Wednesday, 11 November 2015

THE EFFECT OF COAL STOWAGE ON STABILITY.

On the 27th October, 1908, a passenger certificate was issued entitling the "Waratah" to carry 128 first class, and 160 third class passengers, with a crew of 144, a total of 432 persons.

Were the 689 emigrants on the maiden voyage not regarded as passengers? According to the Merchant Shipping Act, 'The expression “passenger” shall include any person carried in a ship other than the master and crew, and the owner, his family and servants'. I can find no reference in the Inquiry transcript referring to the impact of more than 700 emigrants and their baggage on the spar and 'tween decks in terms of weight and contribution to overall GM. Perhaps it was insignificant in terms of overall tonnage.

http://waratahrevisited.blogspot.co.za/2016/05/passenger-crew-certificate-discrepancies.html

On the 3rd November, 1908, Messrs. Barclay, Curle sent to Messrs. Lund a stability statement giving particulars under six different conditions, and also a general statement regarding loading. 

Those statements are as follows: 

Stability in Various Conditions. 

I. Ship light with stores and fresh water aboard G.M.= 2 1/2 inches (0.21 ft.)

Range of stability=57 degrees. 

According to the heeling experiment:

Calculations were made to find the effect on the centre of gravity of removing weights, including water ballast in Nos. 3 and 8 tanks, which were to come out of the ship, and adding the 20 tons referred to above. The metacentric height of the ship in a light condition, viz., vessel empty except that 300 tons of fresh water, stores and crew were on board, was then shown to be .26 feet. 


The figure of 0.21 ft. approximated the results of the heeling test; 0.26 ft.


II. Light ship, with all coal including reserve, all water, all water ballast except forepeak, and 1,200 tons in bottom of hold G.M.= 6 inches (0.5 ft.)

Range of stability=69 degrees.

According to the heeling experiment:

The vessel was about to go on trial and was practically complete, all refrigerating machinery on board, insulation finished, and boats in place. it was estimated that weights yet to be put into the ship amounted to 20 tons. The metacentric height was found to be .556 feet.

Again, the figure of 0.5 ft. approximated the results of the heeling test; 0.556 ft.


III. Ship loaded to disc with cargo at 40 cubic feet per ton in holds, and cargo of 80 cubic feet per ton in 'tween deck, all coal including reserve, F.W., stores, crew, and passengers G.M = 4 1/2 inches (0.375 ft.) 

Range of stability=36 degrees.

As I understand this condition, the Waratah was fully loaded in terms of cargo, coal and passengers. The cargo was distributed such that per cubic foot there was a greater concentration and weight in the lower holds compared to the holds in 'tween decks, which makes sense in terms of improving GM stability. However, only a GM of 0.375 ft. was achieved. This seems odd and does not correlate with the GM of 1.5 ft. when the Waratah departed Durban, 26 July, 1909. It certainly explains why there were stability issues on the maiden voyage; although 0.375 ft. is in positive territory, it is short of the average of 0.75 ft. for equivalent steamers and way short of 1.5 ft. This is even more peculiar when taking into consideration the recommendation that the Waratah not put to sea with a GM lower than 0.83 ft. What were the builders trying to achieve? They had designed and produced a steamer that could not put to sea in a condition which appears to be the condition most likely to represent the Waratah at sea. Whether this was equal to or greater than the stability of the sister ship Geelong, the figures and common sense simply do not add up!!!! Had the builders taken complete leave of their senses???     


IIIA. Condition III. with coal in bridge space burned out G.M.= 10 inches (0.83 ft.)

Range of stability=50 degrees. 

Okay, now we are getting down to the essence of the problem. If there was NO coal on the spar deck (bridge space) the all important GM improved to 0.83 ft. which, voila, is the magical figure recommended by the builders, before putting to sea. So why then, did they agree to and include spar deck coal bunkers on the plans, which they were ultimately responsible for (the owners having submitted a sketch)? They must have made a mistake or else given into extraordinary pressure from the owners! The Waratah under such circumstances could not have had stability equal to or greater than the Geelong. Aha, I hear you say, then the Waratah was top heavy and unstable when she departed Durban, 26 July, 1909, with at least 340 tons of coal in her spar deck bunkers....well at least in terms of the builders recommendation of 0.83 ft. But let's read on before coming to premature conclusions on this important issue.....

