Disclaimer: for those readers who are BPLers this is rather inside baseball; and for those who are not following the threads might be difficult due to members-only citations.
I’ve always loved backpacks. Since well before age 10. They do cool things, and have for me an aesthetic appeal. I first seriously modified a rucksack back in high school, but didn’t attempt to build a pack from scratch until just over two years ago. Since then, I’ve made close to a dozen. That none of them currently exist is a testament to the complexities of pack design and construction, and to the dangerous restless-mind syndrome which MYOG (make ya own geah) engenders. Once you make your own stuff you’re all but guaranteed to become more sensitive to flaws and problematic details, and thus doomed to go through many packs in the quest for more complete understanding.
This post will be the first in a series exploring what makes a pack work, well. The subject: defining framed and frameless packs, and in the process examining the basics of pack load carrying.
My first ground-up MYOG pack. It left a lot to be desired, but I carried ~30 pounds in it across the Bob Marshall in October.
Traditionally a framed pack was one with some sort of structure inside the pack which allowed the torso length to be maintained under load. A frameless pack was one lacking structure of any kind, think of a basic bookbag. There are many earlier examples (mountaineering packs such as the Jensen), but it’s useful to look at things being complicated in the current era by the Ray-way and Golite. I’m not sure at what point the frameless packs in this evolutionary line began to want more support, but pretty soon a frameless pack began to act suspiciously like a framed one.
Torso length is at the center of how and why a backpack works. Weight is any pack is carried on the hips, shoulders, or some mix of both. With heavier loads especially, most folks prefer the ability to select and vary the percentage. Being able to do so is dependent upon the torso length of the pack matching that of the user, and on that length being maintained under load. Succeeding in this respect is a prerequisite for a good pack, something without which other attributes (like a strategically padded, well fitting harness) can only be marginally effective.
The complication between framed packs and frameless started with enclosed foam backpanels. The pack above had no sleeve inside, I just rolled my ridgerest in the classic burrito fashion and stuffed everything inside. There are numerous possible problems with this approach, but perhaps the most serious is that the connection between the foam (here working to do load transfer) and the harness components has much room for play. You can see the sagging above the hip belt wings. Things like this result in shrinking torso length, which as linked to above quickly destroys pack comfort. And true to form, I only got away with that pack on the Bob Marshall trip because I had done plenty of training hikes and upper body and core conditioning prior. Before 2009 was out I added a better hipbelt to try and compensate for torso sag.
The same pack, with a few modifications, at the Buffalo Fork TH in Wyoming, May 2010.
The all-encompassing solution to this is a full internal pad sleeve. Golite figured this out a while ago, and their use of a thin (1/4″), dense foam mat in a snug sleeve is why the various generations of the Jam and Pinnacle have all been especially resistant to torso collapse. Will Rietveld even found that the Pinnacle performed almost as well as the internally framed Exos 58 in a recent test. I know from personal experience that the load capacity of the Jam can be substantially increased by modest beefing up of the pad, and see no reason why the Pinnacle couldn’t be similarly enhanced.
The virtue of the frameless approach here is that a mere foam pad tends to preserve a degree of flexibility and thus when worn agility which internal frame packs too often lack. There is certainly such a thing as too much frame for certain occasions.
In the same article series Rietveld defines an internal frame as a pack having stays with a direct connection to the hipbelt. I don’t really understand what that means. Will excluded the Hornet 46 from his frameless test on those grounds (it has twin rods which go between the back panel and the main pack and connect at the bottom outside corner, as well as a hipbelt with no padding and virtually no structure), while Roger Caffin excluded the ULA Ohm (with a delrin rod which seems more substantial than the Hornet’s “frame”) from his internal frame pack test. Are the Hornet 46 and Ohm framed packs, or frameless? And do either of them carry as much weight as a pack like the Pinnacle?
The third and last version of the pack pictured throughout this post. For reasons hinted at here and discussed in detail next post (read: hipbelt), this pack did not work very well.
For me, the interesting answer is not yes or no, but a recognition that there probably isn’t a categorical difference between frameless and internal framed packs anymore. There are various approaches to matching degree of load bearing with size and intended function, and likely more variance in this respect within either camp than between them. Which approach will prove most effective will have to do with the other factors beyond resistance to torso collapse, to be discussed next.
Bedrock & Paradox 
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