The Effectiveness of Stays
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Angela Zukowski
(AngelaZ) - F

Locale: New England
stays and load lifter straps on 03/31/2009 07:44:24 MDT Print View

Call me crazy, but wouldn't it be fairly easy to attach load lifter straps to the GG gorilla with some simple sewing?

(I was thinking about doing this myself, actually. Haven't bought the pack yet though.)

Huzefa Siamwala
(huzefa) - M
Re: stays and load lifter straps on 03/31/2009 08:07:01 MDT Print View

Angela, (I think) load lifter work effectively only when they are attached to the top of the stays. When the stays end in shoulder staps load lifter arent effective or needed. They are used by manufacturers mainly for adjusting torso length.

You need to find out if shoulder straps in gorilla are attached to the top of the stays or not.

Huzefa Siamwala
(huzefa) - M
Re: Re: The Effectiveness of Stays on 03/31/2009 08:12:32 MDT Print View

>I'm wondering now if stays are more important in helping to keep a pack shaped to the curved human back than in transferring the load to the hips, since a packed pack tends to pull straight, even if the pack's sewing pattern, like that of the Jam2, contributes to a more ergonomic fit...


I think you also need to read this:
http://www.aarnpacks.com/features/multifunction.html#fs


NATURAL SHAPING

Ergonomics Applied

Making all body contact parts a mirror image of your size and shape.
FORM FITTING FRAMES

Why have a frame?

The frame holds the blueprint of your back shape. Our frames are easy to remove and custom bend to match your shape, creating the blueprint. The frame’s job is to maintain this shape when the pack is loaded and to bring the load as close to your back as possible.



Why other packs are a backache waiting to happen

Frameless packs, and the most common internal frame system, twin vertical stays, give the worst possible shape for back comfort. When these packs are stuffed tightly, the backpanel rounds out to a convex shape horizontally (A)—the opposite shape to your back. The side profile is increased so that the load is positioned further from your back, and the load is concentrated down the spine. The the pull back pressure on the shoulders is increased resulting in a greater forward lean and increased back strain! The addition of a plastic framesheet is an improvement as it keeps the backpanel flat horizontally (B), bringing the load closer to the back.

Why our packs are backsavers

We take pack design further with the concave backpanel (C)—a custom mouldable shape- that brings the load closest to your back. The vertical divider further narrows the profile (D). The result is the most upright posture and the least back strain. Even with Balance Pockets, it remains important to keep the load close to your back, because the smaller volume in the front Balance Pockets cannot fully counterbalance a pack that hangs far from your back.




If you look at Roger's external frame (in DIY pack article) it is designed to transfer load to the back by having two important features 1>high center of gravity 2> rgid concave frame.

On the other hand Aarn packs transfer load to the back AND hipbelt.

Edited by huzefa on 03/31/2009 08:19:36 MDT.

Angela Zukowski
(AngelaZ) - F

Locale: New England
Re: Re: stays and load lifter straps on 03/31/2009 08:26:42 MDT Print View

I have a pack right now with no stays (just a framesheet) and load lifters - I like it because tweaking the load lifters brings the pack further away or closer to my back - the weight is carried by the hipbelt but playing with the loadlifters gives me options in terms of shifting the weight a bit as the day goes on, which is nice.

Granted, this pack does not carry more than 20 lbs and usually much much less.

Brad Groves
(4quietwoods) - MLife

Locale: Michigan
frame stays on 03/31/2009 10:31:57 MDT Print View

The point of a frame is to transfer weight to your hips. It does that in a variety of ways... Keeping the pack shape is key. A pack that sags away from your back will alter your center of gravity and change the direction of "pull" of the weight. Load lifters are almost completely ineffective unless linked to a frame of some sort (without a frame the "load lifter" straps are really more load cinchers, and just help prevent some pack sag). Some of the most effective frames we've seen linked stays directly to the hipbelt for great weight transfer. With really light loads it's not as important, but...

