The method of obtaining the pattern of the fascias of a molding covering a curved hip has been given in Problem 6. As it is necessary in obtaining the patterns of the molded portion or roll, that the curve of the hip should be established, this problem really consists of developing from the normal profile of the roof a profile through the hip, or, in other words, a diagonal section of the mansard.
Let A E B in Fig. 422 represent the plan of a mansard roof or tower, the elevation of which is shown by H K, over the hip of which a molding of any given profile is to be fitted, in this case a three-quarter bead, the diagonal line E F in the plan representing the angle of the hip as it would appear if viewed from the top. At any convenient point parallel to E F, and equal to it, draw E1 F1, and from F1 erect a perpendicular, F1 K1, in length equal to the vertical line in elevation G K. Divide G K and F1 K1 into the same number of equal spaces. From the points in G K draw lines cutting the profile H K, as shown, and from the points thus obtained in H K drop lines vertically, producing them until they cut the diagonal line E F of the plan, as shown. Through the points in F1 K1 draw measuring lines in the usual manner, and intersect them by lines erected perpendicularly to E F from the points therein. Then a line traced through these points of intersection, as shown by E1 K1, will be the profile to which the molding covering the hip is to be raised.
Inasmuch as in the usual process of mold raising all curves must be considered as segments of circles, to accommodate both the adjustment of the machine used and the describing of the patterns, the curved line E1 K1 just obtained must be so divided that each section or segment will approach as nearly as possible an arc of a circle. In this case the section from E1 to L will be found to correspond to an arc struck from a center, M, while the section from L to K1 corresponds to an arc struck from a center not shown in the engraving, but which will be found by the intersection of the lines L N and K1 N1 produced.
In the lower part of Fig. 423 is shown an enlarged section of the hip molding, including the fascias, as it would appear at the bottom of the hip, and above it another section taken at the top, which has been derived from the normal section or section at the bottom by the method used and explained in Problems 105,
106 and 107, previously demonstrated. A dotted reproduction of the lines of the upper section is placed here to show the change in the flare that takes place between fascias in going from the bottom to the top of the hip, thus showing that the outer edges" of the roll require trimming after being raised so that the roll may have an equal projection throughout its course.
Fig. 422. - Diagonal Section of a Curved Mansard Roof Obtained for the Purpose of Mold Raising.
Fig, 423. - Enlarged Sections Through Hip Finish at Top and Bottom, Showing Change in Flare of Fascias.
Methods of obtaining the patterns of curved moldings will be found in the following section of this chapter.