Aluminium boat hulls VS steel boat hulls
One of the primary questions naval architects and yacht designers will ask a potential owner when considering a new build yacht is what metal should the hull be made from?
Various metals can be used to build a boat hull but the most common metals used are either aluminium or steel. Each metal has their pros and cons and with the help of leading marine metal work companies Yachting Pages has created this complete guide to aluminium boat hulls vs. steel boat hulls.
Aluminium is light, strong, has good corrosion resistance and is flexible to work with. From a shipyards point of view, aluminium is 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”.
In summary what this means for shipyards and metal fabricators is aluminium is quicker to fabricate and weld than steel resulting in labour 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 hull does not need protective paint
A major advantage of aluminium hulls is that it does not need painting except below the waterline or where anything is 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 benefit. Aluminium weighs about 30% less than an equivalent steel hull. Reduced weight means easier to travel through water, which means faster and more fuel-efficient.
Boat hull resale value
An appealing fact a superyacht owner may also find interesting is that an aluminium boat will have a much higher re-sale value than a steel boat.
Disadvantages of aluminium boat hulls compared to steel hulls
Cost of aluminium boat hull
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. The date this article was written the cost of aluminium is $1,480 dollars per tonne whereas steel is $50 dollars per tonne (source Quandl.com).
Aluminium is anodic to all other commonly used metals except zinc and magnesium. Simply put unless protected the aluminium will start to corrode. Furthermore 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 steel less prone to electrolysis and allowing a steel hull to use regular copper bottom antifoul paint.
Yacht and superyacht owners may find this point of interest. Aluminium may reduce comfort. Lightweight hulls can result in a noisy uncomfortable ride due mainly to the extreme lightness of aluminium, which in some hulls would result in a lot of motion. Boats may be better if built in steel provided that the design has adequate displacement and stability to carry the added structural weight. This is because of the greater distribution of weight.
Steel hulls have better abrasion resistance
Of course, one big advantage of steel is steel is more rugged than aluminium, being tougher and having much superior abrasion resistance when compared to any other boat building material, even aluminium. 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
One more thing to consider it is widely agreed that most places you will find someone with the skills and equipment to perform repairs of steel structures. A yacht may find it more difficult to perform repairs of aluminium in remote places.
Which is better steel boat hulls or aluminium boat hulls?
This question has so many variables as it completely depends on the purpose of why the boat is or was first built. 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 is where steel’s abrasive resistance will be needed.
Mike Adams from K&M Maritime sums this all up beautifully, “Both 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.”