Crux AK47 and Crux AK57 Packs (UK)

Mini-review for the 2010 State of the Market Report on Internal Frame Backpacks.

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by Roger Caffin | 2010-09-28 00:00:00-06

These two packs were designed by Carol McDermott, a New Zealand climber now in Europe, and must be seen as alpine climbing packs for Europe, not as mainstream American walking packs. This has greatly influenced their design: they are made of some extremely tough fabric and are almost entirely lacking in all the frills normally found on American packs. Why? Because they have to take being hauled up cliff faces on the end of a rope. The weather in Europe (and especially the UK) is never as reliable as in America either - unless you count a very high probability of wet weather as being 'reliable.' So in addition to being made of tough waterproof fabric, the majority of the seams and fittings on the back of the packs are welded and sometimes taped, not sewn.

The harness consists of an 8.0-mm diameter 7001-T6 aluminium alloy U-shaped rod, the same as is used on the Lightwave packs (Lightwave is a sister company), plus a very firm foam back. The hip belt is simple, with 50-mm (2-in) webbing and buckles. Even the draw cords on the light waterproof nylon throat are climbing-oriented: they are 4-mm Rivory-Joanny accessory cord and can be used in an emergency as abseil slings. Despite all this strength - or perhaps because of it - Crux do not quote a recommended load for these packs. I guess if a climber can get the gear in, he'll carry it?

The clean exterior means no mesh pockets on the sides or the back and no bulging back pocket. The outer surface is essentially a smooth tube of almost indestructible Kevlar/Cordura fabric, the lid is of the same fabric, and the base is a double layer. Anchor points are reinforced with bonded patches (for sliding over the rock). The insides of the attachment points are all waterproofed. There are 'side pockets,' but they are low-cut and designed to take tent poles and glacier wands. They are not big enough to actually hold gear. The website claims the side pockets are 'stretch,' but the only stretch is the elastic binding along the top edges. They do have grommetted drain holes. The throat is light, waterproof nylon, but is hidden under the lid and not exposed. I know some American packs boast about their strong fabric, but this combination is in a class of its own.

Internally the frame consists an 8.0-mm diameter 7001-T6 aluminium alloy U-shaped rod frame. It looks like Easton tent pole material, but lacks the brand and is a bit more bendable. Getting it out is a bit of a wrestle, but quite doable. You don't need to get it out to alter the tilt at the base though. The back has a good slab of Lycra-covered moulded foam, but no sheet of hard plastic. The lack of a plastic sheet does not seem to be a problem, however: the foam is quite solid. The shoulder straps are not wide, but seem quite adequate with well-padded edges. The hip belt has wiggles in it to try to conform to waist lines and is only 70 mm (2.75 in) wide. The webbing and buckle are 50 mm (2 in) wide.

There is a bladder sleeve inside the main bag. The lid has fully-taped seams and a pocket with a solid waterproof zip - but then, it does rain in the UK. There is a key hook inside the pocket and a not-hugely-obvious zipped security pocket on the underside of the lid. The lid is removable and can be raised up above the nylon throat on its straps should you wish to tuck a tent or a rope under it. There are two ice axe attachments on the back of each pack.

The measured values for weight and volume for both the AK47 and the AK57 came out very close to specification - close enough to make no difference.

These are not packs for the casual walker of easy trails: they just wouldn't make sense. But for anyone looking for a serious alpine pack, or a pack for some very serious arguments with sabre-toothed jungle, these are very good. You might need to pay more attention to picking the appropriate torso length than you would otherwise expect, of course, and it would be best to try one on and check the length before you buy. We have included them in this survey because they meet the selection criteria, and it is always interesting to see the opposite end of the spectrum from the silnylon creations.

Crux AK47 Pack

Pack Rating Qualifications
AK47 Above average Very rugged alpine pack

We found this pack to be very small in torso length, which caused us a bit of a problem until we understood what was going on, and our trouble was compounded by the selection of a Size 1 version - essentially a Small. The torso length is short compared to most other packs because it is designed to have the hip belt up around your waist, leaving room for a full climbing harness around your hips below the pack. Once you adapt to this, it all makes sense. However, a size #1 is probably a bit small for most people, except for serious climbing.

