Down the Evazote rabbit hole and other load hauler pack questions

[Geoff Caplan]

Just in case it’s of interest to anyone, I’ve been googling the software options for designing patterns for the pack, and for some clothing I’m planning to make.

The open source software Seamly2D seems to be quite mature now. It’s parameterised so it’s easy to play around with sizing, seam allowances etc. It helps calculate the most efficient cutting layout, and you can print out your patterns.

Here’s a video where a (relatively unskilled) user shows how he used it to design a pack:

https://www.youtube.com/watch?v=OTcGzXTmtrQ&t=2547s

[Thomas H]

Ivo – I definitely think that laminated and pre-curved Baltic birch or similar would make a great frame for a backpack. I know Fjallraven makes some packs with frames like this as well as many from yesteryear. I don’t think you’re going to match the performance to weight of 7075 aluminum however and it would have the trade offs that Geoff mentions, just like moulded carbon fibre, it can’t be easily reshaped. 7075 in the thicknesses we’re talking about can be bent in the field even if necessary.

Geoff,

The order I put in for 7075 was as follows:

2 x 30” x 0.125 x 1/2 (Heavy weight stays)

2 x 30” x 0.071 x 1/2 (Light weight stays)

2 x 30” x 1/4” rod (Light weight rod, see how it compares to the flat bar)

1 x 14” x 0.125 x 1/2 (Heavy weight horizontals)

3 x 14” x 0.71 x 1/2 (Light weight horizontals)

I actually regret not buying more, as these individual parts are cheap. It’s the shipping that hurts(living in Canada our shipping/import always ends up being 30/40 bucks or more)

These are all a few inches over sized with what I intend to use them for, so I will be cutting them down. I’m even thinking about making the thicker two into bayonet style, so they may be cut down to ~20” and use some of the 14” ones to raise the height to ~27

As far as height goes I have a 19” torso and the hanging style belt means your frame will have to be several inches taller than normal to get that 45 angle for the best heavy load carrying.

Totally agree about using MYOG to test out crazy ideas and generally experiment. That being said I would need more details on that pack’s features to comprehend if it is worth trying to implement. I cant find any good videos or even photos of the details and it seems very complicated.

I had a Black Diamond Mercury 55L bag with a pivoting hip belt and if you pulled the shoulder straps up on one side it would shorten the other, so you could kind of bend side to side. Seemed like it added a ton of weight and complexity. Last time I used that bag was going up Mount Rainer in 2017. It was okay, but not recommended.

I highly recommend SketchUp. They have a free web version that you can use on any computer with a mouse and keyboard. It is simple and I use it for other functions like carpentry, workshop layout at my work and even designing custom metal parts to send off for companies to manufacture.

You can use the ‘offset’ feature to add seams to projects.

I have used this a few times for smaller items, like a pouch or fanny pack, then print and trace to fabric, etc. But with large items like packs I don’t have a large format printer and don’t want to tape multiple 8.5×14 sheets together so I just keep my shapes fairly simple and just measure out the shapes directly on the fabric. Many times I don’t have seam allowance in the pattern, I just plan on everything being ~1/2” smaller once constructed which greatly simplifies the process and removes room for error. Like I’m make the back panel 12” wide knowing than a bunch of it will be eaten up in the seams. My seam allowance is generally guided by the edge of my walking foot (about 3/8) then I bind the edges with 1” grosgrain. Sometimes I do felled seams, but I often find it too much of a pain in the ass on certain parts of backpacks. Joining two pieces of flat fabric will definitely get a nicer seam.

I also have been playing around with Clo3D which does patterning and you can visualize what your bag will look like by ‘sewing’ it together in 3d…very cool stuff. I need to spend more time with it though.

https://www.youtube.com/watch?v=TKXYGookZUw

I’ll watch that Seamly2D video for sure.

[nunatak]

Did get out and use the 3000 cu.in pack I showed earlier on a 3 day 35 mile/7000’ loop with lots of rugged terrain. In addition to my 10 lbs base weight I also carried a BV450, dog bivy, ice axe and microspikes; and of course food/water. Pack weight might have been between 25 and 30lbs, so not a terrible challenge for a reasonably well built pack.

It carried well on the trails and remained predictable and stable on the steeps. Pretty good overall, but I also brought home a list of small changes and potential improvements.

At around 35 ounces it is not lighter than the competition (HMG, SWD, SO, ULA, etc all have framed packs in this range), nor did it carry astonishingly better or otherwise present any groundbreaking ideas. The cottage semi-custom stage, whether framed or frameless, is a crowded place. There are many excellent packs available, albeit very similar in concept. I will play more with this one, but unless I come up with something super unique it will likely remain a MYOG project.

TCP round one

[Geoff Caplan]

Thomas –

Thanks for the cutting list. I’ll get it costed out, but it may be a bit scary expensive to ship over here at this stage when I’m tentatively prototyping.

Just been talking to a local pack maker. They still build the packs in the their own workshop here in the Lakes. They are serious people making technical packs for alpine, big wall, expedition and polar use. Their largest pack is 110 litres! They’ve been using 6 series for the stays for decades and say they’ve never had an issue. They’re kindly letting me speak to a designer to get advice on sizing. If I’m prepared to pay a small weight penalty for a more burly stay, I think I can get by with 6-series for now – maybe invest in the 7075 when I have a settled design, or am visiting the US.

I’ve used SketchUp for years, but they have crippled the free version since they excluded plugins. It’s now very basic indeed, and working with curves isn’t very practical – at my skill-level at least. Still great for playing with shelter designs though.

Clo3D is a thing of wonder, but they don’t have a freemium license and @ $50 a month it’s only of academic interest for me.

I’m sure you’re right that it’s best to design packs around straight lines that can be marked up with a straight edge. But I’m also interested in clothing so mastering the basics of Seamly should be worth the effort. For an OS effort it’s pretty impressive. I have a larger format printer, which adds to the attraction.

