Thursday, September 19, 2013

Zpacks Arc Blast Review

I just received my order from Zpacks and I am quite excited. In this day of one click shopping, made in China products and overnight delivery, there is something satisfying about having to wait 6 weeks to receive your order. Rather than being impatient that I had to wait, I enjoyed thinking how nice it was that my order was being crafted just for me, in the United States. It may also be a savvy business strategy because I was told, in the email informing me that my order was going to take some time, that I could feel free to add to the order at any time before shipping.
As my Gossamer Gear Gorilla (2010 version) pack is starting to die from old age and hard use, I have been in the market for a new pack. After narrowing down what I wanted in a pack to a couple of choices, I went over the reviews I could find and decided to try out the Arc Blast.
Zpacks Hexamid with Arc Blast

As the Arc Blast is a new pack introduced this year, I didn’t find that many reviews on it. Therefore, I want to get this review out quickly, so people have more information when making their next backpack choice. This is going to be a rolling review, that is, I will update it periodically as I gain more insight and experience.

First, I should state why I have been interested in this pack:
1.    Lightweight (about 1 lb)
2.    Should be able to handle up to 30 lbs comfortably (it has a frame)
3.    Arc design reduces SBS (sweaty back syndrome)
4.    Seams are taped and pack is rainproof (maybe waterproof if not submerged for long?)
5.    Perfect volume for me (I chose the 60 liter version)
6.    Highly customizable
I will try to address each of these points over the course of the review as well as my general impressions on functionality and durability.
You can imagine, it was like Christmas in September, when I opened up my package from Zpacks. There was an assortment of smaller items but the most anticipated item was the pack. I have to admit my first impression was “wow this fabric feels like a paper bag”. Indeed, it has a certain paper quality feel to it although it is much much more durable. I have a few items made with cuben fiber, mostly stuff sacks and also the Hexamid but the Arc Blast is made from a 2.9 oz/sqyd hybrid cuben fiber that is supposed to be stronger and more durable than that used in the other products I have. It certainly feels like a much different fabric.


One reason for using cuben fiber in a pack is to reduce overall weight. My 60 liter Arc Blast comes in at 16.5 ounces and certainly qualifies as lightweight. One of the issues with cuben fiber is durability, I will be more careful with this pack than my others but I am not going to baby it, we will see how well this hybrid cuben fiber holds up.
One of the most important characteristics of a pack is the ability to comfortably carry a load. I have high hopes for this pack as I expect to carry up to 35 pounds, although it is advertised as able to carry up to 30 pounds well. For my first outing I had a total pack weight of 18 pounds (9 lb gear + 5 lbs camera gear + 4 lbs food and water) and it carried very well. The shoulder and hip belt padding is fairly thin but I am of the opinion that thicker is not always better. The advantage of thinner padding is that it can form to the curves of your body more easily. I think this increases carrying comfort. One thing to note, if you use the sternum strap and have larger than a medium sized chest you will want to ask for a longer sternum strap. I do not have a big chest and the strap just barely fits me.

Update: I started to notice some very slight discomfort over 25 lbs. This is due to the padding on the shoulder strap not completely covering my shoulder. The padding needs to extend another inch towards the pack body. I think I can add a small amount of padding to that area to improve comfort. I will say that it was not painful just noticeable above 25 lbs and slightly annoying. Below 25 lbs is still very comfortable.

Arc Blast with black belt pouch and grey multipack

The basic pack design is similar to many other lightweight backpacks out there. It is a sack with shoulder straps, a hip belt, side pockets and a mesh pocket on the back. However, what sets this pack apart, and attracted me to it in the first place, is the arcing frame design. I am really excited about this as it is not offered on very many packs and none in this weight range. After using it this weekend I am sure that it is a big improvement for SBS compared with packs without the arc. That is not to say it eliminated the sweaty back, I don’t think this is possible, but it was noticeably better, the Arc Blast allowed enough airflow to reduce sweat buildup.

Approximately a 3" arc

In order to take advantage of the arc design you must tension the pack frame to form a curve away from your back. The recommended amount is 2.5 inches in the center of the arc. I didn’t measure what I did but it looked to be around 2.5 to 3 inches. Tensioning the frame was not difficult and the linelocks holding it in place seem to do a good job. I will be keeping an eye on these over time to see how well they maintain the arc shape.
Update: Still happy with the arc design, it works much better than a flat back design. I read a thread on Backpackinglight where some people were saying that the arc would push the load too far back. This is definitely not the case and is one of those hypothetical complaints that has no basis in reality.

