Backpack Construction
Backpack Material
The earliest examples of backpack fabrics used were cotton canvas
waterproofed with a heavy wax coating. While these backpacks displayed
excellent weatherproofing characteristics the fabrics were heavy,
prone to abrasion and when stored wet would rot. Although there
are very few canvas backpacks manufactured today, there are some
backpacks made from technologically advanced canvas materials, which
promote the combination of synthetic materials to improve the strength
and water resistance of the canvas fabric. However, backpacks made
from cotton canvas in general are not usually waterproof. Due to
a lack of waterproofing and a ready ability to absorb water or moisture,
especially in less expensive materials, cotton canvas is not a preferred
backpack material. Its main advantage is that it is generally inexpensive
and backpacks made of this material are cheaper as a result. This
does not suggest there are not better canvas fabrics available,
but these technologically advanced fabrics are often combined with
synthetic fabrics in production and are generally expensive and
inherently heavier.
Textured Nylon came to replace cotton canvas, as the characteristic
of the Cordura and Kodra material is the rough fuzzy texture similar
to the feel of canvas material. These materials are some of the
most sort after and popular fabrics in use today for high quality
backpacks. The main advantages of Cordura or Kodra fabric are its
abrasion resistance and the fact it is relatively lightweight when
compared to canvas or canvas synthetic blended materials. Both Polyurethane
coated Kodra and Cordura are considered waterproof. The Kodra material
used in the production of White Mountain Backpacks™ was originally
sourced from KOLON Industries, Inc. in Korea. However Kodra is now
no longer a trademark belonging to KOLON Industries, Inc. and the
name Kodra is now used for any textured nylon manufactured by numerous
factories in Asia, which means the quality can no longer be easily
substantiated. For this reason all new White Mountain Backpacks™
will be manufactured with and labeled Invista Cordura material.
Cordura is the brand name for a collection of fabrics used in
a wide array of products including luggage, backpacks, pants, military
wear and performance apparel. Cordura fabrics are known for their
durability and resistance to abrasions, tears and scuffs. Originally
developed and registered as a trademark by E.I. duPont deNemours
and Company (DuPont) in 1929, it is now the property of Invista
(a wholly owned subsidiary of Koch Industries, Inc.). Cordura fabrics
are made using yarns or fibres from Invista, and are made using
100% synthetic fibre or in blends with cotton or other natural fibres.
All qualified CORDURA® fabrics have been validated to ensure they
meet the durability and quality standards of the CORDURA® brand.
INVISTA works closely with its worldwide authorized mills and converters
to ensure consistency of fabric quality and fitness for the intended
use.
Polyester has a higher resistance to ultra-violet (UV) degradation
than Nylon, but overall, Nylon or Rip-Stop Nylon based products
are still a stronger material, and although Nylon degrades faster
than polyester, it degrades to about the same strength. Polyester
pack cloth feels similar to Nylon, however advantage of Polyester
over Nylon is that it is cheaper substantially material. This has
led to Polyester and textured Polyester materials to dominate the
low end of the world market.
Both Nylon 6-6 and Nylon 6 have similar elasticity, however,
both differ in their melting points. Nylon 6 melts at 216 degrees
Celsius and Nylon 6-6 at 263 degrees Celsius, making Nylon 6-6 the
preferred Nylon for temperature performance products. Both Nylon
6 and 6-6 allow easy dyeing and washing and are a chemically stable
product. Nylon 6-6 is preferred over 6 for making backpacks because
of its higher strength and toughness. Nylon 6 is primarily used
in the textile industry for making clothing, ropes, threads, nets
and garments while Nylon 6-6 is used for backpacks, tire ropes,
gear wheels, friction bearings and plug parts.
Rip-Stop Nylon 6-6 has a large market acceptance replacing Nylon
6 and Nylon 6-6, and is easy to distinguish from Nylon by its regular
grid pattern of heavy threads sewn in the warp and weft of the fabric
at regular close intervals. The heavier threads prevent further
ripping if the backpack is punctured or torn. Nylon when torn has
a tendency to continue ripping under slight pressure, and if you
are deep in the backwoods with no thread, dental floss, or duct
tape, a torn pack can present an unwelcome challenge. The Rip-Stop
Nylon 6-6 design can provide extra protection to help ensure that
your pack will not disintegrate from a small tear. The main advantages
of Nylon material is the strength, a ready acceptance of waterproofing,
and it’s relatively light weight.
You'll find most backpacks are sewn at 6 to 10 stitches per inch.
The general consensus here is that, if the stitching is increased
much beyond 10 stitches per inch the strength of the fabric begins
to degrade. Anything below 6 stitches per inch begins to become
suspect in terms of strength. Be aware that backpacks are made of
deniers much higher than you'll find in a tent or sleeping bag,
and close stitching can actually damage the threads used in the
backpack fabric itself. Another factor is the twin stitching method,
where all stitching is doubled stitched for added strength, including
the zipper attachment to the backpack. Constant zipper use on less
expensive backpacks with single stitching can cause the zippers
to be pulled from the backpack, an all too common problem. Note
that there is a direct correlation between thread type and size,
material type and weight, needle size, and stitch type in determining
the stitching method.
The majority of backpack manufacturers and White Mountain™
use plastic "coil" zippers on their backpacks. A coil zipper is
basically a continuous piece of plastic that's been formed into
a coil shape and sewn onto a piece of fabric webbing. The main advantage
of the coil zipper is that if fabric gets caught in the teeth, the
fabric can be gently pulled out without tearing. This is certainly
a consideration since your pack will sometimes be crammed with clothing,
a sleeping bag, or nylon bivvy bags.
Some backpacks may have regular solid tooth zippers, and these
are certainly okay as well. These zippers won't let go of fabric
that easily, but size for size, they're stronger than coil zippers.
Other really inexpensive backpacks may use metal tooth zippers
in either steel or aluminium, which can either rust or corrode badly
when exposed to rain, sea air, or worse salt water, and are not
recommended.
There is also Water Repellent Zippers for backpacks available,
sometimes referred to as waterproof zippers. However choose carefully
as these zippers generally have installation restrictions, some
are subject to damage from heavy items placed on the zip, require
careful use to avoid damage and misalignment of zipper teeth (sharp
bending or twisting should be avoided), and some are also prone
to damage by heat, humidity, and direct sunlight.
Fully waterproof zippers are available, but not generally used
in backpack production as the zipper cost would be greater than
the retail price of the backpack.
The thread used in the manufacture of backpacks is an important
consideration, a factor that is often overlooked and frequently
not mentioned. Many less expensive backpacks made from quite acceptable
backpack fabrics, but come apart under load simply because an inappropriate
thread was incorporated into the finished product.
|