Jan –

You raise a thought-provoking issue – where is the scope for innovation in pack design?

I spent a bit of time trolling through the relevant patents, and most of them are absurd. Which is why almost none are in production.

You very quickly focus in on the few real innovators in the field – McHale, Seek Outside and Aarn are the ones I know of.

I’m thinking that the areas where there’s scope for improvement are fundamental ergonomics, adaptability to different loads, fit, and freedom of movement.

I suspect that the only way to fundamentally improve the ergonomics of load bearing is Aarn Tate’s innovation of the front pocket with a stay that transfers the weight to the hip belt. (Front pockets that hang off the shoulders like the ZPacks offering aren’t the same thing at all.)

By moving half the load to the front, you entirely overcome the problem of a weight hanging off your back disturbing your center of gravity. Walking perfectly upright with a big load is a game-changer – the most important innovation in the field, I think.

The only other approach is to place the load high above the back, so you can move it forwards over the spine as with the classic externals. It’s not a complete solution like the Aarn, but it does improve the center of gravity somewhat. But that comes at the expense of balance, it’s a pain for bushwhacking, and you can’t look up – especially if you’re wearing a helmet.

The Aarn has never taken off commercially, despite its brilliance. I’d put that partly down to plain conservatism in the marketplace, partly to poor marketing, and partly to the fact that Aarn’s implementations are heavy, complex and expensive, with certain irritations that could be show-stopping for many.

I love my Aarn, and it’s by FAR the best carry I’ve ever enjoyed. But I can see how it can be done in a simpler and more flexible manner, which is my main motivation for this project.

Then you turn your attention to the backpack itself.

One major win for McHale is the adaptability of his offering, with his bayonet extensions and bypass harness. Seek Outside offer some ability to adapt to heavier loads as well. This greatly increases usability in scenarios where loads will vary, and you can even adapt them in the field.

And they combine this with much better fit than the big brand offerings. Almost every review remarks on this, and people feel it makes a real difference. With Dan, it’s personal customisation. With Seek Outside’s Unaweep it’s the ability to fine-tune almost every element of the pack. You do pay a small weight penalty for this, but I’m sure that’s easily compensated by the greater comfort and efficiency.

Finally, there’s the issue of freedom of movement, which becomes increasingly important as loads go up. Many of the patents focus on this, but they usually involve heavy, complex and expensive engineering monstrosities that would add weight and points of failure. Aarn’s U-Flow, on the other hand, is failsafe, relatively unobtrusive and works pretty well. I like it. His X-Flow, though, is a step too far – for me at least. I found it constricting and stripped it off the pack.

Now, a MYOG pack that combined the best innovations of these three makers with the odd sprinkle of secret sauce could be very interesting. Commercially it might be problematic – new products that are hard to explain are difficult to sell, and there are patent issues too. But for MYOG, it’s a fun and challenging project with a decent prospect of producing something that works exceptionally well for long and challenging walks.

The older you get, the more this stuff matters. I started off in the ’60s with the Whillans Alpine sack, which was essentially a canvas bag that hung off your shoulders with thin straps and some minimal felt padding. We had a great time, but looking back the loads half-killed us – climbing gear, canvas tent, brass stoves, massive feather sleeping bags… Couldn’t do that today. I’m looking for something that will keep me healthy on the trail as my body continues its inevitable decline into decrepitude :-)

[Thomas H]

Jan,

Thanks for the update. I’m curious about what changes you’d make to improve the pack.

The upswept bottom with the two darts, and the slick profile in general look sharp and great for off trail travel. I’m also a big fan of your removable MSR bottle and water bottle pouches.

I do notice that the frame doesn’t seem very high, and definitely isn’t getting that nice 45. Obviously your only going with 25-30lbs, so its not needed. I’ve certainly carried that much if frameless bags without much discomfort. What specific features does this have/have not in comparison to your other framed plateau pack that makes it not meant for heavier loads? And do you intend to test it with 40-50 lbs?

Geoff,

Other than marketing jargon from Aarn’s website I really can’t find too much about his packs, and I’m not even talking reviews, but even close up photos, videos of all these weird features, etc. The last time I looked at their packs I came away the only thing special was the front packs to better distribute weight, but clearly there is more to it than that.

I’m thinking that a pack with a good frame, hipbelt, etc and nice 45 angled load lifters that would effective take 80+% of the load off your shoulders should be effective at connecting a front pack, like ZPacks or similar. Or is there more to it that Aarn is doing?

Definitely agree about the conservatism in the market, but consumer psychology is more complicated than that. It’s not like there are a large group of hikers that are even aware of these unique packs. I think there are a lot of odd-ball outdoor gear makers selling some snake-oil magic feature…only some of them the snake-oil actually works. So if you’re into the outdoors you’re heavily influenced by trends and fashion, but they aren’t just trendy because they look cool, they’re trendy because they work! They may not be the best solution, but they are a good solution for a lot of people.

And personally, I don’t want something in front of me when I’m climbing, scrambling, even using trekking poles, so I theoretically don’t like the idea of those front packs. I sometimes will carry a DSLR slung around my neck/left arm and its a pain in the ass when its in front of me. I’d totally be willing to try Aarn or similar though.

And about the 6 series of aluminum, a lot of pack makers use it because its cheap, available and is easy to mould. You’ll definitely have to go for something maybe 1”x1/4”. That being said I only have experience with 6061(or at least thats what I was told it was from a hardware store).

[Geoff Caplan]

Yes – Aarn is hopeless at promoting his stuff and the website is epically unhelpful. Just one photo of a highly sophisticated and innovative product? What is he thinking? He needs detailed explainer videos of each product, photos of each and every feature, and pages full of video reviews and testimonials. I suspect that most of his sales come through word-of-mouth from enthusiasts like me, because almost no-one would buy on the info from the website. (I’m the exception – but then, I’m an irredeemable geek).

