Saturday, August 30, 2014

Purlin - Roof Sheathing - Dormer Square Tail Fascia Layover Cuts

Purlin Rafters, Roof Sheathing or Dormer Square Tail Fascia Layover Cuts
(Cutting Roof Sheathing with an Edge Bevel)

Cutting Purlin Rafters from the Face Set in the Roof Surface
Saw Blade Miter = arctan (sin Dormer Pitch Angle ÷ tan Main Pitch Angle)
Saw Blade Miter = arctan (sin 26.56505 ÷ tan 33.69007) = 33.85451°
Saw Blade Bevel = arcsin (cos Main Pitch Angle × cos Dormer Pitch Angle)
Saw Blade Bevel = arcsin (cos 33.69007 × cos 26.56505) = 48.09115°
or use
Jack Rafter Side Cut Angle for the Miter Angle
Valley Sleeper Saw Blade Bevel Angle  for the Saw Blade Bevel Angle

Example
Roof Eave Angle = 90.00000
SS = Main Rafter Slope Angle = 33.69007 -- 8:12
S = Adjacent Rafter Slope Angle = 26.56505 -- 6:12

DD = Main Plan Angle = 36.86990
D = Adjacent Plan Angle = 53.13010

R1 = Hip Rafter Slope Angle = 21.80141
C5m Main Hip Rafter Backing Angle = 26.34404
C5a Adjacent Hip Rafter Backing Angle = 15.56481
Valley Sleeper Saw Blade Bevel Angle = 90° - (C5m + C5a) = 48.09115

P2m = Main Jack Rafter Side Cut Angle = 47.96889
90° - P2m = Main Roof Sheathing Angle = 42.03111
P2a = Adjacent Jack Rafter Side Cut Angle = 33.85451
90° - P2a = Adjacent Roof Sheathing Angle = 56.14549

Cutting Purlin Rafters from the Face Set in the Roof Surface
or
Cutting Roof Sheathing with an Edge Bevel

Jack Rafter Side Cut Angle for the Miter Angle -- 33.85451°
Valley Sleeper Saw Blade Bevel Angle  for the Saw Blade Bevel Angle -- 48.09115°



Cutting Purlin Rafters from Face perpendicular to Roof
Saw Blade Miter = 90° - arctan (cos Dormer Pitch Angle ÷ tan Main Roof Pitch Angle)
Saw Blade Miter = 90° - arctan (cos 26.56505 ÷ tan 33.69007) = 36.69922°
Saw Blade Bevel = arcsin (cos Main Roof Pitch Angle × sin Dormer Pitch Angle)
Saw Blade Bevel = arcsin (cos 33.69007 × sin 26.56505) = 21.84545°








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