1000d Air Textured Nylon (the same / also known as 1000d Cordura) is used for the bag outers due to its strength and excellent abrasion resitance. It is water-resitstant as it has a PU coating to the innerside, but like any material that is sewn, the sewing machine needle makes holes in this for the thread to pass through. This could lead to water seaping in through the seams (this is why your “waterproof” backpack isnt). To prevent this happening all the bags are made using a floating liner. This is so called because it isnt attached to the rest of the bag, apart from around the lip of the opening. This means there are no threads running from the outside into the inner – so no way for water to wick up the seams. The bag is then for all intents and purposes waterproof – obviously if you chuck it in a river its going to get wet, but in terms of rain and spray nothing will get in if its closed properly. This liner is made from v12 vinyl coated polyester (what you would normally refer to as truck tarpaulin) – its strong and completely waterproof. It also has the benefit of being wipe clean should you manage to spill anything on it…
All the thread I use to v92 – this is approximately 30% stronger than the v69 thread commmonly used in bag manufacture (some companies even state proudly that they use v69 as if it were the strongest thread out there…..)
The back and strap pads on the Greyhound are made from 10mm EVA foam, nice and dense foam which doesnt crush under loads.
The webbing (straps) are made from polyester – this is MUCH stronger (the breaking strength for the 25mm thin webbing is over 1000kg!) than the polypropylene webbing often used in bag manufacture. It is also doesnt strech like nylon webbing does when it gets wet.
There is also a lot going on that you cant see – the internal edges are now all bound with webbing to increase the seam strength and the strap attachment points are all reinforced with extra material to stop the thread pulling through under (extremely) heavy loads. Seam allowances are a whole inch – most bags you would be lucky to get half an inch! This all adds to the strength with only a slight addition to weight and because you cant see it is somewhere where a lot of companies can choose to skimp on.