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Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: Re: Re: BFM Says on 08/02/2013 15:29:31 MDT Print View

"aren't the load lifters serving to minimize or negate the "back wrap of the shoulder strap" problem? Just curious."

It isn't the back wrap per se - more like what it indicates. If the shoulder straps wrap they are capable of loading weight on tops of your shoulders. If you use the load lifters they in effect modify both the effective torso length and the force on your shoulder - customized to your body. The load lifters pull some of the weight off your shoulders and apply it to the frame, and hence back on the belt.

If you have a framed pack with a length that is correct for you, and the straps go straight back as shown in Nick's McHale pack pics, then it is nearly physically impossible for the straps to push down on your shoulders - at most they push in on the font of your shoulders to hold the pack close to your back. In my view this is ideal. In this case load lifter are, strictly speaking, unnecessary. Anyway, the main thing is to get the weight off your shoulders and onto your hips as much as you feel you would like - or not at all if that is your bag (um, no pun intended). However you get there is ok, but the straight back rule is a good guideline.

An issue with compensating for wrap with the load lifters it that it only takes a little change of, or slight miss-adjustment of them to suddenly put the weight back on your shoulders. The more wrap, the easier for this to suddenly happen. One the suddenly become slack all that weigh is back on your shoulders. You might find yourself fiddling with them a lot during the day. None of that is as likely if you have the straight back config.


So, to repeat, if the straps go straight back then there can be no downward components of force on the tops of your shoulders - basic mechanics. To be nerdily precise, the force down on you shoulders (without load lifters) will be proportional to the sine of the angle of the straps with the horizontal. The force the load lifters can subtract from the tops of your shoulders is likewise proportion the sine of *their* angle with respect to horizontal as well. So if you have a wraparound with straight back load lifters, for instance, you are guaranteed not to be able to do anything about this loading.

It is more important for more weight, but speaking personally I've grown to appreciate the issue even for LW loads.

BTW I have never been saying it it an unbreakable rule, as some people have implied. Do whatever works! Just understand the mechanics first - that is always more reliable than reading anyone's (or any book's) opinion and not knowing why or even if the advice makes any sense.

Edited by millonas on 08/02/2013 15:57:32 MDT.

Clayton Mauritzen
(GlacierRambler) - F

Locale: NW Montana
Re: Re: Re: Re: BFM Says on 08/02/2013 16:55:07 MDT Print View

The real issue with load lifters is the way that they help balance the load--which depending upon pack design can vary from none-at-all (no matter what you do) to quite a lot. There are a lot of mechanics involved, much more so because of the way that they impact the overall harness system by applying tension to the pack frame.

With the Crown and the Ohm 2.0, I found that the floppy portion of the frame negated any major benefits for load lifters. The delrin hoop at the top of the Ohm's frame is fairly floppy, and since it was a little on the large side for all my gear, I couldn't use that to stabilize the frame. The framesheet on the Crown is just down right bendy, and it had the same effect up top as the Ohm. All that I found them useful for was adjusting pressure points from hiking all day. Not that this is a complaint, it was a welcome tool as I tend to shift my load around in small ways throughout the day. They just don't work like traditional load lifters (which still don't lift any load) that require a rigid frame.

Personally, I have found that with a well-fitted pack, I can achieve the same marginal benefits simply by slightly adjusting the length of the shoulder straps themselves. Perhaps with 35+ pounds of all-day hiking I might miss them, but I never need to carry that much these days. I certainly never had a problem with heavier winter loads.

The real trick with pack-fitting is understanding effective torso length, torso-length collapse with weight, and your own individual style in carrying and positioning the pack. This just takes time, practice, and attention to detail. Once you've done your homework, there is nothing that substitutes for attentive experience.

Edited by GlacierRambler on 08/02/2013 16:56:47 MDT.

Delmar O'Donnell
(Bolster)

Locale: Between Jacinto & Gorgonio
Hips and Shoulders on 08/03/2013 11:25:41 MDT Print View

> It isn't the back wrap per se - more like what it indicates...

