Forged to Float: Metal Boats

Offering strength, durability and longevity, metal boats come in a variety of designs and sizes.

Boatbuilding materials and construction continue to evolve with modern materials and processes, providing many good options, including metal boats. The origins of metal boat building date back to the 1800s, when wood boats were first dressed in iron cladding, after which builders used iron for the entire hull. While iron, an element mined from the Earth, worked to build boats, mixing it with other metals produces the alloy steel, which is lighter, stronger and better suited to boat building.

Lifeproof’s Yachtline 33 model begins life as a shiny aluminum shell before being transformed into a finished vessel with yacht-like qualities.

Benefits of Steel

Steel is the primary building material used in large ships and commercial vessels. In the recreational arena, it is used primarily for yachts larger than 100 feet. Attributes of steel are its strength, rigidity and puncture resistance; in addition, it is inexpensive and found worldwide. Steel and iron ships were once fastened with rivets, but modern steel vessels are welded. Steel plate’s near universal availability and the widespread use of welding equipment mean steel boats can be built and repaired almost anywhere — another notch in the Pro column — and steel is very forgiving in a collision or grounding, because it bends before it breaks, providing added safety.

 

Disadvantages of Steel

Steel (carbon steel, not stainless) does have drawbacks. Number one is rust. The marine environment and salt water are very corrosive and can eat away steel hulls over time. Modern paints, coatings, and foams applied both inside and outside of steel hulls can slow this process, but rust prevention requires special preparation, maintenance and care. Owing to its weight, steel works best in displacement hulls that can handle a heavier load, and it is extremely rigid, so it is a tedious process to bend it into curves, which is why many steel boats have hard chines and boxy superstructures. Knowledgeable builders such as Delta Marine in Seattle can create steel hulls that, once painted, are nearly indistinguishable from other hull types, but it is a time-consuming process with limitations.

Because steel is a ferrous metal and highly magnetic, it creates issues for compasses. On steel vessels, compasses must be carefully calibrated, and “correcting spheres” on the binnacle compensate for magnetic influences.

With an aluminum hull and a buoyancy collar, the Lifeproof Cabin 33 looks like a RIB but feels more yacht-like.

Stainless Steel

Why not build a boat out of stainless steel? Couple of reasons. Stainless steel is an alloy composed primarily of steel and chromium, which gives stainless steel its shiny appearance. Its corrosion resistance comes from a reaction with air that forms a protective chromium oxide layer on its surface that inhibits rust. When stainless steel is submerged, this protection is removed and stainless can corrode underwater. That and the high cost of stainless steel make it unsuitable as a primary boatbuilding material.

 

Aluminum

The most common metal boatbuilding material in use today, especially on the West Coast, is aluminum. Like iron, aluminum is an element, the most abundant metal in the Earth’s crust, but it is not found in a complete state in nature. In the 1880s scientists developed processes to extract aluminum from alum and bauxite ores, and industries began using this strong, lightweight metal. Extremely versatile, aluminum has widespread uses, including foil, cans, furniture, airplanes and pickup trucks.

Modern outboard power drives the aluminum hull of the Tactical T-40.

Aluminum makes a good boatbuilding material for many reasons. It has a very high strength-to-weight ratio, and while it is weaker than steel, it weighs two and a half times less. Aluminum is also more malleable and elastic than steel, so builders can more easily form complex shapes and curves with it. One of aluminum’s greatest attributes is corrosion resistance. It includes no iron, so it does not rust; thus, aluminum hulls and decks don’t require paint, although some builders and owners prefer paint. Aluminum alloys have been developed specifically for marine construction. Those alloys include 5083 and 5086, which top recreational boat builders use in their hulls because of its increased strength, formability and corrosion resistance. U.S. Navy and Coast Guard contracts typically require 5086, because of its weld strength and tensile strength. Another benefit of aluminum is that a worn or broken section can be repaired or replaced by welding in a new piece, which remains as strong as the original.

Aluminum boats don’t fade or crack in sunlight, which helps them retain value. Because aluminum boats are not built in molds, they can be more easily customized than boats built with other building materials.

Lifeproof’s 31 GT Coupe can be outfitted with a hot tub bow, something aluminum construction’s versatility allows.

