Saturday, 27 July 2013

TERROR MODIFIED: THE HISTORIC PLANS (Part 2)

1839 Sheets
The Terror was again extensively refitted for the 1839-1843 Ross Expedition. Some of these modifications, such as the change to a forced air heating system and the extension of a ring of solid chock channels around the entire ship, were obviously a direct result of lessons learned from the 1836/37 Back Expedition. However, many of the 1839 modifications resulted from a process of standardization with her sister ship, HMS Erebus. This was based on Sir Edward Parry’s longstanding policy of outfitting exploration fleets with identical equipment, the rationale being that one vessel’s fittings could be used to repair another in the case of catastrophe (Battersby and Carney 2011:203).  Rice, the shipwright in charge of the 1839 refit, provides an excellent description of the modifications done to the ships at this time, and it is worth noting here in its entirety (Ross 1847).



The 1839 plans illustrate the inboard profile and all decks, although the Terror’s modified lines are not represented. All sheets are labeled “Terror and Erebus”, reflecting both the similar design of the ships and the identical manner in which they were outfitted. Uniquely, the 1839 plans provide a midships cross section which illustrates the planking configuration, the dimensions (thickens and widths) of the planks, and the position and construction of the watertight bulkheads, as well as other inboard details.

Comparing these plans to the Terror’s 1813 and 1836 configuration clearly indicates that the 1839 sheets depict the Erebus. By this time the ships were almost identical in length and had very similar lines, but the draught and breadth of the Erebus were still greater than the Terror and this is reflected in the inboard profile, midships section, and lower deck plans. Furthermore, the upper deck plans included dashed red lines showing alternate positions of ship’s boats, labeled “Terror”, implying that the ship is the Erebus. A noteworthy exception to this exists with the midships section; while the frames drawn match the contours and dimensions of the Erebus in breadth, the height/draught of the decks and bulwarks appear to be based on HMS Terror’s dimensions. It seems likely that this was an error on the part of the draughtsperson, who must have been working from multiple reference sheets for multiple vessels.

The 1839 modifications included a series of diagonal iron riders bolted to the frames in the midsection, with iron crutches and sleepers at the bow and stern to increase strength. Fewer, but larger, iron storage tanks were placed in the hold (reduced from 47 to 22), though the available historical record is mute on the rationale for this change. The unreliable hot water heating system was replaced with a much larger and more reliable “Sylverster’s Patent” hot air heating system, which would remain onboard for the subsequent 1845 voyage (Battersby and Carney 2011:200). Finally, the copper bow sheeting was also extended along the side of the ship below the solid chock channels.

It is important to reiterate that the 1839 plans introduce a critical fact; despite proportional differences in size, the ships were fitted-out in an identical fashion. Indeed, contemporary accounts outline the similarity of vessels (Anonymous 1839:405).


Besides the unseen internal framing and architecture, the only significant difference between the Terror and Erebus was one of proportion; reflected in the alternate positions of fittings and furniture, such as hatchways, masts, capstans, pumps, etc. to account for the difference in size of the vessels. This has obvious implications for model building, as it implies that the 1839 plans, though based on the flagship Erebus, are likely to be largely applicable to the Terror.

1:48 scale model of HMS Erebus as fitted in 1839, National Maritime Museum Collections.
References:

Anonymous
1839   The Antarctic Expedition. Gentleman’s Magazine 12:405-407.

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.

Ross, Sir James Clark
1847    A Voyage of Discovery and Research in the Southern and Antarctic Regions, During the Years 1839-1843: Volume I. John Murray, London.

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