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Maia
(maia) - MLife

Locale: Rocky Mountains
How Packs Work on 12/04/2012 13:05:33 MST Print View

Companion forum thread to:

How Packs Work

Travis Leanna
(T.L.) - MLife

Locale: Wisconsin
Nice work on 12/04/2012 13:18:55 MST Print View

Good write-up, David! This would be a good read for people, especially beginners, to get them thinking about how a pack really works, besides simply holding stuff.

I agree that getting a pack to properly accommodate your torso length is fantastically important, which is why I really like my Osprey Talon 44. As you know, it has the adjustable torso length and lets me perfectly fit it to my own body.

My dad proclaims he wants to do a week-long trip somewhere akin to Glacier. I may show him this article.



P.S. This article, along with a few others, should also be stapled to every employee's green vest at REI.

Edited by T.L. on 12/04/2012 13:20:22 MST.

Dan Durston
(dandydan) - M

Locale: Cascadia
Jam on 12/04/2012 18:18:29 MST Print View

"the Jam 50 went from 99 dollars at the start of the year to 129 as of this writing."

Stochastic indeed. It's at 132 now.

Edited by dandydan on 12/04/2012 18:22:32 MST.

Paul McLaughlin
(paul) - MLife
Re: How Packs Work on 12/04/2012 20:03:35 MST Print View

Dave, nice article. However, I Think your statements about load lifters not being needed if the pack is sized properly require some caveats. Let us travel back in time to the days of the external frame's dominance for a minute. Your typical 1970's external frame pack had no load lifters. But typical fitting protocol was to have the pack fit so that the crossbar to which the shoulder straps attached was slightly above the top of the shoulders. This allowed the shoulder strap to run upward off the top of the shoulder, so that the line of tension would be pretty close to (although a little lower angle than) what you get with a lifter strap if you tighten the lifter and loosen the shoulder strap. This angle is critical. To be able to achieve this with an internal frame pack requires a very direct connection between the tops of the shoulder straps and the stays, and stout stays. It could possibly be done with a particularly rigid framesheet, but again it would require a very direct connection of the shoulder straps to the framesheet. And even then it would still be at a lower angle coming off the top of the shoulder than a lifter (if the pack is properly sized and adjusted) will achieve, tending to put more wight on the shoulders, and also it lacks the secondary function of the lifters, that of pulling he top of the pack forward.

The other point - and I think you state this, but it ought to be emphasized even more - is that lifters can only do what they are intended to do if they are connected directly to the frame. On the packs I make, they attach directly to the top of the stays.

I don't know if you have ever had your hands on one of Dan McHale's packs that have his Bypass Suspension system. If not, I suggest to do, or at least study up on it on his website. Dan understands suspension design better than any other manufacturer, in my opinion - an opinion based on over 35 years of making my own packs and several years of selling packs on the retail level. His understanding of how lifters should work and how poorly most people utilize them led him to design the bypass system. I fully agree with Dan on the idea that most people do not really understand how to get the most out of their packs, fit-wise. I often cringe when I see folks on the trail with packs that do not fit or are far out of adjustment. It happens all the time. I am tempted to stop them and beg them to let me help them get it adjusted better. They could be so much more comfortable. Maybe that's an article we need - one on fitting and adjusting a pack for the best comfort.

Edited by paul on 12/04/2012 20:05:10 MST.

Dave U
(FamilyGuy) - F

Locale: Rockies
Re: Re: How Packs Work on 12/04/2012 20:26:15 MST Print View

If the frame is stiff enough and slightly taller than the shoulders, then load lifters aren't needed until you get to about the 40 pound mark. Mchale packs are designed this way depending on whether you have the pack in "day pack" mode and lengthened or shortened and set up with the P&G stays (which are amazing, by the way).

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: How Packs Work on 12/04/2012 20:45:03 MST Print View

Very interesting, and thanks for the article David.

Hum ... Clearly I must be a renegade, as my thoughts are very different. Or maybe this article merely confirms many of my thoughts.

The Jam keeps changing? Maybe it STILL hasn't found a good design? Or is it that GoLite are now chasing the fashion market?

> buckling of the backpanel (and thus torso collapse) more likely. The stiffer the
> frame the less likely this is to occur, but it is a universal phenomenon
> nonetheless, save with external-frame packs.
Yes, indeed. The Amercian preoccupation with frameless packs, with all their attendant torso-collapse problems, has not really reached either Europe of Australia. The result is that European packs are, imho, generally far more reliable on long trips. Australian packs seem to be reliable too, although they have not yet got their materials beyond steel&canvas.

