64 — C
ONSTRUCTION
M
ASTER
®
P
RO
/ T
RIG
/ D
ESKTOP
Irregular Hip/Valley and Jack Rafters —
Ascending, with Jacks
Mating at Hip/Valley
You’re working with a 7/12 Pitch and half your overall span is 4 Feet.
The Irregular Pitch is 8/12, and the Jacks need to mate at the Hip.
The maximum allowable On-center spacing is 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. (See Preference
Settings on page 83.)
KEYSTROKE DISPLAY
1. Review Preferences until you find “Jack Descend”:
o o 0.
Ç ß
(Prefs)
FRAC 0-1/16 INCH
(If not at 1/16, press
+
until 1/16 is displayed)
ß AREA Std.
ß VOL Std.
ß HDRM 6 FEET 8 INCH
ß RAKE dESCEnd
ß AW outSidE
ß JACK dESCEnd
Set Preference to “Ascend”:
+
(plus sign)
JACK ASCEnd
2. Set Preference to “Jacks Mate”:
ß IRJK OC-OC
+
(plus sign)
IRJK JAC-JAC
3. Find common rafter length:
7 i p PTCH 7 INCH
4 f R RUN 4 FEET 0 INCH
d DIAG 4 FEET 7-9/16 INCH
(Cont’d)
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