It’s important to have the right rucksack on your D of E expedition and there are many factors to consider:-
Size is important, ideally around the 65 litre mark is about right, much smaller and you will struggle to get all your gear in, bigger and you will be tempted to get all your gear in, including a whole host of stuff that you won’t ever use therefore increasing the weight significantly, remember you will have to carry your rucksack for your entire expedition and it should be as light as you can possibly make it.
Some D of E centres will supply you with a rucksack to use and these will generally be sturdy, one size fits all bags, if your budget runs to it I would certainly recommend you buy your own, that way you can go to a store and purchase one that will fit properly and be comfortable, make sure that it is fully adjustable so you will be able to balance the weight as it changes. It will also then become your personal companion on all your trips, there may even be times you forget that it’s even on your back! Hi Gear make a suitable size rucksack that is inexpensive, I will be doing a review on this as soon as it arrives.
Look for a rucksack without too many unnecessary features, simple will generally work best, multiple pockets and a huge number of zips are just more places that will eventually fail. Most of the capacity should be in the main body of the rucksack with a small amount of space in the lid for easily accessible items, I like to have pockets on the waist belt as these are useful for keeping snacks and other items that you will want to access easily and frequently but make sure that they keep their shape when you do the straps up or your cereal bars will turn to crumbs!
Some people like a hydration bladder build into their rucksack, this is a personal preference and I tend to use both bladders and water bottles, I’m not sure which I prefer but both work very well, having a tube in front of my mouth so I can drink on demand is really useful, especially if I don’t want to stop to get a water bottle out, if you go for the bladder option, make sure you can remove and refit it with the rucksack fully packed, this is generally the only way to fill them unless you’re able to get your bag under the tap.