The first point to make is that this is far more than a gimmick. He worked closely with a highly respected UK sports scientist at Leeds Metropolitan University, and his claims are proven both in the lab and in the field.

The fundamental issue with all conventional packs is that if you hang a weight off your back it inevitably moves your centre of gravity backwards and you have to lean forwards to compensate and counter-balance the load. This impacts your gait and your balance and is fatiguing. It also creates a lot of unnatural stresses which can lead to pain an injury.

The canaries in the mine are hikers with neck, shoulder and spine issues. There are whole classes of people who simply find a conventional pack too painful and have problems carrying any kind of load. These people find the Aarn system a total game-changer.

But the centre-of-gravity issue has an impact even if you’re young and healthy – it’s just basic physics. Anyone who claims otherwise is simply not very aware of what’s happening in their body. The implications start to be significant at around 12-15 lbs, and are highly significant at 30lbs or more.

The old approach of carrying the load above the head so you can  move it forwards over the spine is a partial solution, as I’ve said above, but comes with show-stopping drawbacks on rough terrain as we know.

Arne’s solution is to carry your heaviest and densest items such as food and water in the front. This balances the load and completely solves the issue with centre of balance. You can walk upright with a natural gait. This is enormously liberating – unless you are carrying out half a sodding elk, the load simply disappears. Turns out that the main issue isn’t the weight itself – it’s the way we carry it.

There are two key aspects to his design which differentiate it from naïve products like the ZPacks pouch.

The first key point is that there is a stay on the back of each pocket. This can be curved at will to keep the pocket off your chest or boobs to maintain airflow. Some people assume you’ll overheat, but I know from experience it’s a non-issue. But the main role of the strut is to slot into a holster on the hip-belt to transfer the weight off your shoulders and onto the belt. This is a big deal, and it’s Aarn’s major innovation.

When the pack is properly tuned there is literally no weight at all on your shoulders and back. The only role of the straps is to get the pack on and off. It’s liberating to finish a long day in the hills with zero discomfort in the shoulders, neck and spine. And there’s less discomfort in the hips too, because the load is spread over a wider area. You can transfer some weight to the shoulders if you want, but I’ve never felt the need.

I find I can walk many additional miles each day with no discomfort. My last big hike was a tough 6 weeks in the Western Alps, and I had no aches or pains at all, even though I’m getting on a bit these days and was horribly deconditioned when I set out. No night cramps. No stiffness in the mornings. With conventional packs, I get battered. I also suffer from the fatigue disease ME, which reduces the ability of muscles to recover from exertion. So this was a real result and turned me into a believer. I was less battered than I was when I was a super-fit kid.

The second key point is that the dual pockets leave a gap which gives you an ample view of your feet on rough ground.

As you say yourself, the main barrier to adoption is people’s reluctance to consider walking with anything on their front. I personally would draw the line at anything that prevented the free and natural swing of the arms, whether a front pocket or a belt pocket. I find that hugely irritating.

With the Aarn design, some of his set-ups solve this and some don’t. All elements of the system have to work together to keep the front load in the zone that doesn’t affect your view of your feet in the front and the swing of your arms to the side. This will be a central focus of my design. The size and shape of the pockets and the way they are attached both have to be right.

If this is achieved, I can assure you from personal experience that you quickly get used to the front pockets. The brain has a feature that it simply tunes out anything it doesn’t need – it already does this with the nose. After you’ve used the pack for a bit the brain learns to do this as soon as you put it on. But you have to thole an initial period where it feels odd, which is another big barrier to adoption.

Again, Aarn hasn’t got this right on my pack. The pockets are bright orange, which doesn’t help this filtering process. I’ll make them of a more neutral grey or black.

But once you get over the initial unfamiliarity you hardly notice they are there, even if they are orange. With a neutral colour I think they will “disappear” entirely. Until you need to access your kit, at which point you appreciate the convenience of having everything to hand. In bad weather I’ve literally spent entire days without taking off the pack even once…

But then we come to the show-stopping issue I mentioned above and which you have highlighted in your post. This all works like a dream on the open trail. But if you have to do any serious scrambling or bushwhacking it can quickly become a major problem. It’s also a serious pain off the trail, if you are travelling, shopping, hitching and the like.

Aarn’s implementation simply doesn’t address this properly. and it’s the show-stopping drawback I mentioned above.

My solution is twofold:

1. Most important – have a system that enables you to transform the front pockets into side pockets within seconds. Side pockets work very well – the world’s military generally go into battle with packs that have side-pockets – even special forces in the jungle as illustrated below. I’ll make the main bag quite narrow in alpine style so the profile isn’t too wide in side-pocket mode. In most scenarios this will be a perfectly adequate solution. But it’s simply not possible with the Aarn designs – a major oversight in my view.

   

2. Have the main bag large enough that you can carry the whole load and the front pockets inside if you are facing a day on technical ground where even the side-pockets would be a nuisance, or you want to strip down the system for travel. I’m aiming for about 15 litres of combined capacity in the front pockets. An extra 15 litres of capacity in the main pack weighs just a few grams and is a non-issue for most people.

So – ensure that the front pockets don’t interfere with arm-swing or with your view of your feet. Make them a neutral colour. And have effective options to quickly stow them out of the way. This is all perfectly achievable, and should make for a uniquely ergonomic and practical carrying system.

Aarn’s freedom-of-movement innovations are much more marginal. I was playing with my pack yesterday, and realised that the U-flow comes at a cost. The hip-belt and lifters can’t be attached directly to the stays in the optimal way, as they have to have freedom to move. This adds inefficiency that may well cancel out the benefits.

I have developed what I fondly believe is an efficient gait with a minimum of unnecessary trunk motion. This means that the U-flow isn’t doing much until I’m doing something like scrambling, which is less than 1% of my usage. So it’s probably not worth the added weight and complication.

