Spotting Aluminum Boats: What To Look For

Aluminum boats are a popular choice for boating enthusiasts due to their durability, lightweight build, and versatility. They are easy to manoeuvre and can be used in various water conditions, from rivers and lakes to saltwater bays and harbours. One of the key advantages of aluminum boats is their customizability in terms of size and shape, making them suitable for different activities such as fishing, tubing, and wakeboarding. Additionally, aluminum boats are known for their high resale value and long lifespan, with proper maintenance. When identifying an aluminum boat, one can look for specific grades, such as 5086 or 5083, which are commonly used in boat hulls and offer excellent corrosion resistance.

Aluminium boats are lightweight and strong

Aluminium boats are highly sought-after in the marine industry due to their lightweight and sturdy nature. Aluminium boats are constructed from a silvery-white, ductile metal with excellent corrosion resistance, strength and toughness. Weighing 170 pounds per cubic foot, aluminium is about a third of the weight of steel.

Aluminium boats are highly customisable in terms of size and shape, and they are easy to manoeuvre. They are ideal for water activities such as skiing, tubing and wakeboarding. They are also suitable for fishing, with deep-v models being perfect for larger groups of people and modified-v models being more suited to shallow waters.

Aluminium boats are also versatile in terms of the terrain they can navigate, from rivers and lakes to saltwater bays and harbours. They are also long-lasting, with a well-maintained boat lasting for 30-40 years or more.

The strength of aluminium boats comes from the aluminium alloys used in their construction. These alloys have been developed to match or surpass the strength-to-weight ratio of steel. The alloys used in marine applications have high yield strength, allowing them to withstand significant impacts before deforming.

Aluminium's flexibility and formability make it ideal for marine applications. It is highly weldable and can be worked with as aluminium plate or extruded parts. This ease of use results in a more cost-effective manufacturing process, even though the base material cost is higher than steel.

Aluminium boats are also advantageous due to their corrosion resistance. Aluminium's natural oxidisation process forms an aluminium oxide coating that protects the metal from the elements. Additionally, protective coatings can be added to bolster corrosion resistance, making aluminium boats ideal for saltwater use.

The lightweight nature of aluminium boats results in improved performance. They are faster and more fuel-efficient than boats made from other materials. This is particularly advantageous for racing boats, where speed and performance are crucial.

In summary, aluminium boats offer a unique combination of lightweight construction and exceptional strength. They are versatile, durable, and suitable for a range of marine activities. With their corrosion-resistant properties and ease of manufacturing, aluminium boats are a popular choice for those seeking high-performance, customisable vessels.

They are rugged, durable and economical

Aluminium boats are rugged, durable, and economical. They are renowned for their durability and lightweight nature, making them ideal for rugged environments and rough waters. Their ruggedness and durability mean they can withstand rough waters and challenging conditions, offering peace of mind to owners.

Aluminium boats are incredibly durable, with high resistance to impact and corrosion. This durability ensures that aluminium boats can withstand rough waters and challenging conditions. You can still find many aluminium fishing and hunting boats on the water that are 40+ years old.

Aluminium is a silvery-white, ductile metal with excellent corrosion resistance, strength and toughness. It can be easily cast and welded, and weighs 170 pounds per cubic foot—a little more than a third as much as steel. Its strength varies depending on the alloy, but marine-grade 5083 H-32 aluminium plate starts to deform at 34,000 psi and fails at 45,000 psi.

Aluminium's ductility lets it deform, or stretch, some 25% before it fails, and this “plastic region” is one of the characteristics that make it so suitable for boatbuilding. The plating surrounding aluminium welds is about 60% as strong as the surrounding members it joins. Backing plates and longitudinal stiffeners help spread out loads, and hull plates are butted in between, rather than at the frames, to minimize stress at these structural hard spots.

Aluminium boats are also easier to survey. With aluminium, there is no core to rot or delaminate, no fiberglass voids to blister, no faulty skin-to-core bonds, no rotted plywood transoms, no soft stringers or bulkheads around poorly sealed limber holes. What you can see with an aluminium boat is pretty much what you get. And aluminium welds can be X-rayed.

Aluminium boats are also economical. They are often less expensive than their fiberglass counterparts. Their lower weight means they require smaller power plants to attain similar performance and thus have lower operating costs. Their lightweight construction also enhances the boat's manoeuvrability and handling, making it easier to navigate and control on the water, especially for new boaters.

Aluminium boats are easier to survey

Aluminium welds can be X-rayed, and hull-to-deck joints are welded, eliminating the need for rivets and fasteners, which can come loose and cause leaks over time. The hull and deck of an aluminium boat are truly one piece, making it easier to assess their structural integrity.

Additionally, aluminium boats are more resistant to corrosion. Aluminium naturally forms an aluminium oxide coating on its surface, protecting it from corrosion. This protective coating, along with the metal's inherent corrosion resistance, means that aluminium boats require less maintenance and are less prone to issues like rust over time.

The durability and toughness of aluminium also contribute to its surveyability. Aluminium can withstand impacts and abrasion, making it less likely to sustain damage that would require extensive repairs. Its ductility allows it to deform or stretch by up to 25% before failing, further reducing the likelihood of sudden ruptures or structural failures.

Aluminium boats also have a longer lifespan than boats made from other materials. A well-maintained aluminium boat can efficiently function for 30-40 years or more, retaining its value over time. This longevity, combined with aluminium's resistance to corrosion and other forms of damage, makes aluminium boats a more surveyable option.

