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Granite Gear Escape AC 60, Granite Gear Vapor Flash Ki, and Granite Gear Nimbus Ozone Packs

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

Granite Gear makes packs, bags, duffel bags, etc: things to put gear in. The company has recently changed hands, so we were dealing with an enthusiastic new owner. Like many other small companies, the packs have a distinctive appearance. We gathered that some packs are being upgraded and may have changed slightly or be about to change from what we have tested. However, I doubt that there will be huge differences.

Granite Gear Escape AC 60 Pack

Pack Rating Qualifications
Escape AC 60 Above average Adjustable torso length

The design of this pack's bag part is not that out of the ordinary, but the harness is very interesting, so we'll deal with that part first. In short, it has an adjustable harness based on a tough, moulded sheet of plastic. The adjustment for torso length is done by unhooking the shoulder strap from one slot and hooking it into another slot. It's sufficiently novel that I have included a detail shot of the adjustment mechanism in the photos. In the photo the right hand shoulder strap has been unhooked and you can see the metal buckle which acts as the anchor.

Getting to this adjustment is not easy, but once you figure out that the top of the plastic sheet is concealed by some fabric held in place by hook&loop fastening, you are on your way. You do have to disconnect quite a few straps along the way - the first one or two times anyhow. You also probably need to remove the floating lid, which is an exercise in itself. Once you have access to the panel, you can set the torso length to a number of values, as determined by the slots you can see. Just what the top slots (set wide apart) are for I am not sure - someone the size of a grizzly bear maybe! Having moved the metal buckle into the next slot, you then have to reassemble the harness system. It isn't that hard to do, and the ability to match the torso length to your body is good. It would help if they included an instruction sheet with each pack though.

Granite Gear Escape AC 60, Granite Gear Vapor Flash Ki, and Granite Gear Nimbus Ozone Packs - 1
Granite Gear Escape AC 60, 1.48 kg (3.26 lb), 49 L (3000 cuin), Short, Regular. *In addition, there are interchangeable Men's and Women's hip belts in sizes Small, Medium, Large, and Extra-Large.

The padding on the back looks like some Doctor Scholes massage foot bed foam covered by someone's black see-through negligee - but the mesh is actually quite strong and the padding is comfortable. The shoulder straps and hip belt are quite comfortable too. Note that there is a range of hip belts sizes and you can exchange them. The adjustment straps on the shoulder straps are long... very long. The sternum strap is long enough too - and you will need to use it with this pack. There is no stupid whistle on the sternum strap. The load-lifter straps work well, and have excellent thumb loops at the ends. You can see how I am 'resting' my arms using them. I like doing this, and it does help a bit with the balance of any pack.

Now for the bag part. This too is a little odd-ball. The bag itself is fairly standard, but all the bits around it are different. Where most packs have webbing straps, the Escape AC 60 has cord, with cord adjusters and buckles. Yes, the cord can be adjusted the same as webbing. Does the use of cord cut any weight? I doubt it very much. It works about the same, but I would be just as happy with light grosgrain myself. Anyhow, there are quite a few of these bits of cord around the pack.

What's not obvious is that the bottom of the bag can expand a bit, so you need to pack carefully to make sure the bottom end is filled up. Since the capacity is rather less than claimed, you need to use every bit of space there. The throat is of medium length - certainly adequate. There is a conventional webbing strap to go over the throat under the lid. There is a zipped sleeve for a hydration system inside - the hose has to go through a hole at the top of the sleeve. The sleeve would be useful for reserve maps maybe, or as a deep security pocket.

The pack does have two ice axe loops at the bottom, but no dedicated straps at the top to hold the shaft. Perhaps you could wind the lid straps (cords) around the shaft to hold it up. There are several other attachment points scattered around the body of the pack as well.

There is a back pocket with a central vertical waterproof zip. Exactly why it has to be waterproof is not clear, as the black sides of the back pocket are stretch mesh. Why the zip has to be vertical is not clear either: it does mean things can fall out when you undo the zip fully. It's quite a large back pocket too. More curious is the little pocket below the back pocket. It too has a zip closure, but the zip is at the bottom of the pocket. Surely an invitation to disaster - things would fall out? It turns out that this little pocket, which has a key-clip inside, is meant for holding a pack-cover (an optional extra). Not so curious after all! The side pockets are a double layer affair: there is a fabric pocket with a light mesh one outside it. The opening of the mesh pocket is tilted forwards: 'quick-draw water bottles' maybe. The fabric pockets seem capacious when the main bag is empty, but there is little room left once the main bag is full. Why manufacturers even bother with these flat side pockets puzzles me.

In keeping with the central zip on the back pocket, the lid also has a central zip, right on top. Fortunately it is a waterproof zip (if you trust such things) as there is no cover over it. The position on top does make some sense though: you get good access inside the pocket without things falling out. There is a key clip in there, but no security pocket.

The pack held all the Test Gear load in the main bag, but it was close to full. I was also able to get most of my gear for a (real) Wollemi trip into it except for 40 m of rope and slings, but it is not a big pack by any means. The pack rode fine in the field, once I got the torso length set and all the other adjustments to suit me.

Granite Gear Vapor Flash Ki Pack

Pack Rating Qualifications
Vapor Flash Ki Average Neat, but heavy

This Vapor Flash Ki is a Women's pack: the Vapor Flash is a Men's pack, slightly larger in volume. The website claims a 48 L capacity for the Short model, which is what we tested. The hip belt comes in four sizes: Small, Medium, Large, and Extra-Large.