IV. Condition III. but with all coal burned out and W.B. tanks Nos. 5 and 8 full G.M.= 15 inches (1.25 ft.) 

Range of stability=73 degrees. 

According to this condition we are presented with an important clue. The claim is that the GM improved significantly, up to a whopping 1.25 ft (three times). when all the coal was burned out, and two ballast tanks filled. Let us remind ourselves, the Waratah could load 2010 tons of coal in her permanent bunkers (lowest level); crucially, 1819 tons in 'tween deck reserve bunkers; and of course, 614 tons on the spar deck. Filling the two ballast tanks in question, no's 5 and 8 give us 401 tons of additional ballast. We know that the full spar deck component of coal reduced the GM by half. which cannot alone account for the three fold figure (1.25 ft). The problem, or so it seems, was coal loaded in the 'tween decks as well as the spar deck. Also, it did not take a huge weight in the ballast tanks (401 tons) to push up the GM considerably. 

V. About 5,900 tons of cargo distributed as in Condition III., all coal, and tanks Nos. 5 and 8 full G.M.= 10 inches (0.83 ft.) 

Range of stability= 42 degrees. 

It is extraordinary that 401 tons of ballast water could bring the overall GM up to the magical 0.83 ft. with the full component of coal in both permanent and reserve bunkers. So it seems, if this was done, the builders plan held water and was not overtly deficient. In fact, in terms of the average, acceptable GM for a cargo/passenger vessel of this size and the builders recommendations, the problem of GM was solved! In fact, as we shall see further along, the builders recommended the filling of ballast tank 8 (222 tons) to sort out the stability issues manifesting on the maiden voyage.

But this cannot be the full story. We know that the Waratah departed Durban, 26 July, 1909, with a GM of 1.5 ft. confirmed by the expert observations of port pilots etc.. who claimed, under oath, that the Waratah was easy to shift from the wharf, did not fall into a list, and left port, upright and stable.

How then was this possible?

1300 tons of lead concentrates lowest down at 11 cubic feet to the ton and 8 ft. high in the hold!

Was there a price to pay? Reduced buoyancy, in my opinion, was the price paid and the risk of the lead concentrates liquefying and shifting.

General Statement Regarding Loading. 

1. Vessel in her trial condition had a G.M. of about 6 inches (0.5 ft.) 

2. In order to complete coaling, 1,200 tons D.W. must be shipped low down in holds. 

This stands to reason, reinforcing that dead weight at the lowest level in the steamer, offset the GM demands exacted by coal, especially if it was being loaded into 'tween deck and spar deck bunkers.

3. When loaded to disc with cargo of 40 cubic feet to the ton in holds, and 80 cubic feet to the ton in 'tween decks, ship has a G.M. of about 4 1/2 inches (0.375 ft.). This is increased to 10 inches (0.83 ft.) by burning out the 614 tons of coal in bridge. 

Remember, that this condition still includes 1819 tons of coal in the 'tween deck bunkers. Nothing new, we already know that by taking away the spar deck coal component increases GM to 0.83 ft.

4. When loading and coaling at the same time, tanks must be full and all coal except bridge space and trunk may be filled; but before the bridge space may be filled the 1,200 tons cargo mentioned in (2) must be shipped. After this point the tanks may be gradually emptied as the remaining cargo goes aboard. 

This reinforces the delicate balancing act loading steamers of the period.

5. It is strongly recommended that vessel should have a G.M. of 10 inches (0.83 ft.) when going to sea. 

The vessel sailed on the 5th November, and it is not known whether this information reached the captain before departure. In any case it could not have been available for loading on the first occasion in London. 

It did not, and there were stability issues during this initial voyage, rectified by the time the Waratah departed Durban, 26 July, 1909.




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