If you’re young and fit, you can have a great time in the mountains with a conventional pack, even carrying 10 days of food. It doesn’t mean that your pack is optimal – it just means that the inconveniences are minor enough that you’re not motivated enough to look for alternatives. But if you’re an older bloke with ME who gets a sore back over a long day with a conventional pack, it becomes a game changer. Walking into remote country with lots of food and water becomes enjoyable, rather than a painful grind. And that’s worth a lot to me…

[James Marco]

@0 or so years ago, I made up a pair of front pouches that held my tarp, fuel bottle, and other dense items. A 33 pound pack (I used to carry around 30-35 pounds) was used meaning about 6pounds in each front pouch was used. I really saw no benefit except when walking on level terrain, and even then over and around blowdowns was still a b!tch.

No the weight did not disappear. My ankles, knees and hips were still forced to carry the entire load, and, the extra for the front pouches. Up mountains, over rocky trails, and through wet, swampy areas, I was wishing for my standard pack. I went so far as to removing the front pouches and putting them in my pack to prevent the sway they caused when leaping from one rock to another. They did work well as brush blockers to keep from slapping me in the chest and face. Anyway. For the extra weight, they were simply not worth it. I even modified the design to incorporate a piece of arrow shaft as a stay in an effort to remove the delayed sway.. But, this made them very tight against my chest and interfered with breathing. On a final note, I would add that more weight ends up on your shoulders than a normal backpack, regardless of the stays. A better hip belt on a standard pack works just as well, with less pack sway.

Note that every stride will produce some sway (ie side to side motion.) This only wastes energy unless you are turning a sharp corner, but otherwise is basically wasted energy. Most people don’ty even register it when walking, with a standard pack somewhat due to inertia. With front pouches, the sway is distributed over a longer period of time and is quite noticeable. This effects your gait in odd ways, usually making you plant your feet a little further out from your center line, but this is compensating.

[nunatak]

Thomas, 45° load lifters might be the ideal, but I just can’t do it. 15-20° is the absolute max for me, even on a pack like this that clearly can haul upwards of 40 lbs.

At 45°, on my 22″+ torso, the pack becomes to too tall, too top heavy and very disjointed when leaning and scrambling. All deal breakers. And to keep the pack at 3000 cu.in I would have to limit the girth, and then fitting a BV450 inside low becomes a problem.

I love a mid to low center of gravity with the top of the pack at or very slightly above C7 level. Besides, any hint of my head/hat/hood touching the pack drives me bonkers.

At 15-20° the load lifters play a smaller role. Still needed on a pack this size? Probably not. When I give up thoughts of marketing it, the load lifters will likely go away, with the shoulder straps traveling a few degrees above horizontal from my body to the pack’s frame tops. Edit: I thought about having ‘load tighteners’ running to the same anchor as the straps, and then not have foam in the last couple of inches of the straps to make them compress easily when tensioning the load tighteners.

 

[Geoff Caplan]

James –

I think we’ve had this discussion before.

I am talking about the Aarn implementation of the front pockets.

I’m not clear how you implemented yours, but if they were causing sway this is emphatically not something you experience with the Aarn. This has been shown in the lab, where the bodypack system improved balance, and in my experience this very much translates into the field. It’s one of the big selling points, and the packs are notably stable on rough ground. Having all the weight hanging off your back is objectively less stable – because with the Aarn system your load is carried closer to your center of mass.

Again, if the front pockets put more weight on your shoulders, this is emphatically not the case with Aarn’s implementation. That’s why it’s so popular with people who suffer from serious back and shoulder problems. With a properly tuned Aarn pack you have literally zero weight on the shoulders – with some rigs you could literally take the shoulder straps off and the system would work fine.

Clearly, your implementation didn’t work well for you, but it does not reflect on the Aarn system. Everything on the Aarn is designed to work as an integrated whole, and I really don’t see how you could implement your own version without extensive practical experience of the original product so you understand how it works.

I don’t want to highjack the thread with an Aarn debate, but I don’t want misleading statements to pass unchallenged in case they put people off from trying an excellent and innovative product.

Jan –

You have highlighted my main area of indecision about my projected design. To achieve the classic 45% you really do have to take the frame high, and for medium loads in the 40lb range this seems like a bad tradeoff, for the reasons you outline.

If I understand you right, you’re proposing that the shoulder straps run from the top of the stays at a slight downward angle to the top of the shoulders? I’ve never used a pack that didn’t wrap the shoulders from beneath. How do you find that this arrangement carries with a 30-40lb load, provided the hip-belt is well implemented? Does it not pull the shoulders backwards in an uncomfortable way?

[Paul McLaughlin]

Regarding aluminum alloys – I have been using 6061 stays for about 35 years in packs of my own make. I have had good luck with 1/8″ x 1/2″ for loads up to around 50 lbs, and 1/8″ x 5/16″ for loads up to about 30 lbs. I had a Marmot pack many years ago (no longer made, I think it was actually made for them by Dana), that had a single, 1/8″ x 1″ stay and that handled 50 lbs loads just fine. I have never experienced a stay deforming under use. I think if you went with 1/8″ x 3/4″ 6061 you’d be good for something like a 75 lb load.

I suppose, in theory, you could save weight by using a 7075 alloy in a smaller size. But the weight savings would be pretty small – if you can find material in the size you want. A pair of the 1/8″x 1/2″ 6061 stays, s4″ long, is about 4 1/2 oz.. And the 6061 is easier to shape just right.

Way back in the day I worked in mountain shops and sold Gregory packs. At the time, they offered graphite (carbon) stays as an option. But you had to buy the pack, get the aluminum stays bent the way you liked them, trace the curve and send that to Gregory, and they would make the graphite stays to match. f you didn’t like the way the graphite stays felt, too bad, not their problem. all they promised was that the graphite stays would match the curve of the aluminum ones you sent. I never heard of anyone doing it. but I did handle some sample graphite stays – mighty light! If you were making your own you could go that route but I expect the layup would be a royal PITA – and again, no possibility of adjusting them after the fact.

