Probably the most common question I get asked when people hear about this boat is "why aluminum?". The answer is that I was unable to find what I wanted in a fiberglass boat. Once the decision is made to go custom, some options make more sense than others. A custom boat opens up many options other people don't even think about (cold molded, FRP (fiberglass reinforced plastic), aluminum, steel). I've lived on my parent's FRP (Columbia 35') for quite a while and I really like how easy it is to fix. My Dad and I have filled more holes in that boat than most people ever drill. On the other hand, FRP cracks when you hit something, looses it's strength after a few years, can have blisters, and flexes in a seaway.

I wanted a boat that could take a beating over the 40 years I will use it. I like the idea of when aluminum or steel hits something it bends (and eventually can puncture) instead of shattering. I like the idea of welded-on davits, handrails, sail tracks, stanchion bases, pulpits, dorade boxes, and etc (no leaks!). The weight and coating systems for steel were a bit much for me to handle and the steel boats we looked at always had rust stains. I also wanted to avoid a hard chine if possible although I think they are beautiful. I liked the idea that you can not paint an aluminum boat and it is just fine in the weather. For these reasons I chose aluminum.

Cons of aluminum construction

There are some aspects of aluminum construction that make it harder to produce a good-looking boat that will last a long time. The first is that aluminum is less noble that most metals used on boats (stainless steel, bronze). One thing I have noticed on some aluminum boats is the paint chipping near stainless fittings mounted to the deck. This is due to the interaction of the two metals. Usually, grinding the paint off the aluminum and rebedding the fitting is good enough, occasionally there can be some pitting. To counter-act this, alot of the features of this boats are welded in and integral to the design (e.g. davits, dodger, chocks, stanchion bases, cockpit hinges). The rest I am bedding myself with plastic bushings to keep thru-bolts away the from the aluminum and the paint. This is very labor-intensive!

Since aluminum is less noble than copper, copper based bottom paint should not be used on this boat. Some people advocate using it claiming that the epoxy barrier coat will block any galvanic action, but I have decided not to risk it. There are alternative bottom paints that are not quite as effective, I will probably have to haul the boat more often as a consequence.

Most propellers are made of silicon-bronze or other bronze alloys. I have heard numerous stories of these propellers being used successfully on aluminum boats. I will probably end up with a silicon-bronze prop.

More about metal boats

If you want to learn more about metal boats, three good resources are Michael Kasten's articles, the Metal Boat Society, and the Cruising World archives.

The following article by Michael A. Smith, Contributing Editor at both "Yachting" and "Boating" magazines.

The first thing you will ask your naval architect is what material you want to use to build your new yacht. He has to know before putting pencil to paper or cursor to computer screen: Weight calculations, interior volume, horsepower, tankage, sail area, ballast-- all depend on the material. Already you have to make a decision, the first of many; some people think it's also the hardest. It's really the easiest, once you know the facts.

You have three options: steel, aluminum, or fiberglass. Each has advantages for specific applications: You can't beat fiberglass for production boat-building, for example, where dozens, maybe hundreds of similar boats of adequate quality will be built using one set of expensive tooling. Steel, on the other hand, is the default choice for very large hulls where high strength and stiffness must be combined with a manageable plate thickness, and weight isn't such a factor. Between these extremes, it's the buyer's choice.

The more yacht-club "experts" you ask, the more confused you get. But after you do some research of your own, read the articles, talk to builders and naval architects, read more articles, even hang out with professional captains, your choice is obvious.

It's aluminum. Here's why:

Aluminum combines light weight, high strength, easy workability, and acceptable cost in one package. Steel is less expensive as a raw material, but by the time the extra dollars associated with handling it, forming the plates, etc., are factored-in, much of that advantage disappears. Steel takes longer to weld than aluminum an increases labor costs. It must be sandblasted before priming and painting, another expense; it's high- maintenance, which translates to increased operating costs; and it's heavy, so less displacement is left over for the 1,001 other things that must go into a first-class yacht-- things like engines, systems, and fuel. Steel isn't a serious player in this league--leave it for only the largest yachts or commercial boats.

Fiberglass usually means a skins-and-core composite that creates panel stiffness without excessive weight. Cored composites are relative newcomers in the custom- yacht field and vary in quality from excellent to abysmal. Trouble is, you don't know which level you're getting because it's impossible to analyze a composite laminate thoroughly without destroying it. You have to rely on the reputation and track record of the builder, and hope that everyone is having a good day when they lay up your hull.

In the hands of expert craftsmen working in climate-controlled shops, using high-tech autoclaves, post-cure ovens, and exotic fabrics, cores, and resins, composite FG produces a strong, light laminate. The aerospace industry uses lots of carbon fiber and epoxy; supersonic fighter planes, airliners,and the Stealth Bomber soar on carbon. Laminate costs soar, too, often 20 times higher per pound than boat-builders are willing to spend, and yacht buyers willing to pay, for marine composites.

