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Wednesday, November 18, 2009

More on Greenhill's Planking Theory

Yesterday's post introduced Basil Greenhill's shell-built-versus-skeleton-built typology of plank-built hull construction. Today's illustrates a few points further.

Modern lapstrake (clinker) builders set up building forms (or station molds) up on a strongback or backbone, then line off appealing plank shapes, spile the shapes, and then cut the planks to fit properly on the form. This presupposed the existence of carefully drawn plans that can be scaled up to full size, and/or accurate tables of offsets. The traditional clinker builder, in both the Western and non-western traditions, had no such plans or tables -- nothing upon which to base station molds. It was the plank shape that came first, and the boat took shape as those planks were assembled. While most builders relied on memory to copy the plank shapes of their teachers, it must have taken an extraordinary mind to modify the shape of a hull for any reason, for this would require visualizing the shapes of the planks needed to form the hull. Even as simple a boat as a banks dory has very surprisingly-shaped strakes, if you see them "unwrapped" from the hull, and the notion that builders could properly visualize the plank shapes needed for, say, a round-bottomed hull of wide beam, with a hollow entry, spoon-shaped bow, and a tucked-up transom stern -- well, just try and do that without CAD.

But do it they did. Shown below are a couple examples. The first, at the National Maritime Museum (Greenwich, England), was a demonstration to show how it was done without forms. The builder did use a few half-molds, but these were simply held in place by hand, temporarily, to check how the hull was developing. Planks were not bent around them.
The next example is a Bengladeshi boat, similar to the hull shown in yesterday's post. Note the copious use of clamps and shores to hold strakes in place while they're fastened.
The following photo shows a typical, mostly frameless, Bengladeshi working boat built by the method shown above.

Finally, we see a variety of planking styles used to extend (raise) the sides of a dugout canoe. These same planking methods continued to be used after the dugout base had atrophied into a keel. All are examples of what Greenhill described as "edge-joined" planking and, whether lapped or smooth, were methods used to build shell-built hulls.
(All images in this post are from Archaeology of the Boat, by Basil Greenhill.)

1 comment:

  1. Those look like the oar holders on my drift boat. Really dig the site.

    Boat Props