[Fig. 100] is a plan of a few curved steps placed at the bottom of a stairway with a curved stringer, which is struck from a center o. The plan tangents a and b are shown to form an acute angle with each other. The rail above a plan of this design is usually ramped at the bottom end, where it intersects the newel post, and, when so treated, the bottom tangent a will have to be level.
Fig. 106. Twisted Wreath Raised to Position,
with Sides Plumb.
In [Fig. 101] is shown how to find the angle between the tangents on the face-mould that gives them the correct direction for squaring the joints of the wreath when it is determined to have it ramped. This figure must be drawn full size. Usually an ordinary drawing-board will answer the purpose. Upon the board, reproduce the plan of the tangents and curve of the center line of rail as shown in [Fig. 100]. Measure the height of 5 risers, as shown in [Fig. 101], from the floor line to 5; and draw the pitch of the flight adjoining the wreath, from 5 to the floor line. From the newel, draw the dotted line to w, square to the floor line; from w, draw the line w m, square to the pitch-line b″. Now take the length of the bottom level tangent on a trammel, or on dividers if large enough, and extend it from n to m, cutting the line drawn previously from w, at m. Connect m to n as shown by the line a″. The intersection of this line with b″ determines the angle between the two tangents a″ and b″ of the face-mould, which gives them the correct direction as required on the face-mould for squaring the joints. The joint at m is made square to tangent a″; and the joint at 5, to tangent b″.
Fig. 107. Finding Bevel,
Bottom Tangent Inclined,
Top One Level.