No doubt about it: this pack looks neat. The strips of tougher fabric down each back corner, combined with the compression straps, provide very useful strengthening. The colour was also rather nice. The torso length is fixed, but the hip belt is removable, although that is not obvious at first. Removing the hip belt is easy once you realise the padding on each wing sort of locks the hip belt in place. That 'lock' is reinforced by webbing and buckles at the sides.

Granite Gear Escape AC 60, Granite Gear Vapor Flash Ki, and Granite Gear Nimbus Ozone Packs - 2
Granite Gear Vapor Flash Ki, 1.38 kg (3.03 lb) , 37 L (2200 cuin), Short, Regular.

We were able to get most of the Test Gear inside the main bag provided the rolled-up mat was strapped on the outside. In other words, the volume is rather small: we measured just 37 L in the main bag and lid. There is no back pocket. Well, if you are travelling ultralight it may well have enough capacity, but an ordinary lightweight walker might have some trouble.

The floating lid is a bit strange. It could go up a bit if you really filled the throat section of the main bag, but it is threaded onto the load-lifter straps, and it can't be raised very far unless you unthread it from those straps. Doing so looked impossible at first, as the ends of the straps seem to have a strip of hook&loop fastening tape sewn across the webbing. That simply would not go through the buckles. However, eventually I found out that the hook&loop tape is double-sided and could be unstuck from the webbing. A bit confusing at first! Why was the hook&loop tape there anyhow? It lets you roll the excess webbing at the end of the straps up into a little ball and secure it. Um... frankly, why bother? Anyhow, if you do unthread the lid from the load-lifter straps you can raise the lid a bit - but it perches rather precariously on top, and I don't think this is a good arrangement. It's a nice looking pack, except that the lid design is not so hot when you want to fill the bag right up. Less than full - fine.

We tested a Short version. I found it too short for me, and Sue found it "not very long." I think the Regular version might have suited both of us better. This meant both of us found the 'carry' less than optimal: it was hard to get the pack onto the hip belt. However, in this case I think that this was due to the short torso length. It would suit a really petite woman, or better still a young girl. The colour scheme should appeal to either. Most people might find the Medium a better fit.

Granite Gear Nimbus Ozone Pack

Pack Rating Qualifications
Nimbus Ozone Above average Adjustable torso length

You would have to say this is a bit like a big brother to the Vapor Flash Ki - but without a lid. The back padding is similar, and so is the hip belt, except for a slightly different curvature. The difference will be due to the former being a Women's pack while this is not - the website says "Women's belts are sculpted to fit the increased angle of women's hips." You have to burrow under the bottom of the pack to undo the hook&loop flap covering the big screw which anchors the hip belt. Yes, this one uses engineering stuff!

Granite Gear Escape AC 60, Granite Gear Vapor Flash Ki, and Granite Gear Nimbus Ozone Packs - 3
Granite Gear Nimbus Ozone, 1.48 kg (3.26 lb) , 53 L (3200 cuin), Short. *The only size is called Short, but it didn't really seem that way to me. In addition, there are Men's and Women's hip belts in sizes Small, Medium, Large, and Extra-Large, plus shoulder straps in Small, Medium, Large, and Extra-Large.

The torso length is adjustable over a range of 100 mm (4 in), with the aid of a screwdriver. The straps are bolted to a plastic back panel. The mechanism for adjusting is a bit complex, but you shouldn't have to adjust it more than once or twice. In addition, while you are adjusting the torso length, you can also exchange the shoulder straps themselves. When you make an adjustment you have to move a horizontal padded reinforcing bar which sits behind the plastic back panel. How you could lose this bar I don't know, but the company sells spares! Having an adjustable torso length gets brownie points, but whether the different shoulder straps are really required is something I don't know. I guess they wouldn't sell them if they didn't find them useful or popular.

With all the straps and screws involved in adjusting this pack, you are going to need an Owner's Manual to work out how to drive it all. In this case the pack does come with a twenty-page Owners Manual, with good explanations and pictures. OK, some of the pages are about other packs in the range, but there are a solid twelve pages of technical stuff here for this pack!

The back is reinforced with a pretty solid plastic panel. If you didn't know better, you might think the top edge had metal reinforcing as well, but it's just plastic. While the bag fabric is quite light, there is some weight and stiffness in this harness. It showed however in the carry: it felt light.

Without a lid, this pack has to rely on a roll-top. The length is generous. The light fabric used is reinforced with those two blue stripes down the back and a number of webbing compression straps which can actually go right around from back panel to back panel, in three sections. There are two ice axe loops at the bottom of the pack, and the upper side compression straps are held with side-release buckles: they can hold the shafts in place.

There are large side-pockets of stretch-mesh, and a compression strap across the middle of each one. They should hold medium sized things and tent poles well, but don't put tiny things in them - there are little 'drain' holes at the bottom. The holes may be for letting water out. There's a short bladder pocket inside which will have to do for a security pocket, and a key clip at the top of the frame. No hip belt pockets are fitted, although there's webbing on the hip belt for attachment, and no stupid whistle on the sternum strap.

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

"Granite Gear Escape AC 60, Granite Gear Vapor Flash Ki, and Granite Gear Nimbus Ozone Packs," by Roger Caffin. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/granite_gear_escape_vapor_flash_ki_nimbus_ozone.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