Parachutes fabric
A
parachute is a device used to slow down an object by pulling its motion through
the atmosphere or by an aerodynamic lift in the case of a Ram-air parachute.
Parachutes are usually made of light, strong fabrics, mainly silk, usually
nylon. In addition to the structural analysis of fabrics, measured properties
include weight, breaking strength, tear resistance, elasticity, and air
permeability.
Parachutes
are designed to slow the movement of an object or individual as it passes
through the air; these were primarily used by the aviation industry for rescue
purposes and for the deployment of troops in the army. Today, parachuting has
become a popular recreational activity, and horizontal parachutes are employed
to slow down fixed-wing aircraft and drag racing vehicles. These are activities
where there is no room for error.
Parachute
makers are looking for ways to improve their products with better materials and
designs Interesting research is being done to create a parachute with the
ability to control the emergency landing of an entire aircraft. The fabric is
designed for extremely low-porosity and high strength.
Parachute fabric properties
Parachute
fabric properties are-
i.
Weight
ii.
Breaking strength
iii.
Tear resistance
iv.
Elasticity
v.
Air permeability
Types of parachutes fabric
There
are two types of parachutes; the first is a domed canopy that traps air inside
to create a high-pressure area that slows down the flow of air in the opposite
direction. Their shape ranges from a hemisphere to a cone. The second is a
rectangular parafoil or ram-air canopy; it is a series of tubular cells that
act as a wing that allows the jumper to point his / her towards a target. The
landing of the parachute depends on the material and so it is important that
the material is light, flexible, and airtight. It must be able to handle high-altitude air and other environmental elements. Material density, rigidity, and
texture are other key factors that will control motion and provide swing-free
descent.
Why are parachutes made of nylon?
Nylon
replaced silk when the supply of silk decreased during World War II. Nylon has
since become a popular choice because of its excellent wind resistance, good
elasticity, thin resistance, and relatively inexpensive. The material also dries
lightly and quickly. It is abrasion and chemical resistant. Due to its
exceptional strength, it is also used to make parachute harnesses, reinforcing
tape, and suspension line straps. Nylon fabric for parachutes is woven in a
special way with extra thick thread to create a pattern of small squares - this
is known as ripstop nylon. When small tears appear in the canopy, these small
squares prevent the tears from growing.
The manufacturing process of the parachutes
The
manufacturing process of the parachutes is explained below:
(i)
Ripstop nylon fabric is cut according to pattern piece by computer-guided
process or using a round-blade electric knife manually.
(ii)
The four trapezoidal panels are sewn together to form a wedge-shaped
"gore" about 13 feet long. A two-needle industrial sewing machine
sews two parallel rows. To provide adequate strength and to enclose the edges
of the raw fabric, a "French fell" seam is used.
(iii)
Several gores (usually 24) are sewn together to form a round canopy. The seams
are sewn in the same manner as in step (ii).
(iv)
Each panel and each seam are carefully inspected at an inspection table. If a
weaving error, seam-in pleat, or an incorrect number of stitches per inch is
found, the canopy is rejected.
(v)
A tape is sewn over each radial seam using two more rows of stitches equal in
width to the original seam. This tape strengthens the canopy.
(vi)
The upper part of each gore is a few inches wide; After the gore is sewn
together, their tops form a small open circle in the center of the canopy. To
strengthen the canopy and prevent the fabric from slipping, the fabric is
rolled around a piece of webbing and sewn with four needle sewing machines,
which sew four parallel rows at once.
(vii)
2-3 feet wide at the bottom of each gore. Sewed together, these edges form the
outer edge of the canopy (skirt). This end is finished in the same manner as
the vent, as in step (vi).
(viii)
A small piece of reinforcing tape is sewn into the skirt on each radial tape.
It is folded into a "V" pointing outwards from the canopy. A special
automatic sewing machine designed for this particular activity was used to sew
exactly the same number of stitches in exactly the same pattern each time.
(ix)
One end of a 20 feet long suspension line is threaded through each V-shaped
tab. Using a special zigzag pattern that is both strong and resilient, the
suspension cord is sewn to the canopy's hem tape and canopy seam for 4-10 inches
in length.
(x)
After 24 suspension lines are sewn into the canopy, the 1 ft long top line is
similarly sewn to the central vent. One end of each line is sewn into a V-tab,
then the line crosses the vent at the opposite end where the other end is sewn
into a V-tab.
(xi)
The canopy is then attached to the harness by tying suspension lines with steel
connecting links over the harness.
(xii)
Parachute rigging is the act of connecting the lines in the harness connecting
links to their correct sequential position and making sure that the lines are
straight.
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