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5. Find Irregular Jack plumb, level and cheek cut angles:
Jack
Jack
Jack
6. Find regular incremental jack adjustment and Regular Jack lengths:
Jack
Jack
Jack
Jack
Jack
Jack
7. Find Regular Jack plumb, level and cheek cut angles:
Jack
Jack
Jack
IRREGULAR HIP/VALLEY AND JACK RAFTERS - ASCENDING, WITH JACKS MATING
AT HIP/VALLEY
Example: You're working with 7/12 Pitch and half your overall span is 6 Feet. The Irregular Pitch is
8/12, and the Jacks need to mate at the Hip. The maximum allowable On-center spacing in 16 Inches.
Find the Jack Rafter sizes from smallest to largest (ascending order). Complete the following steps:
1. Set Preference display to "JK ASCEND" (Jack sizes in ascending order);
2. Set Preference display to "IRJK JAC-JAC" (Jacks mate);
3. Find the length of the common rafter;
4. Find the length of the adjoining "Irregular" Hip (or Valley) and the cut angles;
5. Find the o.c., Incremental Jack adjustment, Jack lengths and cut angles on the "Irregular"
pitched side;
6. Find the o.c., Incremental Jack adjustment, Jack lengths and cut angles on the "Regular" pitched
side.
Note: After completing this example, you may need to reset the Preferences back to "IRJK OC-OC" if you do
not normally figure jacks in this manner.
KEY INPUT & DISPLAY
1. Review Preferences until you find "Jack Descend":
On/C
On/C
(Prefs)
Conv
Stor
(If not at 1/16, press
Stor
Stor
Stor
+
until 1/16 is displayed)
Page 40
PLMB 33.69˚
LEVL 56.31˚
CHK1 41.19˚
JKOC
16
STORED
Inch
INCR 1
9-3/16
Feet
Inch
JK1 4
0-5/16
Feet
Inch
JK2 2
3-1/8
Feet
Inch
JK3 0
5-15/16
Feet
Inch
JK4 0
0
Feet
Inch
PLMB 30.26˚
LEVL 59.74˚
CHK1 48.81˚
0
FRAC 0-1/16
Inch
AREA Std.
VOL Std.
HDRM 6
8
Feet
Inch
Cont'd on page 41
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