[Paul McLaughlin]

On the lifter angles:

(by the way, I hate the name load lifter straps – yes, if properly configured and used they can “lift” some load off of the very top of your shoulder, but that isn’t really their purpose in my mind). Let us review the purpose. what you want is to be able to have a line of tension that goes from the bottom of the shoulder strap to the top attachment point of the lifter so that if your frame is up to transferring wight to the hipbelt effectively, you can have all the weight on the hips and the shoulder straps are just holding the pack snug against the body. In practice I don’t think most people use them quite this way, as most of us don’t seem to want all the weight on the hips, we want some on the shoulders if only as a way to enhance stability. Dan Mchale explains some of this in his discussion of his bypass system, which I think is more complex (and thus heavier) than it really needs to be, but is simpler for a lot of people to understand and adjust properly than shoulder straps with lifter – that may be part of why he likes it. But they key here as it relates to angles is that unless the strap goes uphill from the top of the shoulder you can’t get that all the weight on the hips option without a lot of swaying out of control. And you can, as Dave Chenault likes to do, leave off the lifter and just run the shoulder straps uphill off the top of the shoulder. But I don’t like that, as I find it gives me less adjustability to suit conditions, from skiing to scrambling to trail walking and as the pack weight changes during the course of a long trip. As to specific angles, I think there is a fairly wide range that works, probably from 10 to 45 degrees, and at 45 degrees your frame has to be pretty stiff to make that work or you’ll end up pulling the top of the stays too close to your head.

Back in the day, we sold frame packs fit so that the straps went slightly uphill off the shoulder, I’m going to say we aimed for about 10 degrees or so, and that worked pretty well. But remember that with those old frames, you had tremendous rigidity, and more or less load did not change the distance from hipbelt to shoulder strap at all, where an internally framed pack is subject to some flexibility that way, and so more adjustability is useful – hence the lifters work better than the simple shoulder strap running uphill, and can handle more variables. The frame packs were really always intended mainly for trail walking – and they were damn good for that, if heavier than they needed to be.

[Geoff Caplan]

Paul –

Really useful info, both on the stays and on the load lifters. The voice of genuine experience.

From what you’re saying being dogmatic about the 45% is more trouble than it’s worth until you get into the really heavy loads. I think I’ll start my prototyping with shoulder straps that wrap from below and a slight angle up with the load-lifters.

As you say, it’s a misleading name, though I can’t think of anything better off-hand. Any suggestions? Shoulder stabilisers?

[Thomas H]

Jan, Paul, appreciate the experience and insight.

I have honestly pretty much only owned packs with less than 45 load lifters and was focusing on the 45 as an ideal solution. In my current prototype as I’m loading it up with 55 lbs I really notice when the frame isn’t high enough, especially as I was fiddling with hip belt design trying to prevent it from sliding down. So anecdotally having a frame at like ~27” height was noticeably better at taking the weight off my shoulders than a 25” especially as the hip belt slid down my hips over the course of a hike/walk.

I think there will be massively diminishing returns as the weight your carrying trends to the 40s and 30s. At this point the freedom of neck movement would be much more desirable as the load lifters aren’t really that useful.

I definitely think that McHale style removable “bayonet” system is a great idea for expedition use, where one can transition from bringing loads to base camp to scrambling and climbing with a lighter pack.

I will definitely be looking at coming up with a system like this, maybe externally, where the frame only goes to shoulder strap height, then two extensions slot in or bolt on. Another thing I find helpful for neck/headroom is not attaching the bag to the top of the stays directly, so a heavy dense load would stop at shoulder height and there would be a gap between the load lifters to lean your head back. The tops of the stays would effectively be 5+ inches above everything else unless the bag was really full then there would be webbing running down to the pack(tensioned with a ladder lock and the load lifters attached to this same webbing. This also is great for Adjustable frame heights by swapping out stays of different lengths or thicknesses.

I had originally made this prototype with two 6061(I think) hardware store flat stays that were 1/8 x 3/4”. I found them to be much too flimsy and the load lifters would bend them all the way to my head because offloading weight from my shoulders. It is possible that they weren’t 6061 but some softer grade. I somewhat successfully countered this by tensioning/supporting the tops of the stays by anchoring them backwards towards the 55lb load I had in the bag.  However this was not an acceptable solution in all scenarios  Cilo Gear kind of does this with an interior compression strap, however they use a single 7075(I think) say and a fiberglass frame sheet.

Geoff,

perhaps you should make something like I described so you could test out different frame heights till you get that balance you like. And like I mentioned earlier, keep the shoulder strap attachment simple so you can seam rip it and reattach it for testing purposes

 

[Geoff Caplan]

A quick supplement to Paul’s excellent guide on aluminium flat bar.

Seems that in recent years 6082T6 has been replacing 6061T6 because it gives 10 -15% additional tensile strength, while retaining the other properties of the 6 series.

This is hardly a game-changer, but does seem to make it the preferred material for struts if 7075 is too hard to source. As Paul says, experience suggests that it’s a good enough solution at the cost of a slight weight penalty vs the 7075.

Local maker Aguille Alpine have confirmed to me that they are using 6082 for their expedition and polar packs. Some of these are monsters rated to handle over 40k/90lbs and they are used in very serious environments. They surely wouldn’t be risking their reputation on a stay that didn’t work as advertised?

The 6082 seems to be widely available from mail-order suppliers in the US and the UK.

[Geoff Caplan]

Thomas –

I like your idea of the stays extending beyond the top of the pack when you are heavily loaded, enabling the 45 degree lifter without constricting head movement. Makes a lot of sense. Personally I’d prefer a wider main compartment to something so high that it starts to get in the way and compromise balance.

As for my own pack, the education I’ve had here from you guys has focused me in on what I want to do.

Given that I have precisely 0% of Dan’s skill in customising fit, I’m going to make something inspired by the Unaweep/BigUgly and have everything radically modular and customisable.

