Tri-Hull Boat – What Is It and Its Pros and Cons

Lots of people like to spend time beside the water and many like to spend time in, or on, the water. If you like spending time on the water, you’re going to need a boat.

People have used boats for time immemorial. Since 70% of our planet is water, we’ve had to find ways to cross the ocean and other stretches of water.

Boat design has advanced so much with technological advances, and the use of ever-more complex materials, that modern boaters have a tremendous choice when it comes to buying a boat.

In the 1960s, the tri-hull boat was a very popular choice. It has many redeeming factors and a few issues.

Unfortunately for tri-hull boats, the issues, and the fact that other boat types are just more appealing to modern boat buyers, has seen a decline in demand for tri-hulls.

Let’s find out more about these boats and why they’re not so often seen sailing the waters as they once were.

What Makes A Good Boat?

A good boat is a boat that is designed effectively for its purposes. The key factors in boat design are materials used in its production, its design or aesthetics, the technologies employed and the features that are built into the boat’s design.

If you want a boat that does what it should, appeals to buyers, is up to date, economical and environment-friendly then these key factors need to be fully optimized.

Despite all the innovations and changes in materials used in boat design, the structural, holistic and technological factors have remained consistently integral. Boats need to float. That’s obvious.

But how they float, how they can be powered to move over the water and through waves economically, and how they can accommodate their passengers while doing so, is the crux of the matter.

The use the boat is going to be put to will have an overriding influence on design, materials, features and aesthetics. A boat that is going out to war has very different specifications to one that you want to spend a lazy day on at your local lake.

In today’s boat market, aesthetic appeal and technological aspects determine design requirements. However, underlying everything and always and forever the trump card is structure.

The structure of the boat has to be the motivation behind everything because a boat is made to go out on the water and the structure is what ensures it floats and stays afloat.

Structure And Design

Boat design has to ensure safety, no matter what the boat is used for, but the use of the boat will determine design and technology. For example, hydrodynamics and aerodynamics are integral to yacht design.

There’s a lot of mathematics and physics in boat design. Erosion, corrosion, and chemical analysis have to be factored in. Structural and architectural analysis has to be done.

Hull Design

The hull design is about materials, shape, and size.

Hull shape depends on the boat’s purpose and the type of water involved.

The main types of hulls are deep-v hulls, associated with offshore and rough water, and flat-bottom hulls, associated with smooth water.

Deep-v hulls have a wedge shape. They aren’t appropriate for shallow water. They require more power due to low buoyancy. They perform well in rough waters, knifing through waves. Offshore sport boats and bulks have deep-v hulls.

Flat-bottom hulls favor shallow and smooth waters. They have a very low deadrise and maximum stability.

Multihulls, such as tri-hulls, are less deep and suit small boats doing offshore or lake sailing. They are flatter at the stern and deeper at the bow. They usually have smaller engines.

Hull dimensions vary depending on boat length, width, height, and angles.

Computational techniques are employed to locate and scale hull segments.

Aesthetic Appeal

Once structural requirements have been met, aesthetic appeal is going to inform a lot of the design decisions that work alongside structural aspects. The aesthetics will depend on the use that’s going to be expected of the boat.

Boats of any type need to be ergonomic and they need to optimize efficiency in operation. The human and social sides of the boat’s use need to be kept in the frame.

People are investing good money in a boat. They want a boat that is aesthetically appealing. That’s just the way people are. People want things to work but they also want them to look and feel good while they work.

Aesthetic appeal is associated with mental well-being and things like taste, status and so on and so forth.

Materials

This aspect of boat design and manufacture has really gone through some major changes. Traditionally, boats were made from wood, steel, and iron.

Iron and steel are strong but they are heavy so are not well suited to small boats. Iron and steel are only really suitable for huge ships and cruise liners.

Materials most commonly used are steel, aluminum, fiber-reinforced plastic (FRP), polyethylene, and carbon fiber. Aluminum is lightweight, facilitating speed without compromising the strength or integrity of the hull.

Aluminum is preferable for smaller boats and even smaller ships. Yet aluminum is expensive and it involves high maintenance costs.

