Aarn Liquid Agility Backpack REVIEW

Dynamic suspension and a unique redistribution of weight breaks the industry mold in backpack suspension design.

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by Ryan Jordan | 2005-07-05 03:00:00-06

Introduction

Aarn Liquid Agility Backpack - 1
Ryan Jordan wearing the Aarn Liquid Agility Backpack with Balance Pockets while climbing cross-country to the crest of Montana's Bridger Ridge. The pack is well-shaped and sized right for compact, stable, heavy loads.

The Aarn Liquid Agility Backpack takes "dynamic suspension" to a new level. Integrating a flexible, multi-component internal frame with shoulder straps and a hip belt that are decoupled from each other should, in theory, allow you to hike or even jog, across rough terrain, with little sacrifice in load stability. The panel-loading Aarn Liquid Agility Pack extends its volume for longer trips with front "balance pockets" affixed to the shoulder straps. These pockets hold a substantial amount of gear and carry a reasonable amount of weight, and are intended to balance the pack load by shifting its center of gravity forward. The primary focus of this review was to assess the true performance of the suspension, and how the balance pockets affect load carrying stability. Does such a break from mainstream suspension design truly affect load carrying performance, or is it another attempt to differentiate a product through marketing? That question is addressed in this review.

In Brief

  • Torsionally dynamic internal frame suspension system offers little resistance against body movement for activities involving torso twisting (backcountry skiing, scrambling, trail running) and overhead reaching (climbing).
  • Front storage pocket system integrates effectively with front side of harness and improves overall load balance.
  • Harness complexity is not conducive to a quick "click and go" approach of removing and putting on the pack.
  • Panel loading packbag and front pocket system keeps weight close to your body's center of gravity.
  • Large front pocket system keeps more items handy, saving time since the pack does not need to be removed to access supplies and gear while on the trail.
  • Compression system is very effective at reducing pack volume and keeping small loads stabilized.
  • An upper harness frame component (a removable stay) interferes with range of motion of the head when looking upward.
  • Pack offers several modular storage and harness suspension options to target a size range of 25 liter (compressible further) to 32 liter and 1 pound 13.5 ounces to 3 pounds 5.2 ounces (specs given for size L).
  • Robust and intelligently designed suspension provides exceptional comfort for dense, heavy loads (e.g., water, climbing hardware, etc.).

Specifications

• Backpack Style

Internal frame (frame stay components are removable), panel loading, with 7 L of storage in a removable front pocket load balancing system.

• Fabric Description

Ripstop nylon (soft face) with Cordura reinforcements used in bottom, high stress and wear areas of the suspension, zipper flap, and front pockets.

• Sizes

Size L tested.

Size Torso Length (in) Torso Length (cm)
S < 15.7 < 40
L > 15.7 > 40

• Volume

Includes front pockets.

Size Volume (ci) Volume (L)
S 1650 27
L 1950 32

• Weight

Size Backpacking Light measured oz (kg) Manufacturer Specification oz (kg)
S n/a 39 (1.10)
L 45.3 (1.28) 49.4 (1.40)
Actual measured weight of dual front pockets is 9.8 oz (278 g). Front pockets include one removable suspension component (an aluminum stay). Removal of the stays brings the weight of the front pockets down to 8.0 oz (227 g). Removal of the suspension components from the main packbag (one set of cross body chest straps, one main vertical aluminum stay, one lateral aluminum stay, one very small frame sheet with a tiny aluminum stay, and an inverse "U" hoop stay brings the weight of the main packbag (originally at 2 lb 3.5 oz/1.01 kg) down to 1 lb 13.5 oz/0.84 kg).

• Volume To Weight Ratio

Based on size L using Backpacking Light verified weights.