And you get what you pay for: Composites assembled by even the best yacht builders can suffer delamination, incomplete cure, resin starvation, water absorption and heat deformation. Finish your hull in Flag Blue or another dark color, and it can lose up to 75% of its strength under the hot Florida sun. According to one classification-society engineer, it's likely that cored-composite yachts built with bottom-of-the-barrel raw materials like E-glass fabric and polyester resin will have water in the core within five years. Even more troublesome is secondary bonding: the attachment of bulkheads, stringers, floors and other structural members to the cured hull. Secondary-bonding failure is a major cause of composite boat owner's headaches. Composite fiberglass is floating Russian roulette--do you feel lucky?

Boat-building in aluminum doesn't involve luck. It's a straightforward process using easily tested, time-proven materials and methods. On a weight-for-weight basis, aluminum alloy is stronger than steel. Strength-for-strength, it weighs about half as much and is 10 times more resilient. Collisions that would puncture steel or composite hulls often just dent aluminum ones. Rather than starting the pumps, the skipper has the yard cut out the dimple and weld-in a new plate the next time its' there for routine maintenance. Nobody takes an unplanned swim, nor does the yacht suffer any downtime.

Aluminum, as defined by SOLAS standards, is non-flammable and non-combustible. Because of this, aluminum yachts can be made to comply to new, more strict I.M.O. commercial boat rules that are nevertheless appropriate for all oceangoing vessels. These rules demand structural fire protection (containment of fire in a particular compartment by the vessel's structure only without help from firefighting systems) and multiple watertight compartments. While watertight bulkheads can be built in composite yachts, structural fire protection is problematic, since composite cannot meet the relevant standards. While these new rules are mandatory for high-speed commercial boats in international service only, a yachtsman planning long cruises far from land can see the advantage of a yacht that's sink-and-fire-resistant.

The 5000-series alloy used to build modern aluminum boats consists of aluminum and magnesium, with a trace of silicon. Sailboat masts and spars are usually anodized 6061 alloy and contains a little copper, as well. Copper increases strength but reduces corrosion resistance: The copper in the 6061 reacts with the aluminum when salt water, or even salty dampness, is present to serve as an electrolyte. This causes bubbles to form wherever there's a break in the paint film and salt gets underneath. The result: Lifted paint, powdery white corrosion pockets, and other maintenance nightmares. Unfortunately, many yachtsmen carry this image with them when they think about building an aluminum boat, but the 5000-series alloys are much more corrosion- resistant because they contain no copper.

At Palmer Johnson, a 78-year-old custom yacht-building firm in the tight-knit community of Sturgeon Bay, Wisconsin, they insulate every dissimilar metal fitting and fastening from the aluminum with bushings and pads of Delrin or another inert plastic. Preventing direct contact between the metals is the key to defeating corrosion. Below the waterline, an array of sacrificial zinc anodes will prevent galvanic corrosion; their service life is predictable, and replacing them becomes a part of regular maintenance. Owners especially concerned about galvanic corrosion can specify an on-board metering system that constantly measures corrosion potential. Checking the meter daily will immediately warn the crew of unusual circumstances underwater. However, most aluminum boats enjoy a corrosion-free life after decades of service, protected only by zinc anodes.

The earliest modern aluminum hulls, built right after World War II, were riveted. When thin plating is required to meet strict weight requirements (as aboard Palmer Johnson's 50-knot, 100-foot motor-yacht FORTUNA, built in 1979 for King Juan Carlos II of Spain) rivets are still often the answer. There are 100,000 rivets in FORTUNA's superstructure, all hidden by painstaking filling and a mirror-smooth paint finish. Her hull is welded, though, for most applications the preferred method of joining aluminum plate.

A proper weld in aluminum is at least as strong as the metal it joins, so an aluminum yacht, including frames, stringers, gussets, bulkheads, deck, and all the other zillion pieces, becomes essentially a one-piece structure. Welds comprise only about 3% of the structure. The other 97% is plating, framing, etc. that's manufactured at the mill under strict control. Both the American Bureau of Shipping and Lloyd's insist on independent analysis of the alloy to ensure its metal content, test its strength, measure elongation under strain, and so forth. Palmer Johnson does that routinely, checking a "coupon" of plate--engineering-ese for a small piece--for every 1,000 lbs or so of raw material. Most Palmer Johnson yachts over 79' are intended for ABS classification; those that aren't are built to identical specs, but aren't surveyed during construction by an ABS representative. ABS won't classify yachts 79' long or smaller, but Palmer Johnson builds them to classification standards.