Excellent, lucid explanation. Now I'm beginning to understand the emphasis on "Does it work for you?" because the amount an individual wants to carry on hips relative to shoulders is an individual variable. For example, my hiking partner for an upcoming trek just hates weight on his hips! He has been looking for a new pack that will throw most of the weight to his shoulders. I now understand that indicates he should by all means avoid an overly-large pack, and he might appreciate a bit more shoulder wrap than normal. Whereas the majority of hikers likely want the weight mostly on the hips (I know this is doctrine).

You also allude to one other function of load lifters (...there seem to be so many explanations and disagreements about what the lifters are for and what they do...perhaps their function varies radically with pack design and fit...) that meshes with something else I was reading here on BPL. That author mentioned that load lifters are often used as pack size adjustment features on otherwise non-adjustable packs. In other words, that LL allow a particular "non-adj" pack to be worn by a larger range of sizes. Add that duty to the others assigned to LLs: pulling the weight close; throwing more of the weight to the frame and thus to the hips; pulling the back of the shoulder strap off the shoulder; being mere marketing devices that make the pack look more technical, etc...

Very interesting topic, interesting in the theoretical realm, not just the applied. I do have an "application" footnote however. Completed my second practice hike with the pack, paying special attention to weight on hips and shoulders. At the end of the hike, when tired, I'm thinking: "I'd like to get this weight off my feet." I'm not thinking: "I'd like to get this weight off my shoulders" or "off my hips." I really can't tell, so far, that the pack is too heavy on any particular part of my body EXCEPT the balls of my feet; the pack seems to be an "all over weight." It also seems easily adjustable, where I'm able to mostly unweight the shoulders (loosen shoulder straps and snug the LLs) or mostly unweight the hips (tighten shoulder straps, loosen hip belt) with ease--yet seldom do I feel a "need" to shift the weight. I take this as a good sign. If anything, I think it is slightly easier to unweight the shoulders than to unweight the hips.

I also tried an experiment: I cut down my CCF sit pad to the dimension that would fit into the frame pocket and added it, along with the frame. It seemed the fit of the pack suffered somewhat, not conforming to the curves of my back as well. I noticed more air cooling the small of my back, possibly indicating a gap, or maybe indicating a windier day. Too rigid, I wonder. Needs more experimentation.

Edited by Bolster on 08/03/2013 11:30:09 MDT.

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: Hips and Shoulders on 08/03/2013 20:00:05 MDT Print View

" Completed my second practice hike with the pack, paying special attention to weight on hips and shoulders. At the end of the hike, when tired, I'm thinking: "I'd like to get this weight off my feet."

Solution - tie about 100 helium balloons to your pack frame.

Sean Passanisi
(passanis) - MLife
Pack Fit Redux on 08/07/2013 10:28:52 MDT Print View

Hello. I received my size large Ohm 2.0 (torso size of 21" – 24", compared to the medium of 18" – 21"). The hip belt is adjusted in the highest position, providing the shortest torso length on this pack.

I hastily packed the bag late last night for the photo. I see that my load lifters are overtightened. The pack isn't quite as full as the previous photos (I was a bit rushed).

Anyway, I would love feedback on fit. It seems like the curve of the straps down the back is similar to the previous photo, which makes sense since I use the max adjustment on the medium and the minimum adjustment on the large. My question is whether I should keep the large and return the medium and continue to refine the fit of the large.

Edit: Thanks Nick!



Ohm 2.0 pack fit

Edited by passanis on 08/07/2013 11:56:57 MDT.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Pack Fit Redux on 08/07/2013 11:30:12 MDT Print View

Open the picture in a photo editor. If it is oriented correctly in the editor, rotate it 180 degrees twice, then save it. Now upload it.

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
re on 08/07/2013 11:39:22 MDT Print View

Why are you adjusting the torso shorter?

Put it at average and take another picture, the shoulder straps should connect to the top of your shoulders.

But you have load lifters so it doesnt really matter at all.

Clayton Mauritzen
(GlacierRambler) - F

Locale: NW Montana
Re: Changing my mind on 08/22/2013 11:20:56 MDT Print View

After some more thinking and experimenting on my last couple of trips, I have changed my mind on the whole wrap question.

I think it's much better to have little to no shoulder strap wrap. After playing with my pack a bit, I've found that this really does carry better and keep my shoulders from being fatigued. A little wrap was never too bad for me, but none feels a lot better at the end of the day.

