By Robert Earle Howells
Picture, if you will, a really crummy backpack— say, a burlap bag chock full of russet potatoes with a pair of hemp-twine shoulder straps sewn on. Sure, it'll carry your load. But spud-induced gravity will wreak agony on your shoulders. The straps will gouge your epidermis. And the load will sway with every stride until it becomes an obnoxious tail wagging you, the masochistic dog.
With this image in mind, it's easy to appreciate the design elements that make a modern internal-frame backpack an impressive conveyor of payload. Through the evolution of trial and error, the shoulder-slung sack has given way to a complex composite of foam, aluminum and plastics conceived to minimize the effort of hauling potatoes and other essentials. These contemporary packs came in all shapes and sizes, from ungainly expedition models to slimmed-down day versions, but the elements that distinguish the better ones are consistent across the board. So what makes the apotheosis of the breed so great? Peel back some Cordura and take a look inside.
Even that stupid potato-sack pack could be made reasonably comfortable if we could put a large percentage of its weight on the hips. The bones of the pelvis can bear a far heavier load that our relatively wimpy shoulders. Obvious solution: Add a hipbelt. But how to get the weight onto the belt? The standard approach is to use one or more aluminum stays, curved to fit the bend of the spine. The stays extend from the top of the pack down to the hipbelt, typically two stays in a V-shape that meets near the center, i.e., the small of the back. The stays transfer weight effectively, yet the pack remains flexible (which is, after all, the primary advantage of an internal over the old-fashioned, rigidly framed external).
Many packs add a framesheet across the back. The framesheet, usually made of high-density polyethylene (HDPE, a flexible but strong plastic) stiffens the back of the pack for even better weight transfer, but at some sacrifice in flexibility. It also prevents sharp, bulky items from poking your back.
Hipbelt Weight transfer is for naught unless the hipbelt, the receiver of this load, is up to the task. That means one that fits (more about fit later) and has just enough stiffness to support a load without sagging. A soft-foam hipbelt may feel great in the store, but after a few miles down the trail it will begin to bottom out and your hips will feel the pressure of the load. One that is too firm can bruise your hips. The most sophisticated hipbelts are a Dagwood sandwich of different grade foams— cell for tactile comfort, closed-cell for support, compression-molded foam for even firmer support. Some add a layer of HDPE. A good hipbelt will compress progressively, like the shocks on your mountain bike. Look for one that cups over your hipbones, which maximizes the amount of weight-bearing surface area.
Shoulder Straps Here too you want to avoid too-soft foam. Another bad sign: puckers in the foam or in the sheath that covers it. These puckers will turn into hot spots against your skin out on the trail. The best pack makers have mastered the art of bending, curving, and covering foam without these dreaded creases— but, of course, you have to pay for such craftsmanship.
Back Panel A sweaty back is an unavoidable consequence of carrying a load, but a good back panel can mitigate the soggy-back syndrome. Some use firm, compression-molded foam with grooves built in to permit a cooling airflow. Others use a swatch of soft, reticulated foam (it looks highly perforated) that does a decent job of dispersing sweat. Some do away with back padding altogether: Your back stays cool; just pack soft stuff against your back to stay comfortable.
Every major maker of packs uses good quality materials and stitches them together with all the requisite back-stitching and bar-tacks so that a pack is very unlikely to fall apart during years of normal use. Cordura nylon, nylon packcloth, ballistics nylon, and proprietary materials (generally similar to Cordura) are all plenty strong and abrasion resistant. Of more concern is the design of the pack bag— and this is largely a matter of personal preference.
Most packs designed for more than a weekend on the trail are top-loaders. The advantage: You can overstuff a pack up top by using a built-in extender, which gets capped off with a floating top pocket. And most packs offer a bottom sleeping bag compartment, so you can access your snooze sack without hauling everything else out in the process. But if you really want convenient access to your belongings, get a pack with a zipper on the main panel— either a side zipper, or for the best access, a full horseshoe.
