The Pros and Cons of an Aluminum Sailboat

OVNI aluminum sailboat at anchor in calm bay

There's a lot of legend surrounding aluminum sailboats. But not all of it is true. So what are the pros and cons of an aluminum hull? Let's find out.

What are the pros and cons of an aluminum sailboat? Aluminum sailboats need a lot of maintenance; especially when they are located in saltwater. They need to be painted quite often (every 2-3 years). They are expensive upfront. However, aluminum is a very strong and lightweight material. If done right, an aluminum sailboat can last forever, and can be very fast.

A lot of people think aluminum is a bad material for sailboats. But it's not all bad: aluminum also has its upsides. Most of the problems with this material are due to bad build quality. So the design is bad, not the material.

Pros and Cons

Some say aluminum is the worst material, others say it is the best. In general, sailors who have actual experience with aluminum hulls are very positive, even saying it is exponentially better than fiberglass and steel.

The quality of aluminum used is crucial. If it's not up to par, it will corrode VERY quickly. So you need a reputable boat builder that only uses marine-grade aluminum.

Aluminum has a bad rep. That's because there are a lot of cheap, badly-built aluminum boats on the market. Its a shame: aluminum can be the ultimate boat building material. But you need to pay attention to details when building or buying one. If neglected, aluminum can corrode away quickly.

Below I'll list all the pros and cons of this material.

Pros Cons
Good strength to weight ratio More complex anti-fouling paint
10 times stronger than fiberglass Electrolysis and galvanic corrosion
Lighter than all other materials You need an anode
Doesn't rust Fittings are more complex
Small boats are cheaper Large boats are more expensive
Scratches aren't a big issue Weak welds
Lower insurance rate Lots of low-quality alu boats
Lifetime hull warranty More noise from water on the hull
Won't crack - so no leaks Condensation (on old boats)
Small repairs are easy Large repairs are difficult
Material is easy to modify Wiring needs to be done carefully

Pros

Good strength to weight ratio - Aluminum is very lightweight and very strong. One of the most important factors that determine your speed is the displacement of the hull - aka the weight. A lighter boat is faster. So a well-built aluminum boat is faster, and also stronger than fiberglass.

10 times stronger than fiberglass - Don't pin me on that number, but aluminum is stronger than fiberglass. Fiberglass tends to crack when under stress. In a collision, aluminum will probably just dent. A dent is not that big a deal. A crack is - you will eventually sink.

Lighter than all other materials - Aluminum is lighter than steel, wood, and fiberglass. While steel is as strong as aluminum, it's very, very heavy, so that's not great. Wood is heavy as well, and prone to rot - so aluminum wins. Even the lightweight fiberglass is more heavy than aluminum, while it isn't as strong.

Doesn't rust - Aluminum doesn't rust, so, as long as it's above the waterline, you don't need any paint to protect your deck. So while you need to be careful in the bilge, and everything that comes into contact with (salt)water, the rest will be absolutely fine without much attention.

Small boats are cheaper - Custom aluminum boats are cheap to build because aluminum doesn't require a mold like with fiberglass. The builder simply cuts the sheets to size and welds the hull together. It's an easy and fast material to work with. The material itself is also cheap. But it also means that larger boats are more expensive, because the price of an aluminum sailboat mostly consists of labor costs.

Scratches aren't a big issue - Because aluminum doesn't rust, scratches aren't a big issue. If you scratch your top paint while docking, it will practically heal itself, thanks to oxidation.

Lower insurance rate - Insurance companies offer lower rates for aluminum sailboats because they tend to get a lot fewer claims from them.

Lifetime hull warranty - Because a well-build aluminum sailboat hull lasts a lifetime, some manufacturers give you a lifetime warranty on it.

Won't crack- If you hit a rock, your hull won't split open like a fiberglass one. You'll just be able to carry on, which can be a game changer. This also goes for the deck, which means you'll never have leaks -period - if you maintain your boat properly. This is probably the greatest advantage of aluminum over other materials.