Seems to me that you don’t really know what you want until you’ve lugged a load for two or three weeks on the trail and begin to understand where you’re getting beaten up.

Something customisable should enable me to discover what I need for a truly comfortable and efficient carry. Plus it would be a nice USP if I decide to make a few for sale as a hobby.

So, this is more a brainstorm for my own benefit, but I’ll post it in case anyone might be kind enough to read it through and perhaps save me from any egregious stupidity:

• U shaped frame with customisable height (bolt-on extenders?) that slots into tape channels on the back of the main bag
• Frame as high as I can take it without constricting head movement. This will enable a 50l main bag that will still be narrow enough for me to stow my front pockets away as side-pockets without having too wide a profile.
• Full-wrap hip-belt with customisable length (I think I see a simple way to do that – not sure why no-one offers this)
• Width of the attachment of the belt to the frame will be customisable so I can optimise the wrap
• Height of the belt attachment also customisable, on the Unaweep model using grommets or ladder-locks
• Belt will be optionally free-hanging, partially constrained (to keep it clean when the pack is on the ground) or fully constrained – to see which works best
•  Fixings for optional belt stabilising straps to see if they are needed.
• Belt will have separate top and bottom waist tighteners
• Belt will have holsters for the Aarn style front pockets with fine sideways adjustment enabling precise positioning of the pockets to optimise the view of the feet and the freedom of arm movement.
• Optional lumbar pad of customisable thickness
• Optional McHale style back pad of customisable thickness
• Top-to-bottom compression through a chain comprising a compression panel attached to bottom of frame to secure the bag, running to bottom of modular clip-on pocket to Y strap securing roll-top.
• Main bag will have a “roll bottom” easily accessible by unclipping the bottom compression panel. This will enable quick access to my down bag for airing during rests on the trail. In the kind of places I walk, opportunities to air your bag can be rare and you have to be able to grab them when you can. This arrangement should be much more failsafe than a zip, and much more practical than fully unpacking and repacking a top loader.
• Bag will ideally be wide enough to carry a vertical bear can but I haven’t done the math yet…
• Bag will have a McHale style daisy-chain and seam-loops for modular attachments.
• All straps and pockets will be modular using the attachment system. Nothing will be sewn into the seams.
• Top of shoulder straps will be attached to a cross-stay with fine vertical adjustment, that will also help prevent barrelling of the main bag
• I’ll try the Zoro idea of a few inches of tape at the top of the shoulder straps to allow them to find their own angle. If that doesn’t work, attach them with two adjustable straps that allows the angle to be customised.
• Bottom of the shoulder straps attached directly to the bottom corners of the frame.
• Daisy chain on shoulder straps for modular attachments
• Stabiliser straps from top of shoulder straps to top of frame. Make them adjustable from the front rather than reaching behind the shoulder if at all possible. I think I agree with Paul that the McHale bypass strap is overkill for a (hopefully) skilled user and a medium load pack.

Wow – who would have thought attaching a bag to a body could be so complicated? Yet every individual element should be pretty simple, lightweight and failsafe. There’s very little there that isn’t already working on a current well-regarded pack.

With literally thousands of potential configurations, I should surely find a way to get the thing to fit me well?

Maybe it will end up as a test mule and the MKII will be hard-sewn to my preferred setup.

But I do know a very experienced hiker who swears by changing your setup on a regular basis to avoid repetitive strain injury on long walks. He’s walked tens of thousands of miles with no serious injury, so it’s probably good advice. In which case the adjustability would be a permanent feature…

As I say, if anyone can bear to read this screed, feedback would be very welcome as this is my first effort at a pack and it’s proving more challenging (and more fun) than I’d ever imagined.

[Doug Coe]

I’d love to see the results, though I have to say, it sounds very complicated! I’m just trying to make a pack that fits my measurements and has non-adjustable shoulder straps and a floating, full-wrap hipbelt.

But we each have our own “what’s important to me” items. That’s what makes MYOG so interesting and fun.

[Geoff Caplan]

Had a chance to visit Aguille Alpine, the well established Lakeland pack maker.

Their larger packs are using a couple of 1″ x 1/8″ 6082 stays, so they’re not cutting  any corners! They are pretty beefy when used internally, but I suspect they would be too springy if used well above the shoulder as Thomas plans to do to get his 45 degree stabiliser straps – so the investment in the 7075 should pay off for that.

They say they are simply using standard Karrimat-grade Evazote for padding their straps and belts. I was wondering if the guy had that right – it felt a  bit more dense. But they said in the early days 40 years ago they literally cut up Karrimats and it worked just fine for them.

A bit like Dan they are great believers in making packs that last. They mainly use 1000d Cordura pack cloth. They argue that even a large pack is only using 1.4 sq meters of fabric, and the few grams you save with a lighter material is a false economy. They hate the idea of disposable packs and build products designed to last decades…

[Thomas H]

Geoff,

I can’t figure out how to directly quote you, so I copied and pasted and my responses are bold.

U shaped frame with customisable height (bolt-on extenders?) that slots into tape channels on the back of the main bag

By U shaped you mean, 3 pieces bolted together?

Frame as high as I can take it without constricting head movement. This will enable a 50l main bag that will still be narrow enough for me to stow my front pockets away as side-pockets without having too wide a profile.

Don’t forget that you can still raise it above your shoulder height quite a bit before it will restrict head movement.Full-wrap hip-belt with customisable length (I think I see a simple way to do that – not sure why no-one offers this)

I would watch out about this. Many pack makers have velco to adjust length of the hip belt, but I think this would have undesirable effects of stiffness, wrap, etc. But I’m curious how you’re looking to do it.
Width of the attachment of the belt to the frame will be customisable so I can optimise the wrap

You could do this easily with just 4 loops of webbing/grommets, 2 of them ~4” apart, and two of them 6” apart on the bottom of the belt.
Height of the belt attachment also customisable, on the Unaweep model using grommets or ladder-locks

Good idea. Remember this effects frame height and torso length.
Belt will be optionally free-hanging, partially constrained (to keep it clean when the pack is on the ground) or fully constrained – to see which works best

Fixings for optional belt stabilising straps to see if they are needed.

