamarans from the side, but a quick glance at the bow or stern can set them apart. Trimarans are faster than catamarans, as they distribute their weight across three hulls instead of two. This helps them stay centered and reduces interference from pitching and rolling.
Catamarans are fast, but they lose out to trimarans when going head to head. However, catamarans are much less expensive to build and maintain and often have roomier cabins due to their larger hulls.
Types of Catamarans
There are numerous types of catamarans, and their uses vary widely. The catamaran is one of the oldest and most useful hull types, and some variants have been used for thousands of years. Here are the most common kinds of catamaran boats and their uses.
Sailing Catamaran
Sailing catamarans are probably what you think of when you hear the name. Sailing catamarans are sailboats with two identical hulls connected by a center deck. The largest sailing catamarans are spacious and stable vessels that are capable of serious offshore sailing.
Sailing catamarans have a number of notable advantages over monohulls. Monohulls, which are traditional sailboats with a single hull, are limited by a simple concept called hull speed. As the bow and stern wave of a monohull intersect, they cause drag which limits the top speed of the boat.
Catamarans are not bound by hull speed limitations, as they have two hulls. Catamarans can go twice or even three times as fast as similar monohulls and achieve excellent travel times.
Catamarans are also more stable than monohulls, as their wide stance and shallow draft reduce the effect of rough water. They don’t heel, as the force of the wind is counteracted by the double hulls. Additionally, modern sailing catamarans can ‘wave pierce’ by cutting through swells instead of riding over them.
Sailing catamarans come in many shapes and sizes. Small sailing catamarans, such as those used in races and regattas, are known for their speed and relative stability compared to light racing monohulls. Sometimes, they feature a smaller second hull for stability—these are called outriggers.
Sailing catamarans have spacious interiors thanks to the large cockpit between the hulls. This cockpit usually contains cooking and eating spaces, a place to sit, and a hallway between the hulls. The hulls usually contain living quarters and often mirror each other.
Power Catamarans
Power catamarans have an even greater variety than sailing catamarans. These vessels are used for everything from party platforms to ferries and patrol boats.
Power catamarans are a recent development, as engineers and marine architects now realize they have numerous hydrodynamic advantages over other hull types.
Catamarans are much more efficient than other hull types, as they have less drag relative to their size. Additionally, you can build a much larger catamaran with less material. This makes them popular for car and rail ferries, as builders can construct a very wide vessel with two small hulls rather than a narrower vessel with a large single hull.
Military and Commercial Catamarans
Even the military has found a use for the catamaran hull shape. The Spearhead class EPF is an expeditionary fast transport vessel designed for carrying capacity and speed. It has two sharp hulls and a huge cargo capacity.
The Spearhead class EPF is 337 feet long, which is about the same length as a WW2 escort destroyer. Yet despite having a similar length and displacement, these catamarans can travel more than twice as fast—43 knots, or nearly 50 miles per hour. Their great speed is a direct consequence of their catamaran hull type.
Power catamarans are also used as patrol and utility boats on a much smaller scale, with either outboard or inboard motors. The State of Texas uses catamarans to patrol shallow rivers and lakes. Texas Game Wardens utilize state-of-the-art aluminum catamaran patrol boats, which are fast enough to outrun most fishing boats.
There’s another form of power catamaran that you may not have considered. Pontoon boats are technically catamarans, and they’re enormously popular on lakes and rivers throughout the country. Pontoon boats aren’t known for speed, but they’re a great platform for a fun and comfortable outing.
Catamaran Houseboats
The final common type of power catamaran is the two-hulled houseboat. Houseboats don’t always use the catamaran hull type, but it’s common enough that most major manufacturers offer it as an option.
Catamaran houseboats have a few notable advantages over monohull designs. For one, they’re easier to build—especially when pontoons are chosen. Additionally, they’re better suited for navigating shallow water. These vessels can support more weight across their two hulls, offer increased stability, and they’re also efficient.
Why Aren’t Catamarans More Common?
With all the advantages listed in this article to consider, it may seem strange that the use of catamarans is still somewhat limited. At the end of the day, it comes down to economics—as monohull boats and ships are simply cheaper to build.
Additionally, catamarans have some distinct limitations. Monohulls have lots of storage space in their hulls and can carry thousands of tons of cargo safely in all weather conditions. Catamarans lack this space and low center of gravity, so they’re not ideal for transporting cargo past a certain point.
Additionally, monohulls work, and many people are reluctant to experiment with new designs when old designs work just fine. This rule applies to both large and small boats.
A large monohull sailboat can be constructed at low cost from stock plans and reliably sail almost anywhere. Very little complex structural engineering is involved, and looser tolerances reduce cost and maintenance requirements.
