Pack Details and Features
Some large packs come with one single compartment, while others have an opening (usuaully a horizontal zip) near the bottom and an internal divider. The latter are called two-compartment packs. The one-compartment pack is obviously going to be more waterp
Single and double compartment packs
Some large packs come with one single compartment, while others have an opening (usuaully a horizontal zip) near the bottom and an internal divider. The latter are called two-compartment packs. The one-compartment pack is obviously going to be more waterproof when you throw it into a river, but it can present a problem with wet tents and parkas. Two-compartment packs solve that: you can put your wet tent and wet parka into the bottom compartment after packing the main compartment safely inside your tent. Any leaking water will just drain out the bottom harmlessly. This is a good idea, but does have drawbacks.
One big drawback we have found with two-compartment packs is that the upper compartment is much shorter. (This may not apply if you have a 90+ litre monster - it's too big anyhow.) The short upper compartment has to hold both your sleeping mat and your tent poles, and may not be deep enough. This means they stick up into the lid space. Maybe this won't harm the mat, but the tent poles are another matter. There is a serious risk of damage to the ends of the poles if they get caught on a branch you have just ducked under. Another problem is that the zip on the bottom compartment is going to leak. There may be a flap to block rain, but if you have to cross a river the bottom compartment can fill up. Finally, in bad weather when you are desperately fumbling around, zips can get jammed and damaged. So the idea of two compartments can be attractive, but it isn't perfect.
A one-compartment pack solves all these problems, but has a few of its own. If all you have is a single compartment pack, where do you put a wet tent in the rain? Under the lid is the obvious answer. After all, you have to access under the lid to put the poles away anyhow - you wouldn't leave them tied on the outside, would you?! The key thing in this case is to make sure any water leaking from the wet tent is diverted outside the pack. This is possible if you put the tent on top of the throat material rather then inside it, and hold it in place with the top inner strap. If the throat isn't waterproof (it should be!), take a little bit of plastic or proofed nylon to put on top of the throat, under the tent, or make yourself a waterproof tent bag. I do both, and I use the square of waterproof fabric as a tablecloth for meals as well.
There is no perfect pack. However, the two compartment Macpac Cascade has often been cited as a classic reference design for an internal frame pack, even if it is rather heavy. The author had one for many years, and hammered it. The one-compartment Macpac Torre is almost the same, and my wife finds it fits her very well, even if it heavy. But the author now prefers his ultra-lightweight external-frame designs: they are more comfortable.
Bag Shape, pockets and things tied on
The design of the bag itself is important, and includes such things as the overall shape, pockets on the outside, and attachment points on the outside.
The shape of the bag may not be something which you immediately think about. However, consider three possibilities: a parallel shape, tapered to a narrow top, and tapered to a narrow bottom. A parallel shape is simple to make and there is nothing wrong with that. A shape which is wide at the bottom and narrow at the top is good at putting the load down low, and that is good for an alpine or climbing pack, when you don't want too much load on your arms. Packing this design is a little more tricky as there is this huge cavity down the bottom which is hard to get to. The downside to this design is that it is the opposite of what you want for bushwalking, as discussed above. Sadly, most current internal frame packs are this way.
Then you have the very few packs which open upwards, placing the load a bit higher on your back. It helps if they are shallow in the front-to-back direction: that keeps the load close to your back and reduces the strain. Sadly, there are few of these designs around and most people do not realise how much better they are. The Aarn packs from New Zealand are a good example of this approach, although I found the Aarn pack I tested to be a bit narrow over all and too tall for my 1.70 m (5' 7"") height.
Some vendors advertise the number of external pockets their designs have. This is misguided marketing, aimed at the tourist/hosteller crowd. The reality is that you don't really need external pockets: you can fit everything inside (or should be able to!). Large external side pockets get caught on our scrub so Australian manufacturers don't fit them. Imported packs often have such pockets and are usually avoided by Australian walkers. Many imported American packs have mesh pockets on the sides and back of the bag: these do not last very long in our bush, and the contents get lost too easily. One or two small outside specialised pockets might be useful (although they often leak); an external map pocket certainly is, but few offer that. A pocket on the top flap is popular, but this usually leaks and exposes things in it to real risk of damage when you duck under branches. Why do people put spectacles and so in in the top pocket? The claim is that external pockets allow you rapid access to things you might need - but how often do you need things that quickly? We have had equal success with a 'day bag' placed just under the top flap: stuff in there is just as accessible and is a bit more protected.
The same applies to ""things"" tied on the outside of the pack. The picture here shows an extreme example. (Actually, the ladder was being carried in to the MUMC Feathertop Hut during its construction: hardly a fair criticism!) You may see people with foam mats rolled up and tied on the outside: these mats get shredded as they go through the bush and the track gets littered with little bits of coloured foam. This is a sure sign of a novice and we strongly object to these bits of litter. You also see sleeping bags tied on the outside. Usually the stuff sack is not waterproof, and whatever is holding it onto the pack is inadequate. I have collected at least one pack off the track this way. (Words fail me here, but I bet the previous owner was cold that night.)
