Tuesday, 4 February 2014

TERROR’S STURDY STEM

Completed bow timbers compared to sheet plans.

Nowhere is the strength of HMS Terror’s frame more evident than in her bow architecture. Already stoutly built as a bomb vessel, Terror’s 1836/1837 plans indicate that the bow was significantly altered for conversion to polar service. The 1836 deck plans show that her stem was sided 12 and ½ inches, the same as her keel, but it was much thicker/deeper than normal. In fact, its moulded depth was greater than a vessel three times her tonnage (see scantlings below). This robustness was also transferred to her apron, which was consistent in size with that used on a 36 gun frigate.

Terror’s external bow timbers were also modified in 1836; all ornamentation pieces were removed, as were the cheeks, forefoot, bobstay piece, gammoning, and lacing. In their place, a very robust and simplified architecture was installed which consisted of a gripe, stem piece, main piece, and a short chock to support the bowsprit. Again, these pieces were very robustly built, and were sided the same as the keel, diminishing to only 10 inches at the fore edge.

Aft of these bow timbers, the stemson was similarly solid, sided the same as the stem and just as thick. However, in 1836, the stemson itself was reinforced by massive oak chocks the same width as the stem, but this time up to 16 inches thick. At the position of the third waterline, this effectively created a single massive block of wood, 12 and ½ inches wide and extending from the stem piece more than eight feet aft.  Indeed, it was strengthening like this that permitted Crozier to use the Terror as an icebreaker during the Antarctic voyage of 1839 (Ross 1847:147). 

Scantlings for Terror’s Stem and Apron:

Stem

Sided:
At Head (same as the keel) = 12 and ½ inches
At the Heel = 12 and ½ inches (larger than vessels of her size)

Number of pieces = 2

Moulded Depth = 16 inches (larger than 36 gun frigate)

Scarphs in length = 3 feet 9 inches (boxing) and 3 feet (upper)

Lips of the scarphs = 3 inches (consistent with standards for a 12 and ½ inch sided keel)

Bolts = 8 (consistent with 76 gun vessel, standard for bomb vessels)

Bolt diameters = 1 and 1/8 inches (consistent with 36 and 74 gun vessels, standard for bomb vessels)

Apron (false stem)

Sided (same as the stem) = 12 and ½ inches

Moulded depth = 9 inches (consistent with 36 gun frigate)

Moulded depth diminishing to the head = 7 inches

Scantlings for Terror’s Knee of the Head:

Sided (all pieces):
Aft part of knee (same as the stem) = 12 and ½ inches
Diminishing to the fore = 10 inches
       
Lower scarph in length = 2 feet and 1 inch

Upper scarph in length = 4 feet 2 inches


References:

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.


Sanding the lower stem piece to size.

Shaping the upper stem piece.

Finished stem and gripe (vellum simulates tarred flannel used on a real ship).

Finished main piece and chock to support bowsprit.

Detail of scarph joints.

Main piece joined to stem piece.

Port side view (note that the fore edge has not yet been shaped).


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