Honestly...? I hate them all, think they add unneeded weight and faf, and are just a gimmick for the rambling crowd.
I'm not generally a fan.
On a big pack they're a complete waste of time because if you've done it right then the pack will tend to rotate back away from the wearer with the lumbar pad/hip-belt as the pivot point, so above the lumbar pad the pack has no need to touch the back at all except at the very top where the shoulder straps come over. You should be able to pull the pack closer in for balance or let it hang a little back for more ventilation, all controlled from the shoulder straps and take-offs there. This is the case on my 80s Lowe: I can scratch my back easily most of the time and if I pull it in close the balance is excellent, and none of this requires a suspnded back.
Day-packs that'll be used for climbing or running don't benefit as the balance is worse and some flavour of frame will restrict freedom of movement.
So there's a bit of a market for day-packs for a dander but even there I go with Cathy's take.
Jay parsons 3 wrote (see)
Clearly some people think it is as you folk keep making (and presumably selling!) them, but its just not a real problem for me either.
Actually I already get plenty of airflow even with 'basic' stuff like a classic 32 - just anchor at the hips and relax the shoulder straps a bit. Entirely possible with the typical sort of load in a day pack.
I'll join the consensus so far. I'll take the stability, comfort, and sensible shape for packing, of a simple, close fitting pack every time. I'll live with having a sweaty back at times and rely on sensible choice of clothing to deal with it.
I've never yet found a "trampoline" style airgap pack to fir comfortably. As Pete says, larger packs can be made to create some form of airgap by adjusting the straps and tensioners, especially if the back padding has been designed sparingly and only put in the places where it's needed. Also any "climbing style" pack with an internal framesheet incorporating malleable alloy stays can generally be bent away from the back a little if desired - Karrimor in the 80s were one of the first to do it with the Fformat system in their Alpiniste packs (Iexpect Berghaus had something similar?). Mike Parsons re-used the idea with OMMs Platformat, but I've also had the same capability on packs from POD, Lowe Alpine and Aarn.
"What about the benefits of more air circulations around the back? surely this is a good thing?"
Well it depends. In warm conditions, possibly, although none of us so far seem to find it so good that we must have it. In winter that air circulation can amount to a cold draft that isn't a good thing, providing unwanted cooling, or places for spindrift to accumulate (and then possibly melt from your body heat, not so good if you're not encased in a waterproof shell). I can think of numerous times when I've been glad of the incidental insulation properties of a close fitting pack against my back.
What about the benefits of more air circulations around the back? surely this is a good thing?
As above, on a pack with a hip-belt you'll get it anyway, or at least you will if the back isn't covered in foam.
I've never been convinced on lighter packs that slots cut in to foam backs make any sort of tangible difference. Not even printing little arrows on to show the air which way to go seems to help... Structured foam with a mesh cover seems to make a little difference, judging mainly from the seat on my recumbent bike. We're in the realm of "very sweaty back" rather than" really amazingly sweaty back" for some idea of relative effect.
I've tried (all) the Osprey Atmos and Stratos models in the shop when they were launched, but found them all very uncomfortable so didn't buy them. It's possible that there is a model somewhere that I'd find comfortable but I've not looked any further.
As for the reduced space, I wouldn't say it's first impressions, more a case of lots of user comments to that effect in blog reviews and on forums such as this. And maybe it's not accurately "reduced space' in measured capacity terms, but an awkwardness in packing rigidly-shaped items into the concavely restricted pack shape.
I use a suspension type pack.
1st was ex-military (green chromed leather and rubberised canvas - weight 3.5kgs). The pack had a very substantial base which supported two curved sprung ali strips, these in turn lead up to the mounting point for the shoulder straps - the curved strips kept the pack away from contact with my back. Basic trampoline across the hips.
2nd Karrimor, almost an exact copy of the military example but made with nylon and cordura, it had a rudimentary 'trampoline' system across the hips and up to the shoulders. Excellent pack and I would very much like another.
3rd Berghaus 'freeflow' system. Lovely looking pack with nice clean lines and a full 'trampoline' system.
At present I use Osprey Atmos & Exos packs mostly for long distance walks in the lowland UK, my walks last between 1 & 2 weeks and I tend to travel out between May & October.
Hope this helps you Amy.
Amy Spencer 2 wrote (see)
Have you all tried this type of back system in something like a Berghaus Freeflow / Lowe Centro / Osprey Exos, Stratos / Detuer Spectro or is it first impressions of the reduced space/overbalancing that have put everyone off?
Well, a dissenting voice here. I've got both the Osprey Exos 46 and the 58 as well as an Osprey Atmos 35 and I like them. I've also got a Gregory Z55.
I do agree that there is a loss of stability with an airflow system. However, I don't think that's much of an issue when backpacking and I'm prepared to put up with it for the benefit of a less sweaty (sometimes much less sweaty) back. I sweat a lot and if you're bimbling along in the pissing rain for hours at a time in waterproofs (surely not in the UK) it does make a big difference to comfort.
In terms of whose system is best, I would say Gregory's. The gap is less pronounced than Osprey's, making the bag easier to pack. The Gregory is also much more stable than Osprey. I had to cross a collapsed wall once wearing the Z55 and it was as stable as a daypack. In fact, if Gregory could get their rucksack weights down to the same level as Osprey, I would favour them.
To be fair, I haven't much experience of framed packs without air gaps. I just can't get on with frameless packs at all, not even as a daypack. The only frameless bag I own is a Lowe Alpine urban 20L daypack for pottering around town.
Stashing gear in colder, dry conditions perhaps?
Iirc the Osprey Atmos packs allowed you to hang your hydration bladder in the airgap behind the trampoline mesh.
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