BOOM, JIB, TOWER, AND MAST
Folio 1316-6
Chord Straightness
Refer to Figure 6.
If visual inspection indicates that a chord may not be straight,
proceed as follows:
1. Remove the suspect section from the attachment.
2. Place wood blocks or steel plates having the same
thickness against both ends of the section (X
1
and X
2
).
3. Stretch a line (string or wire) over the outside of the
wood blocks or steel plates.
4. Stretch the line as tight as possible and tie it off at both
ends.
5. Measure the distance from the chord (on either side of
lacing intersection) to the line as shown in Figure 6.
6. Measurements must be take in two planes at each chord
(dimensions A and B). To eliminate the effect of sag in
the line, take all measurements in the horizontal plane.
7. Take the first set of measurements, then roll the insert
over 90 degrees, and take the second set of
measurements.
8. Tubular and angular chords must not deviate from
straight more than plus or minus 3/16 in. (4.8 mm) at any
lacing intersection (dimension A). Deviation between
any two adjacent lacings must not exceed plus or minus
3/16 in. (4.8 mm).
9. On angular chords,
waviness at toe of chord
(dimension
B) must not deviate from straight more than plus or
minus 1/4 in. (6.4 mm) at any point. Furthermore,
waviness between any two adjacent lacings must not
exceed plus or minus 1/4 in. (6.4 mm).
Gradual and sweeping bends in chords can be
straightened by cold bending them back into alignment.
Take care not to kink or further damage the chords.
FIGURE 6
B231
X
2
Line
X
1
B
A
A
B
A
A
A
A
Line (black dot)
Typ ic al
CHORD MEASUREMENTS
Tubular Chord
and Lacing
Angular Chord
and Lacing
Angular Chord
and Lacing
A = Measurement to Determine Straightness
B = Measurement to Determine Toe Waviness
Measurement
(chord to line)
Wood Block
or
Steel Plate
395143
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