Internal And External Frames

Soft packs with internal frames (fig. 2-10) that help maintain the pack's shape and transfer weight to the hips are by far the most popular packs among climbers and ski mountaineers. These packs allow the weight to be carried lower, and they do a better job of hugging the back. Internal frame packs are designed to move with you, while external frame packs tend to shift suddenly as you climb or ski. The sudden movement of 40 pounds or so can easily make you lose your balance.

The volume of most internal frame packs is easy to adjust. Most have compression straps so that the large-capacity pack used to approach a peak can be transformed into a compact, closely fitting summit pack. The clean, narrow profile of internal frame packs allows them to be hauled up rock pitches or taken through heavy brush with far fewer snags than external frame packs.

External frame packs (fig. 2-10) use a long rigid frame that is held away from the back by taut nylon

Large Frame Pack
Fig. 2-10. Packs: a, small internal frame summit pack; b, large internal frame pack with padded hip band; c, external frame pack with padded hip band.

back bands. These packs provide excellent weight distribution by allowing the load to be carried high over the hips. This design lets the hips—not just the shoulders and back—share in the heavy work. Because the frame is held away from the back, these packs keep you cooler. External frame packs were designed for trail use and do a better job here than most internal frame packs. Some climbers use them for long, easy approaches and carry a small day pack for the summit day.

BUYING AN INTERNAL FRAME PACK

First and foremost, buy a pack that fits. The pack's adjustment range must be compatible with your back size, extending from the top of your sacrum to the top of your shoulders. Some packs adjust to a wide range of sizes, others don't.

Before buying a pack, loosen all the adjustments and load it up. Without a typical load, you can't tell how the pack rides or if the adjustments provide a good fit. Now put it on. The frame should follow the curve of your back. If it doesn't, can the stays or frame be bent so it does? The shoulder straps should attach to the pack about 2 or 3 inches below the crest of your shoulders and leave little or no gap behind your back. Check that the load-lifter straps work. These straps transfer weight between the shoulders and hips, allowing different muscle groups to share in the work.

Once the pack is adjusted to your liking, check the head clearance. Can you look up without hitting your head on the frame or top pocket? Can you look up if you're wearing a helmet? Next check for adequate padding wherever the pack touches your body. Pay particular attention to the thickness and quality of padding used in the shoulder straps and hip belt. Padding in the hip belt should extend beyond the hip bone. See that the hip belt goes around the top of the hip and not around the waist, because you want the bone structure of the hips to carry the weight of the pack.

Decide what capacity is right for your intended uses. A rucksack for day climbs and lightweight overnight trips usually has a capacity between 1,800 and 2,200 cubic inches. Longer trips and winter climbs require a pack with a capacity between 3,500 and 5,000 cubic inches.

Here are some additional questions to ask when shopping for a pack:

• Does it have a double bottom? This feature will greatly extend its life.

• Does the pack have haul loops and ice axe loops?

• Is there a means of increasing the pack's capacity for extended trips, such as an expandable snow skirt and an adjustable top pocket that will slide higher?

• Are there compression straps to reduce the pack's volume or to prevent the load from shifting while climbing or skiing?

• Does the pack offer a convenient way to carry crampons, skis, snowshoes, and other items?

• Are removable side pockets available? This feature can help convert a day pack into a weekender.

• Does the pack have a sternum strap, which will help keep the pack from shifting on difficult terrain?

• If you will be using the pack for technical climbs or in thick brush, does it have a smooth profile so it will not get hung up?

• Is the pack cloth durable enough for the activities you have in mind?

• How waterproof is the pack?

• Does the pack have load-restraining zippers? If the zippers fail, can you still use the pack?

TIPS ON PACKING

Packs constructed from waterproof materials are not necessarily waterproof. They can leak through seams, zippers, pockets, the top opening, and places where the coating has worn off. Individual plastic bags or good stuff sacks can protect the contents. You can use a large plastic bag as a liner, storing dry items inside the liner and wet clothing between the liner and the sides of the pack.

A climbing pack should allow you to carry the load closer to the pelvic area, the body's center of rotation. This prevents the pack's weight from shifting on the shoulders. On trails, however, the load should be carried high and close to the back.

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