Editing SS Great Britain (section)

==Description==

===General description===
[[File:SS Great Britain diagram.jpg|thumb|Sketch of ''Great Britain''. The lower image shows the internal arrangement of her decks and machinery.]]
When completed in 1845, ''Great Britain'' was a revolutionary vessel—the first ship to combine an iron hull with screw propulsion, and at {{convert|322|ft|m|abbr=on}} in length and with a 3,400-ton displacement, more than {{convert|100|ft|m|abbr=on}} longer and 1,000&nbsp;tons larger than any ship previously built. Her [[beam (ship)|beam]] was {{convert|50|ft|6|in|m|abbr=on}} and her height from keel to main deck, {{convert|32|ft|6|in|m|abbr=on}}. She had four decks, including the [[spar deck|spar (upper) deck]], a crew of 120, and was fitted to accommodate a total of 360 passengers, along with 1,200&nbsp;tons of cargo and 1,200&nbsp;tons of [[coal]] for fuel.{{sfn|Claxton|1845|p=3}}{{better source|date = November 2024}}

Like other steamships of the era, ''Great Britain'' was provided with secondary sail power, consisting of one [[square-rig]]ged and five [[schooner]]-rigged masts—a relatively simple sail plan designed to reduce the number of crew required. The masts were of iron, fastened to the spar deck with iron joints, and with one exception, hinged to allow their lowering to reduce wind resistance in the event of a strong headwind. The rigging was of iron cable instead of the traditional [[hemp]], again with a view to reducing wind resistance.{{sfn|Claxton|1845|pp=19–20}} Another innovative feature was the lack of traditional heavy bulwarks around the main deck; a light iron railing{{Sfn|Fox|2003|p=152}} both reduced weight and allowed water shipped in heavy weather to run unimpeded back to sea.

The hull and single [[chimney|funnel]] amidships were both finished in black paint, with a single white stripe running the length of the hull highlighting a row of false gunports. The hull was flat-bottomed, with no external [[keel]], and with bulges low on each side amidships which continued toward the [[stern]] in an unusual implementation of [[tumblehome]]—a result of the late decision to install propeller engines, which were wider at the base than the originally planned paddlewheel engines.{{sfn|Fox|2003|p=149, 152}}

Brunel, anxious to ensure the avoidance of [[Hogging and sagging|hogging]] in a vessel of such unprecedented size, designed the hull to be massively redundant in strength. Ten longitudinal iron girders were installed along the keel, running from beneath the engines and boiler to the forward section. The iron ribs were {{convert|6|x|3|in|cm}} in size. The iron keel plates were an inch thick, and the hull seams were lapped and double [[rivet]]ed in many places. Safety features, which also contributed to the structural strength of the vessel, included a [[double bottom]] and five watertight iron [[bulkhead (partition)|bulkheads]].{{sfn|Fox|2003|p=150}}{{sfn|Claxton|1845|p=5}} The total amount of iron, including the engines and machinery, was 1,500&nbsp;tons.{{sfn|Claxton|1845|p=18}}

===Machinery===
{{multiple image
| align = left
| image1 =  SS Great Britain transverse section.jpg 
| width1 =  120 
| alt1 = 
| caption1 = Transverse hull section, showing arrangement of gearwheels, gear chains and engine cylinders
| image2 =  SS Great Britain engine and gearwheels lateral section.jpg 
| width2 =  100 
| alt2 = 
| caption2 =  Side view of engines, showing arrangement of gears and gear chains between the engines 
| footer = 
}}[[File:Model of SS Great Britain's engines.jpg|thumb|right|upright| A model of ''Great Britain''{{'}}s engines]]

Two giant propeller engines, with a combined weight of 340&nbsp;tons, were installed amidships.{{sfn|Claxton|1845|p=18}} They were built to a modified patent of Brunel's father [[Marc Isambard Brunel|Marc]]. The engines, which rose from the keel through the three lower decks to a height just below the main deck, were of the [[marine steam engine#Direct acting|direct-acting]] type, with twin {{convert|88|in|cm|abbr=on}} [[bore (engine)|bore]], {{convert|6|ft|m|adj=on}} [[stroke (engine)|stroke]] [[cylinder (engine)|cylinders]] inclined upward at a 60° angle, capable of developing a total of {{convert|1000|hp}} at 18&nbsp;[[Revolutions per minute|rpm]].{{sfn|Fox|2003|p=150}}{{sfn|Claxton|1845|pp=3–6}} Steam power was provided by three {{convert|34|ft|m|adj=mid}} long by {{convert|22|ft|m|adj=mid}} high by {{convert|10|ft|m|adj=mid}} wide, {{convert|5|psi|abbr=on}} "square" saltwater [[boiler]]s, forward of the engines, with eight furnaces each&nbsp;– four at each end.{{efn|Some sources, such as Claxton,{{sfn|Claxton|1845|p=3}} state that there was only a single boiler, but others, such as Fletcher and Maginnis,{{sfn|Maginnis|1900}}{{page needed|date=July 2020}} state that there were three side by side. This apparent discrepancy is explained by the fact that there were three separate boilers or boiler compartments sharing a common housing.{{sfn|Dumpleton|Miller|2013}}{{page needed|date=July 2020}} }}

