Subsequently the shipwright can shape and insert transversely oriented framing timbers to conform to the hull shape defined by the shell of planks.
With frame-first construction, only a few widely spaced frames or transverse templates can be raised along the length of a hull prior to establishing some longitudinal relationship between them, which will assure smooth curvature along the length of the vessel. Ship hulls are complex curved surfaces characterized by continuous smooth curvature that changes in all directions, and frames simply do not provide a continuous surface that can be progressively bent or carved into a desired hull shape.
During construction with only a few frames raised, whether by bending on actual hull planks or ribbands as temporary substitutes, the longitudinal curves have to be defined (Figure 15a, b). Once they are shaped and positioned, these longitudinal timbers provide the shipwright with guide points for shaping additional frames (Figure 15c). A shipwright visually judging the characteristics and smoothness, or fairness, of curvature defined by planks, ribbands, or splines is known as visual or free-form fairing (Nowacki 2009:37; Rabl 1941:28). The tendency of planks to bend in fair curves as a result of their material resistance to such bending is a great aid in the evaluation of fairness.
On La Belle, other than the spine timbers, there is no evidence that any longitudinally oriented timbers were in place prior to raising the surmarked frames. The double set of fastenings on VIIIIA supports the conclusion that even the main shape of the forwardmost preserved surmarked frame was determined independent of the use of ribbands during construction. If the shape of the hull was already defined in three dimensions with ribbands, the shipwright would have been able to measure the bevel angles, and frame VIIIIA would display the same fastening characteristics as un-surmarked frames VIIIA and XA. Instead, La Belle's shipwrights must have had some method of determining the shape of frame VIIIIA as well as the other surmarked frames prior to construction—a design method that, like the use of longitudinal planks or ribbands, could provide guide points for defining the frame shapes by delineating the change in longitudinal curvature.
La Belle's surmarks are carved onto transverse structural elements, i.e., the frames. However, when the interrelationship between the surmarks on all the frames is explored, a strong longitudinal feature becomes apparent. A distinguishing characteristic of La Belle's surmarks is that when the frames are superimposed in cross section, the surmarks align along two oblique straight lines, i.e., diagonals (Figure 5a, b) (Pevny 1999). Not only do the surmarks define points on these lines, they are actually carved into the timbers at the angles of these diagonals. NEXT
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