Belt will have separate top and bottom waist tighteners

Belt will have holsters for the Aarn style front pockets with fine sideways adjustment enabling precise positioning of the pockets to optimise the view of the feet and the freedom of arm movement.

I’m having difficulty picturing how this will work. Will it involve stays?
Optional lumbar pad of customisable thickness

Good idea.
Optional McHale style back pad of customisable thickness

I don’t like McHale’s use of Velcro on the back panel, but I was intending on having it removable like a sit pad that you can stuff different thicknesses of foam into. Even simpler you could just use some shock cord to hold foam in place, this would be much lighter.
Top-to-bottom compression through a chain comprising a compression panel attached to bottom of frame to secure the bag, running to bottom of modular clip-on pocket to Y strap securing roll-top.

Love this idea, but make the compression panel removable/replaceable.
Main bag will have a “roll bottom” easily accessible by unclipping the bottom compression panel. This will enable quick access to my down bag for airing during rests on the trail. In the kind of places I walk, opportunities to air your bag can be rare and you have to be able to grab them when you can. This arrangement should be much more failsafe than a zip, and much more practical than fully unpacking and repacking a top loader.

Great idea. You could also look at having two seperate bags, like a sleeping kit roll top one at the bottom and another at the top. Could be dry bags you already own as well. This would work well with a bear can too.
Bag will ideally be wide enough to carry a vertical bear can but I haven’t done the math yet…
Bag will have a McHale style daisy-chain and seam-loops for modular attachments.
All straps and pockets will be modular using the attachment system. Nothing will be sewn into the seams.

Love it. I do think that McHale goes a bit crazy, such as the removable pocket system that looks like it will be very bad for snags. Gussetted pockets out of durable materials can be made almost completely flat with a compression strap if you want it streamlined for bush-bashing or climbing.
Top of shoulder straps will be attached to a cross-stay with fine vertical adjustment, that will also help prevent barrelling of the main bag

Good idea. You could just drill various holes in the verticals to give you 1/2” adjustments.
I’ll try the Zoro idea of a few inches of tape at the top of the shoulder straps to allow them to find their own angle. If that doesn’t work, attach them with two adjustable straps that allows the angle to be customised.

Just put ladder locks and a strap on the top end of your shoulder straps then you can easily tighten them onto the frame or lengthen them. Also think about methods to keep the shoulder straps at specific distances apart horizontally.
Bottom of the shoulder straps attached directly to the bottom corners of the frame.
Daisy chain on shoulder straps for modular attachments
Stabiliser straps from top of shoulder straps to top of frame. Make them adjustable from the front rather than reaching behind the shoulder if at all possible. I think I agree with Paul that the McHale bypass strap is overkill for a (hopefully) skilled user and a medium load pack.

I’m definitely going to try out that bypass system with 3/4” webbing, but I agree it adds a fair amount of weight, and I already cringe when I have to cut up such long pieces of my nice nylon webbing just for a test. 

 

Good to hear about them using the karrimor evazote, which is likely the 45kg stuff, like the one from MEC. I’m still debating about buying the .5 or 1.5cm mats and whether to buy a 1/8” very dense one as well to create stiffness.

That being said, I have no idea if those packs are good at carrying weight.

Totally agree that the design of the packs makes a much larger impact on weight than the fabric choice. Most commercial companies have weirdly complex designs and often cut corners on materials. Osprey for example, does have some lighter packs, but they are ridiculously complicated and use cheap materials that won’t last.

[Geoff Caplan]

Thomas –

Extremely useful feedback – I’m seriously grateful!

I like the Aguille design philosophy: “Everything you need and nothing you don’t“.

Unlike Dan, though – they decide what you need! There isn’t much scope for customisation apart from a basic daisy chain.

We actually discussed the Osprey approach and agreed that they are way over-designed, with so many features that you don’t really need and that simply add weight and potential points of failure.

As they point out, if you’re taking a pack into remote areas, reliability is critical. Their stuff goes to places like K2 and Antarctica, so failure is unthinkable…

The bigger demo packs in the workshop didn’t have much weight in them but as far as I could tell they would carry fairly well, given that they aren’t very adjustable. They didn’t have that uncomfortable rigid feel that I find you get with frame-sheet or trampoline packs. The backs are stiffened by dual stays and a layer of soft foam, so they still flex a bit from side-to-side with your stride. They don’t seem to need a cross-strut, but they are using a winged belt with lumbar pad and stabiliser strap. The belt wraps well enough but doesn’t feel as good as a full wrap would and I suspect it would be more prone to slipping.

I’m not sure I got the whole story about belts though, because I’ve since noticed that the expedition packs have a “bi-laminate” construction. I didn’t ask what the second layer was. It’s foam, though, rather than plastic sheet. It held its shape well, but was nothing approaching as stiff as the big Osprey and and Gregory packs I tried recently, where the plastic stiffener would literally snap into place around your hips. I much preferred their approach to that.

My main area of confusion is how to implement the height adjustment for the shoulder straps. As you say, this will interact with the height of the belt attachment, so has to cover a reasonable range of movement.

The most popular commercial solution seems to be great slabs of velcro under a sleeve. Not attractive to me.

