Billy Dillon's Hexagonal reciprocal roof model.
German Schiftzirkel (Reciprocal ) roofs.
Shift = Shiften
Zirkel = Circle or Compass
Here's a drawing of the geometry for the typical Mandala Reciprocal Roof with 8 sides(Octagonal).
Here's my Pentagonal Reciprocal Roof drawing.
I need to see if there's a theory on the radius's of the two circles that the rafters are tangent to. In the octagonal reciprocal roof their 45 cm and 8 cm. 8÷ 45 = 0.1777 ratio. I don't know if the 0.1777 is a standard ratio for the two radius's. I tried a 45° rafter slope angle for the pentagonal roof, but the seat lines wouldn't connect properly. I readjusted the slope angle to 30° and the seat lines work. I wonder if there's a theory on the roof slope as well.
Use the same geometry for Jack Rafters Plumb To Earth
for the Seat-Claw Angle. This not in any book. This is geometry I developed. I would also classify the reciprocal roof rafters as Jack Rafters Plumb To The Earth offset/skewed from the plate line. Using the same geometry of Jack Rafters Plumb To Earth draw a line tangent-perpendicular to the reciprocal roof rafter that intersects the extended run line of the opposing reciprocal roof rafter. Then draw a line to the rise line of the reciprocal roof rafter. The intersection of theses two lines will give you the seat angle of the reciprocal roof rafters.
I drew the back bevel angles the wrong direction on the 2x4 rafter, but reversed the back bevel angle before I cut the rafters.