They are easier to build for DIYers

Building an aluminium boat can be easier for DIYers than building a fibreglass boat. For one, aluminium boats are easier to repair and maintain. Aluminium is also a more forgiving material for DIYers to work with than fibreglass.

If you're a DIYer who's a knowledgeable welder, building an aluminium boat is quite doable and very rewarding. You can learn the basics of aluminium boat building with some practice. There are reasonably priced designs available online that you can download and build at home.

However, there are a number of pitfalls that could cost you money and sink your dreams prematurely. So, before you rush into building your first boat, consider the following:

Aluminium alloys are not created equal. The aluminium you want is marked by a few possible grades, either 5086 or 5083. It's important to look at what your designer specifies and ensure that your metal supplier is aware of the grade you require.

In general, 5xxx series aluminium contains magnesium. This gives the metal a higher tensile strength without having to heat treat, and still allows for excellent workability and welding. It's also important that you use an appropriate filler material. 5356 was designed to work with 5000 series metal and should be used when welding either 5086 or 5083 aluminium.

Laser-cut vs waterjet vs router table?

After you purchase your design files, you'll need to contract someone to cut the material for you. There are a number of options, and the availability in your local area will likely dictate this choice for you.

Laser: The limiting factor in laser-cutting is not speed or quality but the size of the table. Many companies won't be able to nest your design.

Waterjet: A good option, and many shops have a machine large enough to cut your parts. The downside is edge prep. The waterjet leaves sand particles in the surface of the weld, so you'll need to grind all the edges before welding.

Router: The best option for boat building due to large tables and no edge prep. The downside is that detailed cutting is limited to the size of the end mill being used. While a router is a great option, a bit of cleanup might be required.

Don't think you're going to get away with your trusty TIG welder to weld an aluminium boat. ⅛” aluminium transfers heat very quickly, and TIG welding will warp and distort your boat. So, don't TIG weld everything.

If you can afford a pulse mig machine, this is what you want. Professional boat builders will only use this kind of machine. However, they cost a lot, so maybe see if you can rent one for your build.

If a pulse mig is not an option, you need a spool gun for your welding machine. They are reasonably priced, and most major manufacturers make them. You will need exceptional welding skills to use a standard spool gun, though. Your boat kit will come with lots of crop/scrap aluminium to practice your different welds. Avoid burning through. Take your time and practice.

Even better, hire a friend with boat-building skills. Have them go over the welding techniques with you.

Setting up the jig

The design files come with a jig. You can work off the floor, but it's important that the jig can't move and is completely square. Bolt the jig to the floor or, even better, to some custom-built sawhorses. Then tack-weld the boat to the jig. This will help you control distortion from welding.

Boat builders use the 'incremental backstep' process. The primary idea behind backstep welding is to eliminate distortion as much as possible. Starting from the centre of the boat, work your way out in 6” increments, but weld towards the centre. It's important to work your way out in all directions, skipping every other weld in the process. Try to keep the heat from being concentrated in one area for too long.

Forming the handrails

Don't do this yourself, unless you have experience or access to some expensive machines. You will regret it. Yes, you could heat the aluminium with a torch and make things easier, but if you don't have these tools already, just get a pro to do it. You'll have enough on your plate already if this is your first build.

Aluminium boats and electrolysis

Aluminium boats are a great choice for boat owners due to their ruggedness, durability, strength, and long-term economical value. However, they are not without their challenges, and one of the most significant considerations is electrolysis.

Electrolysis is a misnomer in this context, as it refers to the movement of current between positive and negative electrodes, which is not what happens in boats. Instead, the relevant process is galvanic corrosion, which occurs when the aluminium in the boat reacts with the water it is in, leading to oxidation and weakening of the boat's structure. This is a particular concern in saltwater, where the presence of sodium and chloride ions creates an electrolyte solution that facilitates corrosion. However, galvanic corrosion can also occur in freshwater, as the necessary chemicals exist there too, albeit to a lesser extent.

To prevent galvanic corrosion in aluminium boats, there are several measures that can be taken. One simple method is to apply bottom paint, which acts as a barrier to the chemical reactions causing corrosion. Keeping the inside of the boat dry is also crucial, as the presence of water enables the chemical reaction that leads to corrosion.

Another effective strategy is to use sacrificial anodes, which are pieces of metal composed of either magnesium, zinc, or aluminium that are attached to the bottom of the boat. These metals are more chemically active than aluminium and will sacrificially give up their electrons, protecting the boat from corrosion. It is important to select the appropriate anode material based on the type of water the boat will be used in, as magnesium dissolves too quickly in saltwater, while zinc is the best choice for saltwater and brackish water. Additionally, it is recommended to use multiple small anodes along the bottom of the boat and replace them as needed.

Other precautions to protect an aluminium boat from corrosion include using only products specifically designed for aluminium boats, maintaining the bottom paint to prevent chips or scratches, and keeping the boat on a lift and rinsing it with freshwater when not in use, especially in saltwater. Furthermore, connecting to an isolation transformer when docked can help prolong the life of anodes and prevent corrosion.

In summary, while aluminium boats offer many advantages, it is important to be vigilant about taking the necessary steps to prevent electrolysis and corrosion. By following the recommended precautions, boat owners can ensure the longevity and integrity of their aluminium boats.

Frequently asked questions