Lightweight Internal Frame Packs: a State of the Market Report – Part 2: The Packs

"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?

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.

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

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.

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).

"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.

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 :)

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!

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

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.

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

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

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

"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.

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)

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

Thanks for a nice review Roger.

Perhaps outside the scope of this review, but since the subject of external frame packs has come up: do you have any recommendations for lightweight, commercially available, external frame packs that capture your "H – frame" idea?

Back in the old days, my external frame pack and hip belt could shift almost all the weight onto my iliac crests, or alternatively, onto the greater trochanters.

I find now, with increasing age, a decreased tolerance for prolonged heavy loading of the L5-S1 disk, and the SI joints. Anything much over 20 lbs all day, no matter how it's distributed over the shoulders or the lumbar area, starts to hurt.

Some of the individual pack reviews and comments above suggest some of these packs come close, but it sounds like you think the external frame is better at overall comfort – issues of durability, fragility and standing up to heavy brush aside.

Am I on the right track here? Any advice. How can I get most of the load back on the sides of my hips – the iliac crests – and still go lightweight?

Hi Coin

Sorry, but I don't have a simple answer for you. I think I noted somewhere in the review that my hips are rather narrow, such that many hip belts do not work very well on me. For this reason I have always preferred to carry the load on my back. This does *not* mean 'on my shoulders'.

With my design I find the load does go through the mesh on the back of the pack to the full area of my back. Frankly, I am not really sure why this works so well, but it does work for me.

I am sure that it won't work for many other people, and that a solid hip belt will work better for them. In this sense, fitting a pack to a person is very much like fitting a pair of shoes. I sigh (for the same reason) when I see someone ask 'what shoes should I buy' and then read a reply that they should buy SuperDucksMultiWeb shoes.

However … I will offer the following advice – which is also in the Review somewhere. Try to buy a pack which matches your torso length, but do not buy a pack with a torso length which is too short. Better to have a pack torso length slightly longer than your torso length: that will throw the load onto your hips more effectively.

Even better: pick a pack in the right size with an adjustable torso length. Then fine tune over several trips how it fits you. Yes, I definitely give brownie points to packs with an adjustable torso length.

I also give brownie points to packs with a solid stiff harness or frame. Frameless packs are all very well if my total load is under 6 -8 kg. Over that the weight of the harness is far outweighed by the added comfort it brings. Now, I know this comment will attract numerous responses contradicting me and saying how wonderful a frameless pack is. Well, as with shoes …

Can an external frame pack (like mine) stand up the 'heavy brush'? Chuckle. Trust me, the scrub in the Australian Blue Mountains (and in SW Tasmania) is definitely world class.

A commercial equivalent? Sorry – at this stage I cannot make a recommendation, because I don't know.

Cheers

I had a look at a Shadow this evening at a local distributor. I liked the clean, no frills look. Didn't have time to load it up though. You mentioned the thick webbing used on the hip belt. I found it virtually impossible to tighten the belt once fitted. The webbing was so rough that it wouldn't pull through easily. Combined with the older style of pulling the straps out rather than into the middle.

Any ideas when the 2011 line of packs will be available? The Umbra looks interesting.

Roger (Caffin):
Would any of the ultralight small manufacturers be interested in making your external frame sacks.

The osprey atmos 50/65 has a kind of all back mesh (for ventilation) but I think the gap between back and pack is bigger. I didnt like the shooulder straps.

> Would any of the ultralight small manufacturers be interested in
> making your external frame sacks.

I would be delighted if someone did want to.

Cheers

Roger (Caffin):

Actually, from reviews, the osprey exos 46/58 looks better than the atmos, as still has kind of all back mesh (for ventilation) but the gap between back and pack seems smaller, and the rucsac storage looks less curved.

Perhaps you could borrow one and compare it (not using waist belt) against your external frame pack.

Thanks Roger.

Yes, like finding well fitting shoes. But I did find those (wider), so I keep my optimism for finding the perfect pack for heavier loads. Thanks for the reminder/emphasis on torso length (longer for me).

The Aarn packs, and LuxerLite pack seem hopeful. Discussions of these packs over the last 5 years give lots of opinions both ways. I would love to hear from owners/users of these packs what they still think of them now.

Any other packs in this general class – lightweight with enough frame to transfer all the weight to my hips if I want to – that anyone thinks I should also consider? Any packs in the review above come close for a long torso?

Thanks.

Hi Alan

The survey covered both the Exos 46 and the Exos 58. Nice packs.

Cheers

Hi Coin

The survey lists the available pack sizes. I was testing Medium in just about everything, but many of them have a Large model available.

Which one to choose? Ahhh… Very personal. 'Every body is subtly different …' as they say on the planes.

Cheers