Jan 12, 2014 at 10:36 am #1312034
I re-read Will's article http://www.backpackinglight.com/cgi-bin/backpackinglight/frameless_backpacks_sotm_part2b_2011.html – good article
I tried to measure torso collapse on my pack – tricky measurement – and I am not unbiased
To simplify the problem, what you want is the shoulder straps to attach to pack at top perpindicular so no weight is carried vertically on shoulders:
And what you don't want is for them to attach at an angle, because then some weight will be carried vertically on shoulders:
Torso length is measured from some point on hips to the point where shoulder straps attach at the top. My simple measurement is to measure from the top of the waist belt. I think this is 1.5 inches above where you're supposed to, so I'll just add that.
My pack with 10 pounds. This is as little weight as I can do to measure unloaded case. I need some weight to expand the burrito. I measure 17.75 inch so torso length is 19.25 inches:
The masking tape/felt pen is at 17.5 inches.
19 pounds – this is my typical max weight. I measure 17.5 inches – torso length is 19 inches. Torso collapse is 19 / 19.25 = 98.75%. I've carried this comfortably for many miles on many trips:
26 pounds – this allows me to add a days worth of water for rare cases there's no water where I want to go. 17.25 inches – 18.75 inch torso length – collapse = 18.75 / 19.25 = 97.5%. I've haven't carried this much but maybe it's doable:
This is about the same as the best frameless packs in Will's paper. Jam weighs 29 ounces and carries 3000 in3. Mine weighs 16.5 ounces and maybe 2800 in3.
There are several problems to solve. First you need a solid waist belt that doesn't collapse. 1/8 inch foam, 200D fabric tube, 3D mesh against back, several rows of stitches, 3/4 inch webbing with buckle at front:
Next, firmly attach pack to waist belt. Several rows of zigzag 8 inches long. Through pack, 3D mesh, fabric, foam, fabric. At middle of waist belt, at top edge of waist belt.
Then you need the tent poles to compress the "burrito roll" pack into one solid package that doesn't collapse itself. Top view:
Jan 12, 2014 at 10:38 am #2062709
Thanks for sharing. I think the addition of load lifters to bring the pack closer to your upper back might minimize some of the torso collapse. Possibly?Jan 12, 2014 at 11:06 am #2062718
Steven ParisBPL Member
@saparisorLocale: Pacific Northwest
I just can't believe you have a swimming pool in Portland.
I think I know where the first Portland GGG Summer Bash is going to be held!Jan 12, 2014 at 11:27 am #2062725
Domestic dispute: me – $6000 to demolish pool, wife – no way!Jan 12, 2014 at 11:45 pm #2062915
David ChenaultBPL Member
@davecLocale: Crown of the Continent
Until you get that pack to fit your back better you have bigger limitations to load carry than torso collapse.Jan 13, 2014 at 6:47 am #2062939
You mean it's not S shaped?Jan 13, 2014 at 7:12 am #2062950
I think Dave is referring to the short torso size of the pack. It needs to be taller, hence my nice way of commenting on the lack of load lifters.Jan 13, 2014 at 7:46 am #2062953
But the problem with using my pad as stiffener, is the pad is 20 inches wide. The shoulder strap attachment can't be higher than that. Maybe this leads to a problem that can only be solved with a frame. I have a little longer torso than average person.
With a load lifter, still has the same problem – the load lifter has to attach to a stiff part of the pack.
I've tried raising the pack with sleeping pad up on the waist belt, but then the waist belt itself collapses and folds. I have to have the bottom of the pack even with the bottom of the waist belt. Maybe I can cheat 1/2 inch.
Then, I put the shoulder strap as high up on the pack as possible, even with the top edge of the sleeping pad.
If the shoulder strap or load lifter attaches to the pack horizontally (my first picture) then the waist belt can carry all the vertical load.
If the shoulder strap attaches at an angle (second picture) then you can't put all the weight on the waist belt.
I took the second picture by unfastening waist belt and lowering pack, just to show improper torso length.
The first picture is how I actually carry the pack. Doesn't that mean I have the correct torso length? I have moved everything as far as possible to maximize torso length and I think it's maybe barely long enough.Jan 13, 2014 at 8:50 am #2062963
Okay – now I see how you showed the pictures.
The top picture is pretty close to good for me as I like to have the shoulder straps attach to the main bag at shoulder height (or even a little higher).
However, I like to have the pack snug against my pack. If your stiffener is too stiff then I can see why the pack would be pulling away at the top a bit. With a stay that is shaped, this can be less of an issue.
With load lifters and a more flexible stiffener, I suspect you could completely close that gap and provide a more stable carry but then, as you indicated, you would have to have a taller stiffener to where the load lifters would attach to (i.e. greater than 20").Jan 13, 2014 at 8:58 am #2062965
That was a picture in front of a mirror, twisting around, holding camera in hand
I'll have to think about this the next time I go backpackingJan 13, 2014 at 11:29 am #2063008
David ChenaultBPL Member
@davecLocale: Crown of the Continent
Torso length looks fine based on photo #1. With the pack hanging back off your shoulder like that you're going to get a fair amount of weight on your shoulder irrespective of the quality of the frame.
I suspect the tent pole top compression arrangement exacerbates an issue which already exists due to a non-shaped packbag.
The foam pad issue can be solved in two ways. If you still want to burrito within the pack, pony up for a wide ridgerest and cut it down. The second is to use a smaller pad against the back and/or within a sleeve, folded in half and set long wise. Assuming a conventional 10" wide pad, you're limited to a 10" wide pack, but can cut to any height which suits you.Jan 13, 2014 at 2:18 pm #2063053
I don't sleep good on Ridgerest. I prefer air mat. Thermarest Prolite works okay. 1 pound for regular. Extra 6 ounces for wider version, but that sort of defeats the goal of reducing weight. But I think the 20 inch wide mat is just barely wide enough.
"I suspect the tent pole top compression arrangement exacerbates an issue which already exists due to a non-shaped packbag."
You mean since the bag is not S shaped, it doesn't contact my back from top to bottom? I agree, this may be impossible to resolve with burrito/compression system.Jan 13, 2014 at 4:38 pm #2063090
Daryl and DarylBPL Member
@lyrad1Locale: Pacific Northwest, USA, Earth
You tent pole pack compression technique (here and in the gear forum) came at a good time for me because I've been fooling around with the issue recently.
I too tried and rejected the dual vertical bags and internal strap solutions. I've also tried and rejected the multi bagged horizontal bag technique (old Gerry Packs).
The closest I came to your tent pole compressors was using my ice axe in a manner similar to your poles (see photos below). But I don't always bring my ice axe and I'm usually wearing the pack when I need to use my ice axe.
Your pole compressor idea is the best I've seen and I plan to use it. Thanks.
Carrying the poles in this way also allows one to carry longer length sections than one might if they had to carry them horizontally or within the pack. With my packs, for example, 30" long sections would carry well using your idea.
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