M Frameless Backpacks: Engineering Analysis of the Load Carrying Performance of Selected Lightweight Packs
by Ryan Jordan, Ph.D.
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Article Summary:INTRODUCTION: The objective of this study was to evaluate and compare the load carrying performance of several frameless packs available to the ultralight backpacking community. Frameless backpacks tested in this study include: Granite Gear Virga, GoLite Jam, Six Moon Designs Moonlight, Wild Things AT, Equinox Katahdin, GoLite Dawn, Osprey Aether, McHale Supbop. In addition to evaluating frameless pack suspensions using a closed cell foam pad as a rolled cylinder, a comparison was made between an internal frame comprised of two light frame stays, a closed cell foam backpad, and a closed cell foam rolled cylinder. CONCLUSIONS: The major conclusions from this study are: 1. Using a rolled cylinder closed cell foam pad relative to a closed cell foam backpad does not appear to improve load carrying performance signficantly. There appears to be no justification that the rolled cylinder method is comparable for resisting torso length collapse relative to twin aluminum stays, thus providing evidence for disputing common user claims that a "rolled cylinder pad is just as good as a frame". 2. Four of the eight frameless packs tested herein exceeded conventional expectations of a 20-pound load carrying capacity using a rolled cylinder foam pad technique for improving backpack suspension performance. 3. One pack used a suspension system that appears to offer substantial increases in frameless backpack load carrying performance relative to packs that employ the rolled cylinder foam pad technique, with a load carrying capacity that was 66% higher than the average load carrying capacity (20.4 lbs, n = 7) of all packs reviewed in this study.
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