The Arc Blast is an ultralight backpack featuring Cuben Fiber construction as well as a tensionable, arc-shaped carbon fiber frame manufactured by ZPacks, a smaller gear manufacturer located in Florida. ZPacks have been steadily growing in reputation and popularity among lightweight backpackers due to their line of shelters, sleeping bags/quilts, clothing, and of course backpacks. I have been hiking with their Arc Blast for a little over a year now and these are my thoughts about it.
Specs at a Glance
All specs as claimed unless *noted otherwise…
- Volume: 60 L (~47 L in the main compartment)
- Weight: 17 oz
- Max Load: 30 lbs
- Fits torso: 18-24″ depending on size
- Pockets: (3) 2 side, 1 front
- Frame: External, carbon fiber
- Closure: Roll-top
- Primary Material: 2.92 oz Cuben Fiber Hybrid
- MSRP: $289 (add-on’s available for additional $)
Having previously owned several ultralight backpacks of either the frameless or semi-rigid frame (read: some sort of minimal stays) style I was pretty accustomed as to what to expect from the carrying capacity and comfort of such packs, and I figured the Arc Blast would be predictable in that regard. After loading it up I decided that it did feel pretty similar in those regards. Compared to frameless packs it’s a huge improvement in comfort and carrying capacity. Compared with packs I’ve owned that utilize a semi-rigid frame (most recently Gossamer Gear’s Gorilla) it was more of an incremental upgrade, mostly due to the superior frame design that ZPacks uses. Notably though the Arc Blast is substantially lighter than other “similar” packs, which is what really sets it apart in the market; it’s amazing that a pack weighing so little can carry so well.
The “arc”, which is the namesake of the pack, is created by pressing downward on the upper horizontal frame member to create a bend in the vertical frame members, then snugging up the line tensioner on the guylines (which connect between the mesh back panel and the frame). Once this is done the arc stays in place. It’s a very simple process and can be made more or less bowed to personal preference.
The Cuben Fiber of the pack is a more durable variation of Cuben that you’d see on a ZPacks shelter. It’s heavier too but add’s a measure of water resistance to the pack and of course it won’t absorb water becoming heavier as it’s worn in the rain. There is quite a bit of stitching though, and several seams, which left me curious how accurate the claim of “highly water resistant” would hold up. Speaking of stitching… after seeing a friend’s Arc Blast with the standard light grey back panel and inner hipbelt, I asked ZPacks if they could use black for those areas, which they agreed to – and it made a world of difference as far as appearance goes. All of the stitching is black so it blends in with the black fabric instead of contrasting against light grey. It seems that there are now several color options with black accents which is a good thing; those weren’t choices when I purchased mine.
The closure of the pack is similar to a dry bag. This is fine when it can be folded down a few times, but when the pack is full it can be tough to get it closed tightly. The seal is made with velcro and doesn’t have a backing strip nor is any of it rubberized, so it’s not really a dry bag seal and it shouldn’t be assumed to be watertight. To be fair, it may be like many ultralight dry-bags on the market, which is to say water resistant for the average user, but not something you’d depend on for hiking in extended periods of rain, stream crossings, or for use on a paddling trip.
The rear pocket is nice and roomy and the side pockets don’t require too much contortion to get to. As far as the volume goes, it’s always important to understand how a manufacturer measures this and ZPacks is very clear about how they do it. The main body of the pack is more like 45 liters (47 liters claimed) which leaves enough head space to fold the top of the pack down. The front pocket is a claimed 8 liters (this feels a little over-stated) and the side pockets amount to a claimed 5 liters total (seems about right). For someone who is carrying lightweight or ultralight gear this pack should provide plenty of space for extended weekend trips up to a week or so depending on how much food and water needs to be carried. Most bear canisters will need to be carried upright (BV450, etc…) inside the pack, smaller canisters may be able to pack horizontal.
I opted to get a few of the extras. Loops for trekking poles, ice axe loops, and the lumbar pad. The lumbar pad is a must for me. It adds comfort and gets the pack just a little further from my back (to aid with ventilation). As far as the extra loops go, they’re all very minimalist and could just as easily be added after the fact using extra cord and parts that most of us probably have in our gear closets, if not go ahead and order them and ZPacks will do attach them for you.
After hauling the Arc Blast all over on trips I concluded that 20 lbs (or less) total weight is the sweet spot for me. At 25 lbs I can feel it on my shoulders a bit. With 30 lbs or more it’s getting into uncomfortable territory. This is always a subjective thing so take it with a grain of salt. To draw a comparison, I feel that it can easily go 5 lbs heavier than my Gorilla without any perceived increase in load. This is mainly due to the design of the frame, which works wonderfully. As far as keeping the pack away from my back, it does to an extent. If the pack is stuffed it’s going to contact my back, but when not trying to push the limits of it’s volume capacity, contact with my back is minimal to none, which is nice… no sweaty back! The pack did prove to only be somewhat (mostly) waterproof. It’s hard to determine points of water ingress, but the pocket stitching appears to be one of them. It took several hours of extended rain to amount to any substantial amount of water getting in.
As for durability, mine has held up well so far in what I would consider typical use for most people. The Cuben has held its own against brush and scrapes with rocks. Some of the stitching looks a bit strained, but nothing has failed or started to come apart. Two friends who were on the PCT last year reported seeing a number of Arc Blasts on the trail, and the report I got is that toward the end of the hike they were still going, but looking a little beat up. Both of those friends started with their own Arc Blast and one swapped packs at some point, the other carried his for 2000 miles before having to leave the trail. Both of their packs are still in good shape. Joe Valesko (owner of ZPacks) has taken his on multiple thru hikes. These packs are not built to last forever, but the proof of their durability is out there. For some people 2000+ miles is one hike, for others it’s years worth of mileage. Factoring in that they weigh only a hair over 1 pound I think “only” getting a couple thousand miles out of one of these is a very decent deal, and getting more than that is a nice bonus.
- Excellent frame design
- Very light for its class
- Durable materials
Not So Much…
- The velcro top is not a favorite of mine. I would almost prefer a cinch closure even though it would be less water resistant.
- Lack of means to secure a bear canister externally.
Famous Last Words
The Arc Blast has been one of the most popular ultralight backpacks on the market since its introduction, and for good reason. The ability to carry 20-25 lbs comfortably while the pack itself is only a pound or so is impressive. The volume doesn’t facilitate use with a bear can, nor is it convenient for winter trips where bulk can be an issue, but it’s a great size/weight ratio for the hiker who is already carrying a conforming lightweight/ultralight kit and heading out for more typical 3-season jaunts. That arc frame is really hard to beat! Hike It. Like It.