Scope:

ASTM D7811 is useful when a small specimen or cut parts need to be evaluated for bow and skew, provided a wrap or fill, or both reference lines are available, to aid in aligning the tool. This test method is used for measuring bow and skew in fabrics in rolls.

Test Procedure:

In ASTM D7811 test method, a straightedge is placed across the fabric between two points at which a marked filming yarn, knitted course, or designated design meets the two edges. The greatest distance between the straightedge and designated design is measured parallel to the selvage.

Video 01: Standard test method to measure bow and skew 

Specimen size:

According to ASTM D7811, the specimens should be conditioned at 400 mm in length.

Data:

Bowing (%) = D/W × 100
Where; D= maximum bow in
fabric
W= fabric width (inches)
Skewing (%) = D/W × 100
Where, D = difference between actual and perpendicular path
W= fabric width (inches)

Conclusion:

ASTM D7811 is useful when a small specimen or cut parts need to be evaluated for bow and skew, provided a wrap or fill, or both reference lines are available, to aid in aligning the tool.