I have been having some problems with the Vapor Current suspension on the Granite Gear Crown VC 60 when using it in frameless mode. I chose the pack for its versatility. I rarely need to carry more than 20-25 pounds total pack weight, but I liked the option of using a frame for longer trips or occasionally heavier loads. Per a press release:
“All the Granite Gear Vapor Current packs come standard with a die-cut HDPE frame that can be removed for trips when loads are below 25 pounds.”
The problem has been this: After about 10-12 miles of hiking without the framesheet, the Vapor Current suspension begins to collapse–quickly and significantly–regardless of the load I am carrying. This has happened with 18 lbs. at the beginning of a trip and with 12 lbs. at the end of a trip. I’ve re-arranged the pack contents several times mid-hike with the same result.
Initially, I used a 1/8″ CCF pad folded up to add a little stiffness to the backpanel. This worked well at the beginning of the day, but by the end, the frame sagged poorly. In the middle of one trip, I even stuffed it tightly into the frame sleeve, but the problem came right back. Then I cut a section of a RidgeRest into the exact shape of the HDPE framesheet, and that provided excellent load transfer for light loads–for about 10 miles. So far, my experience has been extremely consistent after about 125 miles with the pack.
What is so odd is that I don’t experience torso collapse from the beginning. But when it goes, it goes fast. Because of the cutouts on the Vapor Current backpanel, the back juts out sharply in a couple of places.
So, this is my theory. If you look closely at the VC backpanel, the foam is very thin at the air channels but significantly thicker elsewhere. The cutouts create weak spots, and they cannot sustain any load for a length of time. Once the stress becomes too great, the backpanel begins to fold along several lines (pictured below). When it starts, it collapses quickly, folding in or at those lateral weak spots like an accordion.
I should say that with the frame in, I haven’t experienced this problem at all. It is stiff enough to keep tension across the backpanel to prevent collapse. With the frame in, all I have gotten is some very, very good load transfer.
So what do you all think? Has anyone else dealt with anything like this with the Crown? Any other possibilities I missed?
