Sunday 25 September 2016

AVERAGED 11.2 / 12.7 / 16.5 KNOTS?

QUEENSLAND.
MISSING STEAMER YONGALA.
BRISBANE, Monday. — The
steamers Taroola and Suraka have
been sent out to search for the
missing steamer Yongala. The 
Suraka returned to port after an 
unsuccessful search, but started out
again.

The following notice appears on
the Devonport telegraphic shipping
board: — 'Brisbane advises on Sunday
— 'Townsville reports at 10.20 a.m.
that the SS Yongala left Flat Top
(Mackay) for Townsville at 1.40 p.m.
on March 23, and has not since been
heard of.' ' Flat Top is 208 miles
from Townsville, and the Yongala 
belongs to the Adelaide Steamship .Co.,
which trades from Fremantle, in
Westralia. right round the Australian
coast line via Adelaide, Melbourne,
and Sydney to Cairns in Queensland.


The distance between Mackay and Dent Island is roughly 55 nautical miles. If Yongala departed Mackay at 1.40 pm and was sighted from the Dent Island Light at 6.35 pm, we can calculate that she averaged 11.2 knots, which was well below average with the wind behind the steamer and no sense of urgency, given the falling barometer. 

Seems highly unlikely!!

If we take the sometimes press reported time of 6.00 p.m., Dent Island, we get an average speed of 12.7 knots. Again this was sub optimal for a steamer with Yongala's 17 knot potential.

If, we take 5.00 p.m., Dent Island ( I shall return to the reason for this in coming posts), we get 16.5 knots which makes more sense in the context of Yongala's potential and the urgency of a serious storm brewing. 

Given that Yongala's chronometer indicated 11.45 p.m. as the time of the disaster (subjected to flooding and excessive pressure through sinking) and the wall clock stopped at 12 midnight, an interesting scenario manifests. 

The distance from Dent Island to the site of the wreck is 105.5 miles via Grassy Island (inner, inside passage). We have three options again:

- Dent Island 6.00 p.m. to 11.45 p.m. = 5.75 hours, giving an average of 18.34 knots which was beyond the sustained limit of Yongala's engine.

- Dent Island 6.35 p.m. to 11.45 p.m. = 5.17 hours, giving us an average of 20.4 knots, which is ridiculous.

- Dent Island 5.00 p.m. to 11.45 p.m. = 6.75 hours, giving us an average of 15.6 knots which is entirely realistic and allows some leeway for the catastrophic, sudden foundering of the steamer.

We shall return to this controversial and highly significant analysis anon.




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