Aluminium Boats vs Fibreglass Boats

Aluminium Boats vs Fibreglass Boats

If you’re in the market for a boat, you’re most likely looking at either a fibreglass boat or aluminium boat – but what are the true advantages and disadvantages of each material?

What Influences a Boat’s Handling?

Understanding what makes a boat handle well is crucial for both seasoned boaters owners and those new to the market. Four key factors play a pivotal role in a boat’s handling: length, weight, width, and the design of the hull.

1. Length: The length of a boat significantly impacts its handling. Longer boats tend to have better tracking (the ability to maintain a straight course) and stability in rough waters. However, they may be less maneuverable in tight spaces compared to shorter boats.

2. Weight: Weight is a game-changer in handling. Fibreglass boats, with their heavier layup, typically weigh more than their aluminium counterparts. This added weight can provide a smoother ride in choppy conditions, as the boat is less susceptible to being tossed around by waves. However, the extra weight might make the boat less responsive to quick maneuvers.

3. Width (Beam): The beam of a boat, or its width at the widest point, also influences handling. A wider beam can offer more stability and room inside the boat but can also create more resistance in the water, potentially affecting speed and fuel efficiency.

4. Hull Design: The shape and design of a boat’s hull are crucial. Deep-V hulls, often seen in offshore powerboats, are designed for smoother rides in rough water. Flat-bottomed hulls, on the other hand, are great for calm waters and provide more stability at rest.

Fibreglass Boats – History and Advantages

The invention of fibreglass, also known as GRP (Glass Reinforced Plastic), dates back to the 1940s. As the name suggests, fibreglass is made up of glass fibre strands usually laid in a mould, embedded with a resin matrix. Once set, GRP makes a lightweight, strong and robust material that is easily mouldable into virtually any shape.

But hang on – my shiny white boat doesn’t look like a mix of glass strands mixed in plastic! That’s because most boats are generally laid up with a “gelcoat”, a material used to provide a high quality finish on the visible surfaces. If you look below the gunnels you will often see the matting and resin in its raw state. Gelcoat is typically laid between 0.5mm to 0.8mm thick – this is what you’re removing to surface a new layer when the boat is polished.

Let’s cut to the chase – what are the advantages of fibreglass? Depending on the thickness of the layup and design, a fibreglass boat tends to have a softer and quieter ride than an equivalent alloy boat. You can mould fibreglass into any shape you can think of and they usually weigh more. An alloy hull is constrained to how you can bend and weld the metal and is usually lighter.

Another advantage of fibreglass is that it’s not prone to corrosion. Yes, you can have similar crippling affects such as water ingress, osmosis and delamination, but a fibreglass hull will never suffer from electrolysis.

Options to Enhance Stability on a Fibreglass Boat

For enhancing stability and comfort, larger fibreglass boats, typically those over 30 feet, are increasingly incorporating gyro stabilisers. These devices use a rapidly spinning ball, often at speeds up to 10,000 rpm, to counteract forces that compromise a boat’s stability. This technology mirrors the stabilizing effect of spinning tires on a bicycle or motorcycle, maintaining the vehicle’s upright position. Gyro stabilisers significantly reduce a boat’s rolling motion, offering an unparalleled level of comfort and stability, especially in rough seas. Though they mainly equip larger vessels due to their size and cost, gyro stabilisers signify a major advancement in boating technology, providing smoother and more enjoyable boating experiences.

What are the downsides to fibreglass?

On the flip-side, although gel coat has a high UV resistance, when constantly exposed it will begin to fade and become porous. This means you will need to keep up with maintenance such as polishing and waxing, otherwise dirt will stain the exterior of your boat and become hard to remove, along with the fading. As well as regular polishing, the centre core on a fibreglass boat can be one of its downfalls. Some, not all manufacturers can include either balsa or foam coring in the deck, structure and transom to improve strength. In some circumstances this means that if any water enters the centre core, it can rot from the inside out. You can read more about fibreglass boat transoms, a common area for water ingress here.

While there are plenty of ways to avoid this, for example sealing anything screwed through the fibreglass, when buying a second hand boat it can be hard to know if the previous owner has done so. The most common areas to check on a fibreglass boat are the transom and stringers, which if soft, will need to be cut out and replaced. This is quite an extensive job.

