I came across this method of drawing out the curves of hip rafters in a Carpentry & Building magazine published in 1880 and thought it was pretty easy way to establish the curve of any hip rafter using this method. It can be used for the curved hip rafters on flared radius eave rafters, curved hip rafters on bay windows or a hip rafters with any eave angle.
To use this method draw the elevation view of the common rafter and hip rafter above the plan view of the radius rafters. Draw the radius/ Arc of the common rafter. Then draw equal spaced horizontal lines that intersect with the hip rafter slope line in elevation view. Drop some perpendicular line where the horizontal lines intersect the hip rafter slope line and the common rafter slope line . Then draw rectangular boxes to establish the cure of the hip rafter based off the curve of the common radius rafter.
Geometric drawing of the curve of a standard hip rafter and Octagon hip rafter with a common radius rafter.
Drawing for the curve of the bay window hip rafter and the curve of the hip rafter against the wall of a bay window.
Section of a Bay window in Plan View
How to draw out the arc of the common radius rafter on a bay window.
Geometric drawing of the curve of bay window hip rafter and the curve of the hip rafter against the wall of a bay window using the rectangular boxes to establish the curves of the rafters.