Hip or Valley, “Jack Rafters”
— Set at 16” on-center
You’re again working with a 7-in-12 Pitch and
the Run of the common rafter is 20 feet 5 inches.
You want to calculate the length of your jack
rafters at 16 inches o.c.: First, calculate the
common and hip/valley lengths, then the jacks.
Hip Rafter
Plate
COMMENTS KEYSTROKES
Clear calculator [On/C] [On/C]
Enter Pitch 7 [Inch] [Pitch]
Enter Run 20 [Feet] 5 [Inch] [Run]
Find Diagonal [Diag]
Answer: 23 FT 7-41/64 IN
Find Hip/Valley [Hip/V]
Answer: 31 FT 2-51/64 IN
Recall 16 inch o.c. [Rcl] [Jack]
Answer: 16 IN JK
Find 1st Jack [Jack]
Answer: 22 FT 1-7/64 IN
Find 2nd Jack [Jack]
Answer: 20 FT 6-19/32 IN
Find 3rd Jack [Jack]
Answer: 19 FT 0-1/16 IN
Etc., Etc.
Repeat, until all jacks are found, or when
calculator displays “0 FT 0 IN.”
44 — Construction Master III
®
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