Emoyan

Saturday, January 31, 2015

Posted by Unknown at 4:33 AM

Planking its more than just carvel vs clinker

Its been over a month since my last substantive post, and I must apologize to my reader/s for the blackout. No problems other than being busy, but who isnt?

In September, I discussed Basil Greenhills "four roots of boatbuilding" as described in his Archaeology of the Boat. Another important theme of this book is the typology of boats based on their planking styles. In the Western tradition, were accustomed to thinking of everything in terms of smooth-skinned versus overlapping planks -- also known as carvel versus lapstrake (a.k.a. clinker). But looking at boatbuilding from a broader cultural perspective, this is not a very useful distinction.

Modern builders of traditional western boat types do much of the setup the same way, regardless of whether theyre building carvel or lapstrake: first you set up building forms or sawn frames; then you bend planks around the forms or frames. Then if you were using forms, you replace them with frames. But this wasnt always the case. The lapstrake tradition is by far the older one in western culture and, in contrast to modern methods, building forms and sawn frames were not used. This is because builders did not work from plans, and did not envision the boat as a series of sections or half-breadths.

Rather, they viewed the boat as a shell. Plank shapes were the starting point, and through experience, ancient builders could envision how a collection or series of plank shapes would go together to create a boat of a given shape. The planks were, in Greenhills terminology, "edge-joined" to one another to create the shell or envelope, and only then was an internal structure inserted.

But beware the term "edge-joined" in the paragraph above. These were lapstrake boats, and the planks were not set "edge to edge" carvel-style. The edges did in fact overlap, lapstrake-style. By "edge joined," Greenhill means that the planks are structurally connected to one another to create the shape of the hull. This, then, is a clear contrast to carvel planking, in which the planks are not attached to each other at all but, rather, are attached to the frames for structural integrity.

So Greenhill largely divides plank-built boats into edge-joined, i.e., "shell-built" hulls, and non-edge-joined, i.e., skeleton-built hulls. This proves to be a far more useful way of looking at boats archaeologically and cross-culturally, because many cultures use (or used) edge-joined planking methods that result in a smooth outer skin. This involves the use of a variety of overlapping methods, one of which is shown below in images from Greenhills book.


The images show a common planking method of Bengladesh. Note the full-length rabbet between the planks, which are joined by iron staples set into mortises on both sides. After the entire shell is thus assembled, frames are added to the inside. As shown in the photo, frames across the bottom (i.e., floors) often do not even touch frame members up the sides. The shell provides the majority of its own structural integrity, and the frames are reinforcements, but not essential structure as in a carvel hulls skeleton.

Greenhill diagrams about two dozen shell-forming methods (unfortunately, the books graphic doesnt scan well for the web), with a great variety of plank-joint styles (e.g., rabbeted/smooth- skinned, normal lapstrake; reverse-lapstrake [in which the lower planks upper edge is outside of the upper planks lower edge]; strip-planking, bevelled/smooth-skinned, flat, flush smooth skinned, and more) and fastening methods (e.g., mortised staples, sewing or stitching, edge-nailing or dowelling, etc.). Its clear that the majority of plank-built boats in what I refer to as indigenous traditions rely on edge-joining/shell-built technology.

Viewing all plank-built boats from this perspective opens up ones understanding of boatbuilding far beyond the carvel-vs.-clinker duology. One can therefore see the Chesapeake Bay log canoe (western culture, yes, but outside the norms of the western boatbuilding tradition) in a new light: although the topsides planks conventionally meet the boats stem and stern, the bottom planks run parallel to each other, their ends curving up to meet the bottom edge of the lowest topsides plank rather than curving inward toward stem or sternpost. The evolution of this type makes sense: originally it was truly a log canoe. It was expanded laterally by adding additional logs; the logs were hollowed out and, over stages, became not hollowed logs but planks -- but they were still joined edge-to-edge to make the shell. Eventually, topsides strakes were added in what has now become the traditional carvel style.