In Figure 49c the forwardmost template was moved inward—narrowed—by the amount yy. Without some method of defining the intervening longitudinal curvature, no additional templates can be raised between the midship frame and this tail frame. In Mediterranean moulding the longitudinal curvature is defined by the arithmetic or geometric methods of generating offsets for a curve, such as the mezzaluna, that were discussed in Part I of this essay. For this example, a scaling triangle was constructed using La Belle's forward "mother sequence" to derive the narrowing offsets. When these offsets for a curve are marked on the floor template, they provide guidepoints for shifting the template inward at specified frame positions, and only when these offsets are correlated with evenly spaced frame positions do they define fair longitudinal curves (Figure 49c, d).
The templates are marked with the narrowing offsets relative to the centerline of the vessel. This allows for the practical shifting of the template, specifically during construction when the template is placed directly on the timber without any external points of reference. In fact, on the vessels associated with Mediterranean moulding, surmarks on the floor timbers are usually accompanied by vertical lines marking the edges of the keel and/or centerline. In addition to aiding in positioning the frames on the keel, these marks would have been used to align the template when it was flipped on a piece of squared compass timber to trace out the opposite arm of the floor timber (Figure 49r).
A hypothetical curve drawn through the narrowing offset marks on the templates would not actually lie on the curved surface of the hull. However, above the flat of the floor the shifting of the templates defines identical narrowing curves along any consistent point on those templates (Figure 49d). Figures 49e and f were created to illustrate the concept that all the change in hull curvature in Figure 49d could actually be defined by lower bilge or chine curves drawn on a flat horizontal surface. This is due to the fact that all the longitudinal curves depicted in Figure 49d are identical and all the templates have the same shape above the flat of the floor. Although the restrictions or rules placed on the transverse geometry—e.g. using one set of templates—are important, it is the definition of longitudinal curvature that actually quantifies the change in hull curvature along the length of the vessel. In other words, although in Mediterranean moulding templates are utilized to enable frame-first construction, Mediterranean moulding does not simply equate with frame-based design.
In a completely flat-bottomed vessel, these chine curves could be drawn on a platform of planks. Once the bottom planking was cut to shape, identical futtock timbers could be secured along the chine. NEXT
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