The Upper Midship Frame
In terms of the vessel's design, all the major changes in curvature occur below the maximum beam, and the shape of this part of the hull is vital to the ship's overall performance. Nonetheless, in terms of the everyday life of a functioning vessel, the design of the upperworks impacts on the handling of armament, sail, and cargo as well as the comfort of officers, crew, and passengers.
The devis provides several measurements for defining the midship section above the maximum beam: the tumblehome or the amount the hull curves inward from maximum beam is listed as 12 inches; the height of the deck beam in a straight line as 7 ft 1/2 [6 inches]; and the depth of hold as 7 ft 3 inches. Although the devis does not provide the height of the midship frame above the maximum beam, comparative documentary evidence enabled the reconstruction of the design of the complete midship frame (Figure 29a–d) (Boudriot 1993:52–53; MnM 1684a:PH 178893; 1697:PH 90251,). In addition, the work of Glen Grieco and the historical research of Jean Boudriot and Jean-Claude Lemineur provide excellent information for the reconstruction of the overall structure of La Belle (Boudriot 2000; Grieco 2003).
My reconstruction of the complete midship section from the designer's viewpoint takes into consideration the physical requirements of the functioning of the vessel (Figure 29d), such as clearance for La Belle's 4-pounder cannons. The one-inch discrepancy between the 7 ft 4 inch depth of hold in the reconstruction and the 7 ft 3 inches given in the devis can be easily reconciled by giving the beam slightly less camber. Since the design of the upperworks relies heavily on documentary evidence and cannot be compared in detail to the articulated portions of La Belle's hull remains, it will not be discussed in further detail in this essay.
Although the longitudinal profile and the midship shape of a vessel can be drawn independently in two-dimensional planes, determining the location of the transversely oriented midship frame along the length of the longitudinally oriented keel begins the definition of the three-dimensional shape of the hull. La Belle's midship section is located at 3/8 from the bow and 5/8 from the stern relative to the 45-ft design length of the keel (Figures 20b, 30). Note that from Figure 20a to Figure 20b, the flat design of the centerline profile has been converted to a representation of spine timbers. In the design of the midship frame, the sided dimension of spine timbers was defined with the lines LM and L'M' (Figure 27e).
By defining the limits of the hull's transverse curvature, the midship frame greatly influences the internal volume of the hull as well as its lateral stability. NEXT
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