 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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