Why Aluminum?

While planning our offshore cruise, we read stories of boats that met with disaster when coming in contact with uncharted rocks.  Fiberglass is a wonderful material and easy to repair but a few minutes beating up and down on a rock will tear it apart and send the boat to the bottom – not a place we wanted to visit.  With thoughts of the strength qualities of steel floating in our heads, we visited our designer, Ted Brewer, who agreed metal was a wise choice and that he had designed many fine boats built of steel, but he would rather design for aluminum for some practical reasons.

Steel is very strong but after a repeated beating, like you would expect from hitting that uncharted rock, it fatigues, fractures, and soon you find yourself at the bottom alongside the fiberglass boat.  Aluminum has different characteristics.  When repeatedly hammered, it dents a little, then a little more, and then a little more – being much more malleable it is resistant to the fracturing of steel or the tearing of fiberglass.

Compared to steel, aluminum is extremely light weight.  Ted said he would design either boat to end up with the same total weight.  Then he asked, where do you want the weight, spread throughout the structure or concentrated in the lead ballast in the keel?  For stability and a comfortable ride, the answer is obviously in the keel – point for aluminum.

Steel not only has the problem of electrically-caused corrosion but moisture-caused corrosion as well – if it is steel, it rusts.  Keeping protective paint coatings intact, especially inside the hull, is a continual battle.  When the correct alloy of aluminum is used, the moisture related problem is non-existent.  A sheet of bare 5086 aluminum could be tied to a rope and submerged in the ocean for years and, when retrieved, it would be the same piece of metal.

Electrically caused corrosion remains an issue but by installing an isolation transformer, the boat never makes a hard connection to shore-side power which means all those incorrectly wired hot boats at the dock cannot affect you.  The vessel is further protected with the limited use of dissimilar metals and properly isolating them when they are necessary.  This is combined with the use of zinc anodes, installed below the waterline, which further protects the vessel.  By adhering to these principles, Millie J’s zinc anodes last as long as on a fiberglass boat – 2 years on the hull and 6 months for the little propeller zinc.

Because it is welded, the leaking problems, caused by failed bedding compounds on fiberglass boats, are non-existent – the hull to deck joint, stanchion base attachment, sail track mountings – none will ever leak.

While steel is heavy and requires many specialized tools, aluminum is worked with common wood-working tools – circular saw, jig saw, sander.  While it still has to be welded, it is much easier to prepare the piece.

Just like boats built of other materials, an aluminum one derives most of its strength from the underlying structure.  Unlike fiberglass that uses bulkheads and cabinetry for support, aluminum boats use frames and longitudinal stringers, leaving the hull open and structurally sound before adding any interior.  Millie J’s frames are spaced every 30-inches and there is no spot where a stringer is more than 7-inches apart.  She is a very strong boat.

Aluminum is becoming a much more popular boat building material.  Many sailboats in Europe are built of aluminum and almost all workboats in the harsh Alaska climate are now built of this material.

We were sold and Ted designed a fine aluminum boat.