Editing SS Great Britain (section)

===Adoption of screw propulsion===
[[File:SS Archimedes by Huggins cropped.jpg|thumb|left | Artist's impression of {{SS|Archimedes||}}]]
[[File:Great Britain propeller and rudder wideshot.jpg|thumb|Replica of ''Great Britain''{{'}}s original six-bladed propeller on the museum ship. This propeller proved totally unsatisfactory in service and was quickly replaced with a four-bladed model.]]
In early 1840, a second chance encounter occurred, the arrival of the revolutionary {{SS|Archimedes||}} at Bristol, the first [[propeller|screw-propelled]] steamship, completed only a few months before by [[Francis Pettit Smith]]'s Propeller Steamship Company. Brunel had been looking into methods of improving the performance of ''Great Britain''{{'}}s [[paddlewheel]]s, and took an immediate interest in the new technology. Smith, sensing a prestigious new customer for his own company, agreed to lend ''Archimedes'' to Brunel for extended tests.{{sfn|Fox|2003|p=148}} Over several months, Smith and Brunel tested a number of different propellers on ''Archimedes'' to find the most efficient design, a four-bladed model submitted by Smith.{{sfn|Fox|2003|p=148, 151}}

Having satisfied himself as to the advantages of screw propulsion, Brunel wrote to the company directors to persuade them to embark on a second major design change, abandoning the paddlewheel engines (already half-constructed) for completely new engines suitable for powering a propeller.

Brunel listed the advantages of the screw propeller over the paddlewheel as follows:

* Screw propulsion machinery was lighter in weight, thus improving fuel economy;
* Screw propulsion machinery could be kept lower in the hull, lowering the ship's centre of gravity and making it more stable in heavy seas;
* By taking up less room, propeller engines would allow more cargo to be carried;
* Elimination of bulky paddle boxes would lessen resistance through the water, and also allow the ship to manoeuvre more easily in confined waterways;
* The depth of a paddlewheel is constantly changing, depending on the ship's cargo and the movement of waves, while a propeller stays fully submerged and at full efficiency at all times;
* Screw propulsion machinery was cheaper.{{sfn|Fox|2003|p=149}}

Brunel's arguments proved persuasive, and in December 1840, the company agreed to adopt the new technology. The decision became a costly one, setting the ship's completion back by nine months.{{sfn|Fox|2003|p=149}}

Reporting on the ship's arrival in New York, in its first issue ''[[Scientific American]]'' opined, "If there is any thing objectionable in the construction or machinery of this noble ship, it is the mode of propelling her by the screw propeller; and we should not be surprised if it should be, ere long, superseded by paddle wheels at the sides."<ref>{{cite journal|url=http://www.nature.com/scientificamerican/journal/v303/n2/box/scientificamerican0810-12_BX1.html |title=165 Years Ago, Happy Birthday to Us |journal=[[Scientific American]] |access-date=14 March 2015 |volume=303 |doi=10.1038/scientificamerican0810-12 |pages=12–13 |url-status=live |archive-url=https://web.archive.org/web/20150405104323/http://www.nature.com/scientificamerican/journal/v303/n2/box/scientificamerican0810-12_BX1.html |archive-date= 5 April 2015 |url-access=subscription }}</ref>