The pack is advertised as water tight, I don’t know exactly what that means and I have not had a chance to test this yet so I will reserve judgement. I expect that it will be waterproof enough under real world conditions during rain or snow events but I will be testing it fully, including submersion (realized I have the drinking tube port so it would not make sense to submerge) in the near future.

Update: We finally have had rain in California, the first significant rain since I bought the pack. Perfect chance to test "rain-proofness". I set the pack up in the backyard for a 24 hour period. Rain was light but steady with a few heavy showers, total rainfall 0.8 inches. I put a bulky sleeping bag, inside a cotton sack into the pack with a couple of paper towels on top. I velcroed the top and rolled it 3 times for a secure seal and left it in the rain.

Results: I will admit some disappointment. While not a total failure, it did not keep the contents dry. I was careful, when opening the top, to make sure no standing water leaked in. Standing water = waterproof fabric. The paper towels I had put on top were quite damp, not soaked completely but damp, as was the cotton sack. I was not able to squeeze any water out of the towels.

Opening roll top

Wet paper towels

Wet sack containing sleeping bag
Additionally, the sleeping bag inside the cotton sack was also fairly damp, indicating that enough water leaked in to soak through to the bag. From the pattern of wetness on the sack and feeling inside the pack, it appears that water came in through the back of the pack (part of the pack that would be in contact with your back). This is where the most stitching is located and so would make sense to be the weakest point. As far as I can tell all the stitching has been well taped over on the inside of the pack, so I am at a loss as to where exactly the leak came from. I think near the top, because the wetness extended from the top to the bottom of the cotton sack, so the water probably leaked down.

I also took the opportunity to test the side pocket, which is also supposed to be rain proof. I placed paper towels inside the pocket as well.

The paper towels were damp but not completely soaked, and there was no standing water in the bottom. They performed slightly worse than I expected but still ok.

Bottom Line: The fabric appears to be quite waterproof, however the stitching is not, even after being taped by Zpacks. Water does get into the pack under light to moderate rain. It will keep out the majority of moisture and definitely performs better than non-cuben fiber packs but it is not completely rain proof. The side pocket will keep out most rain but will not remain completely dry. If you thought you could ditch your pack liner/cover, think again, especially if you are expecting precipitation. I will continue to pack my sensitive gear into water tight stuff sacks.
The Arc Blast is offered in three different volumes: the 45 liter (2750 ci), 52 liter (3200 ci), and the 60 liter (3650 ci). I chose the largest volume because I believe that it allows me the most versatility. My current pack, the GG Gorilla is about 46 liters in volume and I find that while I can fit all my summer gear plus food and water, I frequently want a little more space. And I cannot use it during winter trips as it is much too small. Therefore, I think the 60 liter volume will be a good compromise where it is not too big for my 3 season trips but is still big enough for winter trips. Plus, it allows me to carry enough food and water if I was to ever pull off a more ambitious hike (more on that at a later date).

Multipack, part of my continuing quest to find a good carrying solution for my camera gear

One of the great things about ordering from Zpacks is the ability to customize your gear exactly how you want it. You can choose from a wide selection of accessories such as different configurations of straps, pouches, load lifters and trekking pole holders. If you have a specific design element or specifications in mind you can also directly communicate with Joe to build these as a custom order. I think this is a great service that most other gear manufactures do not offer. Of course it will come at a cost but this seems reasonable.

Belt Pouch

I actually did not choose any customization, except to add the hipbelt pocket, on this pack as the base configuration is all that I need. Although I was tempted by the bright orange cuben fiber, I decided to be boring and stick with a nice neutral grey color. I did ask for a custom built dry sack for my tripod (unfortunately I gave the wrong dimensions, so it doesn’t fit, but that was my fault).

Update: Although I can reach my water bottle in the side pockets with the pack on it is a little awkward. If you use a hydration tube then this is of course not an issue.

Slightly awkward to reach water bottle

To summarize, my impression is mostly very positive: The pack is very comfortable under 25lbs, the arc design definitely works, it is lightweight, I can fit everything I need inside. The fact that it is not rain proof, is sad but not a deal breaker and I wish it were slightly more comfortable with loads over 25 lbs. The other thing I will be keeping an eye on is long term durability but it is too early to make any conclusions on that.
If you have any specific questions that I did not address, feel free to ask in the comment section below.

You can find this pack and many other cool items at

Updated: Jan 9th