Crux AK47 and Crux AK57 Packs (UK) - 1
Crux AK47, 1.17 kg (2.58 lb), 45 L (2800 cuin), #1, #2, #3

The hip belt seemed quite adequate - except that it did not really sit down on Sue's waist very well, and was marginal on mine. The attachment points for the load lifters seemed a bit close to the pack as well. Both of these problems are entirely due to the size of the pack, as described above. When used as a climbing pack (ie with a harness below the pack) it started to work much better, although I would still prefer a size #2 if I needed to carry a lot of gear. However, it may be noted that I was able to get the full load of Test Gear into the pack, despite the apparently small size.

Both packs include two ice axe attachments. The top straps for these are partially covered by the lid straps when not in use, but I don't think this matters in practice. What is nice is that the bottom loops are well clear of the bottom of the pack, so the ice axe head does not dig holes in a wooden floor when you put the pack down.

Crux AK57 Pack

Pack Rating Qualifications
AK57 Above average Very rugged alpine pack

This is the big brother to the AK47 - and we tested a size #2 rather than a size #1 just to be sure. With the larger size, the torso length was fine, and the hip belt sat on my hips and Sue's hips rather better. The load lifters also worked much better. Quite definitely all this was a result of getting the right torso length. The bag swallowed the Test Gear quite easily too, even though the measured volume was not that great. I think the shape of the bag was better able to handle the lumps. There was nothing put in the lid pocket, although there is quite a bit of room available there - about 3 litres, in fact.

Crux AK47 and Crux AK57 Packs (UK) - 2
Crux AK57, 1.30 kg (2.87 lb), 52 (3200 cuin), #2, #3

This larger unit has an extra feature over the AK47. There are what look like extremely tough 'panic handles' at the bottom on each side. You can see them in the right hand photo, especially the one on the right hand side of the pack. No, they are not really for panic :-), they are for holding skis. You drop the ski into this loop and use the top of the compression strap on the side of the pack to hold the top end of the ski. This is easy to do because the top end of the strap is attached with a side-release buckle (just visible in the other two photos). The loops are tough because skis do often have metal bits and edges which can rub, although I doubt skis could do much damage to this pack fabric. The loops are not shown in the company photo at the left: I suspect they may be a recent addition to the design.

The middle photos for both packs show the haulage loop. This is wide - wide enough that one person holding the pack can easily pass it up to a second person to grab. Function drives design.

This is a mini-review in the 2010 Lightweight Internal Frame Pack State of the Market Report. The articles in this series are as follows (mini-reviews can be found in Part 2), and a subscription to our site is needed to read them.

  • Part 1A covers the very basics and lists all the packs in the survey.
  • Part 1B covers the frame and harness which carry the pack itself.
  • Part 1C covers the main bag and all the other pockets, plus the all-important question of comfort.
  • Part 2 in this series covers the individual packs tested.

Citation

"Crux AK47 and Crux AK57 Packs (UK)," by Roger Caffin. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/crux_ak47_crux_ak57_packs_uk.html, 2010-09-28 00:00:00-06.

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Lightweight Internal Frame Packs: a State of the Market Report - Part 2: The Packs
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Dan Healy
(electricpanda)

Locale: Queensland
Measuring CoG effect on 09/30/2010 05:58:17 MDT Print View

Derek, absolutely agree that any backwards pull that causes you to use energy leaning into is not good… what we are trying to determine is in the overall context of carrying weight from one spot to another… is a 1% increase in the effective weight you carry going to trump other factors? Certainly 20% is getting important – but is this really the case?
In the rush to get lighter packs - so that on paper we carry a lighter load - maybe we have forgotten why it was that harnesses got better/heavier in the first place… perhaps in practise we feel more comfortable at the end of the day by using a better harness - albeit making it a heavier pack.

