Frameless Backpacks: Engineering Analysis of the Load Carrying Performance of Selected Lightweight Packs

>> Interesting to see how poorly the Katahdin performed in the tests…This makes me wonder how well the test data relates to the real world comfort and performance…my gear compressed around the tent poles serve to make a VERY solid structure

I do not dispute your findings at all. The important take home from this is that how you pack your pack makes a big difference. The minute you changed your packing technique to deviate from the test packing technique described in the load suspension articles, you deviated from test conditions and thus, results are no longer comparable. What the test conditions are able to show, is that for a moderately dense load where base soft goods densities are the same from pack to pack, one pack maintains torso stiffness better than another. That’s it. It is a testament to a pack’s design if it scores well on these test. It is not a guarantee that it will carry well for all people all of the time. Nor do the tests guarantee that a poorly performing pack (in the tests) are going to carry poorly for all people at all times – your Katahdin experience validates that. I think that the test data does suggest that packs that perform poorly in test conditions need more attention on the part of the user in order for them to carry well on the trail.

Splitting 1″ hairs and weight transfer.

The original article states,
>>”The iliac crest is about one inch higher than >>the point at which the centerline of a pack’s >>hip belt should rest”

This tells me that the centerline of the belt is lower than the iliac crest.

This post states,

>>2) the big one – that the ideal position of a >>hip belt is having its centerline about an >>inch above the iliac crest.”

This tells me the opposite of the original statement?

I have noticed that a wide padded hip belt formed in a semi circle when flat ends up with a truncated conical shape when curved. With the narrow end upwards this tends not to slip and snug better over the iliac crest. Additionally, a wider belt with stiffer foam, or a layer of plastic, seems to “transfer” load where as a flimsy narrow belt tends to “hold” the load via constriction and not by transfer.

Any similar or differing observations?

Sorry, Fred. Typo in my original post. I’ve corrected the post.

I apologize for the pun (for those of you old enough to remember the song.) I’d been quite happy with my Granite Gear Vapor Trail pack and the 13 pound base load I was carrying (including a T-rest UL 3/4.) But, for the last 6 months I’d been trying out the Granite Gear Virga with a folded Z-Rest 3/4 as the frame. (I picked up the pack in an end of year sale for about $60, so what did I have to lose except a pound?) It worked quite well at loads under 20 pounds, though my shoulders were a little tired – but not sore – at the end of the day. Finally, though, my 54-year-old hips convinced me that I needed to use a more comfortable sleeping pad. I had tried the Ultralight 3/4 as a frame in the Virga, but didn’t find it at all comfortable. So, I decided to go back to my old Vapor Trail/Ultralight pad arrangement. When I dug it out, it was inserted into a Lite Chair kit (from an outdoor concert.) A light bulb went on: the kit has stays; why not give the pad/chair combination a whirl as a frame? The stays made all the difference – just leave the pad in the chair, inflate it slightly, and insert it down the back of the pack, with the stays rolled in just enough that the pad is the width of the pack’s back. (Put the stays on the inside, not directly along the back of the pack.) With this arrangement, the Virga rides as well as the Vapor Trail, and I’ve recently been trying it at 25+ pound loads, with no loss of comfort. I haven’t yet decided whether it’s more comfortable with the “thick” end (where the pad doubles over to insert into the chair bottom) as a lumbar pad or a shoulder brace – I’m kind of leaning toward the lumbar pad. But, for the same weight as the Vapor Trail plus 3/4 T-Rest, I get a pack frame that doubles as a chair! Is it the absolute lightest load? No, but the extra pound is well worth it for me – and I’m still at a 13 pound base weight for a summer trip.

carlos fernandez rivas – It is difficult for a foam or self-inflating sleeping pad to provide the same level of support as a rigid frame, whether it be a plastic framesheet or internal stay. I have been experimenting with both the Gossamer Gear Mariposa and Six Moon Designs Starlite. Both of these packs use the sleeping pad as the frame, but also have removeable stays. Without the stays, both perform much better with closed cell foam than with the self-inflater. Bummer, because I really prefer to sleep on a self-inflator. The stays solve the problem, for the most part, but I really enjoyed the idea a few posts ago by Glenn Roberts, who used his sleeping pad chair for a virtual frame. That is pure ultralight thinking at its best. Why carry the extra weight of a frame when a camp chair can serve as both a frame and chair.

The Granite Gear packs are slightly deeper than some, contributing to the need to lean forward slightly to balance the weight.

I think your rationale for going with the Vapor is well justified. When I talk to people about lightweight backpacking, they almost always focus on the pack saying “I wish I had a lighter pack”. However, when I take account of their other gear, the pack is the least of their worries. If you’re really going to do some trail miles, a slightly heavier, but more comfortable, pack (with ultralight stuff inside) may make all the difference. I get much poorer sleep when I’ve carried an ill-fitting pack all day, lowering my potential mileage and enjoyment the next.

