The full suspension spectrum

Today, it’s safe to say that there are more backpack options available for the outdoorsperson than at any other time.  Most of this is due to the ugly inevitability of population growth and the capitalist hegemony, but some of it has to do with a unique diversity of influences on pack design.  As I’ve detailed elsewhere the Jardine thesis concerning lightweight backpacking has been assimilated such that most “serious” backpackers have a hard time looking back beyond it.  Sub 2-pound packs with sub 400 denier fabrics and slim, flexible harness components are expected.  At the other end of the spectrum, human-powered backcountry hunters have spured a revolution in lighter packs which can still carry very heavy loads through rugged country.  Companies like Stone Glacier and Paradox Packs have made it definitive that there are few compelling excuses for any pack to be heavier than four pounds.

IMG_1110The Arc’teryx Altra 62, above at right, is over-engineered with tons of largely purposeless padding, overly complex pockets and straps, and a heavy hipbelt connection, and it is still under 5 pounds thanks to modern materials and sensibilities.

Identity marketing is all the rage, as manufacturers use it to define a niche within a fractured and diverse market.  In order to fight back against the hype it’s useful to examine the full range of backpack suspensions available, take a stab at dividing them into rough categories, and talk about why each category exists, it’s strengths and weaknesses, and the application to which each is best suited.  It’s also worth pointing out how, without fail, every boundary between suspension categories has been blurred and eroded by innovative builders.  It is a good time to be a pack geek.

Backpacks must do a simple job well in rigorous and varied environments, and it is precisely the huge number of hours we spend with packs on our backs which makes that job seem so complicated.

First, a pack must maintain vertical structure under a given load.  This is most commonly and usefully expressed as maintaining torso length.  By resisting collapse which would shorten the distance between the hipbelt and shoulder straps, a pack maintains the ability of the user to adjust weight between these two points as she sees fit.  Collapse in torso length leads to discomfort in very short order, with anything more than low single digits being unacceptable.  To make this possible the supportive components in a pack’s suspension must be sufficiently rigid, and the various connecting points within the design must have minimal ability to flex, twist, and stretch.  As will be discussed below, there are a number of popular packs whose carry capacity is not limited by their frame, but by the poor connection between the frame and the harness components.

IMG_1270Osprey Variants loaded with a lot of beer and packrafting gear.  These packs feature durable fabrics, a ton of features, and a suspension system which is heavier than it needs to be, and they’re still around 3.5 pounds.  If you’re not an obsessive gram-counter there are a lot of good, and cheap, options around today.

Second, a pack must enable comfortable transfer of said weight to the wearer via a hipbelt and shoulder straps.  20 years ago these were often made from thick, stiff padding encased in packcloth.  Fortunately the industry has moved towards thinner, wider, softer, more conforming harness components, as a change in mentality (and a drive to save weight) has prompted ever better foams and laminates.  This is still an area for development, if for no other reason than that it is pretty basic to make a pack which will have no torso collapse whatsoever, making the harness/user interface the sole limiting factor.  80 pound loads are a trial for a hipbelt, and ruthlessly expose any shortcomings.  As above, many packs are limited not by the integrity of their frame, but by the weight at which the hipbelt will cease to be comfortable (usually by slipping down).

There are an infinite number of minor factors which go into making a good pack, but these two are the colossi.  Without them, everything else is just pretty frosting on a shit cookie.

mountain-laurel-designs-exodus-backpack-review-3The MLD Exodus, photo from BPL.

There are remarkably few truly frameless packs still on the market.  I define a frameless pack as one without any provision for a frame structure whatsoever, including a sleeve for a foam pad.  The keystone frameless packs in the recent past are the Golite Breeze, Gust, and first generation Jam.  The best examples currently available are the Mountain Laurel Designs series, Burn through Ark, and the ULA CDT.  The CDT has elastic pad holders, which keep the included foam pad in place, but unlike the packs discussed below this system doesn’t add much of anything to the quality of the load carry.  Frameless packs are of course the lightest, simplest option, and when packed well with a modestly light backpacking load can carry very well up towards 30 pounds, but necessitate careful packing and suffer from a lack of versatility.  With no integral padding or bulky stuff to provide structure a frameless pack isn’t going to carry too well with a wad of cams on board or skis strapped on.  They’ll remain a niche item and continue to be marginalized as the systems discuss below continue to get lighter.

IMG_0464This pack, which I discussed here, is built to accept a folded 3/8″ foam pad in an internal, velcro-d sleeve.  Not the lightest arrangement, but a very versatile one.

For this reason, frameless packs with a pad sleeve are far more common and popular.  Even though packs like the Cilogear 30 liter worksack rely on a 1/4″ sheet of stiff foam folded in half and nothing more, they often represent just enough non-discriminatory support to work well enough in most situations.  Stiff foam well contained with a good hipbelt can carry a lot of weight.  Just as with truly frameless packs, when packed well such that the load forms a sort of frame the weak point of the system will often be the belt-user interface.  Without contour to the back of the pack, there are often gaps which reduce the ability of the hipbelt to work properly.  Under ideal circumstances these packs can approach or even exceed the 30 pound mark, but often circumstances are not ideal, making these packs suited to either plain backpacking, as discussed above, or to varied activities with far lighter loads.  My pack pictured here is almost always used with weights less than 20 pounds.