I just got a Golite Pinnacle and find it comfortable up to 25-30 pounds. Beyond that (and around there) the weight is sort of generally distributed to my shoulders and back, and a little on my hips. For trips up to about a week it's fine. My current base weight is 12-15 pounds; add 12 days of food at 2 pounds per day and I'll have 24 pounds of food. Call it 25 pounds, plus 15 pounds base, and at the start of a typical trip I'll have roughly 40 pounds. For longer trips I need a framed pack. Frame stays would keep the load close to my back and direct/keep the load in-line. Functional load lifters would get the weight more on my hips and off my shoulders. Good frames basically take the weight off your muscular system and put the weight instead on your skeletal system.

Jim MacDiarmid
(jrmacd) - MLife
Re: stays and load lifter straps on 03/31/2009 10:51:21 MDT Print View

Angela,

I have a GG Gorilla right now. I've been testing it for about a week at home. I'll look at it and see if the shoulder straps are attached to the top of the stay frame. Sewing in some load lifters might appeal to me as well if it is possible.

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: Re: The Effectiveness of Stays on 03/31/2009 13:03:25 MDT Print View

"I'm wondering now if stays are more important in helping to keep a pack shaped to the curved human back than in transferring the load to the hips,"

No science here, but the rigid LuxuryLite frame is not shaped to the back, yet many people such as myself find it a much more comfortable way to carry a load. the combo of instantly adjustable back length and super-wide hipbelt linked to a rigid frame allows all of the weight to ride on hips, with no strain on shoulders (an no need for load lifters). maybe not a custom back fit, but the gap between your back and the pack alows superior ventilation that would be lost with curved stays.

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: The Effectiveness of Stays on 03/31/2009 14:00:16 MDT Print View

Transferring weight from shoulders to hip is the primary and thus most important function of your pack frame -- including the stays. As for bending the stays to conform better to your back -- that's more icing on the cake.

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: Re: The Effectiveness of Stays on 03/31/2009 14:03:58 MDT Print View

"Transferring weight from shoulders to hip is the primary and thus most important function of your pack frame "

How about those hard-core old-timers who had rigid framed packs but no hipbelt! Eeeeywww. Them was the good old days!

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: The Effectiveness of Stays on 03/31/2009 14:07:58 MDT Print View

Lynn,

I resemble that remark :)

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: The Effectiveness of Stays on 03/31/2009 14:14:06 MDT Print View

Way before my time... :)

Angela Zukowski
(AngelaZ) - F

Locale: New England
Re: Re: stays and load lifter straps on 03/31/2009 14:37:08 MDT Print View

"I have a GG Gorilla right now. I've been testing it for about a week at home. I'll look at it and see if the shoulder straps are attached to the top of the stay frame. Sewing in some load lifters might appeal to me as well if it is possible."

definitely let me know James! I won't be buying mine until the narrower straps are available, anyway..

dan mchale
(wildlife) - MLife

Locale: Cascadia
predictable on 03/31/2009 19:28:31 MDT Print View

At the invitation of Huzefa: As well as doing everything mentioned in the posts above, a frame system gives the pack load consistency and predictability - it will generally be the same fit and will not need adjustment when you take a jacket out for instance. Even a half empty pack with stays will work just fine without ANY special packing - especially if it is some kind of half empty ( or is that half full? ) load that is still weighty. The rule applies to using pads as stays or framesheets as stays etc. in general. The stays or framesheet in a 'well designed' pack, and a well fitted pack, and a pack that is understood by its owner, will do so many effective things that the most un-cost-effective thing a person can do is consider removing them to save weight.

Edited by wildlife on 03/31/2009 23:18:23 MDT.

Huzefa Siamwala
(huzefa) - M
The Effectiveness of Stays/frame on 03/31/2009 20:46:27 MDT Print View

Dan, thanks for taking time and sharing your insight to the discussion.

Lynn, Ben, Nick, anyone else interested in discussion SHOULD read these two links:
http://www.bushwalking.org.au/FAQ/FAQ_PackTheory.htm
http://www.aarnpacks.com/features/multifunction.html#fs

further discussion is meaningless if you dont have basic objective knowledge of pack theory.

