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.
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.
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?