Johnson Level & Tool Mfg. RAS-1 - Manual (Page 41)

39
The pitched rafter top cut layout (at point C in Figure 21) is
the same as the support rafter bottom cut layout (at point
A). For the pitched rafter bottom cut layout (at point D)
the following equation is used:
BOTTOM ANGLE =
SUPPORT ANGLE + ( 2 x ROOF ANGLE ) – 90°
In our example:
= 57 3/4° + (2 x 33 3/4°) – 90°
= 35 1/4°
Use this equation when the pitched rafter length equals the
support rafter length. We then hold the square tight against
the top edge of the rafter as we did for the top cut and make
a mark at the bottom cut angle (e.g., at 35 1/4°). A line from
this mark to the pivot point gives us the necessary bottom
cut pattern.
STEP 3. RAFTER PATTERN CUTS: If Figures 20 and 21 are
carefully studied, the rafter pattern cuts can be easily made
following the patterns that were laid out. Set your saw at 90°
for all the cuts.
TABLE C
Latitudes for Selected Cities
City, State Latitude N°
Atlanta, GA 34
Bismarck, ND 47
Boston, MA 42
Brownsville, TX 26
Caribou, ME 47
Columbus, OH 40
Fresno, CA 37
Indianapolis, IN 40
Las Vegas, NV 36
City, State Latitude N°
Lincoln, NE 41
Medford, OR 42
Milwaukee, WI 43
Nashville, TN 36
Oklahoma City, OK 35
Raleigh, NC 36
Salt Lake City, UT 41
Tallahassee, FL 30
Toronto, Canada 44