Don't be seduced into thinking a flotilla of external pockets make for a better pack than a clean, nearly pocketless design. A multitude of compartments may help you stay organized, but they add weight and complexity. They also tempt you to add weight around the perimeter of your pack, instead of inside and close to the back where it is least likely to impede movement. I prefer a simple, single front pocket, big enough to hold a rain jacket, or a hinged 'shovel pocket' for carrying wet or bulky items. Add a couple of water bottle holsters and/or a sleeve inside to hold a hydration bladder, and you have all the extraneous compartments you really need.
Up top, it's handy if the aforementioned floating top pocket removes and converts to a fanny pack for day hiking or a summit push. Most packs have this feature. Fine touches to look for if you think you might need them: Ice ax loops, crampon patches, and lash points so you can strap on weird bulky things like snowshoes.
As for capacity, the 5,000-cubic-inch neighborhood should suffice for most of us— that's generally enough for a long weekend to a week-long excursion— and you can typically pile on another thousand cubes by way of the top extender. Figure on spending $200 to $420 for a quality internal-frame pack.
The best contemporary backpacks are virtually bespoke garments compared to the off-the-rack, one-size-fits-most models of yesteryear. Of utmost importance here is torso length, so the pack rests just right on your hips without doing a potato-sack number on your shoulders. It shouldn't sag, nor rest so high it squeezes your kidneys. Look for a pack that comes in two or three sizes, AND offers fine-tuning adjustability. Cheaper packs often come in one size. Though they may offer a ladder-adjustment to raise or lower the shoulder straps, the fit will be approximate at best. As a smallish (5' 8'') guy, I have to drop the shoulder straps way down to get them to curve just right over my shoulders— which usually means that the junction of the straps, where they join the back of the pack bag, pokes me in the small of my back.
Besides overall pack sizes, the best packs offer different sizes of hipbelts and shoulder straps— hipbelts that match the greater flare of feminine hips or the lesser flare of male hips; shoulder straps narrow enough not to gouge slender folks in the armpits, wide enough to disperse a load better than, say, the hemp twine of our potato pack. When you've boiled down your choices to one or two packs, seek out the factory-trained pack-fitting expert at your mountaineering shop to nail down the fit. Because today's packs have so many adjustability features, this is almost impossible to do unaided.
Walk around the shop carrying each pack, loaded with the full amount of weight you intend to carry on the trail. You'll feel the best pack grab onto your back like a pet monkey, with no discernible hot spots, and the load will feel so perfectly distributed that you'll wonder if you forgot something. You should be able to sashay your hips freely, swing your shoulders fully, and raise your legs in majorette's parade step without ever feeling drawn off balance.
If you've followed the lesson thus far, you understand why I hold little regard for the average book-bag style daypack. Most are just zippered potato sacks in pretty colors, with virtually no load support. That's fine if all you're carrying is a sweater and a Norton's Anthology, but if you're out for a full day with the ten essentials in tow— i.e., if you plan to carry more than ten pounds or more than about 2,000 cubic inches— you need a daypack that can bear some weight.
At the very least, get one with a hipbelt. Not just a narrow strap of nylon webbing, but a two-incher, ideally with some padding. In the absence of an internal frame, a contoured fit can transfer a light (say, 20-pound) load quite well. Look at the back of the pack; does it curve in any way similar to human anatomy? If so, it will angle the load onto your hips, preventing droop and sway. A lightweight framesheet will aid the operation. When you get up around 3,000 cubic inches (the size you'll need for a long day of ski touring or foul-weather hiking), the pack should emulate a full-size internal frame, with a framesheet and/or at least one aluminum stay.
Unless I'm going to be climbing or scrambling, I like a daypack with at least a couple of external pockets— under a light load, they're not much of a balance-inhibiting concern— plus at least one internal pocket for little items such as notebooks and car keys. Other features such as ice ax loops, shovel pockets, and hydration pouches are a matter of preference, but I think some provision for lashing on extra items is important. At the very least, you may need to carry a soggy rain jacket that you don't want stuff inside with your peanut butter sandwiches.
As with full-size packs, don't resort to guesswork. Take along all ten essentials and then some when you go to try on packs. Give them a real-world test. Unless you can afford more than one daypack, buy for the heaviest, bulkiest load you can imagine carrying. Someday you'll need it. Till then, even if you'll only be carrying a big sack of Idaho's finest, you might as well do so comfortably and gracefully.