All the After Diagonals

The next step in the design sequence is to establish additional diagonals in the body plan for defining the hull shape above the floor diagonal. The reconstructed design of the hull abaft amidships, in comparison to the hull forward, is much more definitive. Therefore, it will be presented first and in greater detail to illustrate the concepts of the rest of the overall design procedure.

In the stern only the floor diagonal terminates on the centerline timbers. In fact its 5 ft 6 inch height, as listed in the *devis*, establishes the height of the top of the deadwood knee and the bottoms of the fashion pieces of the stern (Figures 10, 20p, 28b, 30). The endpoints for all the other diagonals are located on the fashion pieces at frame position *XVIIID* (Figure 43a, b). For the purposes of design, the fashion pieces are treated as vertical frames, although in the constructed vessel they are actually tilted slightly aft.

The second set of surviving surmarks provides the orientation of the next diagonal above the floor diagonal. Since this diagonal has the same offset values as the floor diagonal, its stern endpoint could be tentatively established. The *devis* provides several measurements for establishing the endpoints of two more diagonals in the stern. These endpoints also serve as guide points for drawing the shape of the transom. The *devis*' 9 ft 4 inch height of the maximum breadth in the stern corresponds to the height of the transom beam, and the width of the transom beam is listed as 9 ft 4 inches as well. The only other measurement in the *devis* relevant to reconstructing the transom is 3 ft 2 inches given for the tumblehome in the stern. Unfortunately, as in the case of the height for the tumblehome at the midship frame, the *devis* does not provide a measurement for the total height of the transom. However, by applying the same approach and drawing procedures that were used in reconstructing the lower and upper parts of the midship frame, several variations of the transom were reconstructed. The differences between these transom reconstructions are minor, and the one used for the rest of the design is presented in Figure 43a. In this reconstruction, an additional 6 inches were added to the tumblehome to adjust for the 15 ft reconstructed breadth versus the 14 ft given in the *devis*. The theoretical reconstruction of *La Belle*'s transom (Figure 43a) combined with the midship frame reconstruction allows for the following diagonals to be drawn: floor diagonal *fa*, upper bilge diagonal *gg6*, maximum breadth diagonal *CC6*, topsides recurve diagonal *UU6*, and the main sheer diagonal *QQ6* (Figures 20p, 43b).

It cannot be overemphasized that these diagonals are straight in the body plan simply because they are drawn as such prior to plotting out any frame shapes between the midship frame and the ends of the vessel. NEXT

© 2014 TARAS PEVNY

REF: tangencypress.com/essay/1/page/36

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