Derek Goffin
(Derekoak)

Locale: North of England
Measuring CoG effect on 09/30/2010 06:28:43 MDT Print View

I am totally with you that, for me, a comfortable carry is worth some packweight.
People are really used to leaning forward to balance their rucksack load. I suspect you were all leaning forward a little.
Some Macpack packs have diagonal straps that pull on the sides of the hip belt to pull the load into the back and reduce the strain on the shoulder straps to some extent. Whether that is as as good (from an energy point of view) as balancing the load completely, like Aarn front pockets can, is not clear.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Measuring CoG effect on 09/30/2010 15:50:35 MDT Print View

Hi Dan and Derek

Yes, I know those packs. It is an amusing thought that Au/NZ packs have such good harness systems because our local gear is otherwise so heavy ... need to think about that one for a while!

Yes, of course we all lean forward a bit for balance. Better that we lean from the ankle than from the waist though. Bad memories of the old A-frames ...

Now, those diagonal straps at the base on the Macpac etc - I think they are there to stop sideways sway. I do notice the improved ride when they are adjusted properly. Quite a few (most?) of the packs tested in this review also had them, so I don't think they are uncommon at all.

Cheers

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Very well sorted out on 09/30/2010 17:21:44 MDT Print View

Thanks Roger, for an excellent, understandable and in-depth series. The data is very helpful for ccomparisons and the photos of each pack were instructive. Must have taken you a lot of time to prepare these articles but really, where else could we go for such comprehensive and thorough information on this subject? Magazine reviews and even "Buyer's Guides" don't lay it out this well, all in one place.


As a result of these articles I am beginning to become a fan of the Lightwave series of packs, and especially their split hipbelts. I'll have to find a US vendor so I can try the largest one on with weight.

Used to be that the best packs mainly came from the US but that's not true anymore. Lots of great packs and innovative ideas from Britian, Europe, OZ and New Zealand.

Edited by Danepacker on 10/01/2010 12:02:43 MDT.

aarn tate
(aarndesign) - MLife
Forward lean and backward pull of the shoulder straps. on 10/01/2010 02:08:21 MDT Print View

All the comments about the importance of packing the weight close to your back are right- this does make a huge difference and validates my point about reducing load leverage. Also the point that leaning forward also reduces the pull back forces on the shoulders is also correct.
However the sports science research is very clear that the greater the forward lean, the more energy is required to carry a given weight and the more strain there is on the body. As the forward lean is the result of both the weight and the center of gravity of the load, it would be the most accurate way to determine the efficiency of the load carrying system. In the research they measure this by trunk angle. A photo is taken from the side and a line is drawn from the hip to the shoulder. The angle between this line and the horizontal is the trunk angle.
The research showed that when walking at 27 degrees downhill, on level ground and 20 degrees uphill, the increase in forward lean with an Aarn Bodypack was 8.2 degrees, 8.9 degrees and 8.2 degrees respectively, while for the traditional backpack, packed in the recommended way with the same gear, the forward lean was 17.3 degrees, 21.6 degrees, and 26.0 degrees respectively.
As a result, there was a smaller physiological cost (eg 6.4% less energy required when climbing uphill), smaller perturbations from normal gait patterns and better scores on a variety of subjective measures such as balance, stability and comfort with the Aarn Bodypack compared to the traditional Backpack. There was the elimination of pain/ discomfort in the shoulders, neck and thighs, and the virtual elimination in the back (loads of 22.5kg) with the Aarn Bodypack. The experience of pain/discomfort in these areas was experienced in an average of 40% of the experimental subjects with the traditional (internal frame) backpack.
I agree with Roger that comparing different backpacks on the basis of forward lean may not show significant differences if all were packed in the optimal way with the heavy items close to the back. But why not compare with an Aarn Bodypack?

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
packspackpacks on 10/01/2010 22:28:41 MDT Print View

"Personally I say bugger all if you have good core strength"

I agree with Dan. Easier to buy a new pack, rather than get fit to carry the old one.

"Why not test v. an Aarn."

Probably because, your comments thus far to the contrary, we're not your marketing tool?

