Thursday, 12 March 2015

HULL DESIGN.

During the course of the Inquiry it emerged that there was dissension between the builders and owners of the Waratah. Contentious issues included, delays in completing the construction of the Waratah; that the Waratah be at least as stable and preferably more stable than the Geelong; stability assurances in various conditions of loading; and an intriguing reference to the Waratah's hull design. Although the Court deliberated long and hard on issues relating to stability, no attempt was made to establish what the owners implied regarding hull design.

The Waratah had a double steel hull consisting of plates riveted together. There was nothing out of the ordinary in this and I have already discussed the short-comings of the brittle steel used and rivets too high in slag particles. But this applied to most steel steamers circa 1908. The concerns regarding hull design had to relate to shape and dimensions. We know that the Waratah design was simply an extension of the Geelong template, a steamer which had proved itself in service. What then did the concern relate to?

The Waratah had a sharp or fine bow, typical of many large steamers. The idea was that this type of bow at operational speeds reduced resistance, further assisted by a substantial length of hull and a rounded stern. This bow design had a tendency to 'split' oncoming swells rather than rising over them. What is difficult to understand given that the Geelong and many other steamers had similar bows, is why was the Waratah different and why did the owners have concerns?

Perhaps the Waratah's performance related to the extent of cargo-loading. If she was very heavy, perhaps the tendency to 'split' oncoming swells became marked with significantly increased volumes of water breaking over the fore deck. This scenario would be amplified by rough sea conditions. The fore hatch was identified by other commentators at the time as being a weak link and if broached, the Waratah would take on tons of water very rapidly and founder within minutes.
But a more rounded bow would increase resistance and running costs, even though it would have been a safer option, but perhaps by the standards of the day, more rounded bows were not yet an option?

There is another possibility surrounding the nature of the query. Waratah was the first of the Blue Anchor Line vessels to have three superstructure decks. In order to maximise stability the hull form had to be narrow and deep to establish adequate GM. The owners might have questioned Waratah's hull dimensions in this context....

See:

http://waratahrevisited.blogspot.co.za/2016/04/needed-12000-tons-cargo-for-stability.html




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