In Fig. 311, let NCDO be the elevation of an elliptical pipe fitting against a roof, represented by A B. Let E F G Q be the section or profile of the pipe. Draw the profile in convenient proximity to the elevation, as shown, and divide it into any convenient number of equal parts. Place the T-square parallel to the sides of the pipe, and. bringing it against the points in the profile, drop lines cutting the roof line A B, as shown. Opposite to the end of the pipe, and at right angles to it, lay off a stretchout, as shown by H I, and through the points in it draw measuring lines in the usual manner. Reverse the T-square, placing it at right angles to the pipe, and. bringing it successively against the points in A B, cut the corresponding measuring lines, as indicated. A line traced through these points, as shown by K L. M, will be the required pattern. In the illustration the long diameter of the ellipse, or E G, is shown as crossing the roof. The method of procedure would be exactly the same if the pipe were placed in the opposite position - that is, with the short diameter Q F crossing the roof. In such case the profile should be turned so that Q F is across the roof, or parallel to C D. and the elevation duly projected from it. The pipe might with equal facility he placed so that the long diameter should lie at any oblique angle desired.

Fig. 311.   The Pattern of an Elliptical Pipe to Fit Against a Roof of One Inclination.

Fig. 311. - The Pattern of an Elliptical Pipe to Fit Against a Roof of One Inclination.

The New Meal Worker Pattern Book.