If you must tie anything onto the outside of your pack, make sure it is well covered against damage, and can't fall off. Better still, put it inside. If there isn't room, ask yourself if you are carrying too much gear. About the only thing the author would ever carry on the outside of his pack would be a fuel bottle in an external pocket (the leaks stay outside!) or an ice axe. Oh yes: skis and poles get carried on the sides of a pack sometimes, as close as possible to your back.
A great debate can be had over the bag material. Once all packs were made of 12 oz proofed cotton canvas: when this got a bit damp the fibres swelled up and blocked the pores, making the bag ""waterproof"" (in theory). What actually happened was the canvas did block most of the water, but the inside surface was wet nonetheless, and so was some of your gear. Then stronger synthetics such as Cordura™ were introduced, but the PVC proofing on them was initially very poor and rubbed off after a (short) while. Once this happened the bag leaked like a sieve, and everyone swore off synthetics.
The cotton canvas has got better: it is now made of a polyester/cotton mix which is very tough. But it still does get a bit wet (and heavier) in the rain, and is not as abrasion-resistant as the synthetics. For this reason some packs are still made of poly-cotton canvas but reinforced with Cordura around the base. However, do not reject a synthetic pack these days: the proofing on the synthetics is much better today, the packs are often lighter, stronger and they can be very functional. But the stitching holes do seem to leak more easily on some loose-weave synthetics (see also Canyon packs). It would be nice if the manufacturers used a decent seam construction on the pack bag, but a second line of stitching seems to be too expensive for them to bother.
Shoulder Straps and pads
The shoulder straps on internal frame traditionally have some padding, but I wouldn't worry about getting thick padding. It doesn't work and adds weight. I have actually used 50 mm nylon seat belt webbing without any padding for a while: it was OK, sort of. If you can limit the weight of your pack then webbing is just fine by itself. Some shoulder straps are shaped to make S-bends over your shoulder, but the laws of physics don't allow this to be very effective. Forces go in straight lines, and a fairly simple design is best. Far more important for comfort is the weight in your pack(!), the correct adjustment of the balance straps, and what clothing you are wearing. If you have a bad fold or crease in a heavy shirt right over your collar bone under the shoulder strap, you are going to get very conscious of it after a while.
But I will concede that a little padding can be useful. Sometimes I use pads of EVA 40 foam about 10 mm thick and 60 mm x 150 mm in size. They have the distinct advantage that they help prevent the shoulkder strap from rolling up. That, rolling up, is the last thing you want!
Strap Buckles and Slipping
In search of a single design with the widest possible market appeal most pack makers use adjustable buckles on the straps, including the shoulder straps and the top straps (balance straps, load lifters, whatever). This is in principle a good idea. However, the designers of the buckles also want them to be easily adjusted, even while under load, and this introduces a problem. The design of the buckle is compromised to get the ease of adjustment, which means it does not lock on the webbing so well. This is exacerbated by random changes in the design of the webbing itself by the webbing makers, or possibly by attempts by some (not all) manufacturers to buy the cheapest webbing and buckles they can find. The end result is that some webbing on some buckles on some packs slips very slowly through, and what was once correctly adjusted ceases to be so after a few hours. Slowly, the shoulder straps and the top or balance straps get longer, and the load starts to drag. It can take a while before you realise what has happened. You may have to re-adjust some buckles at times to keep the pack snug against your back. The improvement in comfort can be surprising.
On a more serious note: some pack makers use cheaper ('generic') buckles made in Asia, rather than top brands such as Fastex and Duraflex. The cheap Asian brands can snap under load. I was ski-touring when the waist buckle snapped on one of my packs. OK, it was given a shock load when I fell over on the ice, but not having a waist strap did make life a little more difficult! Good brands matter here. Unfortunately, it can be difficult to tell whether the buckles on a pack you are thinking of buying re good or not. You could try asking the staff. Of course, if you are buying in a discount shop, you can almost guarantee that the whole pack will be made in Asia.
Waist Band or Hip Belt
These days most packs have a ""waist band"" or hip belt. This is a broad belt around your waist which pulls the pack onto your hips (or bum) and transfers some of the weight off your shoulders onto your hips. The idea of the load transfer seems to be a good idea for internal frame packs since they have poor load distribution anyhow. It has to be matched with a good bit of padding at the small of the back over your bum: this is a key design area to check for comfort. If it is too thin, too small or in the wrong place it won't be comfortable. Some women seem to have more trouble with this than men, for reasons which could not possibly be associated with the shape of their anatomy J . For this reason some pack makers have a 'woman's model' or can swap the standard male waist band for a female version. For a girl this is worth checking. The same applies for shoulder straps: female versions are sometimes available to accommodate that slight but delightful difference in chest shape.
However, life is never quite that simple. Some people have a lot of trouble finding a hip belt which works for them. The reason is that a hip belt only works if your hips can support the belt. If you have slim hips, or a narrow pelvis, you may find that even a tight hip belt can slide down your hips, past your backside. There is just not enough sticking out for the belt to sit on. I have this problem myself. In this case you can't rely on the hip belt support much of the pack weight. You may need to move to an H-frame pack, if you can find one.
