Product Selection
Anatomy of a Backpack
We will begin our journey into the anatomy of a backpack by
explaining the basic differences between the purpose and main
function of each type of backpack available. Then we will list
the common materials and fabrics used in packs, including the
importance of the thread and the stitching that binds the
backpack together. We will follow this with a definition of a
typical harness system, and then explain the symmetry of the
components that combine to form a complete functioning harness
system. Due to the depth of detail required, we will further
explain the method of using these components in customising,
positioning, and securing your backpack correctly at another
time. First, a look at some of the types of backpacks available.
Types of backpacks
Travel Packs
Are backpacks that facilitate ease of travel by incorporating
the best features of a hike pack, a soft suitcase and more.
These features include a fully functional harness system, with a
storable harness cover that protects the harness in transit, a
removable daypack, and shoulder sling. It would also include
suitcase style carry handles generally located at the top and on
the side of the backpack. Travel packs similar to your standard
suitcase, have a zipped front or panel loading access for ease
of use, and would normally have internal compression straps,
which manufacturers sometimes couple with an internal organizer.
Travel packs generally have two compartments with either a zip
or draw cord division, and are usually between 60 to 90 litres
in capacity including the daypack. Although not as important in
these backpacks, we recommend that these backpacks have a fully
featured and adjustable harness system, fitted to provide
optimum comfort. These backpacks are best suited to travel
purposes for reasons that we explain further in the description
and purpose of expedition hike packs.
Expedition Hike Packs
Unlike travel packs are top loading with a storm collar to
prevent water penetration, have no protective harness cover, no
removable daypack, nor any of the travel pack added features
such as the shoulder sling and suitcase style carry handles.
When compared to a travel pack, there are fewer zips and less
stitching, which prevents excessive water penetration. As a
result, this backpack is also lighter in weight. Unlike the
design of the travel pack, manufacturers taper these backpacks
to provide more freedom of movement in the shoulders and arms
during rigorous activity. Expedition hike packs usually have two
compartments with a zip or draw cord division and an extendable
top lid to increase total capacity. These backpacks are most
often between 75 to 95 litres or more in capacity, and have a
fully featured and adjustable harness system. The harness system
must be of a design to carry heavy loads long distances with the
maximum of comfort.
Weekend Hike Packs
Are a smaller version of the expedition hike pack with a
capacity of around 45 to 55 litres to allow enough storage space
for a hike of 3 to 4 days. When carrying heavy weight in your
backpack, even for only a few days, you need a harness with a
fully featured hip belt, including internal staves, a
high-density polyethylene frame sheet, or a combination of both
frame systems.
Daypacks
Come in many shapes and sizes, designed for an endless choice
of purpose. Daypacks are available with internal organizers, a
multitude of pocket designs, possibly a facility for a water
reservoir, and perhaps a provision to store a skateboard or bike
helmet. We still recommend that these backpacks when carrying
heavy weight have a fully featured harness system to provide the
support required. Therefore, it is important to remember when
choosing a daypack, to purchase a daypack that will fulfil your
purpose. Daypacks normally have a capacity of around 15 to 40
litres, and are frameless with only a webbing waist belt.
Materials
There is a very confusing choice of materials used in today’s
backpacks, and you need to be sure that the material used is up
to the task in your choice of backpack. One way to do this is to
purchase a backpack with a renowned brand name and a reputation
for quality. Some reputable backpack providers also supply test
reports on tear strength and tensile strength to guide you in
your choice of backpack material. The following is a guide to
materials available and is by no means a comprehensive list. The
most prevalent materials used in backpack construction are,
cotton canvas, Kodra or Cordura, Polyester, Nylon and rip-stop
Nylon. Also included here is information on the important role
thread and stitching plays in bringing together a high quality
backpack. We have also included some very useful information on
zippers.
Cotton Canvas
Is very durable and breathes, but when wet is very heavy,
takes a considerable length of time to dry, and when stored wet
would suffer severe mildew and rot. Very few backpacks are
manufactured from pure cotton canvas today, and in general,
these backpacks are not waterproof, and prone to abrasion.
However, there are backpacks today made from technologically
advanced canvas materials, which combine synthetic materials to
improve the strength and water resistance of the canvas fabric.
These new technologically advanced fabrics are in general far
more expensive to purchase and inherently heavy. The main
advantage over backpacks manufactured from synthetic materials,
is that synthetic materials rely on a Polyurethane coating to
promote water resistance, and this synthetic coating is in time
prone to degradation.