Aluminium Boats – History and Advantages

The first trace of aluminium boats date back to 1920s, although they didn’t really take off until the 1960s with brands like de Havilland and Quintrex. Physically very similar to steel, aluminium weighs approximately a third of steel – making it an ultra-lightweight option. As well as being lighter than steel, alloy is highly corrosion resistant – but not to the extent of fibreglass. Techniques for moulding alloy aren’t feasible in the boat building industry, which means aluminium boats are usually cut and welded into shape.

So what sort of advantages can you expect with alloy? Aluminium boats are usually lighter than fibreglass, and offer better fuel economy. They can also fit smaller horsepower engines on similar length boats. This also extends to the trailer you need for your boat. You can have a bigger boat with a single axle trailer because it’s lighter, and also have a less powerful tow car. Alloy is much harder to gouge. While it is quite common to find a fibreglass boat has gouges out of the gelcoat, this will be less evident on an alloy boat. Sure, if you hit hard enough you will likely dent the alloy.

Design Factors to Enhance Stability on a Aluminium Boat

Another notable innovation in aluminium boat design is the water ballast system, with brands like Bar Crusher leading the way. These boats have a unique hull section that fills with water at rest, significantly increasing stability by adding weight. This feature proves especially useful for fishing and activities that demand a stable platform. When the boat accelerates, it automatically expels the water, leveraging its lightweight construction for enhanced speed and fuel efficiency. This innovative approach offers a perfect blend of stability when stationary and lightweight performance when in motion, marking a significant improvement in aluminium boat functionality.

What are the downsides to alloy?

Firstly, paint usually covers the top half of an alloy boat. This is because without it, it will have a raw and rugged look. Some people feel the look of an alloy boat is less appealing. However today, manufacturers do a great job of making them look as good, or if not better. Paint also means that if you pull up alongside a wharf and scratch it, you won’t be able to buff it out.

Secondly, they also tend to suffer from peeling over a period of time when exposed to salt water and not washed properly. With a fibreglass boat, you can buff a new layer back. The only option for a painted boat is to respray it or touch it up. Lastly, alloy boats can fall victim to electrolysis. This happens when electricity passes through and causes your alloy surfaces to decompose. This can only happen when the ions are free to move (for example, when submerged in water). This can happen when a sinker or fishing hook drops between the cracks of the deck and into the bilge, and is submerged in saltwater as it rolls up the back.

It won’t happen overnight, but over the course of a few years you’ll likely find electrolysis. You can avoid this by being careful with fishing gear. For moored boats, installing the correct anodes with adequate bonding systems will also help. Many of the manufacturers are now designing aluminium boats with sealed decks and plastic bilges to ensure no metal objects can make their way to the bottom.

What about Plate Aluminium Boats?

Any alloy that’s 4mm thick or more is known as Plate alloy (or Plate Aluminium). This type is popular in the boating and fishing world at the moment. By using a thicker alloy, it can be designed with fewer support ribs. It is usually a more robust grade of alloy. However, design of the ribs design and other hull characteristics are limited because it cannot be pressed. Because it is thicker and heavier, it will also present a softer ride closer to that of fibreglass. There are many popular Australian boat brands emerging. For example, the Bar Crusher, which provides a high quality finish with the thicker plate-alloy material used. 

Comparing the Ease of Repair: Aluminium vs. Fibreglass

When it comes to maintaining and repairing boats, the material from which your boat is constructed plays a significant role in determining how easy and cost-effective those repairs will be. Both aluminium and fibreglass boats have their unique repair challenges and benefits. Understanding these can help boat owners make informed decisions when facing maintenance issues.

Aluminium Boat Repairs

Aluminium boats are prized for their durability and lack of rot, but when they do sustain damage, the repairs can be straightforward or complex, depending on the nature of the damage. Simple punctures or dents in aluminium boats can often be repaired with spot welding, a process that is relatively quick and cost-effective. However, when an aluminium boat is painted, matching the paint over repaired areas can be challenging. Entire sections might need to be repainted to ensure a uniform appearance, increasing the repair costs.

One of the more severe issues aluminium boats can face is electrolysis damage, which causes pitting and can weaken the structure of the boat. Repairing electrolysis damage is difficult, especially when it occurs in areas that are hard to access, making thorough repairs challenging and sometimes expensive.

