Timber Framing Angle: R4P
R4P = Hip-Valley Rafter side cut bevel angle on top or bottom of an unbacked hip-valley rafter. Using a Saw Blade Bevel Angle set to the plan angle and cutting along the plumb line on the hip-valley rafter will produce angle R4 on the top and bottom of the unbacked hip rafter. Angle R4 is parallel to the common rafter run.
Hip-Valley Roof Ratios Angle Formulas
- R4P = arctan( cos R1 ÷ tan DD)
- R4P = arccos( cos P6 x cos P2)
- R4 = arctan( cos Hip-Vally Pitch Angle ÷ tan Plan Angle)
- R4P = arccos( cos(Clip angle on the bottom of the Jack Rafter) x cos(Jack Rafter side Cut Angle))
The Hip-Valley Roof Ratios Angle Formulas were developed by Joe Bartok.
The Timber Framing Hawkindale Angle Formulas were developed by Rees Hawkins Acheson from the Martindale Hip and Valley Roof Angles and Hawkindale angle drawings by Ed Levin of the Timber Framers Guild.
The Hawkindale angles were based on the book by Frank L. Martindale "Bevel Angles for Three Dimensional Connections" 1948 that was based on the book
"Hip and Valley Design" by H. L. McKibben and L. E. Gray published in 1912.