Aluminium Boats vs Fibreglass Boats

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

Fibreglass Boats

The invention of fibreglass, also known as GRP (Glass Reinforced Plastic), dates back to the 1940s. Like 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”, which is 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. Fibreglass can be moulded into any shape you can think of – where an alloy hull is constrained to how you can bend and weld the metal. 

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.

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 that 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, one of the downfalls of fibreglass designed boats are that they usually have a centre core, typically balsa or foam, to improve strength – meaning that if any water enters the centre core, it will tend to rot from the inside out. 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 which is quite an extensive job.

Aluminium Boats

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 weights approximately a third of steel – making it an ultra-lightweight option. On top of being lighter, alloy is highly corrosion resistant when compared to steel, but not to the extent of fibreglass. Because techniques for moulding steel aren’t feasible in the boat building industry – aluminium boats need to be cut and welded.

So what sort of advantages can you expect with alloy? Aluminium boats are usually lighter than fibreglass, meaning you will get better fuel economy and can fit smaller horsepower engines on similar length boats. This also extends to the trailer you need for your boat – meaning 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, and whilst it is quite common to find a fibreglass boat has gouges out of the gelcoat where the owner has missed the trailer, on an alloy boat this will be less evident. Sure, if you hit hard enough you will likely dent the alloy.

What are the downsides to alloy?

Firstly, the top half of an alloy boat is usually painted, otherwise it will have a raw and rugged look. Some people feel the look of an alloy boat is less appealing, although today manufacturers have done a great job of making them look as good, or if not better. The fact that they’re painted also means if you pull up along side a wharf and scratch the paint, you’re not going to have the option to buff it out.

Secondly, they also tend to suffer from paint peeling over a period of time when exposed to salt water if not washed properly. Where as 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. Electrolysis is essentially when your alloy surfaces are decomposed if electricity is passed through. This can only happen when the ions are free to move (for example, when submerged in water). A common example of this happening is 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 over night, but over the course of a few years you’ll likely find electrolysis. This can be avoided by being carful with fishing gear, and for moored boats – installing the correct anodes with adequate bonding systems. 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?

Plate alloy (or Plate Aluminium), usually referred to any alloy that’s 4mm thick and up – is popular in the boating and fishing world at the moment. By using a thicker alloy, it can be designed with fewer support ribs, and usually is a more robust grade of alloy. The downfall is that it cannot be pressed so it will limit design of ribs and other hull characteristics, but because it is thicker and heavier usually presents a softer ride closer to that of fibreglass. There are many popular Australian boat brands emerging such as Bar Crusher, which provide a high quality finish with the thicker plate-alloy material used. 

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. Fibreglass is more common for boats that live permanently in the water, but an adequately maintained aluminium boat can be just as good – and charter operators often choose aluminium because of the fuel savings with day to day use. Aluminium trailer boats are becoming more popular than fibreglass, with bigger and better alloy offshore boats being sold. The maintenance and lifespan of both needs to be taken into consideration when purchasing, and factors that the purchaser may deem important, like ride quality if there’s a lot of offshore work.

Are alloy of fibreglass boats better?

Truth be told, both have their advantages and disadvantages. Alloy is lighter, but cannot be manipulated to form the same shapes and hull designs as fibreglass. Both require specific maintenance, and it really comes down to the individuals desired use.

Explore More

articles | January 12, 2021

Do you need a Boat Survey for Insurance?

Do you need a boat survey for insurance? To answer that question, we first need to ascertain the age and use of the boat. Each insurance company will set their own guidelines so it's best to ask them directly, but as the industry standard, it is common practice for an...
Don from BoatBuy

articles | November 12, 2020

What is the Boat Survey Process?

If you’ve never bought a boat before, you’re probably curious to know the normal procedure. Do you need to put down a deposit? Do we need to slip the boat? Who pays for this? Do I need a survey? If you’re new to boating, it can seem daunting purchasing a...
Riviera M360 in Port Hacking

articles | September 23, 2020

I Bet You’ve Made One Of These Boating Mistakes Before!

Getting out on the water on a new boat is exciting, but it can also be nerve wracking. With a long list of things to remember, it's easy to make little boating mistakes with costly consequences.  Here are seven common boating mistakes I've seen, including some I've done myself. Boating...