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Lightweight Internal Frame Packs: a State of the Market Report - Part 1B: Theory and Technology
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Addie Bedford
(addiebedford) - MLife

Locale: Montana
Lightweight Internal Frame Packs: a State of the Market Report - Part 1B: Theory and Technology on 09/07/2010 14:07:13 MDT Print View

Companion forum thread to:

Lightweight Internal Frame Packs: a State of the Market Report - Part 1B: Theory and Technology

eric chan
(bearbreeder) - F
trying out on 09/07/2010 14:54:01 MDT Print View

all the above youll only find out by trying out the pack

in other words fit, fit, fit is what ultimately matters ... which is why i buy from stores with a generous return policy

George Matthews
(gmatthews) - MLife
Re: Lightweight Internal Frame Packs: a State of the Market Report - Part 1B: Theory and Technology on 09/07/2010 18:50:02 MDT Print View

Good breakdown of the components of a lightweight internal frame pack.

Thanks for your diligent effort on this multi-part report.

Martin Rye
(rye1966) - F

Locale: UK
Lightweight Internal Frame Packs on 09/08/2010 13:42:37 MDT Print View

"You should quite definitely reject any framed pack which doesn't have these" - bit contradictory compared to other BPL views.

Gossamer Gear Gorilla does not have them and it has a frame (U shaped rod). Got top mark when reviewed here.

Do my eyes deceive me but this 50L pack soon to be available has no load lifter straps in the photos.

http://www.backpackinglight.com/cgi-bin/backpackinglight/bpl_absaroka_backpack.html

aarn tate
(aarndesign) - MLife
Biomechanics on 09/08/2010 15:48:17 MDT Print View

I hope your report will discuss the most important factor determining the comfort, load carrying efficiency and strain on the body produced by the load. This is the closeness of the center of gravity of the load to the center of gravity of the body. This is the most fundamental and crucial biomechanical factor to be considered in pack design, as shown conclusively by Sports Science findings on a wide range of load carrying systems. If you fail to discuss this, I believe you are not presenting the full picture to your readers.
A discussion of these research findings as well as a research bibliography can be found here: http://www.aarnpacks.com/sports_science/index.htm

Aarn Tate

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Biomechanics on 09/08/2010 17:00:53 MDT Print View

Hi Aarn

Yes, I have read and studied your web site at some length, and I do agree with most of what you are saying. Especially about the position of the CoG!

On a personal note, I found the pack from your range which I tested some time ago to be too narrow for my way of thinking: the narrow throat made packing very difficult for me. And I found the front pockets to be too tall for my torso - I suspect you are a lot taller than me.

Part 1C of this series will focus very much on the three essentials: comfort, comfort and comfort. But it will try to explain the hows and whys.

Cheers

Franco Darioli
(Franco) - M

Locale: Melbourne
Lightweight Internal Frame Packs: a State of the Market Report - Part 1B: Theory and Technology on 09/08/2010 17:29:51 MDT Print View

Since we have Aarn lurking...
Something that popped into my mind recently is that as much as the pockets work very well for me for logistical reasons (IE I have all the bits that I could want to use quickly at my fingertips) as well as balancing the load on my back, many are not built like this :
Aarn's way


having large front bones (....) they already have weight balancing "front pockets".
Sorry for the non politically correct observation.
Roger, I am about your size, 3 kg heavier.
Franco

Robert Blean
(blean) - MLife

Locale: San Jose -- too far from Sierras
In the eye of the beholder on 09/08/2010 21:59:30 MDT Print View

Reading this article makes me reflect on how much is in the eye of the beholder, and how careful one needs to be to distinguish physical facts from different people's needs/habits/wishes. I'll be interested to see whether this article stirs up much of any controversy.

No one can doubt that Roger is very experienced, and analytically/technically inclined. Nevertheless, I disagree with a couple of his points. Just illustrates that different folks have different needs & experiences. I realize that not everyone will agree with my comments either.

*)The back padding "provides much-needed padding between the bag and your back" -- it seems to me that given properly adjusted hip belt and shoulder straps, along with a good frame and/or the pack being well-packed, there should not be a lot of pressure of the pack against your back. Knowledge, not equipment -- the way to prevent something sticking you in the back is to pack the pack correctly, not add heat and moisture retaining padding that also weighs at least a little.

*)"Every good pack has load lifter straps.... You should quite definitely reject any framed pack which doesn't have these." -- judging by their popularity, they must do good for many people. Perhaps I have just never figured out how to best use them, but for me they mainly interfere with the pack straps fitting correctly and doing their job properly.