Kodra or Cordura
Is a treated Nylon fabric originally designed by Dupont, and
then later Kolon Intl of Korea introduced its own similar
product called Kodra. These materials are some of the most
popular fabrics in use today for high quality backpacks and have
a proven record of outperforming standard nylons, polyesters,
and cotton canvas. The main advantages of Cordura or Kodra is
the fact that it is relatively lightweight when compared to
canvas materials, will not absorb water, and is currently the
standard for a tough, abrasion resistant, puncture and tear
resistant fabric. A notable characteristic of the Cordura and
Kodra material is the rough fuzzy texture. Although, Cordura and
Kodra materials can appear very similar to pack cloth polyester
and only the higher sheen of the polyester fabric, an
experienced eye, or a manufacturers label can denote the
difference in these fabrics.
Polyester
Now referred to as pack cloth has a higher resistance to
ultra-violet (UV) degradation, but overall, nylon or rip-stop
nylon materials including Cordura and Kodra are still a stronger
material and inherently more abrasion resistant. Many
manufacturers use polyester extensively in backpacks, and
although not as strong as nylon, it actually feels heavier and
appears stronger.
Nylon
Fabrics with a polyurethane coating were some of the first
synthetic fabrics to replace cotton canvas, but these earlier
fabrics were heat bonded to the polyurethane and failed to
deliver the revolutionary superior performance promised. Heavy
usage inevitably degraded the fragile heat bonded polyurethane
coating on which these nylons relied for waterproofing, and
delamination was the inevitable result. Now, all premium nylon
materials are cold bonded providing a superior resistance to
delaminating.
Rip-Stop Nylon
Is rapidly replacing standard nylon and easily
distinguishable by its regular grid pattern of heavy threads,
sewn in the warp and weft (length and width) 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 the slightest pressure,
or it can begin unravelling. If you are deep into a hike without
a repair kit, thread, dental floss, or duct tape, a torn pack
can present an unwelcome challenge. A torn nylon backpack put
under stress by 20 kilograms of equipment can quickly start to
come apart. The rip-stop design can provide extra protection to
help ensure that your backpack will not disintegrate before your
eyes. The main advantages of rip-stop nylon are a ready
acceptance of waterproofing and the relative lightweight when
compared to other backpack materials. However, if rip-stop nylon
is used in very light fabric weights, holes from prolonged
abrasion may appear sooner than in polyester. Rip-stop nylon is
increasingly appearing in upmarket backpacks all over the world
and has already established a large market acceptance in Europe
and the USA.
Thread
Strength is a major factor in backpack construction, the
greater the thread strength, or the better the thread quality,
the stronger the seam. The thread used in the manufacture of
backpacks is an important consideration, a factor often
overlooked and frequently not mentioned. Many less expensive
backpacks made from quite acceptable backpack fabrics, come
apart under load simply because an inappropriate thread was
incorporated into the finished product.
Stitching
Is another important factor in backpack manufacturing, and
most manufacturers sew backpacks at 6 to 10 stitches per inch.
If we increase the stitching much beyond 10 stitches per inch,
the strength of the fabric begins to degrade. Anything below six
stitches per inch begins to become suspect in terms of strength,
and when the fabric is under pressure, gapping between the
stitches becomes more evident. Be aware that backpacks are made
of deniers or fibre thickness much higher than in a tent or
sleeping bag, and close stitching can actually damage the
threads used in the fabric. Another factor in creating a better
seam is the twin stitching method, where manufacturers double
stitch all stitching for added strength, including the zipper
attachment to the backpack. Constant zipper use on backpacks
with single stitching can often result in an all too common
problem, the zippers ripping from the backpack.
Zippers
Usually use sliders made of an aluminium alloy that are prone
to corrosion, particularly in sea air or salt water. Always
rinse any equipment exposed to sea air or salt water with fresh
water as soon as you are able and then dry thoroughly. Spraying
the zippers with silicon waterproofing spray, Teflon spray, or
rubbing with candle wax on the odd occasion will protect and
enhance the life of the zippers. Remember, proper care of your
zippers will provide you with many years of service and the
zippers could even outlast your backpack. Zippers are an
excellent innovation, but the problem is zippers are prone to
failure, particularly due to misuse or abuse. Some important
zipper facts are; plastic zippers are less likely to break, than
metal zippers. Plastic zippers are easier to zip up and require
less maintenance. Coil zippers are stronger than solid plastic
tooth zippers. Larger zippers are not necessary stronger, dirt
in a coil zipper or zipper slider will quickly damage it, and
keeping a zipper clean will extend zipper life.
