Seapower - March 2012

A Maintenance-Free Hull?
Material investments can reduce total ship ownership costs
By EDWARD LUNDQUIST, Special Correspondent

Materials Research

Potential alternatives to ferrous materials are being evaluated for their virtues as shipbuilding materials.

; Aluminum, composites and even titanium may offer “total ownership cost” advantages.

; Lighter and stronger, these hull structures may require less maintenance.

There are several materials that can be used for ship construction that do not have the corrosion traits of iron and steel. Aluminum, composites and titanium, although more expensive, do not rust, and are being evaluated for their virtues and how their properties have an impact on total life-cycle costs.

Aluminum

Aluminum ships are not new, but all-aluminum combatants are still uncommon. The second Littoral Combat Ship (LCS), USS Indepen - dence, features all-aluminum construction, as does the new Joint High Speed Vessel (JHSV). The other LCS variant, USS Freedom, has a steel hull but an aluminum superstructure.

Aluminum can oxidize and corrode, but in a different way and to a lesser extent than steel, and really does not require painting.

Aluminum is lighter than steel for its strength, but does cost more. When designing ships for high speed, reducing weight is essential. Steel-hulled ships with aluminum superstructures, by virtue of their reduced topside weight, can have improved stability.

Building aluminum structures can be done differently, too, because the lifting and moving of lighter materials is somewhat easier. Where a steel beam would require a crane to move, an aluminum beam of a similar size might be safely carried by two people.

“We learned a lot from the automotive, aerospace and
furniture industries about efficient production,” said
Anton Schmieman, who works in business development
at Mobile, Ala.-based Austal USA, where Independence
and JHSV are being built. “There is very little waste, and
98 percent of that waste can be recycled.”
Critics point to some notable fires on ships and cite
the fact that “aluminum burns.” But in cases where

; The maintenance-free ship is a “stretch goal,” but helps to focus research.

Nobody likes chipping, priming and painting to control corrosion on ships. But what if rust was not a problem?

Ferrous metals, such as many forms of steel used in ship construction, have a nasty habit of rusting. This oxidation makes for unsightly brown streaks and stains that are symptomatic of the bigger problem of metal actually being eaten away. Coatings can prevent corrosion, up to a point. But in a maritime environment, seawater and oxygen will conspire with time to break down steel.

“We’re learning what we need to do to keep ships
out of dry dock, and get that full ship life with less
labor than we’re expending now,” said Larry Schuette,
director for innovation with the Office of Naval
Research (ONR). “How can we create a ship that needs
less attention, less often, and still performs at its best?
How can we keep a ship out of dry dock and in serv-
ice? So we’re looking at the ‘maintenance-free ship.’
Obviously, a maintenance-free ship is a ‘stretch goal,’
but it does help make the point of our research.”
Schuette says ONR is studying different materials
for ship construction.