Small repairs are easy - Small dents and cracks are easily repaired: they can simply be welded. However, welding aluminum is a bit more complicated than steel, and it requires a lot of skill to create strong welds. It's not as easy as fiberglass, which you can simply patch up using epoxy.

Material is easy to modify - You can literally cut aluminum with a regular sheet cutter. It's a very easy material to modify, and as long as you make sure any attachment points are properly treated for corrosion, you can very easily change things around with just regular tools. It becomes more difficult if you need to weld stuff, then get help from a professional. Especially if it's structural stuff.

Cons

More complex anti-fouling paint - You will probably have to paint the hull below the waterline more often than you're used to. Also, you need bottom paint without copper oxide. Due to the oxidation of aluminum, any kind of deck paint you apply will form bubbles after a couple of years. Some people don't paint the deck at all, which is perfectly fine.

Electrolysis and galvanic corrosion - Aluminum is prone to electrolysis and galvanic corrosion. Electrolysis is the chemical reaction of metals with saltwater. When metal comes into contact with saltwater, an electrical current runs through the metals: it turns your boat into a battery, basically. You need to place anodes on your boat to protect your hull. I'll explain electrolysis in detail below.

You need an anode - Sacrificial anodes protect from galvanic corrosion. If you have an aluminum boat that's in saltwater permanently, you definitely need anodes to protect it. A sacrificial anode is basically a piece of metal that's more anode than aluminum, causing it to corrode before the aluminum starts corroding.

Fittings are more complex - Due to electrolysis, adding fittings is more complex. There's really no error margin here. Wherever your alu hull meets another piece of metal, it needs to be thoroughly painted, fitted, and maintained. Otherwise, corrosion will form pretty quickly. A boat without proper isolation between the aluminum and other metals will weather away pretty quickly.

Hull repair is expensive - Aluminum is more expensive than steel, and finding a skilled aluminum welder can be difficult. So it can really cost you if you need to repair the hull. However, a good welder will be quick, which will save you in labor cost.

Large boats are more expensive - Since aluminum boats are welded together instead of casted, the labor cost increases exponentially with length. Quality, large aluminum yachts are way more expensive than fiberglass yachts. But they are a lot cheaper in the long run since they are made of a stronger material.

Weak welds - Welds on aluminum are prone to contamination. This simply means that they're more likely to contain gas bubbles. Which of course makes them weak. This isn't a problem for the top aluminum welders. Good boat builders use very skilled welders. But cheap aluminum boats are hastily put together, and the welds can be a real problem. So make sure to only buy good quality build when you're looking for aluminum.

Lots of low-quality alu boats - There are a lot of low-quality alu boats out there. Especially US build boats have a bad rep. Because aluminum is so cheap to build, lot's of cheap alu boats are being built. And that means that the overall build quality is lower. So the welds aren't as strong, the hull isn't well-constructed or fitted. If you're buying an aluminum boat, you really need to watch out for these budget ones.

More noise from water on the hull - Water crashing into aluminum makes a lot more sound than water crashing into fiberglass. Nothing disastrous, but important to know in advance.

Condensation - Old aluminum hulls (and steel ones as well) suffer from more condensation than fiberglass. However, this is only the case if the boat is not well insulated. Modern aluminum hulls are properly insulated, so condensation shouldn't be a problem. So if you own an old boat, be prepared for a damp interior every now and then.

Large repairs are difficult - You'll need a professional welder for doing large hull repairs. Not many welders are proficient in aluminum welding, so be aware that this might cost you a pretty dollar.

Wiring needs to be done carefully - Because of the risk of electrolysis and galvanic corrosion, you need to be extra careful with wiring and electrical systems. You don't want any electrical current running to the hull, and you really don't want copper wire clippings in your bilge. It will create small holes or pockets in the hull, which may even sink you when unnoticed for too long.

Why Does Aluminum Get Such a Bad Rep?

