48 — Construction Master IV
Jack Rafters — (with other
than 16 inch on-center spacing)
You’re working with a roof having a
7/12 pitch and a run of 30 feet 9
inches. Find the jack rafter lengths at
18 inch on-center spacing.
Keystroke Display
[On/C] [On/C]
0.
1. Enter Pitch, Run and Spacing
7 [Inch] [Pitch]
PTCH 7 IN
30 [Feet] 9 [Inch] Run]
RUN 30 FT 9 IN
18 [Inch] [Jack]*
OC 18 IN
2. Find Jack Rafter Lengths
[Jack]
JK1 33 FT 10-3/8 IN
[Jack]
JK2 32 FT 1-1/2 IN
[Jack]
JK3 30 FT 4-11/16 IN
Etc......Continue pressing [Jack] until last Jack
is reached or until display shows “0.”
* If the entered value is not dimensioned, the calcula-
tor will assume the value as inches for English and
millimeters for Metric calculations.