So---mea culpa. Nick's pictures are spot on for how I'm fitting my pack these days.

EDIT:

Sean, this may be too late for you, but does that help? I was out when you posted the second pic, so I missed it.

Edited by GlacierRambler on 08/22/2013 11:24:45 MDT.

Nathan Coleman
(RockChucker30) - M
Load Lifter Function on 08/22/2013 14:22:53 MDT Print View

There are a lot of things going on here and everyone is speaking the same language, but maybe different dialects.

I've studied pack design for a long time, and have been fortunate to own a lot of different high end packs before starting my own company, Paradox Packs.

Comfortable load carriage is a function of the hipbelt, frame rigidity, frame shape, and frame height. I don't think you can talk about one piece of the system without the others, because they are an interdependent system.

On the hipbelt I believe that to be comfortable at loads of 10-60 lbs many different designs work well, and lumbar pad designs work efficiently at these loads because they are designed to effectively give very good contact on the lumbar and the fronts of the two iliac crests.

However, at heavy weights the lumbar pad belt is a failed design in my experience because it deforms and slips, lowering the frame height relative to your torso, and in some cases slipping so much it interferes with free movement of the legs.

I believe that a properly executed full wrap belt is much superior at heavy loads, and equal at light loads.

Moving on to frame rigidity, the level of stiffness in the frame required to support the load increases with the weight and awkwardness of the load. So, you can get by with a frameless pack for light loads, but for anything over 15-30 lbs you need some support, and for heavy loads you need a very stiff and strong frame.

Frame height is more important than load lifters, as load lifter function is simply a product of frame height.

The photos Nick posted illustrate this perfectly. His packs have no load lifters, BUT the frame is slightly above his shoulder level, thus the shoulder straps are simply snugging the pack up to his back instead of supporting the load with his shoulders. This type of system is fine for medium loads.

My preference is to have a frame that is 2-4 inches taller than shoulder level for most uses, a frameless pack for daypack use, and a tall frame for heavy loads. I prefer to have load lifter straps.

Here is why:

- Shoulder straps serve three main purposes in my opinion:
1. Provide handles for shouldering the pack, and support the pack while you adjust the hipbelt and get it tight.
2. Snug the pack to your back while you're wearing it.
3. At heavy loads, I like to alternate carrying more weight with my shoulders, and carrying less weight with my shoulders.

A pack with a properly fitted shoulder harness with a frame above shoulder height and load lifters will accomplish those functions at all load ranges, IF you have proper frame rigidity for the load, frame height for the load, and a hipbelt that does not slip.

Edited by RockChucker30 on 08/22/2013 14:26:17 MDT.

Delmar O'Donnell
(Bolster)

Locale: Between Jacinto & Gorgonio
OP Checking In on 08/23/2013 21:12:23 MDT Print View

OP checking in. Just back from a 3-day at Pt. Reyes in California, 22 lb in the GG Crown shown in the photos of this thread.

The GG Crown functioned nearly flawlessly for me. I was not able to detect misfit. I could throw weight to hips or shoulders with a little adjustment here and there. Never got a hotspot or even soreness. The pack sort of melted away into unawareness...it didn't catch my attention much, and didn't require many adjustments.

My hiking partner had a similar sized Osprey pack that weighed twice as much (4 lbs) as my GG Crown. We tried each others' packs. THe Osprey held the pack off the back quite aways, and allowed very good circulation at the cost of pulling backwards. It also let you know you were working against the pack frame. Whereas the GG Crown was more like wearing a piece of clothing. It moved with you, and was also hotter due to less circulation. The Osprey had wider, more comfortable shoulder straps, but I can't say the GG Crown straps caused any discomfort, they just weren't quite as comfortable as the wider Osprey's.

Regards the load lifters, I didn't like to walk without them snugged in. The pack just felt better, tighter, more responsive with the LLs snugged up.

So, fit-wise, I've no complaints so far. Let's see what a week's trip and heavier pack will do.

Fit aside, the pack acquitted itself very well. Just no complaints. Not even any nitpicks yet, and I'm a nitpicker.

Well, OK, one: It got tiresome unrolling and re-rolling the top sleeve every time I needed into the pack. Cost of a light pack I suppose.

Edited by Bolster on 08/23/2013 21:18:43 MDT.