Evolution of the North Fork pack (backpacks for the woods, part 3)

I started building the North Fork pack back in late August of 2010, when I was between finishing up grad school and actually working. My work may look good on the internet, but I’m a pretty awful seamstress, what with my lack of patience and hand-eye coordination.  I go for functionality, but tend to get things wrong the first time around.  I also only have a normal sewing machine, albeit a pretty good one, so the ability to only bartack modest thicknesses of fabric and webbing has to be integrated into a design.

Point being, while this video has been a great hit, and still tells most of the story, I’ve had to change a bunch of stuff on this pack over the last 14 months.  It’s a good case study of how a pack works.

As can be seen from the first photo of the pack, the torso length was too short.  I used to think straps which wrapped back around the shoulders were good, as they worked in combination with load lifters to make the pack respond better to movement while carrying.  This is true, to a certain extent, but it also forces the load away from the body, and with any sort of real weight in the pack you end up doing the hunchback: leaning forward to compensate.  No good.

So I tore out the backpanel and lengthened the torso.  My torso, measured the classic way, is 20.5″.  The effective torso length (distance from straps to place the hipbelt will lie of the iliac crest) of the North Fork pack is 20″.  The distance from the shoulder straps to the bottom of the pack is 22″.

The problem with this measurement is that many (most?) manufacturers use the full back measurement as the effective torso length, which is plainly problematic.  Golite does this, which is why the Jam and Pinnacle have actual torso lengths about 2″ shorter than their claimed lengths.  With a pack like the Jam, which lacks load lifters to blunt the effects of a slightly too short torso length, this means that a lot of folks end up buying a pack which doesn’t fit them.

A large Golite Jam.  This pack does not fit.  Golite should relabel this as a medium and start making an actual large. Paige Brady photo. 

My BD Demon, mentioned in the previous post in this series, has an actual torso length of around 18.5″.  BD claims the large fits 19-23″ torsos, which is a bit generous, but because it has load lifters it fits me very well.

Torso length is crucial for pack fit, and should come very close to the actual torso length of the user when measured from the functional center of the hipbelt.  View manufacturer specs with a cynical eye.  A slightly short torso length has it’s advantages, either with a very light pack or when paired with load lifters.  Due to the likelihood of sagging within the pack system, a pack designed for heavy loads should have a torso length a bit on the long side.

The most important feature of a frameless pack is correct torso length, very closely followed by proper placement, angulation and size of the shoulder straps and belt so they fit a persons anatomy well.  Quality padding, with enough but not too much of both cushion and stiffness, in these suspension components is next.  A good match between the pack shape and load (either via blunt capacity or effective pack compression) is next, as this along with proper packing of the load are what create a “virtual frame”, moreso than any one thing such as a foam pad.

Note angulation of the hipbelt, exact figure arrived at by trial and error.

I nailed the construction of the hipbelt for the North Fork pack on the first attempt.  The attachment of it to the pack, not so much.  I (rather foolishly, in retrospect) left a bit of empty fabric between the padding in the belt and the sewn part.  This sagged like crazy, and moved around a bit under a heavy load.  This not only caused torso collapse, but rubbed my tailbone raw on a few trips before I finally got it right (see above).  The addition of a bit of 3D mesh nicely solved the rubbing issue, and provides a bit of sticky fabric on the lumbar region, further helping load stability.

Hipbelts should not be sewn into the side seams of packs.  There are very few exceptions to this.  In my experience, the bottom of the pack will become rigid when stuffed full, and a belt attached to the sides will leave big gaps right where hipbelt contact is needed most for thorough load transfer.  A light load packed with discipline (Mike Clelland’s fluffy cloud) can remain flexible enough for the pack to conform, but add heavier loads and especially things like packrafting gear and all that goes to hell in a hurry.  Best to just make the hipbelt right from the first.

4-6″ seems to be a good spacing for the two parts of the hipbelt.  A solid, rigid attachment is key, with as little room for sag as possible.  Some sort of cinch strappage tying the bottom corners of the pack to the belt is handy for added load transfer is good.  The Demon uses traditional side cinch straps attached up near the front of the iliac crest, which works fine and is easy to sew.  The above design on the North Fork was chosen for both ease of construction and trying to evoke the system on the 2011 Jam/Pinnacle.  As I’ve noted before, here Golite has a really great system, balancing support and flexibility.  I’ve been happy with this aspect of the North Fork’s design.

The shoulder straps are another area where I’m pretty happy with my selection.  The Arc’teryx straps have nice dual density foam which is cushy and supportive, even over the long haul.  They’re narrow enough that they don’t chafe.  I didn’t sew them on at an angle, like I have with more recent packs, but this hasn’t proven to be problematic.  They are a bit wider apart, and have a bit of slack fabric right where they meet the pack, so that might help.  It’s an idea worth debating, but I’m not sure proper angulation is entirely necessary under all circumstances.

The load lifters have proven very handy, even with the longer torso length.  Just a little tension allows things to be tightened up, and they allow for one more way of varying the load carry slightly throughout a long day with a heavy load.

So then, in summary, a good pack fit depends on:

-proper torso length

-well designed shoulder straps and hipbelt

-proper loading and compression of the pack

-adequate support for the load (given the strength and physiological peculiarities of the user)

 

What have I missed?

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15 thoughts on “Evolution of the North Fork pack (backpacks for the woods, part 3)

  1. Dave, I wouldn’t call you an ‘awful seamstress.’ Your work on the Bandoleer pack/Talon straps was awesome (read: highly functional and bomber). It’s smooth(ish) and pretty (custom). And the pack is better than it came from TrailLite. Chalk one up for DC.
    If you can throw a backpack together and have it perform as well as your’s does, even if it takes two years, I’d say that’s pretty damn awesome.