*)"This goes across the chest to stop the shoulder straps from sliding off your shoulders." -- I am not at all convinced that in the reason. In my experience a properly adjusted sternum strap is valuable to keep the shoulder straps from pulling backward on my shoulder joints. The sternum strap also transfers a small amount of the weight bearing from my shoulders to my chest.

The article does not like sternum straps; I find a good one indispensable. I feel the same way about sternum straps that the article feels about load lifters -- do not buy a pack (that will be used to carry much weight) without a sternum strap that fits you well and works well for you.

I do agree with the article that the sternum strap should not be very tight. If it is interfering with your breathing, try setting it a bit higher on your chest. Furthermore, I do not find it any more interference with my breathing than I find a hip belt interfering with the breathing motion due to restricting my stomach moving in and out with my diaphragm action -- neither one enough to worry about.

*) Haul loop -- seems important to Roger's habits; negligible value to mine. Probably just reflects my doing a lot of heavyweight backpacking before haul loops were common. I consider a haul loop a minor convenience, but something I rarely have much use for.

-- Bob

Edited by blean on 09/08/2010 22:02:36 MDT.

Mary D
(hikinggranny) - MLife

Locale: Gateway to Columbia River Gorge
Lightweight Internal Frame Packs: a State of the Market Report - Part 1B on 09/08/2010 22:12:58 MDT Print View

After reading a bunch of BPL pronouncements that load lifters are unnecessary, it's great to see your giving them their rightful place!

I have very sensitive shoulders and can't get along without the load lifters. That's why I rejected Gossamer Gear packs. Interestingly, my grandchildren have the same problem, especially my 10-year=old grandson. Maybe it's hereditary! I have found my load lifters to be a vital part of what makes my pack (SMD Comet, discontinued little brother of their Starlight and Traveler) so comfortable for me.

There's lots of good info in this article and I will read it again more carefully!

Dave U
(FamilyGuy) - F

Locale: Rockies
Packs on 09/08/2010 22:30:41 MDT Print View

If a pack fits perfectly to your body,, one does not need load lifters except under very heavy loads (at least for this forum- i.e. 40 plus pounds). At lower weights, the shoulder harness itself can be used to 'lift the load,' assuming the torso and shape of the back panel perfectly confroms to the users back. Load lifters are used on 'off the shelf' packs to adjust for differences in personal fit. Which is fine and obviously needed in most cases.

Edited by FamilyGuy on 07/08/2013 23:38:19 MDT.

Dan Healy
(electricpanda)

Locale: Queensland
new harness ideas on 09/08/2010 22:40:33 MDT Print View

Aarns packs are very interesting and it is great to see new ideas – got to try one a few months back… I really liked the way the shoulder straps moved with you as you climbed up. (though to be honest I found the front carry system only good for easy tracks as you can’t see your feet and where to place them – forget scrambling… also the flat backpanel makes for a very hot sweaty back)

Anyway… as Aarn pointed out, centre of gravity is crucial and a good hipbelt arrangement (I really like the Wilderness Equipment harness atm - another new idea in heavy pack carrying) is able to very effectively spread the load to the hips (which are central). I am able to walk all day, for many days absolutely upright with 25kg. I appreciate this type of belt/harness is on very heavy packs which aren’t in this reviews scope and also the lighter hip/harness arrangements in this review are not meant for 25kg loads. (I know you CAN carry them – but it is not the most comfortable way of carrying a load of this weight)

Ike Mouser
(isaac.mouser) - F
aarn on 09/09/2010 05:23:52 MDT Print View

aarn should have been in this review, they are doing more than jsut adding new buckles. They are the leaders in pack innovation without a doubt. Check out the featherlite freedom or mountain magic.

=P

Edited by isaac.mouser on 09/09/2010 08:07:45 MDT.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
torso length on 09/09/2010 09:11:46 MDT Print View

Good article Roger

Reading this article and Ryan's, I'm confused about maintaining Torso length

Is Torso length the ability for the pack to maintain it's height when it's held up on the bottom by the waist belt?

In other words, if there's no waist belt, does the issue of Torso length disappear?

If you have your foam pad unrolled inside your pack, with everything else inside this, and you then compress it sideways, it forms one unit that doesn't collapse, so the frame seems unnecesary.

I agree, sternum strap doesn't make any sense to me, hinders breathing, but definitely a matter of personal preference.

I think a lot of these features are partially marketing hype. People will buy new gear, more expensive, if it has perceived value.

One reason for external frame pack is to have mesh panels against your back for better ventilation so you don't sweat so much, but if you put foam panels for comfort, then you may as well not have a frame.

