66 The length of overhang of course cannot be arbitrarily fixed, but a very fair proportion for ordinary freighters is to of the length. The height of deck or rail at taffrail, or cock-up," will be dependent on the camber of deck at transom frame (No. 0). The midship camber proportioned to the half-breadth at this frame should be set up and the deck line carried through this spot in a fair curve to taffrail. The height so obtained should be then transferred to body plan, and the deck (or rail line) between No. 0 section and taffrail drawn in as a round of beam curve, from which may be obtained the intermediate spots for deck at side (or rail) on sheer plan. 4th. The rail half-breadth will depend on the particular type of ship being designed. In freighters it will be parallel to the center line for probably half the length amidships, whereas in yachts and other fine vessels it will "round" all the way. It is convenient to have rail half-breadths at hand for various types of vessels for, say, ten ordinates with half-end ordinates or whichever number is adopted as the standard. These should be tabulated with the half-breadth amidships as unity, when, with the aid of a slide rule, the half-breadths for the design may be very rapidly proportioned. It will be found convenient to have these for liners, freighters, sound and river steamers, yachts, etc., from good examples of their respective classes. The contour of rail line around taffrail will require careful fairing into the A.P. ordinate spot, and also at center line, where in no case should it be perfectly straight, the effect of such being a hollow. Neither, on the other hand, should it come to a "peak" or point, but carefully drawn as an arc of a circle. The knuckle mouldings, whether they be one or more, may with advantage be delineated by tracing the rail line just drawn and transferring it forward to its exact location. By so doing it will be seen that the stern between knuckle and rail lines will develop with a pleasing gradation from "O" frame to the upper counter line. Table of Rail Half-Breadths for Various Types. 5th. The load water line, as already stated, must circumscribe the area calculated with the aid of the coefficient a. The method of obtaining a has been previously explained. To obtain the form of this water line, and at the same time insure the accuracy of the required enclosed area, it will be found advantageous to prepare a diagram similar to the one opposite, or this one may be used with the aid of proportional compasses. Opposite the value of a for the design in hand half-breadths for ten ordinates may be read off and transferred to the half-breadth plan. Should, however, the line delineated after the spline has been fixed not meet with the designer's individual taste, or where greater fullness or fineness is required for special cases, forward or aft, it will be a very simple matter to modify the line, at the same time observing that whatever area be cut off at any one point be compensated for elsewhere on the water line, as the offsets taken from the diagram will enclose exactly the area required. Of course the designer may make his own diagram for the number of ordinates he prefers to design with. In any case the run of the line for a few feet forward of the post will require special adjusting when the oxter is being faired. In addition to the diagram, the following table is given of actual load water lines of several types with the coefficients of area of same (a). Load Line Half-Breadths Standardized. "0"A.P. a.726. a .857. a .683. a.717. a.797. a .656. a .771. ОСЕANIC. 6th. The construction line for the bilge diagonal is variously drawn from rise line or base line; but the latter is the more useful, being adaptable to extremes of types and unaffected by rise of floor line; i.e., the line should be drawn diagonally across the DIAGRAM OF BILGE DIAGONAL OFFSETS FOR VARIOUS VALUES OF "b" (TEN ORDINATES) body plan from the intersection of the base with the half moulded breadth line to center line at load water line height. It is evident that the area enclosed by this line must bear a close relation ship to the prismatic coefficient which varies with p and is equal to p p where p ranges from .60 to .82, respectively. By determining the value of the bilge diagonal coefficient "b," and referring to the diagram opposite, the offsets for a line enclosing an equivalent area may be taken off and run as a half-breadth line. DIAGRAM OF L. W. L. HALF-BREADTHS 7th. The load water line and bilge diagonal half-breadths having been preliminarily faired, may be lifted off on a slip of paper and transferred to body plan construction lines, when there should be no difficulty in drawing in freehand the sections, having the "dead flat" section as one extreme guiding curve and the transom frame as the other. 8th. After the preceding sections have been carefully outlined 2 1 |