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As will be noted from the scantling list above, the dimensions of several critical architectural components of the Emanuel Point Ship hull remains have been estimated, since only portions of the site were uncovered during limited investigations. Certain measurements, such as the length of keel, length of keelson, maximum breadth of hull, etc., can only be accurately obtained by further excavation of the site. Despite this lack of information, a preliminary estimation of the ship’s original size and cargo capacity can be hypothesized by comparing available data from the hull remains with contemporary 16th-century sources on naval architecture, and recent studies of the topic. While any resulting conclusions can, at this point, only be considered as tentative, the exercise offers a glimpse of the size and volume of what once was a large sailing ship that carried people, arms, and supplies to Pensacola.
The basic unit of measurement used by medieval Spanish shipwrights was the codo, or cubit. Depending on regional usage through time, the value of the codo varied somewhat, causing a certain amount of confusion among modern students of maritime history. Standardization of weights and measures periodically was attempted by the government of Spain, but traditional (as well as colonial) values often persisted far from central authority. According to one scholar (Phillips 1987b:72), the modern value of the official shipbuilding codo (codo real, or royal cubit) is 56.5 cm. Another scholar (Casado Soto 1991:105), defines two kinds of codos: the codo real (also known as the codo cantabrico, or Cantabrian cubit) of 57.5 cm, and the codo castellano (Castilian cubit) of 55.7 cm. These differences in values, while slight, can become compounded to create diverging dimensional estimates, unless a standard unit is used for computation. For the purpose of this discussion, the codo value of 56.5 cm will be used (it falls almost exactly between the values of codos cantabricos and castellanos).
For mariners, the most important conceptualization of a ship’s size is its tonnage, expressed in tons. Medieval tonnage referred not to a ship’s weight, or the amount of water its hull displaced, but to the internal volume of the hold, i.e., the ship’s cargo carrying capacity. Therefore, a ton (from the wooden container called tun) was a unit of volume, rather than weight, and a vessel’s tonnage represented the hypothetical number of containers it could ship at sea. The Spanish unit of volume measurement, tonel, was the equivalent of two pipes (pipas) of wine, or eight cubic codos. Another unit, tonelada, originally was a unit of accounting, which was obtained by adding 20% to 25% to the estimated tonnage in toneles of a ship to increase its rate of pay when hired by the Spanish Crown. By the mid-16th century, the distinction between the two gradually became blurred; fraudulent abuses of customs fees and royal subsidies prompted a royal decree in 1590 that required the tonel macho to be used to measure gross cargo tonnage (Casado Soto 1991:103). Hence, calculation of cargo space (arqueamiento) in the complex and irregular shape of a ship’s hull was subject to varying interpretations, and also was dependent mainly on whether a vessel was outfitted for merchant or naval use. Basically, tonnage calculation evolved to become expressed in arithmetical formulas based on principal dimensions of ships’ constructional components, such as length of keel, maximum breadth, or beam, width of the floor, depth of hold, and overall length. These dimensions were also useful in characterizing the general shape of a ship’s hull by expressing ratios between them, for example, the ratio between overall length and beam.
One of the first published treatises on Spanish shipbuilding was Diego García de Palacio’s Instrucción náutica para navegar, which appeared in Mexico in 1587. Palacio’s discussion of the principal architectural dimensions required to build a nao of 400 tons is a useful template with which to approach a hypothetical reconstruction of the Emanuel Point Ship. The first step is to determine the keel length (quilla), a measurement which is lacking at present. Palacio stated that the midship frame should be placed two codos forward of the midpoint of the keel (Palacio 1944: fols. 92-92v). The site plan of another Spanish shipwreck, San Diego, indicates that the position of this 300-ton galleon’s main frame on the keel was close to Palacio’s recommendation (Carré et al. 1994:147). On the Emanuel Point hull, the distance between the center of the main frame and the estimated point of the keel’s aft terminus is calculated at 11.2 m (19.82 codos). Moving two codos, or 1.13 m, aft from the center of the main frame gives a keel midpoint of 17.82 codos, or 10.07 m. Adding the two halves of the keel together brings the total length of the keel to 20.14 m, or 35.6 codos.
According to Palacio, the beam (manga) of the ship, measured between the outer sides of the main frame without hull planking, should be almost half the keel length (Palacio 1944: fol. 90v). A keel length to beam ratio of 2.125:1 (for every 2.125 codos of keel length there is a corresponding codo of beam), figured from Palacio, produces a beam of 16.77 codos, or 9.48 m. A check to the relative accuracy of this measurement is the floor dimension (plan), or the distance along the flat part of the midship floor to the bottom of the curve signaling the turn of the bilge. Palacio recommended that this distance should be about one third of the ship’s beam, or 0.32 codos for every one of beam ((Palacio 1944: fol. 91). Fortunately, the floor dimension is available on the Emanuel Point Ship. It was determined by recording a cross section of the port side of the hull at the main frame, which measured 1.5 m. When doubled to include the starboard side, the floor equals 3 m, or 5.31 codos, which is just under a third of the ship’s estimated beam. This value provides a ratio of .31 codos of beam to every one codo of floor. A Spanish shipbuilder of the time may have obtained a greater or smaller value depending on his rule-of-thumb.
