4
—
S
HEET
M
ETAL/
HVAC
P
RO
C
ALC
Dividing Offset into Multiple Degreed Elbows for
Manageable Sections .............................................................51
Change OGEE Offset ................................................................53
LAW OF COSINES EXAMPLES...................................................55
Field Measuring for Ductwork Using the Law of Cosines
Introduction
.............................................................................55
Non-90 Degree Triangle Measurement Using Law of Cosines
and Heron’s Theorem.............................................................56
Using Law of Cosines and Pythagorean Theorem to
Calculate Offset, Length, and Angle.......................................58
Sheet Metal Panels for an Irregular Hip Roof............................59
Inline Duct, Single Offset (Computing Offset, Length,
and Angle)...............................................................................60
Inline Duct, Double Offset (Computing Offset, Length,
and Angle)...............................................................................62
Objects at Right Angles .............................................................65
Calculating Angles Between Objects (“Angle Between”)...........69
Calculating Angles Between Objects Example..........................70
FAN LAW EXAMPLES ..................................................................75
Fan Law 1 ..................................................................................75
Fan Law 2 ..................................................................................76
Fan Law 3 ..................................................................................77
ARC/CIRCLE EXAMPLES ............................................................78
Arc Length —
Degree and Diameter Known
.............................78
Arc Length —
Degree and Radius Known
.................................78
Using ArcK to Calculate an Arc Length......................................78
Arc Calculations —
Arc Length and Diameter Known
...............79
Arched/Circular Rake-Walls —
Chord Length and Segment
Rise Known
.............................................................................80
Arched Windows ........................................................................81
CONCRETE/PAVING ....................................................................82
Squaring-up a Foundation .........................................................82
Volume of a Rectangle...............................................................82
Volume of Columns....................................................................83
RIGHT TRIANGLE and ROOF FRAMING EXAMPLES ...............84
Roof Framing Definitions ...........................................................84
Degree of Pitch ..........................................................................86
Percent Grade............................................................................86
Common Rafter Length..............................................................87
Common Rafter Length —
Pitch Unknown
................................87
Angle and Diagonal (Hypotenuse).............................................88