Integrating digital and conventional recording techniques for the documentation and reconstruction of an 18th-Century wooden ship from Alexandria, VA

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Abstract

An 18th-century wooden ship discovered on the waterfront of Alexandria, Virginia was documented and modelled using laser scanning, computer modelling, 3D printing, traditional lines drawings, and wooden ship modelling techniques. This combination of new technologies and traditional ship documentation methods allowed researchers to capture the details of the ship remains with extremely high accuracy. The models of the timbers were then 3D printed, reassembled, and incorporated into an interpretive wire frame model that contextualized the remains of the ship with what it would have looked like whole.

Introduction

In late 2015, construction crews excavating the foundation for the Hotel Indigo in Alexandria, VA uncovered a wooden ship buried on what is now dry land, 80 m from the modern shoreline. Given the current UNESCO guidelines, which urge limited excavation and in situ preservation of shipwrecks, the discovery provided a rare opportunity to fully excavate, study and conserve a historic wooden ship, as the location of the remains required removal (Dizon et al., 2013; Alexandria, 2019a). The ship, now designated the Indigo Ship, was documented and excavated by archaeologists from the Alexandria Archaeology, a division of the Office of Historic Alexandria and the cultural resource management firm Thunderbird Archeology, a division of Wetland Studies and Solutions, Inc., with assistance from maritime archaeologists at the Naval History and Heritage Command (NHHC). Maryland Archaeological Conservation Laboratory for their participation in the excavation (Alexandria, 2019b). All that remained of the vessel was the lower portion of the forward starboard quarter of the hull, which would have been below the waterline when the ship was sailing the Potomac River. Very little of the interior planking remained, and the heavy framing timbers that make up the skeleton of the ship had been sawn through just above the keel, indicating that the ship was intentionally salvaged prior to deposition (Fig. 1).

Between 1749 and 1798, the waterfront of Alexandria was ‘bluffed out’ or ‘banked out’, wherein bluffs were knocked down to extend the shoreline to a deeper section of the navigable channel, which allowed for deeper drafted vessels to dock instead of having to transfer cargo and personnel via lighters (Alexandria, 2019a; McKay, 2018). The Indigo Ship's old, worn-out hull was likely dismantled and used as part of the framework of a wharf that was extended out into the Potomac during this period.

Though the timbers were found buried beneath dry land, the vessel was close enough to the water table that all timbers remained waterlogged, preserving the wood. To prevent any further degradation of the wood, all of the wood had to be kept wet until they could be conserved (Hamilton, 1998). The hull was disassembled and excavated piece by piece, and the timbers were stored in large freshwater vats or kept wet under tarps for 18 months in the City of Alexandria's maintenance equipment depot. In the summer of 2017, researchers travelled to Alexandria to assist the city archaeologists with further documentation and to prepare the timbers for shipment to Texas A&M University's Conservation Research Laboratory (CRL). The ship timbers were then sent to the lab where they were unpacked, and stored in freshwater vats while they awaited conservation (Fig. 2).

Only approximately a quarter of the lower hull was found. The remains were disarticulated either during deposition or excavation, and therefore needed to be re-assembled for researchers to attempt to answer questions about the wreck. Since any reassembly of ship timbers is a painstakingly long process, this step should usually happen after the individual timbers are conserved. To provide researchers with the information necessary to study the ship while it underwent conservation, a digital reconstruction and scale physical model were created using a combination of traditional and innovative documentation methods. This paper outlines the methodologies used to reconstruct the vessel in detail and explains how the results of these processes allowed researchers to interpret the heavily damaged and degraded wreck as that of an 18th-century merchant sloop or brig by using digital models to develop a set of naval architectural lines for the vessel so as to recreate the original shape of the ship.

Section snippets

Methodology

Prior to any treatment that could impact the shape and integrity of the wood, all of the timbers were photographed, laser scanned, 3D modelled, and reproduced at a 1:12 scale via 3D printing. These various forms of documentation allowed researchers to study the vessel without interrupting the lengthy conservation treatment. Using the digital 3D models of the disarticulated timbers, the ship was virtually reassembled, and a theoretical reconstruction of the hull lines based on that virtual model

Interpretation

The modelling of the vessel described in this paper was combined with the research done by the CRL, Alexandria Archaeology, Thunderbird Archaeology, the NHHC, and the Oxford Tree-Ring Laboratory to develop our understanding of this vessel. The interpretation of the shape of the vessel by the authors suggests that the ship was approximately 21.35 m (70 ft) long overall, with a 17.68 m (58 ft) keel made of two timbers joined with a flat scarf spanning the floor timbers F 15 through F 18.

With the

Conclusion

The implementation of comprehensive 3D recording of ship timbers over the last five years has greatly increased the efficiency and accuracy of the documentation and interpretation of hull remains conserved there. Through a combination of laser-scanning, computer modelling, traditional lines drawings, and physical model building, the scant remains of the 18th-century ship found at the site of the Hotel Indigo along the waterfront in Alexandria, VA have revealed a fully realized reconstruction of

CRediT authorship contribution statement

Glenn Grieco: Methodology, Writing - original draft. Peter Fix: Conceptualization, Writing - review & editing. Carolyn Kennedy: Visualization, Investigation, Writing - review & editing. Julia Herbst: Visualization, Investigation, Writing - review & editing. Lauren Shultz: Visualization. Ricardo Borrero: Visualization. Christopher Dostal: Conceptualization, Methodology, Writing - original draft.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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