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Report by Paulo Monteiro
Report by Paulo Monteiro
Latest revision as of 01:32, 4 December 2010
(This article is incomplete)
In 1996 the Institute of Nautical Archaeology (INA) was able to dive and tentatively examine three wrecks in the Porto Novo area of Angra Bay, Terceira Island, Azores. All of the wrecks were locally known and had been picked over to some extent by the diving community. At a depth of 5 m, the site designated as Angra B - or Lead-Sheathed wreck - is comprised of a major ballast pile of stone roughly 15m X 15 m and substantial wood remains. Another smaller ballast pile to the north-west indicates that the ship wrecked against the rock outcrop in this area.
The southern end of the site had several major timbers not completely covered with ballast, including keel, frames, futtocks, ceiling, outer hull planking, and stringers. Because of the limited time to observe the material and the relative accessibility of the timbers, this was the only area recorded. The name of the site reflects the crumpled pieces of lead seen around the site and lead oxidation found on the keel, thereby lending credence to the hypothesis that the ship may have been lead sheathed.1
The extant remains of the keel measure approximately 15 m X 0.27 m X 0.17 m and has a north-south orientation. The surfaces are extremely eroded, but indications of a rabbet are apparent, No indications of keel bolts or other fasteners were observed at this time. Lead oxide is present on the west side of the keel in several areas as well as small nail holes with bits of lead still in place.
Ten frames are present in this area, all eroded near the keel and on most of the upper surfaces. Frames 8, 9 and 10 exhibit evidence of having a flat upper surface near the keel and then slope downward to where they disappear under the ceiling planking.
The extent of ballast and sand on the site made it possible to accurately record only the sided dimension of these timbers. The frames range from 13 cm to 25 cm sided with an average of 20 cm.
Moulded dimensions were attempted at frame 1 (nearest the end of the wreck), frame 8 and frame 9. Based on these measurements, an average of 20 cm moulded was calculated, but this figure is only an estimate.
Frame spacing measured from center-to-center averages 37 cm. Evidence of both treenails and iron fasteners are preserved on some of the timbers.
The futtocks seen the south-east side of the wreck were measured only in relation to the other elements of the hull and no specific dimensions were recorded. The overlap of the frame and futtock were not readily observed and no fasteners were recorded.
Four ceiling planks and two stringers were also found in situ on the wreck. The ceiling has an average width of 26 cm with a thickness of 5 cm. Stringer 1 possesses a side dimension of 19 cm and a thickness of 11.5 cm while stringer 2 is only 14 cm sided. Evidence of iron nails and treenails were observed on ceiling plank 1 over frame 9. The use of iron nails and treenails to fasten planking to frames has been documented on the Highborn Cay wreck, Mollasses Reef wreck, and the San Juan.
Eight outer hull strakes were and recorded including the garboard. The garboard did not appear any thicker than the other strakes measured, so has not been dealt with separately. The average width of the strakes was 27 cm and they possessed an average thickness of 5 cm. Iron fasteners in conjunction with treenails were observed on two strakes, numbers 2 and 3. The fastening pattern of 2 or 3 iron nails and one treenail suggest that this was the butt end of the plank. The Molasses Reef wreck and the San Martin have the same configuration.
The iron fasteners recorded are square in cross-section and measure 1 cm square. Two small nails with a length of 3 cm were recovered in the southern area of the site between frames. The treenails are of an undetermined wood type and average 25 cm in diameter.
The ballast has not been studied at this time, but an interesting feature discovered on the wreck may hint at the use of a primary ballast. A type of concrete was discovered between frames 2 and 3, on the east side of stringer 1 at frame 3 and on the end of strake 3. The concrete looks to have flowed between the frames like molten lead and then hardened. We know from the Nuestra Señora de Atocha's building contract as translated by Eugene Lyon that ballast of a similar type was used. The contract states:
"The lower hull and crutches from stem to stern must be filled with lime and sand and gravel of small pebbles between frame and frame, and above it they must place the planking of the ceiling, from stern to stem up to the extreme end floor timbers."
A fine ballast of this type was observed during the excavation of the Nuestra Señora de Santa Margarita and the San Martin. A further similarity was that these ships were all built in the Biscay region of Spain. These three examples all date to the seventeenth century and may provide a parallel to when and where this ship was built.
While recording the site, crumpled pieces of lead were quite common. More evidence of lead sheathing was observed on the keel, where a fine lead oxide and tack holes with bits of lead were present. Lead sheathing is know to have been used on vessels traveling in warm climates as protection from marine borers which ravaged wooden ships. The stern of the San Esteban had remnants of lead tacked into the seams. The Santa Margarita and San Martin both exhibited signs of lead sheathing in the form of crumpled pieces of lead covering the sites. The lead would have been stripped from the bottom of the vessel as it grounded.
With minimal exploration, the Lead-Sheathed wreck proves to have some interesting features not readily seen in the archaeological record. Evidence of a primary ballast and lead sheathing have only been recorded on two seventeenth century wrecks, and these have not been studied systematically. Trying to associate a place of origin and a date with the limited knowledge in our possession can be an approximation at best.
Wood samples were taken for wood type determination and dating, but the results are not available at this time.
The major timber dimensions fit within the spectrum of known data from Spanish and Portuguese wrecks in the New World from both the sixteenth and seventeenth centuries.
Fastening patterns observed on the Angra B wreck lend support to this range of dates. Planck thickness is thinner than all of the seventeenth century wrecks and therefore we may be looking at a vessel of similar size to those excavated from the sixteenth century.
A more detailed study in the future will hopefully provide more data for a successful evaluation of the site.
1. Report by Paulo Monteiro