I took with me this Gregory Zulu 40-L pack. You can find it online for about $195 and it has what they call a “free float,” or ventilated suspension. The backpack itself is made out of HDPE polyethylene material, weighs 2.9 lbs, and the curved frame is made from 4-millimeter alloy steel and fiberglass (what they call an “anti-barreling stay”). Honestly, I don't exactly know what that means.
It's a nice backpack, but at about three pounds while empty, it gets pretty heavy.
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I tested this backpack with my Vaucluse Gear Cool Dry Frame (found here). I will say that, while I was hiking with this backpack, its curved frame provided airflow right in the middle of my back, but on the top and the bottom, it did not. I equipped the backpack with a Govee Thermo Hygrometer; it's a Bluetooth-enabled thermometer, and I just put it in here so I could track my back temperature.
I noticed that after about 45 minutes of hiking, my back was getting hot. There was some wind but as you can see from the chart, the thermal temperature of my back was definitely increasing. In addition to the backpack weighing in at just under three pounds, I probably had an additional 3 pounds.
Now this backpack is a lot heavier than what I usually use. This was probably twice as heavy as what I normally wear (a 22-liter). So I was having difficulties and was, for the most part, uncomfortable because I could definitely feel the heat. It's a heavy backpack and it's heavy because, for the most part, it's the frame. This is a beautiful backpack but its curved design frame makes it very heavy.
My back temperature was climbing over 65ºF and the outside temperature was climbing as well. So there really wasn't much of a cooling effect as I was hiking. The temperature kept increasing, as did my back temperature. I made a complete rest stop just over an hour into the hike because, even though it was flat, I was tired. This large backpack was causing me problems. I just wasn't used to the weight.
When I put my Cool Dry Frame on, I opted for the black model (this one shown is the white model). I could tell that my back temperature was more stable as the Govee thermometer was telling me it was happening. The outside temperature continued to increase from 50ºF to about 56ºF.
Now, as the temperature kept increasing, my back temperature was staying much more constant.
The chart shows that peak temperature between wearing and not wearing the Cool Dry Frame was just one degree. That is true. However, there are a few points to consider.
I wonder how hot my back would have been with just the Gregory pack, had I not paused to rest? Remember, I paused to rest about 45 minutes into the hike because I was carrying what felt like a lot of weight and I was definitely feeling the heat. I needed to pause and that lowered my back temperature.
The Cool Dry Frame provided more consistency in my back temperature.
The outside temperature continued to increase while the Cool Dry Frame kept my back at a constant cooler and more stable temperature, which definitely made a difference.
What could have been my back’s peak temperature with only the Gregory 40-L Zulu? I don't know. All I know is it kept going up. I will test this out at a later date and assume that I'm going to need probably more than a 40-L, and probably at least two hours to really get a sense of how back temperature performs with this backpack. Because 45 minutes isn't enough overall.
I did notice that the Vaucluse Gear Cool Dry Frame definitely made a difference. That's my personal opinion but… At the same time, the statistics do show that it kept my back at a more stable temperature. So I was happy to have this Cool Dry Frame and, as you can see, it's very flexible and light. If I went with a lighter backpack with this type of frame, I think overall I'd be really good to go.
So that's my review of this hike and the Vaucluse Gear Cool Dry Frame with a Gregory backpack.
Here’s to sweating less. See you on the trails!
You can read our 5-star customer reviews by clicking here. Yes, this gear works.
You can check out the details of the hike we took by clicking here.