A New Mast for William B. Tennison: A Lesson in Discerning Change in Historic Vessel Preservation

By Samuel Hilgartner

CBMM’s Shipyard takes a pragmatic approach to maintaining vessel operability and safety while preserving historical integrity. How do we strategically assess whether it is appropriate to depart from certain aspects of historical accuracy? What do we consider in this process? Do certain elements of a vessel’s historical identity take precedence over others?

Let’s examine a recent project: Since 2019, the Shipyard has handled maintenance on a unique 1886 bugeye buyboat conversion, William B. Tennison, owned by the Calvert Marine Museum (CMM).

This year, CMM commissioned us to build a new mast for the vessel. The first step in all vessel preservation projects is to identify the treatment plan, which defines the larger project’s intention. In this case, we are to restore the mast to a more historically accurate form while maintaining the new rigging built by our Shipyard two years ago.

Restoration requires research to determine the most accurate representation of the vessel. Research restricted by the vessel’s period of historical significance aids in determining the prioritization of certain defining features that should not be compromised.

In the case of Tennison, these features include the buyboat configuration, the pilothouse design, the decked “patent stern,” and the log bottom construction.

The period of historical significance, or POS, is the date or range of dates that qualifies the vessel’s historical value. CMM seeks to represent the vessel’s form during the 1930s to 1950s.

After studying photographs of the vessel from this period, it was determined that the mast should be decreased in diameter and increased in height.

A future project will be to construct a double gaff cargo rig, so the mast will be fitted out with a table to accommodate two gaffs. The mast will also have a more gradual taper as you approach the masthead portion, which then tapers more dramatically. These changes are consistent with historic photos of Tennison and the general buyboat type.

Once we identify the treatment plan, the vessel’s historical characteristics, and the vessel’s POS, we look at options we might employ for the material and workmanship of our new mast. The mast could be made from solid, locally sourced, historically correct material;

solid, non-local material; solid or hollow laminated construction; or an aluminum extrusion.

Historic vessel preservation principles consider seven contingent properties—location, setting, use, material, workmanship, form, and character—while taking into consideration practical limitations of regulation, maintenance, vessel use, time, and material availability.

At CBMM, our new protocol scores the seven factors of historical integrity using a grading rubric that helps offer a more objective analysis of historical integrity.

In the 1930s, Tennison’s mast would have been solid, built from a local yellow pine species, pitch pine, or bald cypress. However, it is increasingly challenging to source material of the necessary size and quality.

The next best option is to use a wood material with comparable properties, such as Douglas fir, a common mast construction material from the Pacific Northwest. As we could not source a high-quality tree, we will use a laminated construction style using high-quality vertical grain lumber.

We have opted for a hollow birds-mouth construction over solid stack laminations for reasons of strength, economy of material, and weight. If the mast’s material lent the vessel its historical integrity, we would prioritize acquiring the material.

Nevertheless, the new mast will still be wood and more accurate in its design and scantlings, resulting in a historically appropriate mast that should also provide great longevity.

This example illustrates our approach to difficult questions at CBMM’s Shipyard. We do not always use “historic methods.” We will employ the full breadth of technology available to us while ensuring our practices are situated within the heritage of Chesapeake boatbuilding and employing techniques rooted in tradition. ★

Samuel Hilgartner was the lead rigger on CBMM’s Maryland Dove build and serves as curatorial shipwright.

CBMM Shipyard’s New Protocols for Assessing Vessel Preservation

Vessel preservation should never follow the course of individual preference or opinion. It is best to develop a protocol of preservation to guide decision-making. A preservation protocol should be adaptable to a diverse range of projects while remaining consistent in its basic implementation. Protocols that are systematic and philosophically consistent allow future work to be performed with more confidence.

Using a process-oriented plan in preservation may expose inconsistencies in a previous approach. Should these conclusions be opposed to common sense or to a broad consensus of professional opinion, the protocol should be reevaluated.

A Simplified Preservation Outline

1. Establish project feasibility and preservation treatment plan (stabilization, preservation, restoration, new construction, etc.)

2. Gather preservation data, including:

a. Identify period of historical significance (can be a range of dates or an era)

b. Research

c. Prioritize typological and idiomatic properties

d. Evaluate each of the seven properties of historical significance

3. Estimate longevity

4. Assess material availability

5. Assess availability of labor

6. Evaluate the interpretive or educational environment

7. Execute work