In considering the gearing arrangement, Brunel had no precedent to serve as a guide. The gearing for ''Archimedes'', of the spur-and-pinion type, had proven almost unbearably noisy, and would not be suitable for a passenger ship.{{sfn|Fox|2003|pp=148–149}} Brunel's solution was to install a [[chain drive]]. On the crankshaft between ''Great Britain''{{'}}s two engines, he installed an {{convert|18|ft|m|adj=mid}} diameter primary gearwheel,{{sfn|Claxton|1845|p=6}} which, by means of a set of four massive inverted-tooth or "silent" chains, operated the smaller secondary gear near the keel, which turned the propeller shaft. This was the first commercial use of silent chain technology, and the individual silent chains installed in ''Great Britain'' are thought to have been the largest ever constructed.{{sfn|American Chain Association|2005|p=10}}

''Great Britain''{{'}}s main propeller shaft, built by the Mersey Iron Works, was the largest single piece of machinery. {{convert|68|ft|m|abbr=on}} long and {{convert|28|in|cm}} in diameter, the shaft was bored with a {{convert|10|in|cm|adj=mid|-diameter}} hole, reducing its weight and allowing cold water to be pumped through to reduce heat. At each end of the main propeller shaft were two secondary coupling shafts: a {{convert|28|ft|m|adj=on}}, {{convert|16|in|cm|adj=mid}} diameter shaft beneath the engine, and a screw shaft of {{convert|25|ft|m|abbr=on}} in length and with a diameter of {{convert|16|in|cm}} at the stern. Total length of the three shafts was {{convert|130|ft|m|abbr=on}}, and the total weight 38&nbsp;tons.{{sfn|Claxton|1845|p=18}} The shaft was geared upward at a ratio of 1 to 3, so that at the engines' normal operating speed of 18&nbsp;rpm, the propeller turned at a speed of 54&nbsp;rpm.{{sfn|American Chain Association|2005|p=10}} The initial propeller was a six-bladed "windmill" model of Brunel's own design,{{sfn|Fox|2003|p=151}} {{convert|16|ft|m|abbr=on}} in diameter and with pitch of {{convert|25|ft|m|abbr=on}}.{{sfn|Claxton|1845|p=13}}

===Interior===
[[File:SS Great Britain 1st class dining room.jpg|thumb|left | Looking down one aisle of the reconstructed dining saloon in the museum ship SS ''Great Britain'']]

The interior was divided into three decks, the upper two for passengers and the lower for cargo. The two passenger decks were divided into forward and aft compartments, separated by the engines and boiler amidships.{{sfn|Claxton|1845|p=4, 6}}

In the aft section of the ship, the upper passenger deck contained the after or principal saloon, {{convert|110|ft|m|abbr=on}} long by {{convert|48|ft|m|abbr=on}} wide, which ran from just aft of the engine room to the stern. On each side of the saloon were corridors leading to 22 individual passenger berths, arranged two deep, a total of 44 berths for the saloon as a whole. The forward part of the saloon, nearest the engine room, contained two {{convert|17|x|14|ft|m|adj=on}} ladies' boudoirs or private sitting rooms, which could be accessed without entering the saloon from the 12 nearest passenger berths, reserved for women. The opposite end of the saloon opened onto the stern windows. Broad iron staircases at both ends of the saloon ran to the main deck above and the dining saloon below. The saloon was painted in "delicate tints", furnished along its length with fixed chairs of [[oak]], and supported by 12 decorated pillars.{{sfn|Claxton|1845|pp=14–17}}

Beneath the after saloon was the main or dining saloon, {{convert|98|ft|6|in|m|abbr=on}} long by {{convert|30|ft|m|abbr=on}} wide, with dining tables and chairs capable of accommodating up to 360 people at one sitting. On each side of the saloon, seven corridors opened onto four berths each, for a total number of berths per side of 28, or 56 altogether. The forward end of the saloon was connected to a stewards' galley, while the opposite end contained several tiers of sofas. This saloon was apparently the ship's most impressive of all the passenger spaces. Columns of white and gold, 24 in number, with "ornamental capitals of great beauty", were arranged down its length and along the walls, while eight [[Arabesque (European art)|Arabesque]] [[pilaster]]s, decorated with "beautifully painted" oriental flowers and birds, enhanced the aesthetic effect. The archways of the doors were "tastefully carved and gilded" and surmounted with medallion heads. Mirrors around the walls added an illusion of spaciousness, and the walls themselves were painted in a "delicate lemon-tinted hue" with highlights of blue and gold.{{sfn|Claxton|1845|pp=14–17}}

The two forward saloons were arranged in a similar plan to the after saloons, with the upper "promenade" saloon having 36 berths per side and the lower 30, totalling 132. Further forward, separate from the passenger saloons, were the crew quarters.{{sfn|Claxton|1845|pp=14–17}} The overall finish of the passenger quarters was unusually restrained for its time, a probable reflection of the proprietors' diminishing capital reserves.{{sfn|Fox|2003|p=153}} Total cost of construction of the ship, not including £53,000 for plant and equipment to build her, was £117,000{{sfn|Fox|2003|p=155}}—£47,000 more than her original projected price tag of £70,000.