As far as the chair kit, you might consider replacing the framesheet and padding in your Vapor with it. This may actually end up weighing more; but, sometimes its nice to have a chair along.

Jay

I received the new version of the Vapor Trail hipbelt a couple of days ago. (VERY speedy turnaround on Granite Gear’s part – kudos to them.) They now secure the webbing to the padded portion with a crampon-patch kind of material. It appears more substantial, but I won’t get to try it until spring. Looks like a good improvement, however.

By the way, if you didn’t like the lidless pack, GG now makes a lid compartment that retrofits to the Vapor Trail and Virga. I’ve ordered one from BackcountryGear.com; I’ll try to remember to let you know how it looks.

Glenn,

I read you comprison of the Vapor trail and Gregory g-pack. Do you think you’ll be doing a retest with Gregory’s redesigned Gpack? Thanks, Jeremy

Glenn,
Thanks for the thoughts. I mentioned the G-pack because I just read the latest Backpacking, and they called the new G-pack there favorite ultra-lightweight pack of all- citing its ability to turn a 30 lbs load into a 20lbs load? Also they claim its got some sort of new system that clamps the pack to the small of the back in a new way?
Glenn have you tried Backpackinglight’s recommended pack, the Go-lite Infinity?

I’ve previously posted about using a chair kit and thermarest as a virtual frame inside a Virga pack; I’ve also indicated that I probably wouldn’t switch permanently from my Vapor Trail. I recently had a chance to try both packs, side by side, over the same trail on consecutive days.

I was leading a troop of Boy Scouts on their first backpacking orientation – we were planning a six-mile hike, and allowing all afternoon for it, on an easy trail with a couple of small hills in it (just for fun.) The park we were using was half a state away, but I caught a break: I was working in the area two days before our trip. I took a day off, and went on to the park a day ahead of the Scouts. I decided to use the time to decide, once and for all, whether I wanted to use the Virga or the Vapor Trail.

I took each pack on an identical hike, though the time to complete the hike with the Virga was only about half what the Vapor Trail was. (I took a couple of long breaks, and didn’t push the hike; the extra time with the Scouts was for teaching the use of stoves and filters on the trail.) The load in the packs differed only on 3 items (other stuff I was trying to decide about.) The Virga’s load included a Clikstand stove/Evernew pot, Katadyn Mini water filter, and tarp/bivy combo for shelter; the total load (including food, water, and fuel) was 16 pounds. The Vapor Trail’s load included a Pocket Rocket/Titan kettle, MSR Miniworks water filter, and Zoid 1 tent; the total load weighed just over 19 pounds. Both packs held the full load without using the extension sleeve, and both were equally easy to pack (though it takes a little care to keep the virtual frame in place in the Virga until you get the sleeping bag and tent loaded, which locks the pad into place.)

What I found was that the heavier Vapor Trail was more comfortable than the lighter Virga.

The Virga was fairly comfortable; the stays in the chair kit, plus the lightly inflated pad (a little less than it will inflate to on its own, without blowing into it), provided a very good level of support, and nothing poked or gouged me. However, I did find that the unpadded webbing hipbelt kept riding up (there’s a switch!) and interfering a little with the transfer of weight to my hips. Although I was never uncomfortable during the hike, it felt good to take the pack off at breaks. At the end of the hike, I was surprised to find that my back and shoulders ached a little – not horribly, but noticeably. (A couple of Motrin handled it just fine – no lingering effects next morning.)

The next day, I carried the Vapor Trail. Though the load was heavier, the pack was never uncomfortable. The nicely padded hipbelt continues to amaze me: it fits well without constricting, and really doesn’t slip down like other belts. The incredibly comfortable back pad transferred the weight to my hips very effectively, and nothing pokes or gouges me through that wonderful back pad. The pack was barely noticeable; I even forgot to take it off during the break where we taught them about water filters! At the end of the hike, when I took the pack off, my shoulders and back were not in the least bit tired – it was like I hadn’t been wearing a pack at all.

So, based on these results, I donated the Virga pack to the troop. I figure that there will be that one boy who will want his own gear, and will be excited about experimenting with ultralight. (Did I mention that I’m not using the merit badge handbook, which is woefully out of date? Instead, I’m using the Fieldbook, recently revised, which includes a fair amount of lightweight guidance, and am teaching them mostly light- and ultra-light technique.) The Virga will be a great first pack for that Scout, and I can supplement his gear with the tarp/bivy combo (which I’ve decided is not as convenient as the tent), the Katadyn filter (again, convenience wins out over weight), and a stove (the jury’s still out over which one I prefer. I’m sentimentally attached to the Pocket Rocket, since it’s been with me on some great trips to Isle Royale and other places, but the Clikstand is a really, really nice stove.) It will be a good start – had my first ultralight pack been the Virga instead of the Vapor Trail, I might never have bought the Vapor Trail.

Final verdict: they’re both good packs; the chair/pad combo makes a very workable frame for the Virga. However, since I’m already spoiled, I’ll stay with the Vapor Trail.