by Jay Ham | 2004-06-26 03:00:00-06
There was a time when frameless packs were little more than a harness attached to a large stuff sack. While there are still several of these to choose from, most manufacturers have expanded their offerings to include packs with extended load carrying capacity, improved volume flexibility, increased durability, adjustable torso lengths, and convenience features (such as hydration compatibility and climbing gear attachments) while maintaining respectable weights and volumes.
By definition, frameless packs lack the self-sufficient support of an internal frame. This used to equate to poor load carrying capabilities, as the majority of frameless packs available lacked the elements necessary to create a "virtual frame." Now, most frameless packs employ designs to reduce sagging of the pack's backpanel, thus transferring more weight to the hipbelt.
Virtual frame: a frameless pack’s ability to create frame-like rigidity in the backpanel, by stiffening the packed contents through compression (many times incorporating a ground pad and/or a foam backpad). This effectively transfers weight to the hipbelt/hips and increases the load carrying capacity of the pack by reducing the weight carried on the shoulders.
The dominant technique manufacturers use to create a virtual frame is the addition of compression straps. Our research shows that packs with more sophisticated compression do a better job of tightening the load, stiffening the overall pack, and transferring pack weight to the hipbelt than those without compression. The GoLite Jam (21.1 oz) and Granite Gear Virga (20.5 oz) both showed improved load carrying capability (comfortably carrying 30 pounds and 25 pounds, respectively) over similar frameless packs as a result of their effective compression systems. In addition, these packs have excellent volume flexibility; denser loads (e.g., climbing gear) carried just as well as standard backpacking loads.
Completely breaking the mold, and exceeding our expectations in load carrying capacity for a frameless pack (35+ pounds!), is the Six Moon Designs Starlite (25.4 oz). The Starlite integrates a zippered pad pocket into the backpanel and harness system. By virtue of its design, the folded sleeping pad is kept stiff by the pocket and firmly connected to the shoulder straps and hipbelt creating great rigidity in the backpanel and excellent weight transfer to the hipbelt.
The Product Review Staff at Backpacking Light evaluates each pack's load carrying capability under varying weights and volumes, both in the lab and in the field. Even so, pack comfort is as tricky and subjective as sleeping bag temperature ratings. We found great variance between reviewers on how much weight a particular pack could comfortably carry. Some didn't mind carrying a sizeable amount of weight on their shoulders. This reduces the need for a sophisticated virtual frame (or hipbelt for that matter), but increases the need for well-designed and padded shoulder straps. On the other hand, a virtual frame, to efficiently transfer load to the hips, is a necessity for those who cannot tolerate a significant load on their shoulders.
Based on hundreds of miles and countless discussions, Backpacking Light's suggested load carrying capacities reflect the maximum load a pack can carry with minimal torso collapse. Our load ratings should approximate a typical experience for average users. However, like sleeping bag temperature ratings, you may find our load carrying capacities too high or too low depending on how much weight you can tolerate and where you prefer to carry that weight.
Likewise, we have found considerable variance in packing styles. Our reviews assume properly packed loads that optimize both the virtual frame and carrying stability of a pack. We keep high density items (e.g., food, water, etc.) packed in the upper third, close to the backpanel. We also ensure the harness and stabilizers are adjusted correctly and that compression straps are properly employed. Attention to these packing and adjustment details make a world of difference in load control, stability, and balance.
Ryan Jordan’s article, M Frameless Backpacks: Engineering Analysis of the Load Carrying Performance of Selected Lightweight Packs, studies and quantifies the result of added weight on pack torso collapse (amount which the backpanel shortens) for seven frameless packs and one with removable stays. Ryan's article demonstrates the fallacy of believing a rolled sleeping pad is "just as good as a frame." His results also show that higher friction coefficients between the sleeping pad and inside pack fabric improve the virtual frame at lower pack weights. Based on these findings, it is not surprising that the negligible slip between the sleeping pad and the Starlite's pad pocket results in exceptional load carrying capabilities.
We have seen lightweight fabrics, such as silnylons and lightweight ripstops, used in ultralight packs for many years, and why not? With conscientious use they can endure considerable mileage. Take the 3-ounce hybrid silnylon GoLite Dawn (15.3 oz), which survived a 235-mile circumnavigation of Montana's Beartooth Range. We have also put thousands of miles on GVP Gear's (now Gossamer Gear) 1.3-ounce silnylon G4 pack (12.8 oz) without rendering it unusable (it accumulated some abrasions and a couple of small holes, but remains to this day a serviceable pack). For those looking for improved durability, perhaps for climbing or off trail hiking, several manufactures are meeting these needs by using heavier fabrics in high wear areas or throughout. One of the most durable frameless packs on the market, Osprey's Aether 45, uses a 210 denier double ripstop in the main pack body and a highly durable 420 denier chain link fabric in high wear areas. This durability comes at a price; our review sample weighed 36.1 ounces. Other packs we have reviewed, like the Granite Gear Virga (20.5 oz) and the Six Moon Designs Starlite (25.4 oz), employ a more even balance between weight and durability.
