Friday, 30 September 2016

WARATAH AND YONGALA.

I have asserted that the 'jerk' described during Waratah's voyage across from Australia to Durban, July, 1909, was due to an over-correction of GM (increased righting force). By adding 1300 tons of lead concentrates at 11 cubic feet to the ton and 8 ft. high in the lower hold, improved GM to a figure of roughly 1.9 ft. which is stiff, not tender - tenderness being associated with top heaviness. Further to this I have asserted that Captain Ilbery needed to load about 250 to 300 tons of coal on the spar deck to reduce GM to a more palatable 1.5 ft. and thus remove the jerky recovery - passengers had fallen on deck due to this jerky recovery. There are many skeptics who dispute my assertions. The following is taken from my Yongala Revisited Blog. I believe the point is very well made:

http://yongalarevisited.blogspot.co.za/2016/09/enquiry-opened-yongalas-fate.html


Captain Mackay asked the witness about
the rumor that 400 tons of ballast had 
been taken out of the vessel, and the 
witness said he had replied to that. He 
pointed out that when the vessel was 
on the Western Australian trade she 
generally travelled from Fremantle to 
Adelaide with very little cargo, and often 
none at all. Her mean draught from 
Fremantle to Adelaide would be from 
16 ft. 8 in. to 17 ft. 6 in..

If the reporter documented the figure accurately 400 tons of pig iron were significantly more than the 164 tons of pig iron quoted in the Inquiry transcript:

'it was explained by the general manager that this ballast, amounting to 164 tons, became unnecessary, owing to cargo being obtainable both up and down the Queensland coast.'

It must be said at this juncture that the mere fact Yongala required between 164 and 400 tons of permanent pig iron ballast, over and above the water ballast component, indicates an inherently tender (top heavy) vessel. The point is well made that there might have been significantly less cargo between Fremantle and Adelaide, but the witness failed to mention that Yongala, as late as December 1910, periodically serviced the route between Adelaide and Fremantle, and not exclusively the east coast! If Yongala was an inherently stiff steamer there would not have been the need for additional permanent ballast.

The water ballast she then carried would
be 400 tonsIn May, 1904 it was decided
to put some stiffening in her for the run
across the Bight, and on May 17, at Sydney, 
184 tons of pig iron were stowed in the
after end of the No. 2 hold. In May, 1907,
when the vessel was put on the trade from
Melbourne to Cairns, this was discharged,
as the vessel could rely on having cargo
both ways.

It appears that the reporter confused the figure of 400 tons with ballast water, as he or she might have done referring to 184 tons rather than 164 tons. I am going to take 164 tons of pig iron ballast as given (Inquiry transcript). If Yongala had retained the 164 tons of pig iron, taking into consideration that she was 36% full in terms of cargo, 23 March, she might have survived the storm. After all, the pig iron was added with reference to storm conditions off the Australian Bight and reduced cargo component.

The witness read a letter from Captain
Knight, dated June 11. 1907, stating that
the vessel seemed much better since the
iron was removed. It had done away, he
said, with the jerking recovery which had
been so noticeable when the iron was on
board and the vessel was in ballast trim.

This is a significant passage. Improved GM stability did not equate with passenger comfort. Further to this I cannot help but draw a comparison with the Waratah. Captain Ilbery of that vessel significantly improved GM stability (reducing the top heaviness factor --> stiffening) for Waratah's final voyage by loading 1300 tons of lead concentrates at 11 cubic feet to the ton and 8 ft. high in a lower hold, creating a significant shift of Waratah's centre of gravity downwards - reducing top heaviness. However, during the voyage over from Australia to Durban (South Africa) there were reports of just such a 'jerking recovery' described above which caused passengers to fall on deck. It seems to me that in both cases, making corrections for relatively top heavy vessels, created its own set of problems. 



SS Yongala



SS Waratah

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