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Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
JACK RAFTERS - USING OTHER THAN 16-INCH ON-CENTER SPACING
Example: A roof has a 9/12 Pitch and a run of 8 Feet 11 Inches. Find the incremental jack adjustment,
jack rafter lengths and cut angles at 18 Inch (versus 16 Inch) On-center spacing.
Note: The On-center spacing is used for both regular and irregular jack calculations.
KEY INPUT & DISPLAY
1. Enter Pitch, Run and spacing:
On/C
On/C
9
Inch
Pitch
8
1
1
Feet
1
8
Inch
Stor
2. Find regular incremental Jack adjustment and regular Jack rafter lengths and cut angles:
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
Jack
3. Reset On-center spacing to default 16-Inch:
1
6
Inch
Stor
Inch
Run
5
(o.c.)
5
(o.c.)
Page 37
JK1 10
6-3/16
Feet
Inch
JK2 8
11-11/16
Feet
Inch
JK3 7
5-1/8
Feet
Inch
JK4 5
10-5/8
Feet
Inch
JK5 4
4-1/8
Feet
Inch
JK6 2
9-9/16
Feet
Inch
JK7 1
3-1/16
Feet
Inch
JK8 0
0
Feet
Inch
PLMB 30.26˚
LEVL 59.74˚
CHK1 45.00˚
0
PTCH 9
Inch
RUN 8
11
Feet
Inch
OC
18
STORED
Inch
JKOC
18
STORED
Inch
INCR 1
10-1/2
Feet
Inch
JK1 9
3-1/4
Feet
Inch
JK2 7
4-3/4
Feet
Inch
JK3 5
6-1/4
Feet
Inch
JK4 3
7-3/4
Feet
Inch
JK5 1
9-1/4
Feet
Inch
JK6 0
0
Feet
Inch
PLMB 36.87˚
LEVL 53.13˚
CHK1 45.00˚
OC
16
STORED
Inch
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