Saturday, 27 July 2013

TERROR MODIFIED: THE HISTORIC PLANS (Part 3)

1845 Sheets
The ships were again extensively refitted in 1845 to convert them to auxiliary steam propulsion, a modification deemed necessary to save precious time during the ice-free season “providing the wind should prove contrary or a dead calm”.  An excellent plan of the stern modifications exists (from which the preceding quote was drawn), which displays the complete redesign of the Terror’s stern. These exact plans are reproduced in green ink on the 1836 plans of HMS Terror, indicating that the ship was shortened at the position of the lower and upper decks, but the sternpost was moved aft to provide room from the new screw propeller. Above the screw propeller a massive well was constructed through which it could be easily shipped and unshipped. When the screw was not in use, the well was filled with a series of solid wood and metal chocks to add strength to the vessel’s stern.


The 1836 inboard profile of the Terror shows that partitions on the orlop deck and in the hold were modified to accommodate the new propulsion system, which was an unmodified steam locomotive engine, anchored just aft of the mainmast. Much speculation has occurred about the type of engines utilized, but recent research by Peter Carney (see Battersby and Carney 2011:203) argues that the locomotive was the Croydon/Archimedes type, for which partial plans exist (Brees 1840):




If these were the engines installed in the Terror and Erebus, they were an excellent choice, as they were known to be exceptionally reliable (Brees 1859:90):


Green-ink modifications to the 1836 inboard profile also display that the extensive copper plating was removed in favor of thicker iron plating which covered the entire bow and extended ca.  15 feet aft. This is also confirmed by contemporary sources (Anonymous 1845:279). The plans also indicate that the Terror’s bowsprit was raised by approximately 4.5 feet; the reason for this is unclear, but the Terror had a much shallower draught than the Erebus and given her sailing qualities, this modification was likely necessary. Further alternations to the partitions of the decks are depicted (in green ink) in both the 1836 and 1839 plans, the most significant of which appears to be the extension of the watertight bulkhead system forward, which must have resulted in a significant reduction in hold capacity.


OwenStanley, 1845, " Departure of H.M.S. Erebus and Terror for the North Pole,1845", courtesy National Library of Australia.

References:

Anonymous,
1845    Literary Gazette Journal for the Year 1845. Robson, Levey, and Franklyn, London.

Battersby, William, and Carney, Peter
2011    Equipping HM Ships Erebus and Terror, 1845. International Journal for the History of Engineering & Technology 81(2):192-211.

Brees, S.C.
1840    Second Series of Railway Practice: A Collection of Working Plans and Practical Details of Construction in the Public Works of the Most Celebrated Engineers. John Williams, London. 

1859     Railway Practice: A Collection of Working Plans and Practical Details of Construction in the Public Works of the Most Celebrated Engineers. R. Griffin and Co., London.


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