When new customers approach a shipyard with their dream of having a custom yacht built for them, one of the first decisions they must make is the choice of the hull material. The most common materials are wood, fiberglass or composite, steel and aluminum. 

While the crew at Naval Yachts does refit and custom work on yachts built of all these materials, when it comes to building custom yachts, they will always recommend to their customers the advantages of building an all-aluminum yacht.

 

Why metal over fiberglass?

Today, with all the benefits of CAD drawing, computer modeling and CNC – Computer Numerical Control - machines, building custom metal superyachts is becoming the standard. Computer-driven laser or waterjet cutters turn sheets of metal into a giant jigsaw puzzle for boat builders to weld into beautiful yachts. Building one-off yachts in metal is generally less costly than building in fiberglass as there is no need to build a mold. This also makes aluminum boats more customizable. In addition, fiberglass hulls that contain petroleum-based resins can catch fire and burn. Finally, the strength of metal hulls when they come into contact with reefs, rocks, or submerged shipping containers is superior to fiberglass which cracks and fractures on impact.

 

Why aluminum over steel?

Both steel and aluminum are excellent materials for shipbuilding, and each serves a different sort of vision. Steel might be the preferred material for a tugboat or heavy trawler, while aluminum works better for high performance superyachts, sailboats, and multihulls. Here are some reasons why.

 

Cost

There is no getting around the fact that aluminum is much more expensive than steel. Though the prices of these metals do fluctuate, it is fair to say that in terms of the cost of the material, the price of an aluminum hull will be about twice the price of a steel hull. These days the price of aluminum is much more than twice the price of steel, but there are many factors other than the price of the metal that come into play.

First, because aluminum weighs less than steel, fewer tons of aluminum are necessary to build a hull of the same strength. The lighter weight also translates into more labor saving in that a 3/16 inch steel plate weighs around 3,000 pounds while a roughly equal ¼ inch aluminum plate weighs about 1400 pounds, requiring less man power and heavy gear. Aluminum is easier to to bend and faster to work with due to it being easier to cut (can use common carpentry tools). Welding aluminum is easier than welding steel resulting in approximately half the man hours in welding an aluminum hull. This labor savings does help offset the initial higher price of the material. 

As you will see in these other categories, the cost savings from using aluminum will continue to accrue.

 

Weight

Aluminum is lighter than steel for the same strength. To get that same strength, aluminum plate needs to be 1.5 times thicker than steel plate. However, aluminum weighs significantly less than steel. This means that steel hulls generally weigh about 30% more than aluminum when built to the same strength standard. In other words, you can build an aluminum yacht that is stronger than a steel yacht, but which weighs less.

Stability is a very important factor in building a safe and comfortable yacht. Because steel hulls are heavier, this means they will have a higher center of gravity, and this impacts their stability resulting in top-heavy yachts. It is for this reason that many steel boat builders today build the yacht’s superstructure in aluminum. However, even with just the hull built out of steel, builders must either add lead in the keel and/or increase draft to achieve a desirable level of stability.

This greater weight in steel-hulled yachts means that to get the same range under power as an aluminum hull, the steel yacht will need a bigger engine, drive train, more tankage, and more diesel fuel. All of which add to the cost.

With an all-aluminum and therefore lighter yacht, the owner and designer will have the freedom to allow more weight for interior furniture or to simply take the greater efficiency in the fuel burn.

 

Corrosion

Steel rusts if not painted or treated. Unpainted aluminum forms a tough outer coating of aluminum oxide that protects the metal. There is no need to do anything to it. So, another significant savings in building an aluminum boat is due to the fact that marine aluminum alloys are very resistant to corrosion. Unlike steel hulls, there is no need to sandblast or paint the interior of an aluminum hull, and this labor and material savings is significant. Actually, many yacht owners today are choosing not to paint the exterior of their vessels above the waterline either. This can be a huge savings, one that continues to pay for yacht owners who no longer need to maintain a fancy exterior paint job.

Both steel and aluminum boats need to be protected by zinc anodes and builders need to pay careful attention to isolating electrical current from the hull. But because aluminum is more vulnerable (less noble) than steel to galvanic corrosion from electrolysis, not doing this well can have more serious consequences for aluminum hulls. However, through the use of isolation transformers and great attention to detail in the yacht’s wiring, electrolysis need not be an issue on a well-built aluminum boat.

 

Good Resale Value

The fact that aluminum is a more expensive and premium commodity than steel works to the owner’s benefit when it comes to the resale market. Aluminum boats are do not wear out, rust, or deteriorate over time.

All in all, when it comes to choosing the material for the custom yacht of your dreams, the choice is clear. Aluminum hulls are the superior choice.