My MYOG external frame pack weighs 40 oz. I can carry as little as a few lbs in it, or as much as 45 lbs, in comfort. But note that it has a real frame, and suffers ZERO torso collapse. It does not have to rely on load transfer to the hips either, which is fortunate as I don't have much in the way of hips to support it. Which is entirely consistent with David's comment that 'For example, once the back panel of the Jam was reinforced with an aluminum stay, the mode of failure quickly switched to hipbelt creep.'

OK, OK, I am a curmudgeonly old renegade. But I have to carry a pack so often, and I just don't find the fad of frameless packs to be convincing.... In fact, far too many of them are just ... wierd. I think it is time American manufacturers woke up to reality. (I see Kelty still has.)

Cheers

Luke Schmidt
(Cameron) - MLife

Locale: The WOODS
Re Re How Packs Work on 12/04/2012 21:17:01 MST Print View

David - Great article I'd love to geek out over it but I gotta run, hopefully the thread will still be active when I get back.

Roger - You aren't the only renegade. I like a light (about 32 oz) internal frame pack for longer trips and/or trips where I need to carry more gear.
I do like my little frameless MYOG pack but I only use it when I have a truly light load (usually less then 15 pounds total). At those weights I don't really notice much difference between a frameless pack and a framed pack. Now when I go on longer trips I grab my internal frame pack.

a b
(Ice-axe)
Re: Re: How Packs Work on 12/04/2012 21:22:02 MST Print View

Yea, I used a GoLite Pinnacle for 2,650 miles. Had folding back panel and hipbelt creep.
Switched to an MLD Exodus and used a Ridgerest 3/4 length foam pad inside as my sleep pad and frame sheet.. problem solved for over 5,600 miles now.

In my opinion the design of the shoulder straps has everything to do with the success and comfort of a frameless pack.

Hipbelt only acts to secure the load and transmits nearly no weight.
the hipbelt of the GoLite is way too big and the angle of the shoulder straps and the spacing behind the neck is wrong.

Load lifters are useless and unneccesary if the shoulder straps fit right.

Although, even with proper design these things have their limits carrying anything more than 30 lbs with a frameless pack is asking for pain.
Some manufacturers are upfront about this, others.. not so much.

I agree they are a fad these days... But lets not throw out the baby with the bath water here.
There have been huge strides made in the design of some of these packs and though they may all lack a frame, they are lightyears apart in the way they perform.
I also agree that they have their place and when loaded properly and with lighter loads they can be quite comfortable.
My advice; ditch the Golite junk and try a quality made Mountain Laurel Designs product.
From personal experience, the difference is night and day.

(I was not paid to say this, never asked for or recieved any compensation from MLD to write this or any other testimonial. I actually believe in their designs based on my own experience. Your Mileage May Vary.)

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
re: frameless packs on 12/04/2012 22:10:10 MST Print View

Paul, I have examined but not extensively used a McHale. The first harness on my B&W pack had a bypass-esque lifter system, and while the execution wasn't ideal (seemed like I'd need at least 5-6 inches between the shoulder strap attachment point and that of the lifters) it was enough to slake my curiosity. It is a very clever design. For that pack and the weight it will carry, I don't think I need lifters. If I build or buy a real load monster in the future I'll include lifters.

While having shoulder straps which attach substantially above torso length is indeed required to both not have load lifters and guarantee no weight on the shoulders no matter the load, I don't think most will find this desirable. Indeed with a frameless or lightly framed pack the lack of dynamic mobility such a design creates negates the primary virtue of such packs.

Roger, whether one buys into the benefits of frameless packs is a matter of ideology, not data. They have limits, which are easily understood, and that they fail when pushed beyond those is not an especially poignant critique. What I take issue with is persistent design shortcomings which make many frameless packs work not nearly as well as they ought to. Fairly minor redesigns could give us a Thruway that could for many carry 35 pounds day after day and retain all the benefits of the current iteration.

a b
(Ice-axe)
Re: re: frameless packs on 12/04/2012 22:50:13 MST Print View

"While having shoulder straps which attach substantially above torso length is indeed required to both not have load lifters and guarantee no weight on the shoulders no matter the load, I don't think most will find this desirable. Indeed with a frameless or lightly framed pack the lack of dynamic mobility such a design creates negates the primary virtue of such packs. "

David, I think i disagree.
The success of my frameless pack use and from what i have heard from friends that use them is that ALL the weight IS tranferred to the shoulders in a comfortable way.
NONE of the weight is transfered to the hips, nor needs to be.