Harness Systems
The Harness System
Is a combination of backpack, shoulder straps, and hip or
waist belt that offer the facility to carry a backpack. Further,
better designs also have an internal High Density Polyethylene
Frame Sheet, an Internal Frame, or maybe a combination of both.
These harness systems can also include adjustable shoulder
straps to allow for differing torso lengths and body types, a
sternum strap, upper and lower load stabiliser straps, and a
lumbar pad. In the following text, we have listed the key
components that make up the typical harness system, including
the role and the importance of each component that work in
conjunction, to provide a high functioning harness system.
The Internal Staves
Are two flat bars usually of aircraft grade aluminium that
are approximately 30 mm in width and have a 3 mm depth. These
internal staves in the harness of the backpack run vertically
from the top to the bottom of the backpack, and are generally
positioned at a point either side of the spine. The internal
staves can be made of plastic, fibreglass, or a composite
material, and contouring the internal staves is essential for
correct backpack fit and functionality. We recommend removing
all internal staves from the backpack, and then carefully
contour these to the individual back. Yes all! If the Internal
Staves are not removable, we then proceed to mould the entire
backpack to the individual back. Contouring the Internal Staves
to the back enables these internal staves to simulate the flex
action of the spine, and when required allows an effective
transfer of approximately 80% of the weight to the lower back.
With the internal staves carefully contoured to the back, the
backpack in the optimum position and provided the backpack is
loaded correctly, the distribution of weight through the
Internal Staves will ensure maximum comfort.
The Upper Load Stabilizer Straps
Are adjustable straps that run from the shoulder strap at the
top of shoulder, to an attachment point on the backpack at the
top of the internal staves. These upper load stabilizer straps
allow you to adjust the distance between your back and your
backpack. It is critical that we correctly position the pull of
the upper load stabilizer straps from the shoulder straps to the
top of the backpack. The optimum pull position from the shoulder
is below the clavicle, 25mm to 40mm lower than the top of the
shoulder. This ensures the pressure or pull of the backpack is
placed equally on the back of the shoulders and the chest. It is
also important not to over tension or have the upper load
stabilizer straps pull at an excessive angle from the shoulder
to the backpack. These actions would then draw the shoulder
straps up and away from the shoulders, render the sternum strap
ineffective, place excessive pressure on the chest, and cause
the backpack to ride up from the hips. On uphill treks, tighten
the upper load stabilizer straps to pull the top of the backpack
close to your body and draw the weight close to your back.
Conversely, loosen the upper load stabilizer straps on downhill
treks to adjust the centre of gravity, or to provide ventilation
between the back and the backpack in hotter weather.
The Lower Load Stabilizer Straps
Are included in all effective backpack designs. These lower
load stabilizer straps connect the harness usually at the top of
the backpack lower compartment, to either side of each hip belt.
When tightened these straps minimize backpack sway at the base
of the backpack and provide for effective weight transfer to the
lower back. Although this weight transfer is only possible with
correctly contoured internal staves. To use these lower load
stabilizer straps if scrambling or climbing, tighten the
shoulder straps to put more of the weight on the shoulders, and
then loosen the lower load stabilizer straps to allow for hip
movement. When walking an even path, pull these two lower load
stabilizer straps simultaneously to draw the backpack close to
the back and into the lumbar region. Then loosen the shoulder
straps, this will then provide for a greater distribution of
weight on the lower back rather than the shoulders.
The Hip Belt
Consists of two substantially padded wings either side of the
lumbar pad at the base of the backpack. These padded wings or
hip belt on all good backpacks is made of two different foam
densities, with the softer foam (low density foam) on the inside
against the body and the more rigid foam (high density foam) on
the outside. With the backpack in the correct position on the
back, we should find the hip belt positioned across or just
below the hipbone or Iliac Crest, and the hip belt would appear
to slightly angle down from the backpack to the front of your
body. With the hip belt in the correct position, secure the
buckle and pull the hip belt snug, then position the hip belt
further by pressing down with your hands until the belt settles
in the right spot. If after positioning the hip belt you find
the backpack is riding up, even under weight, you simply need to
loosen the shoulder straps to lower the position of the hip belt
and the backpack.
