Lightweight aluminium alloys – the eco-friendly answer to fibreglass

By Godfrey Zwygart

Fibreglass, or FRP, is the preferred construction material for the majority of production yacht builders around the world. But there is a price to pay for these continuous FRP production runs.

FRP only has a practical lifespan of 50 to 60 years, so Western countries are now facing a serious problem when it comes to scrapping boats. As with most plastic products, recycling FRP is difficult. Recent research has focused on reducing FRP to small particles and then using those particles in construction materials or road tarmac. Yet, this is a costly process.

Fibreglass hulls now lie abandoned in fields around Europe and the US, where they will remain a polluting material for hundreds of years. With the growing popularity of yachting in Asia, this problem can only deepen.

Ten years ago, France started promoting responsible management of decaying boats through the establishment of 40 specialised recycling centres. French shipbuilders are now charged a fee for each yacht produced.

Could new, lightweight aluminium alloys could be the answer? Larger superyachts are typically built in steel for the hull and aluminium for the superstructure. Both are 100% recyclable, and such yachts can also be refitted after many years of intensive use.

A growing number of yacht shipyards are favouring all-aluminium construction, and there are good reasons for this. First, aluminium has improved a lot over the last decades. Gone are the days of uncontrollable corrosion and falling coatings. New generation aluminiums (T6 or 5083 grade, or even better, 5383 Sealium) do not rust or corrode, even after years at sea.

 

 

The key advantage is weight: aluminium has one-third the density of steel. The reduced weight means smaller engine requirements, lower fuel consumption, longer cruise ranges and less pollution. Coupled with modern design and propulsion systems, many aluminium yachts have a range of well over 3,000 nautical miles.

The key advantage is weight: aluminium has one-third the density of steel.

Smaller engines also mean more space for accommodation. Yachts over 24 metres need to comply with the new TIER III emissions regulations, and they will have more room to install SCR (selective catalytic reduction) systems. A cruising range of 3,000 to 5,000 miles means larger yachts can wait to refuel in a proper harbour offering top-quality fuel, which boats equipped with SCR systems require.

Aluminium is also basically maintenance-free, resulting in significant cost savings. Another plus is that the construction involves fewer processes with chemicals and shipyard contaminants.

There are no limits on size. Some shipyards build very small boats, such as tenders, in aluminium. It is especially popular with working boats, thanks to the lower maintenance.

Hundred-plus foot yachts motoring at 40 knots are an intolerable waste of energy – if you want a surge of adrenaline, jump into a fast tender.

There are drawbacks, of course. Aluminium can be damaged with acids that may be stored on board. But the main downside is the price. Aluminium is much more expensive than steel or FRP – Sealium even more so. Sealium is 15% stronger than regular aluminium and 20% lighter, but also 25% more expensive. Aluminium is higher in density than FRP, but Sealium is about the same.

Cost is an issue. While owners of superyachts do not mind spending the extra money to get the best product, Sealium is rarely used in production boats.

Another difficulty is in production. Aluminium welding, as well as surface finishing and coating, are very demanding processes that require a highly qualified workforce. Production cannot be as quick as with FRP, but FRP production does not yet price in environmental costs.

New generation long-range vessels that combine smart design, new engineering and low environmental impact seem to be popular with intelligent, savvy young buyers.

 

 

Hundred-plus foot yachts motoring at 40 knots are an intolerable waste of energy – if you want a surge of adrenaline, jump into a fast tender. Today’s trend in large yacht cruising seems to be gradually shifting, as owners look for remote locations and idyllic beaches away from crowds and photographers. They also increasingly search for unique destinations, generating a broader market for expedition boats.

There are quite a few shipyards worldwide using aluminium now. For good specimens of modern yachts that can cross oceans in style and maximum comfort, look no further than Dynamiq in Italy, whose aluminium yachts compare on price with similar-sized FRP ones (they post their prices online). There is also Silverfast in Australia or Jin Long in China. Others will surely follow.

About the Author

Godfrey Zwygart is marina director at Sanya Serenity Marina, which has hosted the former Volvo Ocean Race and Clipper Race since his arrival in 2010. Trained in the French Navy, Zwygart has spent over 30 years in the marine industry, including as a superyacht captain and chief engineer. He speaks fluent Mandarin and is a recognised yachting authority on China. In October 2019, Zwygart was a recipient of the Central Government’s Friendship Award.