I have a number of ideas on how to make a hipbelt work more efficiently with such packs, but given how effective and light true frames currently are, I can’t see myself prioritizing these projects any time soon.

OHM_2-0_Backpack_MainVersion 1 of the ULA Ohm, photo from the NOC.

The logical extension of using a foam pad in a pocket to enhance load carry is to use very light frame components to do the same job for less weight.  A stiffer foam pad is multi-use, but the pad and associated fabric and velcro can easily add six ounces.  Lightly framed packs try to maintain a weight close to that of frameless packs, but with more effective load transfer which works with a wider variety of loads and load shapes.  My favorite example here is the original version of the ULA Ohm, pictured above.  The Ohm added a bit of size, load lifters and a carbon hoop along the perimeter of the back panel to the CDT, at the cost of 8 ounces  (18 to 26).  Though it was replaced by the Ohm 2.0, which added a much larger and heavier (5 oz) belt, the original Ohm has remained an enduring classic because not because it’s raw upper carry limit was so high, but because it carried so well across a variety of weights and settings.

There are many such packs on the market, and they’re justifiably popular because they provide a good blend of light weight and forgiving load carry.  The most effective system will depend on variations in anatomy to a large extent, and is a question too large to address well today.  Rather, the more relevant question is when to distinguish between a lightly framed pack and a fully framed, traditional internal.  Over at BPL a number of years ago Will Rietveld proposed that this distinction be made by stating that internal frame packs have a direct connection between the frame (usually stays) and the hipbelt.  It’s a useful idea, but one with enough grey area that as a diagnostic tool it’s almost useless.

hunting_frameKifaru Duplex frame, from Kifaru, International.

The best example of the classic internal frame is the Kifaru Duplex frame, shown here.  Two stays, shaped to the users back, insert into sleeves from the bottom and are held in place by pockets sewn into the base of the removable hipbelt.  The shoulder straps adjust for length via webbing and a buckle which run parallel to the stays.  A comprehensive pictorial overview of the system can be found here.  With only enough fabric to hold the stays in place and enough foam to prevent point pressure between the user and the stays, the Kifaru suspension is almost as direct as is possible

Of course, many good designs use a mediated version of this system for a variety of reasons, mostly having to do with the extra weight and complication added by Kifaru’s hinged lumbar pad.  The classic Dana Designs internals used a single aluminium stay which inserted from the top and ran into the lumbar pad, behind which the hipbelt attached via velcro.  Hyperlight Mountain Gear, a lighter and more relevant example of an internal frame pack, uses two thin stays which insert from the top into two sleeves inside the pack.  The sleeves are stitching through padding into the non-removable belt (aside from the Ice Pack).  The lack of direct connection in the HMG system has proven to be a limiting factor, and saw the addition of a framesheet in the 4400 series of packs to better stabilize things (at the cost of ~6 ounces).

IMG_3550The Unaweep from Paradox Packs.

The material and padding required to optimize the connection between the hipbelt and the stays of an internal frame pack are a liability, and amount to weight which only serves one purpose.  Oddly enough, a far simpler and lighter system has been around for decades, the full wrap belt bolted directly to the frame which has been a haulmark of external frame packs ever since the original Keltys.

Externals died out just about everywhere aside from moose hauling a long time ago, due to fashion and the bulky, often lurch-prone frames (often 15 inches wide and close to 30 tall).  Their belt system is still the best available, and when Seek Outside figured out how to shrink the frame and introduce flexibility into the system without degrading load transfer, they invented something I’ve been very excited about for the last 15 months.  The Paradox Packs really aren’t internals, and really aren’t externals either, but rather a hybrid of both, and simply put, a major evolutionary step in pack design which goes a long way towards making internal frames irrelevant.

IMG_1306My current project pack; making the Paradox system as light and sleek as possible.  When suspension this robust adds less weight than most internal frames, there is no downside.

I think the most interesting developments in packs during the years to come will be in the areas between the old categories.  How do you make a pack which is almost as light and simple as a frameless pack, but offers better and more versatile load carrying abilities?  (Not yet answered.)  How do you get a pack which will carry anything you can, and do it while being sleek, flexible with light loads, and less than 4 pounds?  (Buy a Unaweep.)  Because of new technologies and the diverse range of influences and demands, pack development is enjoying a golden age at present, and we get to be around to see it.


11 responses to “The full suspension spectrum”

  1. I loved the original Jam pack. I also loved the suspension on the Gregory Baltoro 70 but I did not like all the zippers and seemingly needless weight. I look forward to meeting their love child.