Aluminum is cheap to build with, so it's used a lot for budget boats. As a result, most aluminum boats are hastily put together, so of bad quality. The thing with aluminum is that if it's used in the wrong way, it will become less and less very rapidly.

A lot of cheap (US) boats are welded badly, or just spot welded, making the hull weaker. So these boats are not very suitable for open seas, as they can't take the current.

Another reason is that aluminum is a popular material for self-builders. Believe it or not, but sometimes self-builders don't deliver the quality needed for a boat that will last you a lifetime.

But it's not really fair because a hull that's welded properly is very strong and will last you a lifetime.

Overall, if you stick to reputable boat builders, and make sure to get advice from a boat surveyor that's specialized in alu, you'll be fine. It may even be the finest boat you've sailed.

Aluminum Hulls From Other Countries

Especially aluminum hulls from France, The Netherlands, Australia, and South Africa are of better build quality. United States manufacturers have produced a lot of aluminum hulls of bad quality. But these are mostly inland, flat bottom boats, pontoon boats, power boats, and so on. There are actually very good US and Canadian sailboat builders as well.

Some Considerations on Aluminum Sailboat Maintance

When you have an aluminum hull, your number one concerns are electrolysis and galvanic corrosion.

Aluminum is anode to almost all other metals, except for zinc and magnesium. That means that when it's in contact with other metals, aluminum will corrode away. This is called galvanic corrosion.

So you will have to install a sacrificial anode. You will also have to replace this quite often, (on average every couple of years, but in some conditions every couple of months, or even weeks).

I recommend to use OEM anodes. If you don't want to, this is the kit you want (click to check current price on Amazon).

Make sure everyone who steps onboard puts all of their cash change in a jar. You don't want any metals in your hull. A copper coin that's left unseen can ultimately sink you.

If you add an electric current to this process, it speeds up the corrosion. This is called electrolytic corrosion. This can happen if you have a short in your electrical wiring. Aluminum, in particular, can corrode away very quickly this way. So you need to make sure your wiring is properly insulated. You don't want any electrical current running through your hull!

In general, you need to be extra careful with electrical systems and wiring on an aluminum boat. You also need to pay attention to the marina. If you dock your boat besides steel boats, this can increase the galvanic corrosion. If you add dock power to the mix, your baby starts devouring anodes like it's chicken noodles.

Aluminum also needs a lot of attention paint wise. All fittings and the bottom needs to be painted more often than fiberglass. It's important to keep up with corrosion; once saltwater comes between your fittings, there's no stopping it.

But the horror material some people claim aluminum to be is just not true. There are experienced sailors out there with tens of thousands of miles on there aluminum hull, that still use the original paint. They only repaint the bottom every couple of years.

Reputable Aluminum Hull Builders

So where to start? Here are some reputable aluminum sailboat builders:

  • Kanter - One of the best North-American aluminum builders. Canadian. Very good-looking boats
  • Alubat - smart designs and well build, from France
  • Ovni - well-known range from Alubat
  • Garcia Yachts - France
  • Futuna Yachts - Also French
  • Boreal - French yachts

What is the best material for a boat? The best material for a boat depends on the water and sailing conditions, but generally aluminum is the ultimate boat building material. It has a very good strength-to-weight ratio, which is important for a boat. It does, however, require proper maintenance. Especially in saltwater, it needs quite some maintenance, due to electrolysis.

Is aluminum stronger than fiberglass? Aluminum is up to 10 times stronger than fiberglass. It's one of the strongest hull materials if properly built. Fiberglass will crack on impact, which creates leaks. Aluminum doesn't crack as easily and is famous for never leaking. Aluminum is, however, prone to galvanic corrosion, which fiberglass is not.

What's the difference between galvanic corrosion and electrolysis? Electrolysis is an oxidation process in which metals corrode when submerged into an electrolyte. It leads to galvanic corrosion. The most anode metal will eventually corrode. When an electrical current is added to the electrolyte, it speeds up the corrosion process; we call this electrolytic corrosion.

Photo courtesy of Richard Tanguy - CC BY-ND 2.0

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