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USER’S GUIDE — 91
Jack Rafters — Using Other Than 16 Inch On-Center Spacing
A roof has a 9/12 Pitch and a Run of 6 Feet 9 Inches. Find the Jack
rafter lengths and cut angles at 18-Inch (versus 16-Inch) On-Center
spacing. The On-Center spacing is used for both Regular and
Irregular Jack calculations.
KEYSTROKE DISPLAY
1. Enter Pitch, Run, and On-Center spacing:
o o 0.
9 i p PTCH 9 INCH
6 f 9 i R X 6 FEET 9 INCH
1 8 i j j JKOC 18 INCH
2. Find Jack rafter lengths and cut angles:
j JK1 6 FEET 6-3/4 INCH
j JK2 4 FEET 8-1/4 INCH
j JK3 2 FEET 9-3/4 INCH
j JK4 0 FEET 11-1/4 INCH
j JK5 0 FEET 0 INCH
j PLMB 36.8699°
j LEVL 53.1301°
j CHK1 45.°
3. Reset On-Center spacing to 16 Inches:
1 6 i j JKOC 16
INCH
STORED
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