The holes cut in a roof for vent pipes require elliptical templates. A formula for determining the length of the major axis of the ellipse is given by

where D is the (outside) diameter of the pipe and H is the “rise” of the roof per D units of “run”; that is, the slope of the roof is H/D. (See the figure below.) The width of the ellipse (minor axis) equals D. Find the length and width of the ellipse required to produce a hole for a vent pipe with a diameter of 3.75 in. in roofs with the following slopes

(a) 3/4 

(b) 2/5

Transcribed Image Text:

L = f(H, D) = VH² + D²,