As shipped with front pockets and all suspension components 43.0 ci/oz
Packbag only with no front pockets or suspension components 51.7 ci/oz

• Load Carrying Capacity

Aarn claims a load carrying capacity of 30 lb (14 kg). In our own independent assessment, which includes a perception of comfort as well as visual observation of the collapse of the suspension system under increasing loads, we estimate a reasonable maximum load carrying capacity in excess of 35 lb (16 kg). This is a higher load carrying capacity than what I would normally attribute to packs in this size range; however, the front pocket system, which is integrated with the suspension, greatly improves the maximum load carrying capacity of the Liquid Agility pack. It carries a 30 lb (14 kg) load in outstanding comfort relative to most 30 L-range internal frame packs on the market. Because of the dynamics of the suspension allows for freedom of motion due to shoulder straps and hip belt straps that are decoupled from the suspension components, this comfort is particularly noticeable at long distances.

• Carry Load To Pack Weight Performance Ratio

12.4 (based on 35 lb load carrying capacity divided by 2.83 lb pack weight)

• Model Year

2004

• MSRP

$219.95 NZD (New Zealand Dollars) manufacturer's suggested retail price (the Aarn Liquid Agility is available for a street price of approximately $140 USD at dealers in the USA).

Frame, Suspension, and Pack Load Carrying Performance

Aarn Liquid Agility Backpack - 2

The Liquid Agility's load carrying comfort is extended when the optional front Balance Pockets are in use, shifting center of gravity of the load forward so that it coincides better with your body's center of gravity. The end result: more stable walking, especially when moving fast or in rough terrain.

The frame and suspension of the Aarn Liquid Agility pack is no simple affair. Herein, we'll not only describe the suspension components and their purpose, but we'll address the following questions:

Suspension components

In the main packbag (we'll address additional suspension issues related to the front pockets a bit later), the following harness and suspension features are worth noting:

Hoop stay

Aarn Liquid Agility Backpack - 3
Top of the pack showing the shoulder strap load lifters secured to a pivot point at a D-ring affixed to the rear panel seam (near top of photo). Red outline shows the approximate shape of the bikini framesheet that maintains pack shape of the upper packbag and resists collapse when load lifters are activated.

An inverted "U"-shaped fiberglass hoop stay (1/4" diameter) is the core load-transfer component of the system. This is the stay that is responsible for allowing the user to transfer load from the shoulder straps to the hip belt, with, however, one important caveat. The hoop stay cannot work alone - the shoulder straps are actually attached at a single pivot point to a joint that is integrated with the vertical aluminum stay (see below) which in turn transfers weight to the hoop stay. In addition, load lifter straps are integrated with a joint integrated with the bikini framesheet (see below), which then transfers load to the hoop stay.

Vertical aluminum stay

A vertical aluminum stay (1/2" width x 1/8" thickness) provides the main load transfer component for "load lifting" (transferring weight between shoulders and hips) through its integration with the hoop stay. In addition, the vertical stay provides important load bearing capacity to the suspension, and prevents the hoop stay from collapsing with a heavy load (as would occur if the shoulder straps were directly integrated via load lifters to the hoop stay, a common configuration in hoop stay internal frame packs).

The vertical stay is shapeable, and cyclists will appreciate the ability to shape a dramatic bend into the vertical stay to make the pack more comfortable when the mode of transportation is via two wheels instead of two boots.

It is important to note that the vertical stay only works if it's used in conjunction with the lateral stay (see below). You shouldn't use the vertical stay without the lateral stay, and vice versa - the two stays are integrated and work together - with the hoop stay, of course.

Lateral aluminum stay

Because the vertical stay isn't as long as the pack length, it is used in conjunction with a lateral aluminum stay (3/8" width x 1/8" thickness), which is placed in a sleeve at the bottom of and perpendicular to the vertical stay, forming an inverted "T" with the points of the "T" providing the effective load transfer joints to the hoop stay (see Figure 1).

Single pivot shoulder straps (upper)

Shoulder straps are manufactured as a single component, and attached to the pack via a single vertical daisy chain (thus, their height is adjustable to dial in fit) behind the back padding at what effectively constitutes a single pivot point that is directly coupled to the pack's vertical aluminum stay for load transfer.

