TM 5-1940-321-13&P
c. Threads Direction and Fabric Stretch. The direction in which the threads lay in the fabric
determines the fabric s stretch characteristics. The threads that run the length of a roll of fabric are called
the warp threads. The threads that run the width of a roll are called the weft threads. This is illustrated in
Figure F-1. Composition of Coated Fabrics.
( 1 ) Fabric has little stretch when pulled in the direction of either the weft threads or
warp threads. The maximum stretch is obtained when the fabric is pulled at an
angle of 45 degree to the threads. This is illustrated in figure F-2.
( 2 ) When new fabric is on a roll, it is easy to determine the direction of the threads,
as shown in figure F-2. When the fabric is cut into a smaller piece, the direction
of the threads must be determined by stretching the fabric with your hands.
The direction of maximum stretch is at a 45 degree angle to the threads.
( 3 ) Fabric stretch is necessary when patching the craft in a place that curves in
two directions, such as the bow area or the cone ends of the buoyancy tubes.
Without stretch in the fabric, the patch will not lie smoothly against the curves
in the craft. The patch will have a wrinkled and puckered appearance and will
not be firmly in contact with the craft.
( 4 ) Fabric stretch is not required for repairing flat areas of the craft, such as the
bottom or areas that curve in only one direction, such as the buoyancy tubes
near the center of the craft. Patches that will not stretch are referred to as
straight cut patches. Patches that will stretch are referred to as bias cut
patches.
F-3