My Exodus and Prophet have no load lifters.
Yet the shoulder straps are not attached above torso length.
The design is such that the top of the shoulder strap goes horizontally over my shouler without the pack sagging.

Here is a picture i took some time ago related to just this issue.
.This is a picture of a MLD Prophet, notice no load lifters needed
.
Load lifters are not needed with proper strap design.
Hipbelt is only there to keep the pack stable and transmits zero weight.
The sleep pad stuffed inside along with gear makes the pack ridgid and comfortable.
Light loads of 30 lbs or less make this perfectly comfortable for all day use.

Trying to put the weight on the hipbelt is unneccesary with this load range, pack loading strategy, and shoulder strap design.

(edited to correct some of my ridiculous spelling errors)

Edited by Ice-axe on 12/04/2012 22:52:33 MST.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: re: frameless packs on 12/04/2012 23:19:48 MST Print View

Nice article Dave

I don't think the point is whether any individual agrees with you, because each of us has different conditions.

You and other people say frameless packs are no good because they collapse with more than 20 pounds or so. I never do more than 20 pounds, maybe 22 or 23 occasionally, so no need for a frame. Adding a frame would add weight for no benefit. But then I haven't tested that, but my shoulders are never sore. In the bad old days with a Kelty with 50 pounds and an external frame, my shoulders got sore even though I carried much of the load on my hips.

I have a hip belt on my frameless pack and can put most of the weight on my hips. It does more than just stabilize load. I think it works better to have the hip belt be one unit, cinch it up good. The pack is sewn at multiple places to the waist belt, so there is no torso collapse between pack and waist belt.

I like your three modes of torso collapse - I understand better now.

I have to read you article again a couple times and people's comments...

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: re: frameless packs on 12/05/2012 00:14:29 MST Print View

Yeah, Jerry hit it. Packs are as different as loads are. People are different. Pack comfort for any one individual *will* be different.

Like Jerry, I rarely go out with more than 20 pounds. There is a huge difference between a half pound pack and a two and a half pound pack. The 2 extra pounds is *always* with you. Using a Murmur or Miniposa, the pad pockets on both accept up to 2.5" of fan folded CCF pad. That is a lot of frame for a pack rated at 15pounds. I use it. The Murmur goes along for a week or so with 20-25 pounds. It is definitly not uncomfortable sitting on the narrow belt. And, I have a bad back in my neck/shoulder area forcing me to keep things light on my shoulders.

The big difference between frameless packs and internally framed packs is nothing. It is all a matter of how much you carry and how you arange the gear you *do* carry...a matter of technique. Using a pad as a frame is a good example of dual use gear to accomplish the same purpose as a frame. With modern materials available for packs, there is simply no reason for any serious backpacker to need a framed pack for a week outing weighing more than 16oz. My old Miniposa weighs about 15oz *including* two stays...this is my *big* pack.

Frames are good for heavier loads, about 25-45 pounds. Hopefully, I will never return to my old Kelty, though. Even my old Tough Traveler had a light magnesium, internal frame that weighed about 4oz. It weighs just over 2 pounds (2#2.) It is about 35-40 years old and still goes out every morning, loaded with close to 50 pounds of weight. It has MUCH higher durability compared to the Murmur, but, you *always* carry the extra weight.

Load lifters I really missed on all the UL packs. The Jam is way to heavy to consider, but I am happy to see them returning.

Edited by jamesdmarco on 12/05/2012 05:39:02 MST.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: re: frameless packs on 12/05/2012 08:12:30 MST Print View

Another thing is if you have irregular loads, or different load on each hike, then maybe a frame is better

With frameless, I put the same gear at the same place in the pack every time, so I have an order that works - no hard things poking me in the back, good rigidity. The only thing that varies is how much food and how much a couple other items weigh.

I need to measure torso collapse

Brendan Swihart
(brendans) - F - MLife

Locale: Fruita CO
Re: Re: Re: re: frameless packs on 12/05/2012 08:47:28 MST Print View

" With modern materials available for packs, there is simply no reason for any serious backpacker to need a framed pack for a week outing weighing more than 16oz. "

Maybe a week outing on wide trails. I do a lot of off trail travel in canyon country, which means lots of rock, willow/tamarisk bashing, the occasional pack haul up or down a drop, and long stretches with no water. A 16 oz frameless doesn't cut it.