Pass through shoulder strap pivot (lower)

The lower shoulder straps are coupled to each other via a length of 1 inch webbing that is affixed to each end of the lower strap. That webbing is housed in a sleeve underneath the bottom of the packbag. The result of this construction is that when one arm is raised (as occurs mildly while walking with trekking poles and dramatically while running or climbing), and the other is lowered in the body's natural striding motion, no loss of load transfer from shoulder to shoulder occurs - because the shoulder straps move in response to body movement.

Bikini framesheet and load lifters

A bikini-shaped framesheet containing a single small aluminum stay is present in the top panel of the packbag, with the narrow end (bottom) of the bikini facing outward and the wide end (top) of the bikini facing the user. A D-ring at the narrow end provides a single anchor point for the load lifter straps, which are attached in normal fashion to the shoulder straps. Consequently, activating the load lifter straps results in framesheet tensioning, with virtually no collapse in the packbag configuration, as occurs in conventional packs. The end result is that the shoulder strap load lifters work nearly 100% for load transfer with little efficiency loss as a result of packbag collapse.

Pass through hip belt pivot

The hip belt consists of two padded side fins, through which are threaded two 1-inch webbing straps. The lower straps consist of two straps that pass through the back of the pack and are coupled to anchor points on the back of the packbag. Each upper strap (there are also two of these) is also coupled to an anchor point on the back of the outside of the packbag. Thus, the hip belt straps act as packbag compression straps when they are cinched tight. Both lower and upper hip belt straps terminate at a dual-strap, 2-inch, hip belt buckle and tension on each of the four buckle strap termini can be independently configured.

Aarn Liquid Agility Backpack - 4

Figure 1. Suspension schematic of the Aarn Liquid Agility backpack. Black line is the fiberglass hoop stay, blue lines indicate the two aluminum stays configured in an inverted "T". Upper red dot indicates the point at which the single pivot point shoulder strap assembly is attached to the vertical aluminum stay. Lower red dots indicate the points of attachment of the hip belt to the fiberglass hoop stay. Upper green dot indicates the point at which force is transferred to the aluminum stay by the bikini framesheet, when the shoulder strap load lifter straps are activated.

To what extent does each suspension component contribute to the effectiveness of the load carrying capacity and stability of the pack? - They really are all integrated as a system. Take one of the components away, and the others will be impacted in a negative manner.

To what extent does the overall suspension outperform a traditional, single vertical aluminum stay-and-framesheet internal packframe typically found on internal frame packs in this size range? - For regular-old-trail-hiking for a short distance weekend, probably not much. I found the differences to be more meaningful when long distances began to impact your musculature and joint structure. I found none of the usual sore spots (shoulders, hips, upper back) when I loaded the Liquid Agility with 35 pounds for a 20-mile day, as compared to virtually any other traditional internal frame pack. I'm rather convinced that decoupling shoulder and hip belt movement from the load bearing suspension components has a significant impact on muscle fatigue when carrying weight for long days.

And what if I remove all suspension components to save weight? - Forget about it. Go buy a simple frameless rucksack if that's what you're looking for. The option is available on the Aarn Liquid Agility pack, but it defeats the purpose of what the pack is intended for (stable load carrying and dynamic body movement). If you remove all of the suspension components and load the pack up, you're simply going to have a too-heavy frameless ruck that carries like slop.

Bottom Line - The suspension of the Aarn Liquid Agility pack is unconventional because it's designed for a very specific purpose, which most pack makers ignore: bringing the center of gravity of the pack's load as close as possible to the center of gravity of the hiker. And, because Aarn's strategy for this is to balance the load using voluminous front pockets, the suspension is necessarily designed to perform the following unique functions:

  • Carry a substantial amount of weight in the front pockets (hence the need for stays in the front pockets and the bikini framesheet in the top of the packbag).
  • Maintain shape and load stability for improperly packed or under capacity loads (bikini framesheet, lateral stay, and lower circumferential compression straps).

