of the bend in radians. The radian relates the length of
the arc generated to the size of the angle. For the
ba = 3.250 × 1.57 = 5.10 inches
purpose of computing bend allowance, the number of
radians per degree of bend is 0.017453. Thus, the
EXAMPLE 2 (fig. 13-50)--What is the bend
formula for bend allowance is:
allowance for a 180-degree bend which is to be made
in a length of l/2-inch stock?
ba = r × R
r = 1.0 + 0.250 = 1.25 inches
8 = 0.017453 × 180 = 3.14 radians
ba = bend allowance
r= radius of the neutral axis of the bend
ba = 1.25 × 3.14 = 3.925 inches
θ = size of the angle of the bend in radians
EXAMPLE 1 (fig. 13-49)--What is the bend
REPAIRS AND FABRICATION
allowance for a 90-degree bend with a 3-inch
radius which is to be made in plate that is l/2 inch
Much of your work will consist of repairs and
alterations made to the existing ship's structures.
r = 3.00 + 0.250 = 3.250 inches.
Repairs are different from alterations in that the design
(Remember you must add one-half the thickness of the
of the ship's structure is not changed by repairs.
plate to be bent to the radius of the bend.)
For example, if you remove a deteriorated section
8 = 0.017453 x 90 = 1.57 radians
of a watertight bulkhead and install a new section, it is
Figure 13-50.--Computing the overall length of a U-bolt.