|Mfr / Model||Frame||Features||Volume Range||Load Carrying||Durability||Value||Average Score|
|Gossamer Gear G4||2.5||4.0||2.0||3.0||2.0||4.0||2.9|
|Granite Gear Virga||4.0||3.0||5.0||3.5||4.0||4.0||3.6|
|Osprey Aether 45||3.5||3.0||4.0||3.5||5.0||3.5||3.2|
|Six Moon Designs Starlite||4.5||4.5||3.0||4.5||4.0||4.5||4.1|
|Mfr / Model||Weight (oz)||Carrying Capacity (lbs)||Cost ($)|
|Gossamer Gear G4||12.8||20.0||$85.00|
|Granite Gear Virga||20.5||25.0||$100.00|
|Osprey Aether 45||36.1||25.0||$99.00|
|Six Moon Designs Starlite||25.4||35.0||$135.00|
This Frameless Pack Ratings Chart summarizes the ratings from the various frameless packs we have reviewed to date. Though we have included an average score for each pack, don't overlook specific ratings for each category. A pack like the GoLite Dawn scores fairly low overall. However, its weight and simplistic design make it ideal for certain applications. Also, if you're a hiker that carries low volume loads and/or under 20 pounds in weight, don't be seduced by a large volume and/or high carry capacity packs. The Starlite, which had highest carrying capacity and second highest average rating, performs exceptionally for heavy, high volume loads, but does not compress well to lower volumes and is one of the heavier packs tested. Bottom line: pick the lightest pack that meets your needs!
The average score summarizes all ratings except for cost. The values for Weight were normalized to a 1 to 5 scale before averaging (from a value of 1 for 36.1 ounces to a value of 5 for 12.8 ounces). The values for Carrying Capacity were also normalized to a 1 to 5 scale before averaging (from a value of 1 for 20.0 pounds to a value of 5 for 35.0 pounds). Unless otherwise indicated in the header row, ratings are on a scale of 1 to 5, with 5 being the best.
Click here for the index
Note: Inclusion criteria assumes volumes and weights in a size medium.
Though most of the specifications are self-explanatory, the following need quantifying:
The ratings that follow subtitles are on a scale of 1 to 5, with 5 being the best, and are relative to other frameless packs.
Here we describe the components of the frame and suspension, including shoulder straps, hipbelt, sternum strap, shoulder strap stabilizers, and hip belt stabilizers. Although frameless packs do of course lack a frame, many integrate sleeping pads or sophisticated compression systems to create a "virtual frame." We describe the "virtual frame" here, but its performance is measured in the Field Performance section. We also describe the adjustability of the suspension and harness components. If a pack has the ability to adjust to different torso sizes, that feature is discussed.
Here we describe the usable features of the pack (the "extras"); including but not limited to pockets, top flaps, bottle holders, hydration systems, axe loops, bungee cord systems, etc. We also consider the design and use of these features, such as the type, size, location and shape of the pockets. We consider it a plus if you can reach back and get a water bottle or camera out of a side pocket without having to take the pack off. Mesh pockets are a plus since they enhance gear drying and content visibility. Hydration pockets get higher ratings if the bladder can be replaced without unpacking the main pocket of the pack. "Ease of use" considers how complicated it is to properly use a pack.
This measures the pack's ability to control larger or smaller volume loads. The need to control volume happens on long trips where you start out with a lot of food. As you consume the food your pack might end up at half its original volume. This also happens during cold weather trips: when temperatures drop, you may end up wearing a lot of high volume synthetic insulation garments that started out in your pack. Finally, you may decide to unload most of the gear in your "trail pack" and use it as a day or summit pack. Packs that compress well and stabilize smaller loads, thus maintaining the "virtual frame," get the highest ratings.
A few manufacturers offer options for their packs, such as alternate fabrics, add on pockets, hydration sleeves, padded hip belts, frame stays, etc. This section is only included for those packs that have options that need to be described.
This is an evaluation of how well the pack can carry a load. The pack is tested beyond the manufacturer's suggested load carrying capacity and carried with progressively less weight in order to validate the manufacturer's suggestions. This is done with the pack packed as optimally as possible so we can push the pack to its limit. We also evaluate how different volumes affect the "virtual frame" by testing lower volume loads. If a sleeping pad is part of the frame, we try to test the pack with several pads to evaluate what works best and what you can expect with your pad. Finally, we test the load stability of the pack and how this affects center of gravity.
How well did the pack hold up to abuse (e.g., scrapes against granite and brush)? Are there reinforcements or heavier fabrics in high wear areas? We describe the seams and webbing attachments. We also evaluate the durability when using the pack for off trail or climbing use. Higher rated packs are those that have more durable fabrics in high wear areas, reinforcements, double or triple stitching, bar tacking on pack straps, etc.
This is our most subjective rating. It takes into account all of the above criteria, along with the pack's price. Some adjustment is made for the type of pack. For example, a lower capacity, 14 ounce, webbing-belted pack with light fabric is not directly comparable to a larger capacity, 20+ ounce pack with a fully padded hipbelt and heavier and more durable fabric.
"Frameless Pack Review Summary," by Jay Ham. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/frameless_pack_review_summary.html, 2004-06-26 03:00:00-06.