Fig. 30. Method of Finding Bevels for All Timbers
in Roofs of Equal Pitch.
Fig. 31. Method of Finding Bevel 5,
Fig. 30, for Fitting Hip or Valley
Against Ridge when not Backed.
When jacks are placed between hips and valleys as shown at 1, 2, 3, 4, etc., in [Fig. 14], a better method of treatment is shown in [Fig. 29], where the slope of the roof is projected into the horizontal plane. The distance from the plate in this figure to the ridge m, equals the length of the common rafter for the main roof. On the plate a n n is made equal to a n n in [Fig. 14]. By drawing a figure like this to a scale of one inch to one foot, the length of all the jacks can be measured and also the lengths of the hip and the two valleys. It also gives the bevels for the jacks, as well as the bevel to fit the hip and valley against the ridge; but this last bevel must be applied to the hip and valley when backed.
It has been shown before, that the figures to be used on the square for this bevel when the timber is left square on back as is the custom in construction, are the length of a foot run of a hip or valley, which is 17, on tongue, and the length of a hip or valley that will span over 17 inches run, on blade—the blade giving the bevel.
[Fig. 30] contains all the bevels or cuts that have been treated upon so far, and, if correctly understood, will enable any one to frame any roof of equal pitch. In this figure it is shown that 12 inches run and 9 inches rise will give bevels 1 and 2, which are the plumb and heel cuts of rafters of a roof rising 9 inches to the foot of run. By taking these figures, therefore, on the square, 9 inches on the tongue and 12 inches on the blade, marking along the tongue will give the plumb cut, and marking along the blade will give the heel cut.