The Sternum Strap
Is an adjustable strap that in the correct position connects
the shoulder straps together across the chest in the middle of
the sternum or breastbone, and is an essential item on all
backpacks. Usually elasticised to promote effective breathing,
the sternum strap must be a snug fit and positioned correctly to
avoid putting excessive pressure on the lower chest. It is also
important that you do not over tension the sternum strap to the
point of full extension of the elastic, as this would also
prevent the sternum strap from operating effectively. The
sternum strap in conjunction with the shoulder straps
distributes some of the backpack weight across the chest and
pulls the shoulder straps closer to the centre of the body. This
allows increased arm flexibility, prevents the shoulder straps
drifting onto the shoulder joint, or from slipping off the
shoulder. We recommend always using a correctly positioned
sternum strap particularly on any extended walk where the
sternum strap will generally ensure greater backpack comfort.
The sternum strap although necessary for shoulder strap comfort
and better load distribution, should not be necessary to achieve
close contact or correct positioning of the shoulder straps.
The Shoulder Straps
Consist of two substantially padded straps that rest on the
shoulders and hold the backpack to the upper body. This padding
on all good backpacks is made of two different foam densities,
with the softer foam (low density foam) on the inside against
the body and the more rigid foam (high density foam) on the
outside.
The shoulder straps can be either fixed to the backpack or
incorporate an adjustment for the varying torso lengths and body
types. There is a common misconception that adjusting the torso
length and the anchor position of these shoulder straps on the
harness changes the size of the backpack. This is an incorrect
assumption, and you must choose the length of backpack that best
suits the individual torso length. The torso length adjustment
on the shoulder straps is there to accommodate the heavy,
medium, or slight build of the individual. A heavy built
individual would need longer shoulder straps, whereas a slightly
built individual would require shorter shoulder straps. The
shoulder straps adjust at either a single junction or yoke in
the centre of the backpack, or are separate and adjust
independently along each of the internal staves.
Further, shoulder straps that follow the natural contours of
the body typically represent good backpack design. Contoured
shoulder straps have a customised curvature that follows the
natural route of the strap over the shoulder, away from the
neck, down the side of the body into the chest area and then
away from the body underneath the arms. The shoulder straps when
properly positioned should be far enough apart so as not to rub
on your neck, yet close enough together to prevent the shoulder
straps slipping onto the shoulder joint, or off your shoulders.
Quite obviously, contoured shoulder straps are more comfortable
than a straight shoulder strap. Backpacks designed for women
would always incorporate contoured shoulder straps to allow for
the natural body curvature at the bust. The position and angle
of the anchor point of the contoured shoulder straps at the base
of the backpack also contributes to overall functionality and
comfort. It is also important to remember that we use the
shoulder straps to pick up, put on, and position the backpack.
Therefore, it is essential that the shoulder strap attachment to
the internal frame is very secure to prevent damage to the
backpack under heavy loads.
Compression Straps
Are an essential feature of all backpacks and allow you to
compress the backpack around loaded equipment to provide a tight
and stable load. When there is not enough equipment in the
backpack to fill it to maximum capacity, the compression straps
close up that extra space, preventing undesirable load sway.
Compression straps are located on both sides of most backpacks
and usually comprise of 25mm webbing straps, ladder lock
buckles, or side release buckles. Backpacks come with a single
compression strap or as many as three or more compression straps
on either side. Top loading hiking or hybrid backpacks also have
compression straps that run down the front of the backpack, that
secure the top lid tight against the backpack. These backpacks
may also have height adjustable lids with three to five
compression straps securely fixing the top lid to the backpack.
Most backpacks also include vertical sleeping bag compression
straps that run over the lower sleeping bag compartment. When
fully packed and before zipping closed the lower compartment,
tighten down the sleeping bag compression straps and compress
the contents. The lower compartment is then easier to close and
this will protect the zipper and prevent backpack damage. The
sleeping bag compression straps are usually long enough to
provide another means of carrying a sleeping mat securely on the
outside of the backpack.
Conclusion
All of the components within a well-designed backpack work
together in symphony to produce a truly balanced backpack. This
symphony of backpack engineering is achieved over many years of
field-testing, which is ever evolving. This evolution continues
led by companies that commit themselves to building the better
backpack. However, these backpacks will only function as the
manufacturer intended in correctly fitted or customised
backpacks. It is for this reason we strongly recommend having
all backpack harness systems professionally fitted, particularly
when using backpacks on extended hikes.
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