Collar Beams. The method of finding the lengths and of cutting collar beams is illustrated in Fig. 85. The distance ab stands in the same proportion to the length of the collar or tie beam as the rise of the roof to the width of the house. Thus, if the distance ab is given, the following mathematical formula will give the length of the collar beam.

A = distance between the bottom of the collar beam and the apex of the roof.

C\ = length of collar beam.

C2 = denominational constant of the pitch of the house, or 2, if half pitch; 3, if third pitch; and 4, if quarter pitch.

Formula 26. C1 = A X C2

Fig. 85. - Method Of Finding The Lengths Of Collar Beams.

The application of the above formula upon the steel square is as follows: using the bevel board as illustrated in Fig. 84, slip Bl. along the base line, ab, until A on To. intersects with the pitch of the roof (cb). The reading of Bl.X 2 = C1. The cut of the end of the collar beam is found by placing the square as in marking the pitch of the roof (see Fig. 72). Bl. = end cut.