There has been a real shift towards fiberglass. Fiberglass is glass-reinforced plastic or fiber-reinforced plastic. Fiberglass, or FRP boats, are reliable, light, extremely effective, capable of high speeds, enjoy a longer life, have low maintenance costs, and are able to resist corrosion.

Polyethylene is used mainly for boats for professional fishermen because it’s buoyant and chemically resistant.  

Carbonfiber is strong and light. It’s stable for a long time, both chemically and thermally.

It resists abrasion and corrosion. Carbonization of the fibers during manufacturing strengthens and stiffens the material. Carbon fiber is generally used for racing yachts because it lowers weight and is moldable.

Technology

The advances in technology that are now integrated into boat design are amazing. Boats today give their users the sort of smooth ride and comfort boat users of the past could never have dreamed of.

Technological advances in navigation and the advent of location software have vastly increased levels of safety. Advanced personal safety devices give people security on the open water they never used to have.

Thermal imaging has revolutionized boat use. Having automated controls has changed the entire experience of controlling a boat.

The fact that boat manufacturers are seeking to produce boats that are environmentally friendly is absolutely crucial to the survival of our planet and its beings.

Sustainable boat design, the use of renewable energy to fuel boats, advances in how we reuse and recycle hazardous waste, in a bid to limit the human tendency to treat the ocean and other waters as waste deposit sites, cannot be applauded enough.

We need to keep on finding ways to design boats that do not impact the environment in which they operate.

Buyer’s Mindset

There are various types of boat buyers who are looking to buy a boat for personal, and often emotional, reasons. These psychological needs have to be factored in along with practical needs.

The boat buyer wants a boat that will appeal to him or her, make him or her feel happy when they’re on it, serve the purpose the buyer has in mind and fit the buyer’s budget.

Types Of Boats

Types Of Boats

There is a vast array of boat types: flatboats, V-hull boats, bass boats, pontoon boats, and tri-hull boats to name a few.

The Tri-Hull Boat

The original tri-hull design was based on traditional boats used in some southeast Asian countries which have a double-outrigger design.

Tri-hull boats have the standard ‘V’ hull bottom along with two additional hulls, amas or outriggers, one on each side. This design feature means that the bottom of tri-hull boats looks to be shaped like the letter ‘M.’

Having the three hulls, instead of the one hull that most boats have, gives the tri-hull boat a larger surface area at the bow.

Tri-hull boats may be referred to as trimarans, Cathedral boats or Tunnel hull boats because of the large tunnels formed with their more pronounced bottoms when these boats move through the water.

Tri-hull boats are classified as multi-hulls and are categorized in the same category as the catamaran and the tri-hull pontoon boat.

They range in length from 10 – 12 feet. Tri-hull boats are usually smaller boats, similar to dinghy-style boats, but the tri-hull design has also been used on ferries and warships.

Tri-hull boats are particularly popular among recreational boaters, tournament or sports users. The stability of these boats is good so they are great for parties on deck.

Some recreational fishers really like the tri-hull and others don’t. They can make for a good angling platform, liked by those with young children and families.

There have been improvements in the performance, speed and buoyancy of tri-hulls with modern technology and later developments but the boat has never really regained the popularity it enjoyed in the 1960s.

Pros: Tri-Hull Boats

A Flatter Sailing Experience

The design of tri-hulls means they don’t tip to one side when they turn and they don’t roll in the way a monohull does in certain sea conditions.

The overall result is that when you’re on a tri-hull and the water is not choppy, you can have a very peaceful sailing experience.

A Faster Sail

Load is distributed over the three hulls instead of over just one hull and the boat sits higher in elevation from the water. This means less of the boat is in contact with the water.

Drag is minimised and the boat doesn’t require as much force as a monohull boat to cut through waves. Consequently, you can have a speedy ride in a tri-hull boat.

Won’t Sink

Flotation materials, such as closed-cell foam, within the three hulls make tri-hull boats significantly harder to sink than mono-hulls. Good to know when you’re out at sea or in the middle of a vast lake!

Enormous Stability

Having such wide, flat hulls gives tri-hull boats impressive stability on the water. The two side hulls are mostly responsible for this enhanced stability, providing increased surface area at the bow.

