THE NAVAL ARCHITECTURE
AND DOCUMENTATION OF
By W. Boris Kirilloff
The naval architect's responsibilities to the Maple Leaf Project include the following tasks:
· To record measurements into computer files.
· To develop measurement data into usable information.
· To assist in the depiction of the Maple Leaf as a ship both in the overall sense and in detail of components.
· To give advice to underwater support staff when on site.
· To assist the archaeological team in their efforts to properly document the activities of the project.
Designing a new ship, or documenting a ship while visible - either above or below water - is much easier than in zero visibility on the bottom of a murky river. But not being able to see the Maple Leaf creates a challenge which we cannot ignore and have to overcome. By the use of computer programs that will numerically fit the pieces of information together, we can develop a picture of the ship and its contents.
A good example of how the computer was used to predict the shape of the main deck, was the analysis of the main deck toe rail recovered from the bow of the Maple Leaf This piece depicts the general shape of the forward part of the main deck. From this information, plus known length and beam dimensions, it was possible to use a polynomial regression program in a Computer Aided Design (CAD) system to predict the shape of the main deck. As other pieces and parts of the ship are measured and documented, the CAD system can be used to improve on the graphic depiction of the ship.
A great concern, of course, is the lack of actual evidence of the shape of the superstructure of the ship. Because the structure above the main deck has been destroyed by both man-influenced clearing and natural environ mental means, there is a big gap in the documentation of that area. Because of the lack of historical data on the ship in either the form of drawings or other types of construction in formation the only input available will be data from photographs and historical accounts, as well as from the study of other ships of the era.
Recording Data in a Computer
Computers allow us to manipulate data from a single file for a variety of uses. This aspect of the Maple Leaf Project assists in development of graphic tools such as maps, drawings and diagrams, that help the archaeological team to visualize that they are dealing with. And not only while working on the site, but in the post-dive debriefings as well.
In order to prepare a site map, a two dimensional grid
system was established for horizontal control, and the vertical control was provided by
probing and excavations. The team developed the grid system by the use of cables and rigid
PVC pipe made into a ten-foot grid. This grid section was used by sliding it along a
tensioned cable, running along the centerline of the ship that is physically tagged in
ten-foot increments. This enables the grid numbering system to be labeled in ten-foot
increments, fore and aft, and alpha labeling for athwartship identification, A, being zero
to ten feet, B, being ten to twenty feet, and so forth. Therefore, a diver and the surface
support team, which includes a record keeper, can easily identify which site geographic
area a diver is operating in. With the grid system developed, it is now possible to
use the graphic tool (see figure 3 page 155) to assist in the further documentation of the
Developing Usable Information
Once the data from the field is processed onto the CAD system, it is then turned into usable information for field work. The on-site dive team uses the output of the computer in both the numerical and graphic forms to pre determine what the dive activity will be for any given dive.
The trend of the main deck's shape, which was developed from the toe rail previously described (see figure on page 194) by the use of polynomial regression program also indicates the data collected from a series of dives to verify the shape (see figure 4 page 156) of the port side of the deck. At some future date the starboard side will also be surveyed. When this is accomplished, it will probably verify the symmetrical geometry of the hull. During the data collection on the starboard side, the numbers that will be called to the surface will be analyzed by the surface support team against the data shown in figure 4 page 156. If any anomalies are noticed then the surface support team will be able to immediately identify the discrepancies and request the divers to check the data. One very interesting note to make at this point about figure 4 page 156, is that the fitted curve of the port side of the main deck, which was developed from the survey data, matched almost exactly the curve that was predicted from the research done earlier by the computer analysis of the bow rail. Similarly, though the paddle wheel location shown in figure 4 was modified to fit the data collected, it is interesting to observe that the earlier research was generally confirmed by the later data. Once the main deck line was revised, all the other drawings that show the main deck line were revised to the new shape.
In the case of artifact recovery, CAD is used as a tool to understand the placement relation ship of the artifacts in relation to each other and their overall placement within the ship in a three dimensional sense. Although the possibility is high that artifacts shifted in the hull for a variety of reasons, some natural and some man-made, as more recoveries are plotted on the computer, we should have a useful graphic representation of the arrangement of artifacts in the holds. By the use of the zoom feature of CAD, one can go from the overall site plan to the drawing of the entry into the aft cargo hold ( figure 2 page 154). From here one can visually enter the cargo hold and see the placement of artifacts in a three dimensional representation. Since all artifacts are tied to their locations on the computer, the viewer can go directly to the location of a specific artifact, or a more elaborate feature of the program is the ability to formulate a walk through the ship by use of freezing two- dimensional views, which can be consecutively viewed to animate motion through the ship. This would give the viewer the ability to see what it might look like to walk through the Maple Leaf.
One other use of the collected data is the ability to construct a scale model of the Maple Leaf Because a model is not easily changed, and because it should be historically correct, the final museum quality model will need to be put together after data collection is completed. A three-foot museum-quality model has been contracted to be built for the project.