 

Concerns About Aluminum
Corrosion

Common concerns about metal boats are that the boats will be noisy and have issues related to corrosion. Aluminum, like all metal, can be degraded by electrolysis and galvanic corrosion, which occurs where dissimilar metals are placed in contact with each other in the presence of an electrolyte, such as sea water. The weaker metal degrades as it yields molecules to the stronger metal. No owner wants his boat to slowly dissolve, but the corrosion issue is easily rectified with sacrificial anodes. All boats with metal components in the water should be protected by zincs that act as sacrificial anodes. Attaching sacrificial anodes, usually made of zinc, directly to the hull of aluminum boats protects them from corrosion. On all boats it is important to monitor and maintain zincs to prevent this type of corrosion, but proper care eliminates this problem.

Electrolysis occurs when stray electrical currents enter the water and speed up the galvanic process. Proper wiring and grounding of both the vessel and dockside power typically prevent this. In certain “hot” marinas or slips, isolators can be used to counteract this issue. Paint can help protect aluminum from corrosion by insulating the metal from electrolytes — and it creates a more finished look.

Raw aluminum, like stainless, protects itself with natural oxides that form on its surface when exposed to the air. Aluminum boats, especially after a trip on a trailer or after being winterized, should be cleaned thoroughly with fresh water to help prevent surface corrosion. They can last for many years both in and out of the water.

Noise

Some people think aluminum boats are noisy, but the noise level varies widely depending on design and insulation. Many people have experience with popular Jon boats and other aluminum utility and fishing boats, and these small, lightweight boats with large flat-surface hulls can be noisy, but quality aluminum boats designed with thicker welded plates, stringer systems and insulation are much quieter.

 

SIDEBAR

PNW Metal Boat Builders

The Pacific Northwest is home to many quality boat builders that specialize in metal boats. Many commercial operators prefer metal boats, so commercial, police and military vessels are often built of aluminum, as are many pleasure craft. But the notion that metal is a commercial building material causes many people to think metal boats lack the fit and finish of other types of boats, but the reality is that metal boats can be finished to the highest standards attainable. Most of the world’s largest megayachts are made of metal. The level of finish depends on the capabilities of the yard building the boat and the purpose of the vessel, not the hull and deck materials.

Coastal Craft, coastalcraft.com. Coastal Craft started building aluminum commercial fishing boats more than 23 years ago but now specializes in recreational boats: inboard-powered cruisers up to 65 feet and three new models in the popular outboard market, including the 30 ProFish, 33 ProFish and 33 Express.

Tactical Custom Boats, tacticalcustomboats.ca. Affiliated with Crescent Custom Yachts, which has been building quality motoryachts near Vancouver for years, Tactical recently launched its first Evan Marshall–designed T-40 Express Yacht, with more on the way, including a Tactical T-77 for a U.S. customer. Yacht-quality finish throughout will dispel any misconceptions about metal boats.

Lifeproof Boats, lifeproofboats.com. Lifeproof Boats makes boats from 15 to 55 feet out of commercial-grade 5086 aluminum. Its boats have patented hybrid air/foam buoyancy collars that increase stability, provide additional flotation and aid in docking. Lifeproof builds commercial, law-enforcement, and search-and-rescue boats, but its recreational boats have high-end finishes and interior accommodations. The builder just completed its first twin diesel outboard boat, which came complete with a built-in hot tub.

Rozema Boat Works, rozemaboatworks.com. A family-owned and -operated builder of both commercial and recreational aluminum vessels up to 75 feet, Rozema’s most recent recreational project, the 37-LC, is a sport landing craft featuring outboard power, a cabin complete with a galley, and a head and sleeping area. A hinged door at the bow is lowered to create a ramp when the boat is beached, something only a metal boat can do.

Metal boats don’t come out of a mold, so boats such as the Rozema 37-LC Sport (shown here complete and below in build) can be somewhat customized.

Duckworth Boats, duckworthboats.com. Duckworth Boats has been building aluminum boats since the 1960s. Originally designed for the Snake River and its fierce whitewater, Duckworth’s jet-powered boats now have outboard siblings from 18 to 30 feet. They are welded continuously from inside the boat with a tongue-and-groove style to add strength and integrity.

Other notable PNW metal boat builders include:

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