ALUMINIUM BOAT HULLS VS STEEL BOAT HULLS
Last updated: 19/10/2018
One of the primary questions that naval architects and yacht designers will likely ask a potential owner when considering a new build yacht is what metal the hull should be made from.
Various metals can be used to build a boat hull, but the most common are usually aluminium and steel. Each has their pros and cons, and with the help of leading marine metal workers, Yachting Pages has created this complete guide to outline the advantages of aluminium boat hulls compared to steel boat hulls.
Advantages of aluminium boat hulls over steel boat hulls
There are several advantages of working with aluminium in superyacht construction projects. Not only is it light and strong, but it also has increased corrosion resistance and is flexible to work with. From a shipyard's point of view, it's therefore a great material to use; it can be cut with power tools, dressed with a router, filed and shaped easily.
Mike Schooley from Ruben Donaque, a marine metal repair and fabrication business agreed, he said, “Aluminium, is light and ‘clean’ to work with”. This means that aluminium is quicker to fabricate and weld than steel, resulting in labour and cost savings.
Schooley went on to say, “Some yacht metal fabricators tend to be afraid of welding aluminium, but if the fabricator is Lloyd's certified and has the adequate machinery it should not be a daunting task.”
Aluminium hulls do not need protective paint
A major advantage of aluminium hulls is that they do not necessarily need painting, except below the waterline or where fixtures and fittings are touching the hull surface. Bare aluminium forms an aluminium oxide coating on its surface that creates a barrier and prevents the metal from corroding. This results in a huge cost saving.
Aluminium boat hulls weigh about 30% less than steel hulls
One of the biggest benefits of building a yacht out of aluminium is the performance output: Aluminium weighs about 30% less than an equivalent steel hull. Reduced weight means it's easier for the boat to travel through water, which makes it faster and more fuel efficient.
Aluminium hulls have an increased resale value
An appealing factor is that an aluminium boat will often have a much higher resale value than a steel boat.
Disadvantages of aluminium boat hulls compared to steel hulls
As flexible as it is, there are also several disadvantages of using aluminium in superyacht construction.
Aluminium boat hulls cost more
The biggest disadvantage of using aluminium for a boat hull is the cost. Tonne for tonne, the cost of aluminium is much greater than steel. According to Quandl.com at the time of writing, the cost of aluminium is $1,480 dollars per tonne, whereas steel is a much more reasonable $50 dollars per tonne.
Aluminium requires special corrosion care
Although it does not necessarily require complete painting, aluminium is anodic to all other commonly used metals (except zinc and magnesium). Simply put, unless protected, it will start to corrode. This means aluminium hulls require special bottom paint, since the copper in most antifouling bottom paints will react with the aluminium and corrode it.
Steel is more 'noble' than aluminium, making it less prone to electrolysis and allowing a steel hull to use regular copper bottom antifoul paint. Read more in our guide on yacht antifouling paint here.
Aluminium creates reduced comfort on board
Superyacht owners may find the reduced comfort of aluminium hulls a concern while travelling the globe: Aluminium hulls can result in a noisy uncomfortable ride, due mainly to the featherlight nature of aluminium, which in some hulls would result in a lot of motion. Some owners may therefore prefer that their boats are built in steel, provided that the design has adequate displacement and stability to carry the added structural weight. This results in greater distribution of weight and a more comfortable ride.
Why choose steel for marine construction?
Steel hulls have better abrasion resistance
One big advantage of using steel in boat building and construction is that it's much more rugged than aluminium, being tougher and having much superior abrasion resistance when compared to any other boat building material.
Abrasion resistance is the ability of a material to withstand actions such as rubbing, scraping, or erosion that tends progressively to remove material from its surface. Such ability helps to maintain the material's original appearance and structure.
Steel is a material that is more widely used
It's widely known that, in most places, there are more materials and equipped metal workers to perform repairs and installions in steel over aluminium. A owner may find it much more difficult to perform repairs of aluminium hulls in remote places.
Which is better, steel boat hulls or aluminium boat hulls?
This is a difficult question to answer definitivly, as the choice of aluminium vs. steel completely depends on the design of the boat and what it is largely used for. For example, a racing boat built for speed makes aluminium the better choice because of the weight saving and performance increase. An explorer yacht on the other hand will require a hull that is much more durable, and that's where steel’s abrasive resistance will be needed.
Mike Adams from K&M Maritime sums this all up beautifully when he says, “Both steel and aluminium hulls have their own advantages and merits, whether it be yield and tensile strengths and lightness in the case of aluminium. With proper corrosion protection, when applied correctly, means these materials have many years durability, whatever the hull is built from.”
The realisation that a superyacht dream is soon set to become reality is an exciting time for any new or existing yacht owner, as he or she works to find a design and build team who can understand and interpret their vision. Whether they opt for a steel or aluminium hull, it's important they hire a naval architect or yacht designer who understands their vision and goals. Read this guide on working harmoniously with your yacht designer to find out more.