Miguel Arboleda
(butuki) - MLife

Locale: Kanto Plain, Japan
Re: The Effectiveness of Stays on 03/31/2009 21:21:47 MDT Print View

Huzefa, thanks for the further information. As with your earlier link, I read and thought about the Aarn pack link a long time ago, when Aarn first started his business online in NZ, and he still only had three packs to offer. I'm not new to any of this information, including reading Dan McHale's site about five years ago when I considered get a McHale pack. I used to be very much into designing and making my own gear, and I read everything I could get my hands on online and off.

Dan's evaluation of the stays and frame makes perhaps the most sense of anything I've read until now. I still don't see how stays and frames make any measurable difference in terms of keeping a fully-loaded pack from collapsing vertically, since the pack itself would be a stiff, vertically stable object. The pack itself should therefore act as a load transfer unit between the shoulders and the hip belt. Perhaps the more important element would be a stiff and capable hip belt?

The trend I see in the elements of this discussion is that it is horizontal load transfer that is more important in keeping the contents of the pack both close to the body and safe from sagging, namely the compression straps and the cut of the pack's pattern. By pulling the weight and contents in and stabilizing them the pack doesn't pull away from the body and the load gets nicely transferred between the shoulders and the hips.

But, as Dan pointed out, a frameless pack that is not full will of course not carry well and sag. The pack cannot then transfer the load between the shoulders and hips, and here is where stays or a frame seem to make a difference. This and the conforming shape that the frame makes. Aarn's diagrams shows the differences between how a fully loaded frameless pack fills out and one with the limiting form of a frame... the limitation is what keeps the pack against one's body.

Dave U
(FamilyGuy) - F

Locale: Rockies
Stays on 03/31/2009 21:50:27 MDT Print View

"I still don't see how stays and frames make any measurable difference in terms of keeping a fully-loaded pack from collapsing vertically, since the pack itself would be a stiff, vertically stable object. The pack itself should therefore act as a load transfer unit between the shoulders and the hip belt."

Really? Frame collapse refers to the effective torso length changing due to reduced vertical rigidity in the frame, virtual or otherwise. It can depend on fabric and horizontal compression to some degree, but a stiff frame or stays may an enormous difference.

Measure the torso length of a frameless pack with 20 pounds in it and then add in 5 pound increments for experimentation. Post your results.

Denis Hazlewood
(redleader) - MLife

Locale: Luxury-Light Luke on the Llano Azul
Re: Stays on 03/31/2009 22:01:44 MDT Print View

If your pack has load lifters you probably can't pack it hard enough to resist collapse when you tension the load lifters, without stays of some sort. I had a Golite Trek and had to make a CF back panel to get the pack to keep its torso length. No matter how hard I packed it, and tugged the compression straps, the top would collapse when I set the load lifters. The Trek is a very robust pack and lighter packs might not stand having the compression straps "romped" on, as I did with the Trek.

That's how it makes a difference.

dan mchale
(wildlife) - MLife

Locale: Cascadia
weight of stays on 03/31/2009 22:49:33 MDT Print View

Miguel: I think you are making too much of the weight of stays. When they are matched to the load they carry rather than being made for a variety of loads, they are more effective than anything else you can do. One way to understand why a pack can never be packed tightly enough to not collapse is to look at a steel cable that you might tighten to walk across. It is almost impossible if not impossible ( I'm not sure these days ) to have a cable strong enough and tight enough that when you walk on it it will not depress. In the same way it is very difficult to stuffa pack tight enough that is can become a structure that can have nuances of adjustment when quarter inches count. And to the degree that a pack is stuffed like a rock, it becomes more and more uncomfortable. In a framed pack the function of load transfer and distribution is separated from the pure bag function and both become more effective. The frame clings to your body and the much more loosely packed bag is easier to dig around in, and whatever you do there does not effect the frame function much. Trying to make the load into a frame reminds me of a raven I saw once that thought it could carry 2 bagels. It would try but could not. I actually watched it put one bagel down to pick up the other and it kept doing it!