Aluminum plate doesn't leak, doesn't soak up water, doesn't delaminate, doesn't deform under heat in normal service--it just sits there, depending on the welds to keep it in the shape of a boat. Worried about a weld being less than perfect? They're easy to inspect whenever you want, using ultrasound and X-rays. Palmer Johnson always spot-checks welds during construction, and ABS and Lloyd's require it. Their surveyor decides where and how much to test. First-class boatbuilders like Palmer Johnson employ expert welders, certified ABS and/or the U.S. Navy. Welding is a skilled craft, and learning to do it right, to develop the eye-hand coordination, to master the submerged-arc processes required for joining aluminum, to lay down a weld that equals or exceeds the strength of the plate, takes time. Palmer Johnson figures on 1-1/2 to 3 years before a man is skilled enough to pass certification, and he's not allowed to strike an arc on a critical component of a new yacht until he has. Is this too much time to spend creating a productive employee? Not at Palmer Johnson. Once a part of the team, people tend to stay: Average length of service for employees is currently 10+ years. It's not unusual to meet a 40-year-old foreman with 20 years' seniority--and he's way down the list. For instance, the construction manager has been there for 35 years.

In catastrophic mishaps, a welded aluminum hull's ruggedness can pluck your yacht from the Total Loss category. Visit Palmer Johnson, Incorporated, in Sturgeon Bay, Wisconsin, and they'll show you pictures of Yankee Girl, the great Sparkman & Stephens IOR racer built of aluminum there in 1971. After a successful racing career, Yankee Girl fell victim to errant navigation and washed ashore on a rocky beach in southern New England, coming to rest in a foot and a half of water and unfortunately drew nine feet. By the time she was dragged off three months later, a large section of one side was nearly flattened from pounding against the rocks at every high tide. But she didn't leak. She was towed to a nearby yard, the damage cut away, new frames welded in, and replated. She sailed away literally as good as new.

It's almost as straightforward to modify an existing aluminum yacht.

FORTUNA, for instance, started life as a 86-footer, until H.M. the King decided he needed more speed and a bigger cockpit. When you modify a composite yacht, you depend on the adhesion between the new and old laminates to keep body and soul together. It's easy to make the changes look good cosmetically, but will the glue hold? With aluminum, you inspect the welds--if the welds are good, the new structure is 100% as strong as the old. No guesswork. Ditto for surveying an aluminum yacht before purchase: The surveyor can check everything visually, hire a lab to spot-check welds and even audiogauge plate thickness, although aluminum plate, unlike rust-prone steel, rarely loses enough gauge to worry about. Again, there's no guesswork, no "We think..." or "We hope...."

Except for cosmetic purposes, 5000-series alloys don't even have to be painted above the waterline. The unpainted metal reacts with air to form aluminum oxide, a hard, protective, and, unfortunately, dull-grey coating that protects the underlying metal. Commercial aluminum workboats, whose cosmetic appearance concerns no one, are often left unpainted above the waterline. Yachts are seldom so ill-treated. Palmer Johnson takes advantage of modern paint systems to enclose the yacht in a durable, low-maintenance linear-polyurethane shell, and uses a schedule of primers, fillers and polyurethanes manufactured by U.S. Paint, and offers a three-year paint warranty. One redcoat--prep and spray--during that period is included in the price of the yacht.

Creating the shell is a multi-step, labor-intensive process demanding painstaking attention to even the smallest detail. First the finish crew--it doesn't seem accurate to call them painters anymore--coat the abraded and cleaned aluminum with anti-corrosive primer. This etches the metal and creates a tenacious base for subsequent applications. After sealing the anti-corrosive with a high-build epoxy primer, the crew fairs the surface with a two-part filler. Here's where good building practice pays off: The less filler you need to create a perfect surface, the less unnecessary weight you add and the few man-hours you spend. After more primer, and more filler if necessary, the surface gets a final spray of epoxy primer, a thorough sanding, and the first coat of Awlgrip linear polyurethane topcoat. After about two weeks of drying time, the finishing crew sand again, and spray on a final coat of Awlgrip. Palmer Johnson practice demands that the finish be mirror-smooth.

Below the waterline, there's less fairing and more attention to creating an impervious shell between metal and seawater, with four applications of barrier-coat, followed by one of primer and then antifouling per the paint manufacturer's recommendations. Most experts endorse a non-copper-based antifouling on an aluminum hull; however, some feel that copper-based paint can be used if the barrier coat is maintained, and the yacht's crew inspects the bottom regularly for damage that exposes bare metal.

The finish process takes time: Figure eight months to prep a typical 150' yacht at Palmer Johnson, and a couple of weeks to topcoat. The actual painting time might be as short as five hours, with five painters working simultaneously. Applying the paint is only 2% or so of the total job. Finish painters tend to work odd hours (nights and weekends) to avoid interference from carpenters, joiners, and other dust-raising craftsmen.

Palmer Johnson employees are proud of their boats, too, and rightly so: They build the best custom boats in the world........and they do it with aluminum.

Author's bio: Michael A. Smith is a Contributing Editor at both Yachting and Boating magazines. For 20 years he was a professional crewman and captain on a variety of vessels, both pleasure and commercial, sail and power. Since 1986, he's specialized in writing on the technical aspects of boating. He lives in Stamford, Connecticut.

peter dahl