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Forward lean and backward pull of the shoulder straps. on 10/02/2010 04:43:27 MDT Print View

Hi Aarn

> for the traditional backpack, packed in the recommended way with the same gear,
> the forward lean was 17.3 degrees, 21.6 degrees, and 26.0 degrees respectively.

I haven't checked the research you are citing, but I strongly suspect that the 'traditional backpack' was an A-frame, or something similar. With one of those it is quite possible that someone could bend forward from the waist by that amount. Like, been there, done that, and suffered!

But there is NO WAY I lean forward that much when wearing my external frame pack. That amount of lean would leave me on my face on the ground. What lean I do is not confined to the trunk either: I lean forward from the ankles. My spine stays largely straight. That is how any experienced walker uses either an external frame pack or an internal frame pack.

0429 Standing up straight with pack on

What leaning forward from the ankles means is that the physiological cost is far smaller, the balance and stability are close to normal, and comfort is similar. Back pain? Don't experience it.

But I am quite happy to believe in all these problems with an A-frame style of pack!

Cheers

Edited by rcaffin on 10/02/2010 04:50:32 MDT.

Michael Davis
(mad777) - F

Locale: South Florida
Re: Lightweight Internal Frame Packs: Part 2 on 10/04/2010 19:21:20 MDT Print View

Great article Roger!
Something I noticed in your comparisons, which I have often seen talked about elsewhere, is the volume to weight ratio.

I've never been impressed by this statistic because I can picture a 100 liter gunny sack made from the lightest weight cuben, tied up with a dyneema string, suspended from ones neck. Extreme, I know, but it illustrates my point. That configuration would get a "great" score.

The statistic that would impress me would be the weight carrying capacity vs. the weight of the backpack itself. A backpack, in order to have a high weight carrying capacity needs a sturdy frame and formidable suspension - however - those things add weight to the pack.

The ultimate pack would be capable of carrying 40 lbs but weigh only 4 ounces. Weight carrying capacity to weight of pack, I believe, is the challenge in making an "efficient" pack. Not the volume to weight ratio: that's too easy!

I fully realize that the weight carrying capacity is a subjective measurement, but, obviously from your article, so is a volume measurement. As long as the same person is rating the weight carrying capacity of a series of packs, like your excellent article could, the measurement could at least be "accurate" relative from one pack to another.

E J
(mountainwalker) - MLife

Locale: SF Bay Area & New England
great review; additional usable volume on the Exos on 10/04/2010 20:48:52 MDT Print View

Excellent thorough analysis and review Roger - much appreciated. And as usual I'm impressed with the wisdom BPL readers have added in comments.

I just wanted to add regarding the Exos - another BPL member pointed out to me in a PM conversation that the Exos has usable volume between the mesh back support and the pack bag - that member user packs this space to hold a water bladder and extra clothing - that's not a small amount of extra usable volume. That member added that this helps keep out snow in winter as well (to the BPL member who pointed this out - feel free to jump in and comment - it was a good point).

Arapiles .
(Arapiles) - M

Locale: Melbourne
Re: Very well sorted out on 10/05/2010 04:47:04 MDT Print View

"As a result of these articles I am beginning to become a fan of the Lightwave series of packs, and especially their split hipbelts. I'll have to find a US vendor so I can try the largest one on with weight."

I'd support that - I've always been impressed by Crux. From 2001 to 2006 I travelled to London regularly and checked out the Crux packs and was suitably impressed. Lightwave came along later. Oddly, when I was living in London in 2006/2007 Lightwave was almost impossible to get my hands on - they seemed to have very limited dealers.

Martin RJ Carpenter
(MartinCarpenter) - F
Lightwave on 10/05/2010 05:38:39 MDT Print View

They still are horribly limited in terms of UK distribution, even in the more technical shops. (rare in London, like locusts in the Lake district ;)).

The Crux packs are much easier to find. No idea why its that way round! Especially as the Lightwave sacs always seem to do well in the magazine tests.

Its a strange world sometimes :)

Edited by MartinCarpenter on 10/05/2010 05:39:44 MDT.