    The fit of the hipbelt, as in if it forms to the hips well and doesn’t create pressure points over the iliac crest, is a big one in my book.

  2. “Due to the likelihood of sagging within the pack system, a pack designed for heavy loads should have a torso length a bit on the long side” – I wish I read this when I bought my Pinnacle, no wonder it always feels too short.

    “A good match between the pack shape and load (either via blunt capacity or effective pack compression) is next, as this along with proper packing of the load are what create a “virtual frame”, moreso than any one thing such as a foam pad” – I think this is another area where the Pinnacle falls short sometimes. If you don’t load the pack inside a rolled sleeping pad inside the pack it tends to bulge out and push you centre of gravity way out back. As I often like to have my foam sleeping pad somewhere on the outside of the pack (so I don’t have to empty the entire pack when I stop for a longer break) I find this sub optimal. Sometimes I carry a two pad sleeping pad system and this helps. The ‘ultralight’ compression straps on the Pinnacle aren’t up to the job of keeping everything in shape. I also don’t like that outside pocket. Too easy to fill it with crap and push more weight out the back. Some kind simple compression pocket or flap (for snowshoes, shovel.etc) would be better.

    This is an excellent series of articles Dave, keep ’em coming. No one has ever really dissected this subject to such an extent and it’s good to know there are other people out there who, like me, spend a disproportionate amount of time pondering the finer points of pack design…

  3. Nailed it again Dave. I love it. Your comments on the hipbelt sagging were intersting. A friend of mine on the Colorado Trail complained that his Gossamer Gear Maripossa put most of the weight on his shoulders. I thought that was strange because it looked like it should have fit him. When he put it on it didn’t look to small for his frame and the hipbelt wasn’t too large for his waisnt. Now that I think about it I wonder if the hipbelt was sagging. His hipbelt looked wide and comfortable but I noticed it had a lot of slack were it was attached, no stiffness at all.

    1. The Mariposa still has removable padding in the belt and straps right? Seems like that design could foster sagging. Some stiffer foam that just barely fits might help.

  4. This is a great thread of posts. Love the evolution of the pack, generous of you to share all the trials and errors along the way. About the hipbelt and shoulder strap attachments, if I want waterproofness, stability and wrap hipbelt at the same time, which I do, any recommendations? I got a second package of material from extremstextil the other day so I’m in the starting blocks for my second pack. I’ve also made up my mind on adding a aluminium hoop frame (smd) and planning on fitting it on the outside of the pack, inside tubular webbing, linking it to the hipbelt. Hope it’ll be a big +.

    1. Daniel, I think having a truly waterproof pack is not an especially desirable realistic expectation. Seems like you’d need a very thick fabric to guard against holes, and thus a heavy pack.

      A very water resistant pack, on the other hand, is great. Add some light dry bags for crucial stuff and you have a pretty bomber system. That being said, don’t worry about stitch holes in the fabric. With VX-21 they don’t leak much at all. I like to have the back panel be one full piece, sew the belt to that, sew the shoulder straps to a separate piece of fabric, then sew that to the pack. It’s easier to position the straps precisely that way. You can see that on the last photo, the gray fabric was sewn on top of the black fabric.

      1. Well yes, you’re right about the waterproofing. When you say it, I realise I might have put my mind too much into that part. After all, I’m not aiming to go diving with it; and if you’ve managed with the packrafting and all, I think my pack will do well in the rain. Thanks for the tip about attaching the shoulder straps to a separate piece of fabric, that will most certainly make the positioning easier.
        I’m a bit confused or intrigued by the whole shoulder strap placement. On one hand we have the standard way of attaching them, hugging or draping the scapular/soulders and on the other hand Bpl’s research in the subject. One remark though is the addition of top tensioners, which sum the forces to a ~horisontal force.

        1. The strap placement is an interesting issue. Zpacks recommends a torso length long enough to place the shoulder strap attachment point above the tops of the shoulders, something I haven’t tried as it seems rather uncomfortable.

          My current thoughts are that for smaller packs (like the race pack, next post in this series) load lifters are not needed and a torso length right in line with the users is in order. For bigger packs, load lifters and a torso length perhaps a hair longer are the way to go.

          Of course, I’m still learning, and could be quite wrong.

  5. Dave on the Maripossa I don’t think the padding in the hipbelt was removable. The entire hipbelt was removable and if I recall the attachment point was considerably thinner than the rest of the hipbelt.
    I think the hipbelt sag you’ve pointed out is a very important issue and its one that doesn’t seem to be discussed a lot. I’ve noticed a lot of lighter interanl frame packs seem to max out at about 35 pounds (ULA Circuit, Osprey Exos etc.) some of this way be the lighter frame but I wonder if improving the hipbelt is part of the issue. For example the hipbelt on the Exos seems pretty flimsy to me. I think the pack is stiff enough to carry a lot more weight without collapsing, I think the hipbelt is the limiting factor.

    1. First time finding this site…. but I do have a Exos and COMPLETELY agree. The hipbelt and shoulder straps are way too flimsy. I’ve often wondered if I could replace the straps (shoulder and hipbelts).

  6. I just made my first backpack, a Ray Jardine kit, and I recently started packrafting as well. The kit has shown me the basic idea of how to assemble a bag, I have some ideas on how to make my own packrafting friendly bag in the future. I just came across your video and blog and I’m blown away with your work. Your bag is so well thought out, things I’d never even considered, although I’m sure they would raise there ugly heads as I used the pack. Thanks for sharing all of this info and I look forward to reading more.

    BTW-Having made quite a few bags for bikepacking with XPac, I think your bag looks great.

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