Ice-axe, just because the MLD fits you (which is the bottom line here) doesn't mean that everyone should "ditch the Golite junk". Golite clearly has done some things right, as evidenced in this as well as Will R's article linked above. Hell, Skurka carried a Pinnacle 5000 miles across Alaska. I've never used either pack, just sayin' that fit can be different for different folks.

Erik Basil
(EBasil) - M

Locale: Atzlan
Great Article on 12/05/2012 09:12:27 MST Print View

Dave, I think it's an excellent article and one that helps me be more informed as I try to help younger, smaller people with the creation of truly lightweight packs and fitment issues on trail. As a longtime user of an established "Torso Compression Proof" system originated by Dick Kelty, I appreciate the insights beyond what I can easily observe from alongside more modern packs.

Where do you fellas strap the 14" cast iron skillet on them frilly things, anyway? Ho ho.

Dave U
(FamilyGuy) - F

Locale: Rockies
Re: Re: Re: Re: re: frameless packs on 12/05/2012 09:14:23 MST Print View

Load lifters are unnecessary on a framless pack assuming you are using a pack that is close to the correct torso size and not grossly off. With a frameless pack, a load lifter attached to fabric lifts nothing. All it does is bring the pack closer to your back, which can be negated with proper sizing.

David - I was referring to a framed pack and not a frameless pack with respect to having the frame taller than the shoulders (with shoulder strap attachment higher than the crest of the wearers shoulders). My Bad. However, with a frame, it works so well as to be shocking when you first try it. In fact, you then realize that most packs sold and marketed as a specific size are much too short for most wearers. It becomes apparent to consider sizing up in almost all cases to minimize any shoulder fatigue, over long days with even light loads.

Regarding Skurka, he has been using the ULA Catalyst for many trips over the past twelve months, which has a frame. Also, for the majority of his trip across Alaska, he used a ULA Epic with a Pinnacle main bag - this pack also has a frame.

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
re: frameless packs on 12/05/2012 09:18:00 MST Print View

"You and other people say frameless packs are no good because they collapse with more than 20 pounds or so."

I said no such thing. While frameless packs is probably an overly general term here, I've demonstrated that a pack with only a foam framesheet can carry over 30 pounds.

Dave U
(FamilyGuy) - F

Locale: Rockies
Re: re: frameless packs on 12/05/2012 09:30:28 MST Print View

But that is still a general statement because that assumes the pack fits to begin with, has long enough shoulder straps for the user, takes into consideration hip structure, etc.

I could carry 50lbs in a school bag. It would suck.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: Re: Re: re: frameless packs on 12/05/2012 13:21:53 MST Print View

"Maybe a week outing on wide trails. I do a lot of off trail travel in canyon country, which means lots of rock, willow/tamarisk bashing, the occasional pack haul up or down a drop, and long stretches with no water. A 16 oz frameless doesn't cut it."

I disagree. I do some High Peak hiking in NY. Some of the woods I bushwack through are nearly impassible with scrub. There is one campsite in particular that requires dropping the pack and literally going sideways through the trees to get to it. 16oz of internally framed pack works fine. The internal frame is a dual purpose sleeping pad.

Lucas Boyer
(jhawkwx) - MLife

Locale: 38.97˚N, 95.26˚W
re: on 12/05/2012 13:28:05 MST Print View

It's really too bad we can't have the variety of packs available via cottage industry in stores to try out. I have never fitted packs but have fitted running shoes for people thousands of times and there is no replacement for testing side by side and comparing the deviation of every model. Unfortunately, retailers are sticking their necks out to carry that kind of inventory.

Some good points of discussion here. I have found a lot of happy miles in an old ULA Ohm w/ the crappy hipbelt. The hoop distributes weight decently and the weight of the pack is a scant 25 oz or so. Dave has commented on the shape of the contour in the back seam. I have a 2011 or so Pinnacle that I am trying to trick out for a heavy packraft load and if you turn it inside out and measure the width of the pack's side panel traveling upward after each measurement, you will find that Golite did put some contour into this pack. I may eventually disembowel the back panel and rebuild it w/ a lumbar support device like Dave mentions, but first I'm going to try mimicking HMG's dual stay system w/ a laminated foam pad and aluminum flat bar.