In addition, because the pack is designed for action sports that may require significant torso twisting and/or overhead reaching, both the shoulder harness and the hip belt are designed to accommodate this motion in an intentional, and meaningful way.

The bottom line: the suspension works. We can comfortably carry more weight in the Aarn Liquid Agility than any pack of its size, and it's one of the very few internal frame packs on the market for which a significant load (and of course, light loads) can be carried while running or climbing over very long distances and times without you having to "fight" the pack suspension: the dynamics of the pack harness are noticeable and the positive effects on your perceived comfort are very real.

Usable Features and Ease of Use

Aarn Liquid Agility Backpack - 5
The large open 3D mesh panel across the back of the pack is breathable, comfortable, and durable.

  • Thin, wide shoulder straps are comfortable, pliable, and not bulky. Some of the most comfortable I've ever worn.
  • Padding in the hip belt fins is pretty stiff. I would have preferred softer padding for aesthetic reasons, but I didn't find the stiff fins to impair suspension performance or hip belt fit, and they never caused discomfort.
  • Open 3D mesh back panel was breathable and comfortable in hot conditions, and provided just enough padding, it seemed, so that the frame was never noticeable.
  • The packbag compression system, which is coupled to the hip belt webbing straps, was reasonably effective at compressing under volume loads, but was not always controllable - the amount of compression was governed by the amount of tension on the hip belt, and when the pack was removed, compression was lost and if the compression straps were securing items on the outside of the pack, those items tended to fall out.
  • Ice axe loops are adjustable, and shaft anchors are present on the upper portion of the outside of the packbag; however, the distance between lower and upper tool loops was too long for short (less than 60 centimeter) ice tools.
  • The packbag compression system consists of straps (coupled to the hip belt) and tension fins attached to the packbag, and can be loosened to the point where strapping a tent or sleeping pad vertically was a simple and effective means of storing those types of items.
  • An interior zippered hydration bladder sleeve holds mid-sized hydration bladders, but is too short for large (100 ounce) bladders.
  • Lack of any exterior pockets (even "wand pockets") limits options for securely carrying long, thin items like camera tripods, tent poles, or trekking poles, that have the potential to slide out of the pack's rear compression system (especially when the hip belt is undone).
  • Large, stable front pockets capable of carrying a lot of weight and volume are remarkably effective at extending the pack's range and preserving ease of use by maintaining access to everything you might need while hiking: a wind shirt, food for the day, water bottles, you name it. I could even fit a 1-pound down sleeping bag in one of the pockets. Their primary disadvantage: they are a little hot and uncomfortable when the temperature rises.

Durability

In eight months of testing, I observed no meaningful deficiencies with respect to durability. The packbag exterior suffers some abrasion wear, but nothing out of the ordinary or unexpected, considering that it suffered its way down scree slopes a time or two. The open 3D mesh back has held up surprisingly well, as this type of material is one of the first areas to fall apart on packs using it. However, Aarn has apparently sourced a high quality product. There are no signs of wear whatsoever and the mesh is holding up just fine.

Value

At $140 (US), I'd buy it. It's unique enough, and effective enough, to make this a top contender for long distance fastpacking, where you are covering big miles but need the load carrying capacity to haul some food or water. Its primary limitation is its size - but the combined volume using the front pockets makes this pack a 300+ mile performer for those in good condition and with ultralight base weights.

Recommendations for Improvement

Lighter fabrics and lighter suspension components would add a lot of appeal to the pack, but only for the select few of us that would be willing to sacrifice durability. Perhaps Aarn could manufacture a "racing" model?

More important recommendations would be to increase hip fin width, add zippered pockets to the hip fins, wand pockets to the lower sides of the packbag, and to provide an alternative compression system that does not depend on hip belt tension to stabilize the load.


Citation

"Aarn Liquid Agility Backpack REVIEW," by Ryan Jordan. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/aarn_liquid_agility_backpack_review.html, 2005-07-05 03:00:00-06.

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