The Charlestown Navy Yard has been a fixture of the Boston Harbor shoreline for more than 200 years. Until its closure in 1974, the Navy Yard was a city-within-a-city, with facilities constantly evolving to meet the changing needs of the nation. Shipbuilding’s transition from the almost exclusive use of wood to that of iron and steel is, of course, one of the most dramatic of these changes, and one that draws my attention as a carpenter with an interest in historical technology.
Storage ponds are a traditional way to accumulate and maintain an inventory of timber. The low-oxygen, underwater environment discourages deterioration and slows the drying of wood. This minimizes the development of defects such as splits and checks, and wet wood is much easier to work with hand tools. At Charlestown, the saltwater storage ponds were stocked with various species of timbers, held submerged by granite blocks, at the ready for shipwrights needing the perfect piece for the rib of a new hull or for the constant repairs required to keep wooden ships in service (including the USS Constitution, which has been berthed in Charlestown since 1897).
Charlestown’s last wooden warship, the USS Vandalia, was launched in 1876. The storage ponds were mostly gone by 1898, the year of the Spanish-American War, when more than 50 steel- and iron-hulled ships were repaired at Charlestown. While the timber storage ponds were filled in and forgotten, the Navy Yard continued to evolve until its eventual closure. For example, it hosted a workforce of 50,000 during World War II, and was an important manufacturer of rope, chains, and anchors.
Although part of the shipyard became a unit of the Boston National Historic Park, most of the land has been redeveloped. The timber storage ponds came back into the spotlight in 2008, when an excavator beginning work for a new hospital unearthed a field of timber from the brackish mud. I remember hearing about this discovery at the time, but didn’t give it much attention until earlier this year, when my friend and colleague Brad Morse of Uncarved Block Inc., out of Becket, Massachusetts, asked me to cut the frame for a vacation cabin out of some of this ancient wood.
Most of the newly discovered timbers, some with sections up to 3 feet square, were donated to the Henry B. duPont Preservation Shipyard at Connecticut’s Mystic Seaport for use in the restoration of the Charles W. Morgan whaling ship. During this work, researchers from the University of Arizona cored tree ring samples from many pieces of the wood, and analyzed them to reveal more about their history, a science known as dendrochronology. The sampled timbers were of white oak and live oak, the prime shipbuilding species that gave the USS Constitution its reputation as “Old Ironsides.” The white oak proved to be from somewhere in Ohio, harvested in the 1860s, while the live oak could not be dated or located with any confidence. This is, at least in part, because live oak is an evergreen species – its growth rings are not as distinct as those of deciduous species – and because white oak has been studied much more extensively due to its prominence in early timber-framed buildings.
The material for the cabin frame was purchased from Jarmak Reclaimed Wood, a Massachusetts salvage timber dealer, who obtained the wood that was surplus to Mystic Seaport’s needs. These large pieces of rough stock were milled to the much smaller sizes appropriate for the scale of our cabin frame by Scott Brockway of Berkshire Wood Products in Windsor, Massachusetts, using a carbide-tipped bandsaw blade. Fresh oak timbers usually shrink and distort significantly as they dry, but the slow curing of this timber in salt water for 150 years made it very stable. This allowed us the rare opportunity to mill the timbers right through the pith, showcasing book-matched quarter grain (where the tree’s medullary rays display as bold figure) in the cabin frame.
Although these newly milled faces were impressive, we did not want to lose the character of the historical surfaces, which were hewn or pit sawn and then charred before going into the timber storage ponds. Retaining the organic form of these rough, original surfaces, often including undressed wane edge from the log, necessitated the use of scribing to join the timbers into a cabin frame.
Scribing, often referred to as “scribe rule,” is a broad set of techniques that can seamlessly join variously out-of-square, curved, or organically formed members into a timber frame. When scribed, every joint in a frame is unique, created using plumb and level as references to record the shape of intersecting timbers on each other. Although principally derived from European framing traditions, my approach to scribing often integrates techniques from contemporary log building, and even lasers, to deal with unusual circumstances. Nonetheless, there remains much in common with how early shipwrights would have worked with this wood.
The first step in scribing is lofting, where we use geometry, careful measurement, and chalk lines to create a full-scale drawing of an assembly on the shop floor. Most of the lines represent the top or outside surfaces of the timbers, where wall and roof sheathing will be attached to enclose the building, and flooring will be laid. Using the same lofted drawing for multiple assemblies – such as the three bents of our cabin frame – keeps their surfaces consistent, regardless of the particulars of the individual timbers.
Next, timbers are positioned in multiple layers over the drawing, leveled, and carefully aligned to their respective chalk lines. Once a piece is set in position, or laid up, it shouldn’t be moved until the marking process is complete. Stacking the components in multiple layers allows their ends to pass by each other where they will be joined together. With the timbers aligned in the two dimensions defined by the lofted drawing, but offset in the vertical dimension, the string of a plumb bob, or another device, is used as a reference to mark the unique intersection of surfaces between the joining timbers. Once these lines are marked on the timber faces, and knowing the vertical offset between the two timbers in the layup, mortises, tenons, laps, and any other joinery can be set out. Scribing often requires the carpenter to focus on making precise marks in awkward positions, therefore leaving enough room to move around in your layups is important. Otherwise, you’ll find yourself having to double as an acrobat and contortionist. Starting with stout sawhorses, rather than blocks, can make a big difference.
Sometimes you can lay up and scribe all the timbers in an assembly at once, stacked three or four layers high. But that method did not work for this cabin frame. Marking the joinery between two round surfaces, such as where the scissor ties cross, required using specialized bubble scribes, the mechanical limits of which only allowed for a two-layer layup. That required several cycles of assembly and disassembly to get to the finished assembly; extensive material handling is typical of scribed work. The extra effort was worth it, though, to contrast those rough, original surfaces with the bold figure revealed in the smooth, newly sawn faces once sanded and oiled.
We raised the cabin at a remote site in northwestern Connecticut on a beautiful, early June day. There’s always a particular satisfaction in seeing your work come together as a building after weeks of juggling details in your mind. Seeing your client’s enthusiasm for their new space is an added bonus. This turned out to be a full-circle project for me, too, as it stands only a few hundred feet from the frame I cut as a student during my first timber framing workshop, back in 2005.
