Question about the curve in the Zpacks Arc Blast

Oh, nevermind. I figured it out. The pack is black and has so many things to pull and tighten but they are also black so I couldn’t see how they all work. I had to find a brighter room where I could see everything.

Just be aware that it takes a bit of experimenting to get the fit how you want it – kind of frustrating at first but great when you dial it in!

Note that you can slide the mesh panel up and down by either tensioning the arc from the bottom or from the top. It’s worth experimenting with the positioning of the mesh panel (both higher and lower) to feel the difference and figure out the most comfortable fit

Also know that there are two schools of thought on another subject… WHEN to tension the arc, before or after loading. I have had an ArcBlast for ~1.5 yr and tend to tension after loading. Honestly, not sure why I’ve done it that way. But I never seem to achieve anywhere close to the same arc you see in the pics. Maybe one of these days I’ll start trying it before instead.

Overall, I LOVE this pack though :) hope you do too!

I’ve had my Arc Zip since they were introduced about 5 years ago.  If I don’t arc the stays while the pack is empty then I don’t seem to be able to do anything.  While the pack is empty it’s really easy – I just push down on the stays and lock them into place.  I always do release the tension at night so they stay straight.

Purchased my Arc Haul when they first came out and echo what David and Kevin said. There is a lot to be gained by playing with the multitude of adjustment options…adjust, load, test, unload, adjust etc. until you get it right.  It’s worth the time. Also agree that moving the mesh panel up or down can make a big difference in comfort…where it works best is entirely dependent on your body. Once I settled on an optimal mesh position and arc, I have never touched the adjustment…for me its a set-and-forget thing. Lastly, I found the optional lumbar pad to be worth every cent and ounce. My pack carries “practically unnoticed” all day long :)

It’s easier to load your pack if you arc it after loading, but perhaps that changes the effectiveness of the arc as others mentioned above. Also, how you load it and how much (volume) you put in it affects the air gap created by the arc.

I haven’t had mine very long, so I’m still experimenting for the ideal setup. After getting a drenched with sweat back using another pack on a cool day, I’m hoping this arc will help in that regard. I took off that other pack and my back was freezing!

You have to un-arc it when you’re not using it? I better go un-arc it then.

I didn’t mind it being straight out in the field. It still get the weight onto my hips really well. And being a winter trip, the pack against my back kept me warm.

As for the position of the mesh, I don’t think that matters so much with a size small pack. There’s only an inch or so you can move it up or down. Not enough to significantly change the position of it against my back. It covers most of my back.

I “un-arc” when storing it at home but not each night on the trail.

While flexing the arc after packing might be ideal in theory, try that when carrying a bear canister…

While flexing the arc after packing might be ideal in theory, try that when carrying a bear canister…

No question, a rigid item like that would be a problem to flex post-loading.

I think “un-flexing the arc” when the pack is not in use it totally unnecessary, and will make it hard to get that perfect dialed-in setup each time you use it.  I bought the Arc Haul in April 2015, dialed it in and haven’t touched the setup since.  And yes, it is *very slightly* harder to pack when it is flexed, but honestly, I have never thought it a problem.  HYOH.

There is a how to fit your pack video on Zpacks YouTube page. It covers how much arc to put into the pack.

I thought I had read that you’re supposed to release the tension daily, but that was when I first bought the pack years ago and I could easily be making it up.  I’ve hiked a number of 10-12 mile days without any arc at all because I remembered to “unarc” it when I got into camp (usually when I’m hanging my pack at night) but then forgot to arc it before loading it in the morning and couldn’t put the arc in while the pack was stuffed.  I’ll try leaving the arc in the entire trip the next time I use it.  Thanks for the thread.

From Zpacks site,

”Our patented ‘Flexed Arc’ frame creates an air gap against your back for a super comfortable fit. The air space keeps your back cool and also provides a buffer from any lumpy items in your pack. The curve of the frame is adjustable for optimal air flow and fit. No extra padding necessary.”

“The frame is curved to allow air flow and keep your back cushioned from the pack’s contents. You can adjust the curve by tensioning the mesh back panel. The recommended arch is about 2.5″ (6 cm).”

No mention of relieving tension when not in use.