Tuesday, 8 March 2016

STRUCTURAL STRENGTH

The most important deck in terms of providing integral hull strength is that which forms the upper flange of the main hull girder i.e. strength deck. In the case of the Waratah this was the controversial spar deck. The watertight decks, lower and main were divided into 6 watertight compartments (one not water tight to upper deck) by bulkheads to the spar deck and also contributed to integrity of the main watertight hull.

The Waratah was unique in the dual function of the spar / strength deck. The following extract from the Inquiry transcript describes the layout of the spar deck:

The bridge had a steel bulkhead at the forward end. In it were two doors, 5 feet by 3 feet, each in halves, secured from the outside with turnbuckles; these led into the spar deck bunker. There were also two plug doors, similarly secured, leading into the cold chamber. The after end of the spar-deck bunker on both sides of the ship was divided from the accommodation (for the engineers, stewards, &.) aft by weather boards extending to the deck above. The after ends of the alley-ways under the bridge deck were 10 feet from the middle line of the ship, and were fitted with weather boards to half height. There was access from the alley-way on the starboard side at its forward end to the deck above.

The spar deck coal bunkers were interchangeable with emigrant accommodation. Weather boards were used to demarcate the zones as described and could not be considered structural supports. This implies that the spar deck relied on adequate thickness of plates, particularly over amidships. If shortcuts were taken, with reference to Waratah's classification as spar deck class with freeboard instead of three deck class, her hull might have been subjected to excessive stress over and above dead weight load.

One of the challenges confronting teams searching for the wreck could be that instead of finding the remnants of an intact hull, the Waratah could have broken up resulting in two or more sections scattered in a debris field on the ocean floor. This would also explain why the wreck has not been discovered by accident. After more than 100 years it is going to require patience and reliance on computer technology to identify objects from the steamer most likely to have survived eg. the five boilers.


    
Boiler being installed.




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