The weight of a rucksack is carried by its shoulder straps and hipbelt: it’s an understatement to say these are important. Good straps should fit the body’s contours evenly so there aren’t any pressure points, wrinkles or gaps. Pre-shaping the straps improves the fit and reduces the chance of wrinkles forming.
To improve the comfort of the straps, materials of different densities are used. Stiffer material is used for support, while closed-cell foam helps to distribute the load evenly. Softer, open-cell foam is then used for comfort close to the body. A durable, breathable material is used as the contact fabric against the skin, giving a low-sweat, wrinkle-free surface. The foam also needs to be durable as it will be subjected to pressure and the heat of an Australian summer, as well as soaking up its fair share of moisture.
Shoulder straps should distribute the weight over a large area so that they are comfortable and don’t dig in.
The hipbelt transfers the majority of the load from the pack to the body. It should match the individual’s shape and contour to their hips, and be easily adjusted in use.
Pack frames are usually made up of one or two alloy bars inserted into the pack’s harness on either side of the spine. These provide structure to the pack and channel weight to the hipbelt for comfortable carrying.
The frame should be strong and relatively rigid so that it keeps its shape and directs the pack’s weight effectively. It should also be moulded to fit the natural arch of the back so that it doesn’t restrict natural posture.