## Sunday, May 4, 2014

### Roof Framing Geometry Propositions – Axioms #4

Testing the Roof Framing Geometry Propositions – Axioms  on a rotated purlin rafter intersecting two rotated hip rafters. The DP Line of the purlin rafter is drawn using the Roof Framing Geometry Propositions – Axioms. However, laying down the purlin rafter plane onto the plan view requires a couple of more steps. To lay down the purlin rafter plane in plan view you have to swing two arcs or circles using the lengths of the vertical plane tilt for the radius of the arcs. Then you have to draw a line that is tangent to the two arcs-circles to establish the correct purlin rafter plane in plan view. Then the standard  Roof Framing Geometry Propositions – Axioms work for the upper and lower claw angles on the rotated purlin rafter.

Swing arcs from Point V  with radius equal to V-A then draw the tangent line to the two arcs thru Point B to establish the purlin rafter plane in plan view.

The Roof Framing Geometry Propositions – Axioms also work for a Jack Rafter Plumb to the Earth Skewed from the Plate Line with Edge Bevel.