Aluminum Hull Sailboats: Advantages and Caracteristics of aluminum boat hulls [Episode 1/5]
Technical focus with Olivier Racoupeau
5 videos to understand the architectural choices behind Allures sailboats
For several decades now, aluminium has established itself as the ideal material for building bluewater cruising yachts. Its strength, and therefore the safety it provides, is a major advantage, and so are its repairability and recyclability. Let’s take a closer look at the benefits of aluminium hulls, the very reasons that led Allures Yachting and Olivier Racoupeau to adopt this choice from the start.
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Aluminum hull sailboat: safety first
The primary reason for choosing an aluminum sailing yacht for bluewater cruising is undoubtedly safety. Long passages, poorly charted areas, unexpected encounters, potentially harsh conditions, and navigating in ice all demand exceptional hull strength. The robustness of an aluminium hull provides genuine reassurance to aspiring circumnavigators.
Impact Resistance and Reinforced Protection
A major advantage of an aluminum hull lies in its ability to withstand impact. Aluminium's greater elasticity allows the material to deform far more before breaking. GRP (Glass-Reinforced Plastic) composite, by contrast, is more rigid and therefore less forgiving: it tears or breaks more abruptly on impact.
Enhanced Safety when Facing the Unexpected
An aluminium hull sailboat therefore offers greater safety and more peace of mind when faced with the unexpected at sea. The recent example of orca interactions in the North Atlantic is particularly telling: the repeated impacts on the rudder can place heavy loads on the hull. Composite structures may absorb these shocks poorly and can fracture or delaminate, leading to water ingress. On an Allures yacht, the rudder stock tube, through which the rudder shaft passes, is welded to the aluminium hull. This virtually eliminates the risk of hull damage in this area during orca interactions.
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Aluminium Thickness in Yacht Building
Aluminium alloys are classified into series according to their composition, their characteristics, and therefore their recommended uses:
- 1000 series aluminium, over 99 percent pure, is mainly used for electronics and packaging.
- The2000 series (aluminum and copper alloy) is widely used in aerospace.
- 5000 series (aluminium-manganese) and 6000 series (aluminium-silicon-manganese) are used in marine applications thanks to their high mechanical strength, excellent weldability, and outstanding corrosion resistance, which is essential in a marine environment.
At Allures Yachting, the structural elements of our aluminium monohulls, including frames, stringers, bottom structures, and reinforcements, are built using 6005, 6060, and 6082 alloys. These are chosen for their rigidity, particularly when used for extruded profiles or machined parts within the yacht structure.
For the hull plating, the outer skin of the hull, we use 5000 series alloys. They offer high ductility, which is necessary for shaping a round bilge hull, while also providing very high mechanical strength, even after welding.
Understanding the Mechanical Strength of Aluminium
Mechanical strength is measured in megapascals (MPa). 1 MPa equals the pressure of a 10 kilogram force applied to 1 square centimetre. 250 MPa equals the pressure of 250 tonnes on 1 square metre.
However, a material's mechanical strength is not just a single number, but a set of behaviours observed under force. Among these, two key reference points are: Yield strength (Re): the limit up to which the material returns to its original shape, beyond this, permanent deformation occurs. Tensile strength or Ultimate Tensile Strength (Rm): the maximum load the material can endure before breaking, it's ultimate load.
Comparing the Mechanical Strength of Aluminium and Composite
Highly resistant, an aluminium hull is above all ductile: it dents, bends, absorbs energy, and provides visible warning signs (such as buckling).
Composite, on the other hand, reaches a sharper point of failure, with cracking or delamination and local collapse of the sandwich structure. Energy absorption depends on skin and core thickness. GRP is more rigid and therefore less flexible, tearing or breaking more abruptly on impact.
Mechanical strength values
For a hull, however, strength is not assessed by MPa alone but by the ability of a complete plate to absorb impact, a capacity influenced by thickness, shape (curvature), and internal stiffening (frames, beams, floors).
Thicker plating resists puncture better, dissipates more energy, and bends rather than tears. Mechanical loads are distributed across both the plating and the structure. Curved, stiffened hulls further multiply resistance. One of the advantages of an aluminium hull is its ability to deform rather than crack, a vital safety feature in bluewater cruising.
On Allures aluminum monohulls, depending on the model, plating thicknesses are: 8-10 mm for the bottom and immersed sections, 10-12 mm for internal reinforcements, 5-6 mm for the topsides.
With a tensile strength exceeding 300 MPa, it would take more than 300 tonnes per square metre to rupture the aluminium hull, roughly the weight of four Eiffel Towers!
A Well-Designed, Well-Built Aluminium Hull Remains Light
Aluminium has a density of 2.7 g/cm3, far lower than steel (7.85) and only slightly higher than composite (1.5-2). Yet, for an equivalent structural design, aluminium hulls can be lighter than conventional GRP hulls because they do not require very thick skins or heavy reinforcements to achieve excellent strength. And this is even more true for yachts over 40 feet.
Allures sailboats combine a robust aluminium hull with a strong, lightweight composite deck. The 14 and 16 metre bluewater models from Allures Yachting therefore match the weight of similarly sized composite yachts. With hulls designed by renowned naval architect Olivier Racoupeau, Allures aluminium monohulls also deliver exceptional performance.
Discover the architect's vision in this video:
Recyclability of an Aluminium Sailboat
Beyond its strength, aluminium is a durable and recyclable material. The aluminium used by Allures Yachting is made from around 80% recycled aluminium, itself fully recyclable. When properly maintained, an aluminium hull sailboat retains its mechanical properties for decades and offers outstanding corrosion resistance, a significant advantage for environmentally conscious sailors.
Repairability anywhere in the world
Another major advantage of aluminium boat hulls is their ease of repair. Aluminium can be repaired almost anywhere, even in remote regions, without sophisticated equipment.
Any competent welder can carry out at least a temporary repair without being a marine specialist. And welders can be found all over the world. Simple, watertight aluminium patches can be welded on anywhere, keeping the voyage going.
Repairing a composite hull, by contrast, requires genuine specialists, resins, chemical catalysts, and very precise temperature and humidity conditions.
Aluminum Hull: Peace of Mind at Sea
Choosing an aluminum hull sailboat means opting for a safe, durable travelling companion, ready to face any horizon. Thanks to its remarkable impact resistance, its ability to deform without breaking, and its repairability all around the world, aluminium remains the most reliable material for sailing far and for many years.
Light, robust, recyclable, and built to last for decades, an aluminium hull boat offers unmatched peace of mind to demanding sailors.
This philosophy, centred on safety and performance, has guided Allures Yachting from the very beginning: to design aluminium sailboats capable of carrying their crews with complete confidence to even the most ambitious destinations.
Discover episode 2: twin rudders centerboarder essential technical choices for blue water cruising
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