    1. It’s rather silly that no one makes that, yet. I’ve never been a fan of that Dana-esque suspension, but plenty of folks are, and it wouldn’t be too hard to build it with a little less fat.

  2. I should add here, something I came across the other day. Kurt Racicot, of Stone Glacier, said that when he was researching materials for what became their Krux frame all the alu stays he tried had to be too thick and heavy to support really big loads, which is why he went with straight carbon stays in the final product.

    To support >60 pound loads over the long term it seems like you need to go to 7075 alu, probably in a thickness greater than 1/8″, and possibly as much as 1/4″. Bending such stays requires a lot of work, and fine tuning the lumbar curve become a serious nuisance. They’re also heavy.

    Four different approaches immediately spring to mind when thinking of ways various companies tried to work around this issue. Kifaru came out with their carbon/wood laminate stays, Stone Glacier with their straight carbon stays, Kuiu with a molded carbon stay/framesheet combo, and of course Paradox with the tubular alu U frame. Kifaru offers their stays in two profiles, because they cannot be reshaped at all, and their packs have a mondo lumbar pad, at least in part I assume to make up the difference when a given profile doesn’t fit someone exactly right. The Kuiu Ultra frame seems like a good idea, but comes in one profile and cannot be reshaped, which I assume it part of the reason why the packs to which it is attached have had mixed reception this year. Stone Glacier and Paradox use one-piece, full-wrap belts which do not rely on stay shape to stick to the lumbar region.

    The problem with the Stone Glacier straight frame is that it can’t be bent a little at the lumbar and above the shoulders to really keep the load close to the user. Not a huge issue, but less than ideal.

    1. Great thoughts. I’ve used a Unaweep this summer and fall and feel I’ve gotten to know it enough to embark on some modification/rebuilding. Interestingly your postscript here addresses exactly what I’ve been thinking: Unaweep harness with a 7075 flatbar frame. While the Unaweep feels sufficiently flexible with large loads, it’s still not as flexible as I’d like for lighter loads (and I’d like it a bit narrower). With 60+ lb loads tubing makes sense because you’re probably not going to be doing the type of movements where flexibility is advantageous, but I still feel like there’s room for improvement between most internal frames and a rigid external (acknowledging that the Paradox moves much more than other externals) for that 25-50 lb range, at least for hiking with a fair bit of scrambling/reaching/etc.

      7075 behaves totally differently than 6061 and is certainly how McHale has pulled off using flatbar for big load carriers, though I suspect his big load frames are probably not very flexible and wouldn’t really offer any advantage over tubing.

      1. I’ve been thinking along the same lines. It’d be simple to use a Paradox-style belt with a 12″ wide pack, and integrate a pad pocket, which I occasionally miss. I do wonder if a narrower stay spacing would detract from the belt’s efficacy, and how little structure you could get away with in a two stay arrangement with no hard support between them.

  3. What are your thoughts on the Exo frame design?

    1. I’ve to hear of a lumbar pressure issues, which given the narrow ti rods is a testament to good design. Assuming the ti was well chosen, the fatigue life should be pretty much infinite, which is a pretty cool way to build the flex into a heavy-use frame. My armchair guess is that the first failure point will eventually be fabric wear of the frame encasement, but that’s easily fixed.

      I’d be interested in taking a test drive, certainly. The bag design is pretty busy for my tastes, but seems well done.

  4. I’ve only started to play with the Unaweep frame and belt but I’m thinking I may eventually be looking at a flat bar design myself. What I’m thinking about is something similar to an HMG Porter but with the stays a bit wider. I’d put grommet holes through the pack so the belt could bolt directly onto the frame stays.

    1. My current idea is to make the stay pockets external, and the stays insert from the bottom. Nothing but the bolts would be needed to hold them in place. External pad sleeve between the stays and user, which should help maintain horizontal structure.

  5. My small version of the “DaveC Unaweep” it basically finished and I like the way its turning out. With no talon pocket it currently weighs 1.8 pounds. This is with very cushy shoulder straps and using a combination of Xpac and Dyneema gridstop. Once this one is finalized I’ll try to take it out for some desert hiking. Then I’ll probably build version II to fix any mistakes and then version III will be a bigger packrafting pack. I should be busy for a while!

  6. I have been thinking, isn’t some of the changes in hunting expedition backpacks basically trimming down the extraneous and returning back to the basics? I am having a hard time seeing the difference in total weight between the Stone Glacier Solo (1.7 kg) and my grandfather’s Alaskan packboard (also 1.7 kg including the canvas bag) or my uncle’s Bergens moose-pack (1.8 kg). Both are about 70-plus years old.

    I feel kind of gipped by the backpacking industry now that my family members brought out their old packs and put them on the scale. I was led to believe that Stone Glacier, Kifaru and other manufacturers are lighter than the older backpacks. So, I am not really sure what those companies were comparing themselves to. Probably to Barney’s, Kelty or Cabala’s.

    I would have to measure the suspension and comfort level between the old packs and the newer ones though and see if there’s a difference.

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s