Mechanical steam power
Replica of the ill-fated six-blade screw
As a fast luxury liner to the United States, carrying a small number of passengers, many of whom paid high fares, she was to steam continuously, with sails as auxiliary power. For this, and to reduce the number of seamen needed, she carried a fore-and- aft rig on five of her six slim iron pole masts. Only no. two, the mainmast, carried a square rig. The large number of alterations at a time of rapid technological change, increases in dimensions and difficulties over actually getting the big ship out of Bristol resulted in a drawn-out building, launch and fitting-out schedule.
From laying the keel in July 1839 to her maiden voyage to
New York took six years. Her cost increased by over 60 percent, exacerbated by the long delay before she started actually earning a return on her investment. Inevitably, teething troubles struck, the worst being the loss of blades from her propeller in mid- Atlantic. It was Brunel's own design. He should have stuck to building bridges.
No sooner had these problems been solved than she ran aground on the Irish coast, taking several months and a small fortune to refloat. This broke the owners, the Great Western Steamship Company, and she was sold for a fraction of her original value.
The new owners completely refitted the Great Britain, repairing and strengthening the hull and replacing the boilers, engine and propeller. The new engine, also an inverted V, was an oscillating engine. Each conrod was fixed rigidly to its piston, which slid in and out of a cylinder which oscillated about the steam inlet. A wheel-and-cog assembly with the same gearing-up ratio replaced the chain drive. Technology had advanced in the short period since her construction, so the new machinery freed up enough space and weight to increase her cargo capacity by 1000 tons.
The stern was rebuilt to incorporate screw-lifting gear. A common fitting on sail-and-steam vessels of the time, this was used when the ship was under sail power alone and reduced drag. The rig was changed to an odd-looking four-masted one in which the fore and mizzen were fore-and-aft rig and the other two were square rig.
This lasted for one voyage to New York and back. She was sold again and changed to a conventional three-masted square rig. The slim pole masts were replaced by massive "built masts" made of wooden composite constructed from full-length, interlocking components clamped together by iron bands. The rationale for the change to square rig was that she would be used on the migrant trade to Australia, sailing, like modern round-the-world racing yachts, mostly downwind as she rounded the Cape of Good Hope and went east-about, returning by way of Cape Horn. The square rig was the most suitable for this. Her passenger capacity was increased from 360 to 730. This was the best and most successful phase of the ship's
career, beginning in 1852 with the first of 32 round-trip voyages to Melbourne. The 30-year service was interrupted by occasional use as a troopship to the Crimea and India. Popular with
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September/October 2011 Professional Skipper 31