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: great review; additional usable volume on the Exos on 10/05/2010 13:14:43 MDT Print View

Hi EJ

It's not meant to be a secret, and this is a good place to point it out. many folks shy away from the mesh backed packs for winter use, but at least in the case of the Exos, that mesh space can be well utilised. In winter I put my hydration bladder there with a thin piece of evazote between it and my back. this keeps out snow, keeps the cold water off my back, yet also keeps the water from freezing. It adds around an extra 3 litres of usable volume as well, which also comes in handy on winter trips, and it's easier to get your bladder in and out of this space than the internal hydration sleeve. other stuff like rain jacket, wind layers, ground sheets etc...could also be put there if you prefer to carry your water in bottles. It is all these little extrs that make the Exos 58 (really a 61 in large, but who know what the true main pack volume is) a suitable winter pack for me. Generous top pocket, generous hipbelt pockets, generous side pockets and a generous kangaroo pocket for sleeping mat, sit pad etc...just don't try bushbashing in this configuration or something is going to get shredded!

Mike Alford
(mikebpl) - MLife
Re: Lightweight Internal Frame Packs: a State of the Market Report - Part 2: The Packs on 10/11/2010 01:50:38 MDT Print View

Thanks Roger, great analysis!
Just one question - how come theGoLite Pinnacle, wasn't included in your selection? At only 930 g it seems to fit nicely into that space on the upper left of your weight-volume chart.
Cheers,
Mike

Oops, I can answer my own question - just noticed that the Pinnacle is frameless.
Cheers

Edited by mikebpl on 10/11/2010 02:04:03 MDT.

Paul Hatfield
(clear_blue_skies) - F
Bending at the waist on 10/11/2010 22:11:12 MDT Print View

Bending at the waist doesn't seem to affect Lance Armstrong's performance terribly. Sure he would probably perform better on a recumbent bicycle, but it's clear that athletes can perform for many hours at very high levels of exertion with extreme bending at the waist.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Bending at the waist on 10/12/2010 03:39:20 MDT Print View

Ha!
And how long is a day's stretch on the Tour de France? NOT as long as a day's walking for sure, AND he has a team of masseuses at his beck and call AND a super-soft bed at night (and a cook).

A totally different situation, and not really relevant to walkers imho.

Cheers

aarn tate
(aarndesign) - MLife
: Forward lean and backward pull of the shoulder straps. on 10/13/2010 14:20:14 MDT Print View

Hi Roger,

The research compared an Aarn Bodypack with a Karimor Alpiniste internal frame pack - state of the art at the time- not an A Frame! Are A frames still available?

The picture shows you with quite a bit of forward lean. Forward lean is least when standing still as in your picture, greater when walking forward, and maximum when climbing. (The same is true without any load).

Trunk angle does not measure forward bend at the waist as you suggest, but the difference between a line drawn between the shoulders and the hips- and the HORIZONTAL. So bending forward at the ankles with a straight back is an economical posture to assume with the forward lean. As most of the subjects in the study were experienced backpack users, I assumed they also leaned forward in this way, but this could be checked with the original research photos.

Ray Lloyd, who did the original pioneering research on forward lean, has been doing some more work on load carriage. He recently wrote regarding his latest work: I quote "my current work seems to suggest that freedom of movement of the trunk is a determinant of economy (your double pack system allows more than either a backpack (which constrains to lean forward) or head-loading (which constrains to upright). In addition, our current findings suggest that individual variability of response in relation to economy is greater than we might have anticipated. Consequently we are intending to look at relationships between economy and kinematics at a range of loads and speeds and wondered if you might be interested in having some of your more recent designs tested in this context and, if so, if you would be able to send a sample(s)".

If you want to contact Ray his details are below:

Ray Lloyd
Head of School
School of Social & Health Sciences
Level 5 Kydd Building
University of Abertay Dundee
Dundee
DD1 1HG
Scotland

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: : Forward lean and backward pull of the shoulder straps. on 10/13/2010 15:44:03 MDT Print View

Hi Aarn

> The picture shows you with quite a bit of forward lean.
Well, maybe 4 - 5 degrees, yes.

> So bending forward at the ankles with a straight back is an economical posture
> to assume with the forward lean.
I agree, of course.