There’s none of that wobbling about when people step onto the boat and, once on deck, you can move around comfortably without feeling like you’re going to capsize the boat. Shorter boats enjoy more stability.

Buoyancy Extraordinaire

The middle hull, which is long and narrow, does most of the buoyancy work – 90% of it. The design makes good uses of flotation materials and the layout works to the advantage of buoyancy.

Great For Getting To The Plane

The long and narrow middle hull helps get the tri-hull to the plane quicker than for other boats. When the engine is revved, the boat rises up on a plane, or level, on the water and then travels on top of the plane with its bow lifted out of the water.

Spacious Deck

The three-hull design really opens up the deck.

Lightweight But Load-Bearing

Tri-hulls have smaller cross-decks so they don’t require as much in the way of supporting structures as monohulls in order to have structural integrity.

This means the boat weighs less than monohulls but its spacious deck means it can carry more than monohulls.

Engine

Tr-hull boat engine design depends on whether the boat is a small sailboat size or a large ferry. Usually, they have a high horsepower outboard motor and can reach good speeds.

The fact there’s less drag because the boat has less contact with the water means the boat can accelerate better and reach fast speeds quicker than many other boats.

This speed is ideal to plane the boat on the surface but not so great when it comes to cutting through waves, due to the design.

Cheaper

Tri-hulls are generally cheaper to buy than other boats of the same size and require less power to operate because less contact with the water means more buoyancy and less drag.

Cons: Tri-Hull Boats

Hull design issues

Modern materials decrease the weight and increase the speed of tri-hulls and other multihulls. Required buoyancy decreases, allowing smaller section hulls and amas.

However, as the hulls become increasingly narrow and achieve ever higher speeds, the risks of damage to the cross-sectional areas increases when these boats smash into big waves.

The cross-sectional points close to the attachment for the forward aka of the ama can be fractured.

In 2012 the Sodeb’O design opted to use the main hull’s larger cross section as the longer hull. The reduction in length of the amas means their cross section can better cope with imposed loads.

Even smaller tri-hulls are potentially compromised by the design and construction of composite, moulded akas.  

Not Good On Unsettled Water Or Open Water

When on unsettled water, the boat takes something of a pounding from the waves. Running the boat ‘bow high’ can help.

Deck Gets Wet

Tri-hulls are not v-hulled, which means they aren’t good at cutting waves. When the tri-hull encounters a large wave the wave slams against the amas or outer hulls, on both sides of the boat, causing a lot of spray. When sailing on the upwind side, you will get wet each time the hull hits the water.

Over-Modified

Tri-hull boats have been modified over the years to embrace multifunctionality, but, in the process, they’ve lost the original tri-hull design. Instead of rigid amas, more modern tri-hull designs have made the outer hulls, or amas, foldable to convert the tri-hulls into a V-shaped hull, better able to handle the waves. The modification has helped but the original tri-hull design has been lost.

Limited Use

Many boat buyers want a boat that copes well with varied water types and the tri-hull is not great for open water or any water that’s unsettled.

Costs

The large cross-decks and extra hulls require extra materials in production, which can increase the price. Despite this, tri-hulls tend to be cheaper than many other boat types.

However, if you have a tri-hull and want to use it on choppy waters you may have to invest in a larger motor. Modified tri-hulls with foldable amas and a massive center hull cost more.

Conclusion

Tri-hull boats are beautiful and provide a stable, spacious experience for those spending time on tranquil waters. However, issues with the design have arisen largely due to unceasing modifications aimed at resolving issues with choppy water.

Unfortunately, the modifications may help solve some issues but they open up others at the same time.

Tri-hull boats are still manufactured by a number of brands but their popularity has definitely waned. The tri-hull design is found in limited sailboat models nowadays.

Another very pertinent reason for the waning interest in tri-hull boats since the 1980s, is increasing interest in v-hull boats and deck boats. There have been great advances from the 1980s that have ensured that v-hull and deck boats are increasingly desirable for all water types and boat users.

An offshoot of this has been a decline in demand for tri-hulls. The rise in popularity of pontoon boats is also influential. There is potential for tri-hulls to come back if a hybrid model, that’s recently been designed, takes off.

This hybrid model uses wave momentum as the source to power the tri-hull.

Danny White