Austal responds to MCA study

Austal has issued a press release in response to a study commissioned by the UK’s Maritime Coastguard Agency (MCA) in early 2003 which has subsequently been selectively quoted without full consideration of the hull forms tested, their relevance to current day designs or operational experience.

The West Australian shipbuilder has been monitoring the recent reporting and commentary concerning the performance of monohull, catamaran and wave-piercing catamaran designs in following and quartering seas and has made a number of comments.

It says that, whereas the concept of the centre-bow has always been promoted as being beneficial in preventing bow dives, a problem that has been experienced with dramatic consequences in the design prior to the addition of the centre-bow, the Austal catamaran has never needed such a device because of a higher freeboard.

This point is actually made in the study?s conclusions “To reduce bow immersion, increasing freeboard at the bow is more beneficial than increasing upper bow buoyancy at a fixed freeboard”. Austal is not aware of any of its vessels experiencing a bow dive as described in the report. The study also suggests that the wave-piercer design was more susceptible to broaching and that the addition of underwater fins and skegs would assist in the area of directional stability; “it would seem that some sort of passive fin arrangement aft would improve matters of directional stability on those vessels propelled by water jets”. It is well known, based on extensive research in this area, that Austal developed a passive fin which has been integrated into our large fast ferry designs since 1998 to assist with directional stability for operations that experience large following seas.

Also confusing is the fact that the modern day large wave-piercer design is very different today to the original concept reflected in the reports both in terms of the centre-bow position and hull shape. The current hull shape has evolved in recent years away from the original chine hull to more closely reflect the semi-SWATH, round bilge design of the Austal catamaran.

Austal prides itself on its large design capability and the use of sophisticated computer numerical modelling tools allowing it to study in detail bow diving characteristics and all other aspects of a vessel?s handling. The shipbuilder is not aware of any other shipyard that has this capability that is used in conjunction with actual sea conditions and weather pattern information to develop and refine a vessel?s design for each specific operation.

At Austal there is an understanding that there is no ?one size fits all? solution to the needs of commercial and defence operators seeking to maximise their return across varying criteria such as, maximum speed, payload, passenger comfort, varying sea conditions, endurance, durability and range. It is for this reason that ongoing research and development has led Austal to offer a range of monohull, catamaran and trimaran solutions.