I think all of this anti-stay business and anti-structure stuff is similar to the anti-mechanical romanticism discussed in Zen and the Art of Motorcycle Maintenance. The more complex a sytem is, especially a system that works, the more effort it takes to understand it, but that takes much less effort than trying to understand something that does not work at all. With the whole soft pack thing there is much running around in circles people do. It would be much like someone taking the wheels off of their car and thinking they have accomplished something new and sexy. The soft pack craze will finally go away like it did in the 70s - except for people that call running from food cache to food cache backpacking.

Edited by wildlife on 03/31/2009 23:15:44 MDT.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: The Effectiveness of Stays/frame on 04/01/2009 02:21:24 MDT Print View

H -

Thanks for the links. I had read both of them a while back, but it is always good to refresh one's brain.

Nice quote from Roger too :)
"There is a group of fanatics in America who strive to get their base pack weight (not counting food, water or worn clothing) down to 5 lb (2.272 kg) from 6 lb (2.726 kg)."

There is a certain weight for most people where a frame is a non-issue, perhaps a total weight of 15lbs for me. However, when going above 20lbs, a frame is necessary. Here is the crux of the matter, IMO. Many would say to lighten up and make your trips convenient to re-supply points. And Dan does point that out.

Now I am not ready to give up my frameless packs, as they have their utility and I am now using them often for 'short' trips. On the other hand, I am not ready to give up my big heavy ones either; an old Kelty Serac with a full-length bag or my Gregory Whitney 95. They are mass-merchandise equipment and work well. I am sure that a McHale would work even better.

Generally I hike off trail or on old low-use trails, and sometimes need to carry a lot of food and water; especially in the desert. Other than these two packs, my gear has really been lightweight for many years. However, over the past year I have really parred down some items. But no matter what your style, if you need food for a couple weeks or more, you cannot get away from a stout pack and be anywhere near comfortable. I usually avoid people and have only hiked with a partner less than probably a dozen times in more than 40 years of wandering around Mother Earth. I live at the base of Mt San Jacinto, and have pretty much avoided the state wilderness for years, other than ocassional Cactus to Clouds trip during the week when it is empty. Which means that where I am interested in going, there are not going to be convenient re-supply points.

Thru hiking does not interest me. Sometimes I like to stop for a few days and explore from a base camp. Like Dan, during the 60's and early 70's, I spent a lot of time in the southern Sierras. A favorite trip was to hike from Kernville to Horshoe Meadows and back. My only re-supply was a hike into Lone Pine. And these trips usually included some fishing everyday and exploring. So a big pack with plenty of food was a requirement for me.

I am mechanically inclined and have spent many years in the automotive industry, so it is easy for me to explain complex automotive systems to others. Dan did a great job explaining the mechanics of frames in layman terms. To be honest, I have not been that interested in exploring the details of how and why a frame works... because I know from experience that with heavier loads, a good frame and hip belt take the sting out of weight. And he explained it in a few well thougt out sentences.

So the bottom line is that I will be mostly hiking with lightweigt packs without frames or simple stays... but sometimes I will be pulling out the old standbys for trips I want to take and enjoy.

I hope this doesn't start a debate of lightweight philosphy versus "Old school." I get the ultralight school of thought, and for the most part it is how I now hike. But sometimes other options work better. Try carrying 4 or 5 gallons of water, and you will wish you had an external frame... and you aren't going to cut down the required water in the desert significantly by using an ultralight pack and hiking faster. Plus I don't want to hike fast through a desert, I want to look at it and explore any side canyon that might strike my fancy.

Good thread, lets keep it on track.

Dan McHale, thank you for the insight.

Dave U
(FamilyGuy) - F

Locale: Rockies
The Effectiveness of Stays on 04/01/2009 08:02:55 MDT Print View

Excellent post Dan - thanks for that!