Backpack fabrics have come a long ways since the
days of canvas packs and thing packcloth. The material used, type of
fabric weaves, overall design, stitching, thread and weight of material used all
contribute to the packs durability, weight and other features (such as water
absorbability, UV resistance, elasticity, etc).
Fabrics come in a variety of weights which have
a large impact on pack weight, durability and strength.
One way to measure fabric weight is by denier.
A denier is a unit of fineness of yarn equal to one gram per 9,000 metres of
= 1 gram per 9,000 meters
= 0.05 grams per 450 meters
A fiber is generally considered a
microfiber if it is 1 denier or less.
A 1-denier polyester fiber has a diameter
of about 10 micrometers.
9000 meters of 400 denier fabric would
weigh 400 grams.
An important consideration in pack construction
is the denier of each fabric used. The higher the denier, the greater
the strength, durability and weight of the material. For example, 210
denier silnylon is made up of very thin yarn and the fabric itself is quite
thin and incredibly light, where 1000 denier Cordura is made up much thicker
yarns, is incredibly durable and weighs significantly more.
Tenacity is a measure of the fabric's ability to resist
additional tearing once a tear has started. It is calculated by
dividing the tensile strength by the thickness of the thread. This resistance to tearing
differs between fabrics and even between fabrics made of the same materials.
Nylon can be found in type 6 (tenacity of 3.0 to 6.0 grams per denier) and
type 66 Nylon (tenacity of 6.0 to 9.5 grams per denier) which is much
This varies greatly between fabrics. Denier, weave,
special laminates/treatments and material used all play a part in the
tensile strength of fabrics used in pack construction. A lower denier
ripstop nylon may be stronger than a higher denier polyester.
Older packs were were often made of cotton canvas and
waterproofed with heavy wax. These fabrics are generally heavy and
prone to rot. Newer canvas bags may incorporate new canvas materials
that are stronger and more water resistant but are generally not waterproof.
Inexpensive canvas pack can still be purchased may have a nice soft and
quite feel to them. Since cotton canvas fabrics heavy, soak up water
and tend to rot, they are not recommended for backpack construction or
Cordura is Dupont's, "air treated" nylon fabric and
Kodra is a similar fabric made by Kolon Intl of Korea. They have a
rough fuzzy texture and have great abrasion resistance. Neither is as
puncture resistant as Oxford Weave Nylon and does not waterproof as well as
Nylon. Polyurethane coated Cordura and Kodra are considered
Cordura Military Ruck
These fabrics are often used in heavy duty packs and
luggage and often used on the bottom of packs. Pound for pound, it is
not as strong as nylon rip-stop, but is generally made in a heavier
weight and is more durable by the square foot/meter.
DSM Dyneema is possibly the strongest fabric in the world
and is similar to Spectra.
It's used in fishing nets, ropes, cables, bullet-resistant vests and safety
Gregory Makalu Pro with Dyneema
It has only a small presence in the backpacking world due to
the great cost of this super strong fiber but is used as gridstops/ripstops in nylon
fabrics and exclusively in very high end custom packs such as those made by
McHale & Co.
There is an old debate as to whether nylon used in backpacks
should be made waterproof. Some felt that a pack that doesn't breath
will lead to wet and mildewed clothing, while others like the potential of
waterproofing their packs.
Today most packs are made as water resistant as reasonably
possible. Modern made packs made of untreated nylon are less common to
find than treated ones. Therefore, most packs made of nylon either
have a polyurethane coating or have been treated with silicone. Both
make the fabric more waterproof, much stronger and a bit heavier.
Rip-stop nylon has a regular grid pattern of heavy threads
sewn in the fabric at regular close intervals. These heavier threads
help prevent the progression of a tear once started. Since light
weight nylons are more likely to where than pack cloth or heavier weight
fabrics, the rip-stop feature is a must. Nylon is stronger than
polyester by weight but is more susceptible to UV light. Nylon rip-stops are being
used by many US and European manufactures.
Polyester pack cloth has a higher
resistance to ultra-violet (UV) degradation but are not as strong as nylon or
ripstop nylon materials. This material is use in many of the packs
made in Europe and Australia.
A is an ultra-high molecular weight polyethylene fiber made
by Honeywell with a very high strength-to-weight ratio. It is highly
resistant to abrasion and does not absorb very much water. It has
resistance to UV light similar to polyester. This fabric is very
expensive and comes in white (but can be tinted).
This material is mostly used in ropes and at
the ripstop material in nylons (identified by the white grid pattern).
Since it is an expensive material, few manufactures have used full Spectra
fabric for pack making.
Most backpacks use 6 to 10 stitches per inch. Many feel
that with the new tightly woven fabrics used today, using more stitches than
10 per inch will damage the fabric thread while anything less than 6
stitches per inch isn't strong enough for heavy duty use.
Twin stitching is of course stronger than single stitching
adding will increase the life of zipper attachment to your pack.
Another important factor in pack construction and repair is
thread use. Inexpensive packs may actually use good quality fabrics
but will fall apart under loads due to use of poor quality or inappropriate
Open cell foam is made up of interconnected air chambers throughout the
material, which allows it to be extremely soft and highly compressible.
It is used in self-inflating mattresses since it is light and highly
compressible. These may not be ideal for pack use and they will
collapse under minimum loads. You can determine if padding in your
pack is open cell foam if you can compress it to less than half its size
with your fingers.
Closed cell foam such as Ensolite is made up of open air chambers
encapsulated by foam that are not interconnected. This foam does not compress easily yet provides good padding.
These are used in closed cell foam mats and provides excellent insulation and absorbs very
little water. Because this foam is dense yet comfortable and doesn't
absorb much perspiration, it is a great choice for backpack padding.
As the name implies, it has both closed cell and open cell
foam are combined together. This allow for the soft feeling of open
cell foam against your pressure points without losing the better load
bearing qualities of closed cell foam. High quality dual density foam
is more comfortable than either
open or closed cell foam alone, supporting the load well and providing
comfort for body.
Compression Molded Foam is a different manufacturing technique
for closed cell foam. Through a special process that incorporates
heat, foam is custom molded into varous shapes and often combined with
different densities of foam to provide flexibility to the final shape.
Acetal (aka polyoxymethylene, POM, acetal resin, polytrioxane and
Acetal has great stiffness and tensile strength and is often used in the
male half of side releases buckles. It is able to resist moisture
absorption, and performs very well under freezing or arid conditions.
This resin also has excellent flexural memory and property retention when
subjected to repeated loading. Compared to Nylon, acetal has better fatigue resistance, creep resistance,
stiffness, and water resistance, but lower impact strength and abrasion
Delrin is brand name for a DuPont acetal resin engineering plastic.
Nylon is a thermoplastic polyamide resin that offers great impact resistance under normal operating temperatures
and has great resistance to repeated impact loads. It is light, flame retardant and has a softer feel for side release buckles.
It can obtain a 20-30% increase in tensile strength over acetal and is often
used in the female part of side release buckles. Since nylon is a
hydroscopic resin, its physical properties will vary as the relative
humidity changes. When dry, tensile strength is higher and impact
strength is lower. When wet, tensile strength is lower and impact strength
is higher. And under freezing conditions, nylon can become embrittled.
ITW-Nexus-Fastex made the original "hammer proof" plastic hardware
and is still one of the better durable plastic hardware companies out
there. Most of their side release buckles are now constructed with
acetal, but most of their hardware is still available in nylon for
National Moldings has a selection of Duraflex acetal quick release
buckles that are durable with a nice texture and are smooth locking.
National Molding buckles are often compatible with Nexus Fastex buckles.
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