The bigger Aguille packs have  a yoke with a molle-like webbing adjustment system – a lot of makers seem to go with this. On the plus side it’s low-profile, so won’t damage clothing, and it’s simple and totally failsafe.  I guess that’s why the military like it. The adjustment is only in 1″ increments, but I’m thinking that this is good enough? It does seem a bit heavy though, with lots of webbing you’re not going to be using at any specific height. If you’re using a burly fabric and foam to stiffen the back of the pack, I don’t think you need a cross stay, which is a saving. My old Lowe in 1000d Cordura and some foam in a sleeve doesn’t have any kind of cross-stay and barrelling has never been an issue even overloaded with climbing gear. I just squeeze it flat with my knee after packing and that does the trick for the day. Mind you, I’ve never had to carry a bear can…

My Aarn has a single daisy chain adjustment in stiff 1″ webbing, and a yoke which attaches with a keeper-clip rather than the molle idea. The clip is metal and not well sleeved, and trashed some expensive clothing before I noticed – something to watch for. They run a thin aluminium strut vertically in a pocket behind the daisy chain to give it structure, which is an interesting solution that works well. But they don’t have foam stiffening and they’re just using a light Robic fabric which is why this is needed, I think.

As you say, an obvious solution is simply to drill holes in the frame and bolt a cross strut to that. But I suspect that would make the top of the frame too rigid to flex from side to side with the stride, something that the Seek Outside folks seem to regard as important. So you’d potentially lose the benefits of the U-shaped frame. On their Revo frame, the anti-barrelling struts slot into channels in the fabric back panel and aren’t attached directly to the frame, presumably to allow this freedom of movement. So you would have to dream up some kind of attachment that was stiff vertically but flexible from side to side. Not sure that’s very practical?

I find the height adjustment on their Revo frame  a bit baffling – it’s not very clear on their videos. It does involve running 1″ webbing from the top to the bottom and back again, which must be heavy. It seems to rely on the stiffness of their tubular frame, while the flat-bar Bug Ugly style frame might not be strong enough? Maybe overkill for us?

So this is an unsolved problem. The Aarn solution is probably the lightest, but it does involve faffing with a yoke instead of simpler separate straps. Suggestions most welcome!

[Geoff Caplan]

Oops…

[Geoff Caplan]

By the way, there’s a new pack fabric in town from Challenge.

67% Ultra PE blended with 33% recycled polyester 

200D face, 0.5 mil matte recycled film backing

Available from Rockywoods as” DiamondHide”.

According to Dan Durston it’s now the clear winner for a premium pack.

Horribly expensive, but you only need 1.5 meters so worth thinking about. Consensus seems to be that you’d get away with the 200d for the body and the 400 or 800 for the base, but no-one seems to actually have the stuff.

Some discussion here:

https://www.trek-lite.com/index.php?threads/move-over-dcf-and-xpac-theres-a-new-backpack-material-sheriff-in-town.9234/

[nunatak]

I have a commercially made pack  with this or something similar; mine is the 400 and 800 variety and white. It’s the Pa’lante Desert Pack.

The weave is super coarse, more so than Cordura, and the 800 is very stiff.

I would like to see the 200 since the other two are so overkill for most applications besides the bottom area.

Might be hard to cut.

[Thomas H]

That fabric is looking quite impressive, but at $15 a foot I would rather wait for others to test it long term. I see Rockywoods has a black and blue in 400/800. It will be nice when more colours are available.

Geoff,

I don’t think thin aluminum flat bar bolted together will be very stiff from rotational forces, I definitely think a rectangle of 4 pieces bolted together will twist a very reasonable amount not unlike the Seek Outside inverted U.

Take a look at this Seek Outside YouTube video, it demonstrates quite well how their shoulder yoke adjusts vertically.

https://youtu.be/BbQjdhp3uwQ

You cannot see it, but apparently there are hidden metal loop locs or similar sewn in behind the back pack that the webbing runs down to before returning upwards.

Here is another resource for some ideas:

https://sectionhiker.com/adjustable-frame-backpacks/

Zpacks has a pretty neat adjustment system too:

You should start doing some diagrams and drawings while those ideas are fresh in your mind Geoff. I’d love to critique them and provide some advise while you’re designing and building it.

Unfortunately I am away from home with work until mid-august, so I cannot test or fiddle with any of these ideas currently…otherwise I would’ve already been posting some progress shots! However I do have more time for planning, research and posting on BPL.

 

 

[Geoff Caplan]

Thomas –

Priceless info on the shoulder adjustment – you really are expert on this stuff!

You’re very likely right that the cross-strut is workable in terms of freedom of movement. And it’s certainly the most straightforward solution, so that’s the first thing I’ll try.

Plus, I’ve been following the Ursack thread, and it’s clear that hard-sided cans are going to be increasingly required across the US and Canada. So a cross-strut would  also help with a design intended to enable a comfortable carry with the can inside the bag.

Time to get going with some prototyping – I’ll order the bar today. I’ve been rather stuck with this project, but the ideas so generously shared by you folks on this thread have given me the confidence I might be able to pull it off…

Just in passing, that Seek Outside fitting video drives home the reason why I’m keen to try and improve the convenience of the Aarn bodypack design. Whenever Aarn comes up here, there are those who argue that their packs are so good that they somehow defy the laws of physics and don’t experience any forward lean. Or that the lean is not significant.

The model in the video is carrying 50 lbs in one of the best packs in the business, and I was struck by the angle of his lean. If you were to force someone to adopt this pose for 12 hours at a time you’d be indicted for torture! It’s not good for comfort, for efficiency or for balance. And it must surely increase the risk of strain injury on a long hike. With a properly dialled in bodypack, this problem is entirely solved. There are some minor downsides, for sure, but to me it’s the right trade-off, especially if I can mitigate the main irritation as discussed earlier.

 

[Thomas H]

Geoff,

Here area few more ideas.

This gentlemen has copied Zpacks for much of this very beautiful, but unnecessarily complicated pack. Some changes he made to the Zpacks formula also seem like downgrades to me, but there are some great construction shots. I would probably stay away from the G-hook connections he has used as well, as they may pop out or fail.

https://imgur.com/gallery/Nj8rvGb

Ever heard of Chicago screws? I will be using these to assemble the frame of my upcoming pack and it would make height adjustment pretty quick for those shoulder straps or for adding/removing frame height extensions. Once you are more set on the positioning you could put a drop of glue in the screw or swap to bolts with nylon locking nuts.

[Author]

Posts