Even with small day packs and H-frame packs which do not need the load transfer to the hips, a belt around your waist is a good idea. The benefit a waist belt brings is more stability of the pack on your back: it stops the bottom of the pack from moving sideways when you are bouncing around. However, such a waist belt can be far lighter than the reinforced girdles you see on some internal frame packs.
Many packs have a webbing or haulage loop at the top between the shoulder straps. This can be very useful in two ways, as long as the loop really is secure. The first use is as an anchor point should you have to do any pack hauling. The second use is as an aid for picking up and donning a heavy pack. Strangely enough, it is usually better to pick up a heavy pack by this loop than by one of the shoulder straps. The reason is that swinging a pack around off the shoulder strap can damage the harness mechanism - although once the pack is on your back it is quite safe. You pick the pack up by the loop doing a one arm press to the shoulder and then thrust your elbow through the shoulder strap as it goes over your shoulder. On second thoughts this action is better demonstrated than described. The strength of this loop is actually an extremely important factor in design: the stitching holding the loop and the shoulder straps to the bag is crucial. Some cheap packs are reported to have failed here.
Top Compression Strap
A little pack will keep it's shape well enough, but a large pack tends to bulge a bit at the top. For this reason good large packs have one or two top compression straps. These go from the top bar, over the throat material, to the material at the front, When your pack is full (or before!) you do the top drawcord up, do the throat up (to keep the water out), then you do up this compression strap to hold the top of the pack in. It prevents the bag from leaning backwards too much. It is also useful for holding a few large objects in place, like a wet tent and a parka.
Even if your pack is completely waterproof it will probably absorb a fair bit of water on the surface under heavy rain. More often a little will creep in at some of the stitching or zips. For very little extra weight you can stop this: a light pack cover is all that is needed. This consists of a bit of light waterproof nylon cloth shaped to cover the top, sides and back of your pack. A draw-cord around the edge holds it on and makes your pack look a bit like an astronaut backpack. Tying the end of the draw-cord to the pack is a very smart move: I lost a bright orange pack cover on the top of Mt Carruthers once in a storm - it sailed off like a parachute, headed for the Barry Way.
You can buy pack covers at bushwalking shops for not too much money. They come in a variety of weights - often rather heavy. Or you can make your own, and tailor it to fit your pack better than the heavy all-purpose units sold. From experience, I don't think the heavy ones are worth the extra weight - our very light ones have lasted many years of rough treatment. After all, the pack cover is following you. It's your clothing which gets the most wear from the scrub. Even cheap light not-very-waterproof acrylic-coated nylon is going to deflect most of the rain. Even if a little bit does get through the cover, very little will then get into your pack.
Revert for a moment to the picture near the top of the page, of the guy in the snow with his pack dragging backwards. He has a pack cover on his pack, but he still has problems. The pack is leaning backwards: the snow is going to land in the gap between his pack and his back. It is going to melt there, and what doesn't leak into his pack through the vast amounts of stitching there is going to soak into his clothing. This can still happen to some degree even if your pack is riding properly, and we have seen this happen. However, the poncho idea mentioned elsewhere can serve three purposes here: it can cover your pack, it can cover you, and it can also cover that gap between you and your pack. It can be very effective.
Packs can leak, especially two-compartment ones, and especially when thrown in a river. Sometimes you have to swim across a river with your pack; sometimes you even have to do this many times. It would be nice to keep the contents of your pack dry. You can package everything in small nylon bags lined with plastic bags (freezer bags are readily available), and this is highly recommended anyhow. It is especially recommended for dry food, sleeping bags and spare clothing! But we sometimes line our packs with some sort of waterproof bag as well. This can be a simple as one or two green garbage bags. These are a bit fragile, but may be suitable (with care) for a single river swim. A heavy plastic bag is good, but finding these is difficult and they may be a bit too heavy at times. Easily available bags (like in supermarkets) are as follows:
- Cheap house-brand bags are typically about 18 - 22 micron thick, and rip fairly easily. They aren't very reliable: sometimes they tear while you are stuffing things into your pack.
- Large green garbage bags by Glad & Multix with draw tapes are about 30 microns thick, and will certainly last one swim - more if you pack carefully and take some light wide packaging tape for a few repairs.
- ""House and Garden"" bags by Glad (IGA stores) & Multix are large: 80 - 90 cm * 120 cm, are big enough for almost any pack, and are about 40 microns thick. These won't stand daily use without developing holes where they rub, but they will work for a swim or two very well. The extra weight is very small - grams.
- Vetinary 'dead dog' bags have been reported as being very rugged: the author knows not about these!
Some people make a waterproof liner bag to fit their pack from genuinely waterproof nylon or polyester material, taking care to seal the seams properly. Such a bag may be weaker than a ""canyon dry bag"", but it will also be a lot lighter. The DIY section covers such materials: silnylon (properly sealed) has been used very successfully, and 'weldable PVC-coated nylon' has also been used. But caution: a lot of what is sold as 'waterproof nylon' in the local shops is not: it's coated with acrylic and barely showerproof. Shower curtain material may not even be proofed.