Sloping Ridge On Pentagonal Ground Plan

Looking at plate # 11 in "Traité Théorique et Pratique de Charpente" by  Louis Mazerolle I revised his geometry technique to easily establish the angle of the sloping ridge and the edge bevel on the sloping ridge.

The key to establishing the sloping ridge angle is to use the profile rafter slope angle and extend the profile rafter slope angle to locate point S, that is perpendicular to point S on the ground plan view.  Then you can easily develop the sloping ridge angle and the edge bevel on the sloping ridge. As in Fig. 3. It is not necessary to extend the sloping ridge out as in Fig. 4 to find the edge bevel of the sloping ridge.