But I find it hard to imagine some bending forward from the ankles at 26 degrees, as your first posting stated. OK, maybe a severely overloaded SAS trooper carrying his FULL load of munitions and water might do that for 100 m from the chopper which landed him, but a walker with a reasonably light-weight pack???? Photographic proof would be needed.

As noted in some other postings, the backwards tension in the shoulder straps has been measured as not all that high *in practice*. This suggests to me that a reasonably light-weight load carried upright in a reasonably good pack is not really going to present that much of a problem. The amount of tilt needed to balance this will not be high.

Now, do we lean forward some more when going forward? Yes, we do, but that is needed to keep the CoG of the whole walker somewhere between the front and back feet. You would fall flat on your face if you didn't do this. And it may also be that the faster you go, the further forward the CoG needs to be.

That necessary forward displacement of the CoG has to be assessed in combination with the weight of the pack *relative to the walker's weight*. I weigh 64 kg; my pack weighs 10 kgs. The influence of the pack weight on how much my CoG has to move is not going to be all that large. This suggests that the change in position of the CoG due to a light-weight pack is not supremely important.

If there are other factors coming into play, such as the ability to see one's feet, than any small benefit from a shift forwards of the CoG due having front packs in place may *in practice* be inconsequential. This seems to be the experience of many walkers: they rate being able to see their feet far higher, especially in rough terrain.

Other factors which can detract from the front-mounted load include the increased heat load on the body from the reduction in ventilation, the increased difficulties experienced in swinging a pack on and off one's shoulders when there are large weights on the shoulder straps, and the increased problems when scrambling with a bulky thing at the front pushing you off the face. The importance of these factors will depend very much on the individual and what he is doing.

So while some people undoubtedly like having front-mounted packs to alter the CoG, the market place seems to be putting other factors higher in importance. Well, that's what the sales figures and walker preferences indicate, anyhow.

I hope this explains my thinking.

Cheers

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: Re: : Forward lean and backward pull of the shoulder straps. on 10/13/2010 16:35:37 MDT Print View

"If there are other factors coming into play, such as the ability to see one's feet, than any small benefit from a shift forwards of the CoG due having front packs in place may *in practice* be inconsequential. This seems to be the experience of many walkers: they rate being able to see their feet far higher, especially in rough terrain.

Other factors which can detract from the front-mounted load include the increased heat load on the body from the reduction in ventilation, the increased difficulties experienced in swinging a pack on and off one's shoulders when there are large weights on the shoulder straps, and the increased problems when scrambling with a bulky thing at the front pushing you off the face. The importance of these factors will depend very much on the individual and what he is doing."

+1 to all of the above. However, Aarn packs used without the front pockets work very well too. It's mainly the lack of a hydration port that stops me from using them in this way...yet another factor important to *some* walkers.

Alan Bradley
(ahbradley)
R Caffin / Aarn: External frame / front aux pack on 10/16/2010 05:50:55 MDT Print View

Roger (Caffin):
Do you still think your external frame sacks are a lot better than commercial internal frame ones.

Aarn packs:
Doesn't the front rucksack cause overheating: now you have a lot of insulation over your temperature regulated core (chest)

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: R Caffin / Aarn: External frame / front aux pack on 10/18/2010 15:19:09 MDT Print View

Hi Alan

> Do you still think your external frame sacks are a lot better than commercial
> internal frame ones.
Let's say I still prefer my external frame pack for most conditions. It is very light, the harness suits me very well, and it handles anything between 8 kg and 28 kg happily. yes, I am able to carry up to 28 kg with it when portering in to a remote hut for a ski trip. I can't normally get that much capacity with the IF packs.

However, it does have one disadvantage. The frame is very light and could be damaged if mistreated. I package it up in a cardboard box every time I fly. If you are planning on flying and don't have a high load, an IF pack might be a safer (less worry) choice.

> Doesn't the front rucksack cause overheating
I found that it did on me, at least in an Australian summer. Perhaps I am a bit sensitive to this, as I normally travel with very light clothing.

Cheers