Dave U
(FamilyGuy) - F

Locale: Rockies
Lightweight Internal Framed packs on 09/09/2010 10:12:01 MDT Print View

Some good points Jerry - have a look at this analysis done by Ryan Jordan a few years back. There is a distinct torso collapse even with a rolled pad. A rolled or folded pad will never equal a stiff frame with respect to load transfer and stability over about 15lbs.

http://www.backpackinglight.com/cgi-bin/backpackinglight/00194.html

scott Nelson
(nlsscott) - MLife

Locale: So. Calif.
Frame Height? on 09/09/2010 19:00:34 MDT Print View

Is it important or not to have the frame extend above the attachment point of the shoulder straps? Does this shift the Center of Gravity higher and/or closer to the spine? Does it help prevent collapse of the torso length? If load lifters are important, do they need to have a frame extending up to support them?

Philip Werner
(earlylite) - F - MLife

Locale: New England
Measuring Pack Volume on 09/09/2010 19:49:18 MDT Print View

Roger and Sue,

I found your technique for measuring pack volume across pack manufacturers and the effect of pack width on the ease of packing to be quite informative. Thanks for this careful and well-reasoned analysis. I'm looking forward to your subsequent posts on this tricky topic.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: torso length on 09/09/2010 20:17:23 MDT Print View

Hi Jerry

No, 'torso length' is an actual measurement of length. You have a torso length, and how to measure that is described in the article. Manufacturers make packs with different torso lengths, although whether their claim matches your body is not always clear. Fortunately, many of them do specify what 'medium' means in terms of a (human) torso length.

Yes, some features are marketing hype for sure. Bugs me too. But some other features are essential imho, and this is discussed in the articles.

> One reason for external frame pack is to have mesh panels against your back
> for better ventilation so you don't sweat so much
Well, that's ONE reason. Load-carrying ability is another.

> but if you put foam panels for comfort, then you may as well not have a frame.
Can not agree with you there.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Frame Height? on 09/09/2010 20:22:48 MDT Print View

Hi Scott

> Is it important for the frame extend above the attachment point of the shoulder straps?
Hum - opinions may differ, but in general I think it is usually a good thing. That said, there are a number of quite functional packs where this does not happen. So it may not be 'essential'.

> Does this shift the Center of Gravity higher and/or closer to the spine?
Not by itself, really. I think the CoG is affected more by pack shape, or cross-section.

> Does it help prevent collapse of the torso length?
Not really. I think the important bit in a pack is the stiffness between the hip belt and the shoulder straps.

> If load lifters are important, do they need to have a frame extending up to support them?
They do not HAVE to have a frame supporting them, although it is often easier if there is a frame.

Cheers

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Split Hip Belts... on 09/10/2010 13:14:56 MDT Print View

I have 2 internal frame packs with varying hipbelt comfort. One, an original Dana Designs Terraplane, fits wonderfully (only B/C it's the 3rd belt from Dana that I tried!).

The other is the 2nd generation REI Cruise UL 60 with a much thinner and skinnier (& less comfortable) hipbelt. I REALLY like the split hipbelts of Lightwave's packs and am thinking of cutting my REI belt to try to effect that more contour forming fit. I do have a great shoe/luggage repair shop that patiently does mods on other packs for me. If a mere long split doesn't get the job done I can try removing belt material as well to open up the split.

REI can always send me a replacement belt if I screw it up irretriveably but I think it's worth a try since I love every other aspect of this pack, especially its Velcro-adjustable harness for torso length adjustment.

I feel split hipbelts may become much more popular as they may conform to many different hip shapes better than a solid belt ever could.

Edited by Danepacker on 09/10/2010 13:27:23 MDT.

Travis Leanna
(T.L.) - MLife

Locale: Wisconsin
Comfort on 09/10/2010 14:22:52 MDT Print View

I'm looking forward to the Comfort section of the article.

I remember when I first started trying on packs (incorrectly, I might add) I had no idea what was considered "comfortable" with 10, 20, 30, or 40 lbs on my back.

Sure, some packs felt better than others, but what was it SUPPOSED to feel like? Even today, I often wonder how what I consider to be comfortable compares to what everyone else considers comfortable.

I've got 3 packs. SMD Swift, Osprey Exos and Osprey Talon. Yes, they're all "comfortable" to me and I can spend all day in them with a loaded pack, but there are so many other packs out there, that how do I know I'm nowhere near as comfortable as I could be with a different pack!? I need to try ULA, MLD, Gregory, REI, Cilo, Granite Gear, and the list goes on. But time and $$ prevent that from happening.

I'm rambling now.