Saturday, 23 January 2016

DESIGN FLAW.

This extract gives us an interesting comment about Lund ships:


To us the 6,612 tons S.S. Commonwealth seems a relatively small ship for such a long voyage. However, the list of ships plying between Europe and Australia which appears in The Australian Handbook for 1902, the year she was built, shows that she was fairly typical of vessels employed on that run. The largest vessel in the list is P&O’s Moldaira (11,000 tons), and most of the ships in most of the fleets are 7,000 tons and below – some well below. The S.S. Commonwealth had been built with capacity for 75 Saloon and 300 Third Class passengers, and she originally belonged to William Lund’s Blue Anchor Line. Her early years were spent on the north Atlantic, and she ferried many emigrants across to America. The design of Blue Anchor’s ships was strictly utilitarian – indeed, in their day they were even described as ugly. They had hardly any sheer on their hulls, and their massive masts and funnels were set virtually vertically. Apparently the unattractive designs were made to look even worse by coffee-coloured superstructures topping plain black hulls. In 1910 P&O had bought the troubled Blue Anchor Line, and they renamed it P&O Branch Line. After the P&O take-over, S.S. Commonwealth was altered to carry 450 Third Class passengers only. This maximised capacity for her new primary rĂ´le – the conveyance of emigrants to Australia. 

The 'massive masts and funnels set virtually vertically' must have influenced the top heaviness factor. In the case of Waratah it could have been part of the solution to reduce the size of the funnel and masts (after returning from the maiden voyage). Although this would not have cured the problem entirely, the GM would surely have improved to some degree, and reduced the wind-catching factor. On the flip side of the coin, if this had been done it would most certainly have sent a clear message to the public - this was a top heavy steamer which required major alterations. Bad publicity.

It is also interesting to note that these steamers had hardly any sheer on their hulls. 


The sheer is a measure of longitudinal main deck curvature, in naval architecture. The sheer forward is usually twice that of sheer aft. Increases in the rise of the sheer forward and aft builds volume into the hull, and in turn increases its buoyancy forward and aft, thereby keeping the ends from diving into an oncoming wave and slowing the ship. In the early days of sail, one discussed a hull's sheer in terms of how much "Hang" it had. William Sutherland's The Ship-builders Assistant (1711) covers this information in more detail.
The practice of building sheer into a ship dates back to the era of small sailing ships. These vessels were built with the decks curving upwards at the bow and stern in order to increase stability by preventing the ship from pitching up and down.[1]
Sheer on exposed decks makes a ship more seaworthy by raising the deck at fore and aft ends further from the water and by reducing the volume of water coming on deck.


This would certainly have contributed to the tendency of Waratah to plough through oncoming swells and taking seas over her decks. Sheer contributed to buoyancy - something sadly lacking in Waratah.




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