Depth of hold (puntal), according to Palacio and reinterpreted by Phillips (1993:295) puts forth a ratio of 0.48 codos to one codo of beam. This equals 8.05 codos, or 4.55 m, for depth of hold, and was measured from the top of the floors to the top of the lower deck planks. Overall depth of the hull in the midships section, using the ratio 0.71 codos of depth for one of beam (Phillips 1987b:72), equals 11.9 codos, or 6.72 m.
To the Spanish shipwright, the overall length (esloria) of the vessel was expressed as the distance from the stem to sternpost along the lower most deck, or the deck above the hold. This measurement was crucial in calculating the tonnage of the vessel. Palacio explained that to extend the hull beyond the keel, the stem post should rake forward one-third the distance of the keel length, while the stern post should rake aft one-sixth the length of keel. Another source on contemporary shipbuilding, Fernando de Oliveira, illustrated how the stem and stern post rakes could be obtained (Smith 1993:58). According to Oliveira, the height of the stem, as well as the stern, should equal one-third of the keel’s length, which corresponds with Palacio’s estimation of the stem post’s rake. To obtain the bow shape, a height of 11.9 codos, or 6.72 m, is measured from the bottom of the keel upwards. A compass is then placed at this point, and an arc is drawn from the bottom of the keel to a height equal to the above mentioned height. Excavations revealed that the stern post has a rake of 60 degrees, which was documented by an electronic leveling machine. By extending a line aft from the proposed end of the keel upwards to the height suggested by Oliveira, the basic outline of the hull begins to take shape.
At this point, the overall length of the ship can now be estimated. Although the molded height of the keel is unknown, by taking into account its known sided thickness of 22 cm, and using this figure as a minimal height of the keel, then adding the height of the floors (25 cm), the depth of hold can be computed. The estimated depth of hold is 4.55 m, or 8.04 codos, which when measured from the top of the floors, provides a point from which to draw a level line to the bow and to the stern. The distance equals 29.5 m, or 52.21 codos.
These computations, based on actual measurements of the Emanuel Point hull remains and the extrapolated dimensions of timbers that could not be measured, when guided by contemporary 16th-century shipbuilding proportions, appear to harmonize with those of Palacio’s 400-ton model. Palacio wrote that a ship of 400 tons should have 34 codos of keel and 16 codos of beam, 11.5 codos depth of hold (which is a third of said keel), and a length of 51.33 codos (1944: fols. 90-91v). The Emanuel Point Ship is estimated to have had 35.65 codos of keel and 16.77 codos of beam, 8.05 codos depth of hold, and a length of 52.21 codos. The shallower estimated depth of hold compared to that listed by Palacio may be due to his depth measurement of all the enclosed area of the hull, including the upper deck, which was 3 codos above the lower deck (Phillips 1987c:194).
Given these calculations of the basic hull dimensions (length of keel, beam, depth of hold, and overall length), the tonnage of the Emanuel Point hull can be estimated. Using a formula common in Spain during the 16th and 17th centuries—depth of hold times beam, the result divided by 2, times length on deck, the result divided by 8 (Phillips 1993:236)—gives a tonnage of 441 toneladas. Using a Cantabrian formula prevalent from 1520 to 1590 in northern Spain—length on deck times (beam divided by 2, plus depth of hold, the result divided by 2)2, the result divided by 8 (Casado Soto 1991:106, Table 2)—and converting the metric hull dimensions to the codo cantabrico, the Emanuel Point Ship had a tonnage of 418 toneles machos. Using yet another formula used in Seville and Cadiz around 1560—length of keel times beam times depth of hold, times two-thirds, the result divided by 8 (Casado Soto 1991:106, Table 2)—and converting the metric into codo castellano, produces a tonnage of 419 toneles.
The Emanuel Point Ship’s hypothetical tonnage, according to these three formulas, ranges from 418 toneles to 441 toneladas. Comparison with another formula reported by Jean-Pierre Proloux, working in conjunction with the Basque galleon project in Red Bay—beam divided by 2, times overall length, times depth, all divided by 8, the result multiplied by 0.95 (Morris 1993: 13)—using the codo real of 56.5 cm as the basis of measurement, produces a tonnage of 418 toneladas. This formula is similar to an official formula for warships—depth times beam, divided by 2; the result times length on deck; minus 5%; the result divided by 8, plus 20% (Phillips 1990:62)—which subtracted 5% to account for reduced cargo capacity due to heavier internal bracing, but added 20% to account for increased weight of men and munitions. Using the warship formula, the Emanuel Point Ship’s tonnage is estimated at 418 toneladas, increased by 84 to become 502 toneladas.
Fig. 22. Sixteenth-century architectural plans, showing the principal dimensions of a 400-ton ship’s hull in codos (Palacio 1944).
Fig. 23. Cross sectional view of a 400-ton Spanish nao of the 16th century, with two decks and a complement of 150 men. 1) quarters of the officers and pilot; 2) quarters of the minor officers and mariners; 3) pilot house; 4) passengers’ quarters; 5) soldiers’ quarters; 6) locker of anchors and cables; 7) provision storeroom; 8) cargo hold and ballast; 9) boatswain’s storeroom.
(after Etayo 1971).