DENT ISLAND LIGHTHOUSE.

wikipedia:

Dent Island Light is an active lighthouse located on Dent Island, a small island off the coast of Queensland, Australia. Dent Island is part of the Whitsunday Group of the Whitsunday Islands. Located on the south-west tip of the island, the light guides ships passing in the Whitsunday Passage, between Whitsunday Island and the islands to the west,^[2] and marks the Dent Island Passage.^[3]

From its inception, the lighthouse was closely connected to Cape Cleveland Light. Both lighthouses were recommend, approved, tendered and finally, in December 1879, constructed together.

The lighthouse is a typical for Queensland, made of a timber frame clad with galvanized iron plates. It is topped by a Chance Brothers lantern room, and painted white with a red dome.

From its beginning, the lighthouse was closely related to the Cape Cleveland Light. The construction of both lighthouses was recommended by Commander George Poynter Heath, the Chairman of the Queensland Marine Board, in February 1878.^[2] The lighthouses were formally approved in April 1878 and tenders for the construction of both stations, each including a lighthouse and two keepers' cottages, were called in May 1878 and closed in June 1878.^[5] The tenders were awarded to W. P. Clark, who also constructed Bustard Head Light (1868),^[6] Low Isles Light (1877),^[7] Double Island Point Light (1884) and Pine Islet Light (1885).^[6] However, following personal difficulties,^[6] the contracts were transferred to John Clark and James Wiseman who completed the construction of both stations in December 1879.^[5]

The tower was constructed in the unique Queensland method of constructing a timber frame and cladding it with non-structural iron plates or iron sheets.^[2] The original apparatus comprised a fourth order lens with an oil wick burner^[8] of 4,000 cd intensity.^[2] Like other lighthouses at that time it used a clockwork mechanism with weights, which had to be wound periodically. Due to its short height, only 6 metres (20 ft) from the base to the lantern,^[4] the mechanism had to be wound every 75 minutes.^[9]

6.35 pm, 23 March, 1911, (actually 5 p.m.) Yongala passed the Dent Island lighthouse and was sighted by the keeper as she navigated the Whitsunday Passage. This was not the last sighting of the doomed steamer as the residents of Cannon Valley saw the steamer passing at dusk, an hour's steaming from Dent Island. Yongala did not have wireless apparatus and would have relied on signals from this lighthouse to warn her of the approaching cyclone. However, Dent Island had no means of communication with the mainland and would not have been privy to the storm warning.

Yongala departed Flat Top, Mackay, 1.40 p.m., Thursday, 23 March. She was in relatively light / tender condition (top heavy). Cargo weight accounted for 29% of maximum load and 164 tons of stabilising pig iron ballast had been removed because it caused a jerky recovery uncomfortable for passengers.

Captain Knight elected to depart for Townsville despite strengthening wind from the southeast and a falling barometer. I believe the decision was based on an assumption that the weather system was coming up the coast, rather than one into which they would be steaming. 

There was no cyclone warning.

Heading north to Townsville and believing they could outrun the weather, Yongala made an average of 16 knots assisted by a 2 knot current. Yongala passed Dent Island, inside passage, Whitsundays, at about 5 p.m. (erroneously reported as 6 p.m.) and was subsequently seen by residents of Cannon Valley Beach an hour later, coinciding with dusk at 6 p.m.. This was the riskier but quicker, inside passage passing between Armit and Gumbrell Islands. 

Having cleared the Whitsundays without mishap, Yongala headed northwest in open water parallel with the coast and the outer Barrier Reef. She cleared Nares Rock without difficulty and arrived at a position 11.5 miles out from Cape Bowling Green Light, 17.7 miles from where Grantala lay anchored to the west due to deteriorating weather conditions.

We know from the chronometer time, 11.45 p.m. (conclusive in my opinion) and a wreck site within the large steamer track, that the disaster must have been sudden and catastrophic. Also, the time and site matches a plausible 15 - 16 knots (favourable, 2 knot current).

My belief is that the intense cyclonic system 30 miles in diameter was actually a hybrid cyclone (see image below) predominated by a gale from the south - the masters who experienced the storm reported gale force wind directions in keeping with this.

By the time Yongala was almost upon the eye of the cyclone, the gale would have shifted rapidly and violently from south to north, bringing the wind force to bear on the top heavy steamer's starboard bow and beam. 

Heading northwest, Captain Knight would have been confronted by an unfolding catastrophe and certain knowledge of Yongala's inability to recover quickly enough in such conditions. I believe he attempted to bring the steamer's bow into the gale. 

What followed must have been extreme and sudden, Yongala capsizing within minutes. The rudder is still in the half to starboard position and the wreck lies facing north. If there had been enough time for recovery, I believe the rudder would have been corrected to maintain the heading.

An explosion was heard by residents south of the disaster site, suggesting that the furnaces burning under full steam reacted to the cold sea water rushing in. 

The main hatch was compromised as the steamer foundered and lighter cargo in hold 3 liberated into the tumultuous sea. 

Passengers would no doubt have been confined to cabins due to conditions, essentially trapped as the disaster unfolded. 

I choose to believe that Yongala foundered so quickly there was little time for protracted suffering and Yongala's 122 souls now rest in peace, cosetted by some of the Coral Sea's most illustrious and doting residents.  

courtesy Google Earth

courtesy Google Earth

Max Gleeson presents an engaging theory based on dive observations that lifeboats on the starboard side of Yongala were swung out in preparation for evacuation of the ship rather than a sudden, extreme event.

A great deal of wreckage was subsequently discovered after the disaster spanning large swathes of the coast from Cape Bowling Green to Palm Island in the north. No lifeboat(s) or section thereof from the starboard side were discovered. Only a section of lifeboat 1 from the port side was found, suggesting that no one escaped Yongala.

A possible reason for starboard davits being in the 'swung out' position could be forces linked with Yongala coming to rest on her starboard side. 

The following extract gives us an idea of the forces unleashed by the cyclone:

Cairns Post, 17 October, 1911. 

Captain McKenzie further stated that 

between Cape Upstart and Cape Bowling 

Green there is now visible in the bush the 

track of the awful south-west tornado, which

it is believed drove the Yongala out onto

Broadhurst Reef. For a width of fifteen miles

the whole of the trees, including many immense

ones, being torn out by the roots and levelled.

It is clear from this description that Yongala was subjected to an intense, narrow, system of formidable force, causing her to capsize rapidly. One could argue that such a force would have destroyed even the most 'stable' of vessels.


The Week, Brisbane, 31 March, 1911.

A veteran master mariner firmly adheres

to the belief that the vessel turned turtle

in the cyclone, and explains the fact that

the cargo mentioned had come ashore by

pointing out that it was quite likely that the 

cargo of the overturned vessel falling upon 

the hatches, would burst them open, the 

lighter portion finding its way to the surface.


courtesy Trove

For all readers with an in interest in this subject Max Gleeson's online video, 'Mystery of a Generation' is compelling and beautifully compiled.