Fibreglass Boat Repairs

Fibreglass boats, with their gelcoat finishes, can also be repaired, but the process is usually more labour-intensive than with aluminium. Damage and chips in the gelcoat can be relatively easy to fill and blend into the surrounding area, making the repair less noticeable. However, more significant damage requiring structural repairs, especially when involving a core material, can be costly and time-consuming. Large sections of the boat might need to be cut away to access and repair the damaged area, followed by a careful process of rebonding and finishing to restore the boat’s integrity and appearance.

Specialised Knowledge and DIY Repairs

Both types of repairs require specialised knowledge and skills. Aluminium boat repairs are typically performed by alloy welders, while fibreglass repairs are the domain of skilled shipwrights. Hiring a qualified tradesperson can make a significant difference in the quality and durability of the repair.

DIY repairs on either type of boat can be tempting for those looking to save money, but they often lead to mixed results. While minor cosmetic fixes might be within the reach of dedicated amateurs, significant or structural repairs are best left to professionals. Improperly executed repairs can lead to further damage over time, ultimately costing more to fix.

What Material Makes a Better Boat – Aluminium or Fibreglass?

Truth be told, there really is no “better” material, although people will have their own personal preferences. Boats that permanently live on water are more commonly made from fibreglass. However, an adequately maintained aluminium boat can be just as good. Charter operators often choose aluminium because of the fuel savings with day to day use. We are seeing a rise in the popularity of aluminium trailer boats. This is thanks to the sale of bigger and better alloy offshore boats. You must take the maintenance and lifespan of both needs into consideration when purchasing. Other important factors include ride quality if there’s a lot of offshore work.

Now you know the difference about aluminium and fibreglass boats, learn about the four major drive types here.

FAQs: Aluminium Boats vs Fibreglass Boats

What are the main differences in handling between aluminium and fibreglass boats?

Aluminium boats are generally lighter and more fuel-efficient, which can result in better performance and lower operational costs. They can also navigate shallower waters due to their lighter weight. Fibreglass boats, on the other hand, offer a smoother ride in choppy conditions due to their heavier construction, which makes them more stable in rough waters.

How does the maintenance of aluminium boats compare to fibreglass boats?

Aluminium boats require less maintenance when it comes to dealing with corrosion and osmosis, common issues in fibreglass boats. However, aluminium is susceptible to electrolysis if not properly cared for, which can cause corrosion. Fibreglass boats require regular polishing and waxing to maintain their gelcoat but are not prone to electrolysis.

Can fibreglass boats be customized as easily as aluminium boats?

Fibreglass boats offer more flexibility in design and customization because the material can be molded into various shapes. This allows for a wider range of boat designs and aesthetics. Aluminium boats, while durable and lighter, are limited to the shapes that can be achieved through welding and bending the metal.

What innovations enhance stability in fibreglass and aluminium boats?

For fibreglass boats, gyro stabilisers are an innovation that reduces rolling motion, enhancing stability and comfort in rough seas. In aluminium boats, the water ballast system is a notable innovation, providing stability when at rest by filling the hull with water, which is expelled when the boat accelerates, combining stability with lightweight performance.

What are the repair considerations for aluminium vs fibreglass boats?

Aluminium boat repairs may involve welding for punctures or dents, which can be straightforward. However, matching paint on repaired areas can be challenging. Fibreglass repairs, especially for structural damage, are more labour-intensive and involve working with the gelcoat and underlying materials, which can be costly and time-consuming.

Which boat material is better for long-term investment, aluminium or fibreglass?

The choice between aluminium and fibreglass depends on the owner’s priorities. Aluminium boats offer durability, ease of repair, and fuel efficiency, making them a good choice for those who prioritize these factors. Fibreglass boats, offering a smoother ride and potentially long lifespan with proper maintenance, may appeal to those prioritising comfort and aesthetics. Ultimately, both materials can be a good investment if the boat is well-maintained and suits the owner’s usage patterns.

About the Author

Aaron O’Donoghue is a qualified Marine Surveyor & Engineer with nearly two decades of experience in the industry. He is an experienced boater from Sydney who grew up on the waters of Sydney Harbour. He left school at 15 to complete an apprenticeship as a Marine Mechanic. In 2015, he founded BoatBuy, where he has inspected thousands of boats and is passionate about helping others enjoy their time on the water. He has a wealth of knowledge and experience in the field. Do you have a boating related question? Feel free to reach out to me via email here.

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