Shaving nearly 3 ounces off my backpack with custom 7075 tubular frame stays.
The Art of Tinkering
Lock me in my house long enough, and odds are I’m gonna find some stupid shit to start tinkering with. This year, I did a lot of tinkering, almost always on some piece of backpacking gear. And given enough time to tinker, turns out I can occasionally stumble into some modification that actually makes a piece of gear a little bit better. This here might be one of those moments.
The short of the long is – stock stays in my Hyperlite Mountain Gear (size Large) weigh 4.2 ounces. My custom 7075 aluminum stays weigh 1.4 oz – for a net savings of 2.8 ounces.
Not insignificant on what is only a 32 ounce pack to begin with.
How I arrived at the final stays is a bit more long-winded – the rest of this post is for true ultralight nerds only.
Stock frame stays for ultralight backpacks are, generally speaking, rather overweight for what they are. This is because they are usually made of ½ inch wide 6061 aluminum bar stock, like what you can find at the local hardware store. This is works well enough, and can easily be formed to fit the contours of your back. Perhaps best of all, it can easily be formed in the field by the backpacker for cases when they need a non-standard shape. The downside, of course, is weight – 6061 bar stock is much heavier than say something like carbon fiber or 7075 aluminum tubing. Carbon fiber tubing that is shaped with a lumbar curve is labor and material expensive, with limited weight savings compared to 7075.
Thus began an entire months-long saga of me buying all sorts of different tubing trying to figure out how to bend it. And not just bend it, but do it with perfect AND repeatable results. I bought a few variations of pipe benders from the hardware store and that didn’t work. I bought a bicycle wheel from the thrift store and that didn’t work. I tried anything else I could think of. Sometimes it would work, sometimes it would fail. And when this stuff fails, it fails in violent ways, shattering shrapnel that may or may not pierce right through your hand. (Pro-tip, if you try this by hand like my dumbass, wear some denim, some gloves, and safety glasses.)
Nevertheless, I got a few decent bends that worked, and a whole bunch that did not. But the successes were enough to convince me it was possible, if I could just figure out how to keep the tube from kinking or cracking.
After much trial and error, and probing the depths of the YouTube rabbit hole in search of every tube bending video I could find, I finally got a radius roller jig built with a couple of dies that could make reliable, repeatable bends without cracking or kinking.
Way too much work just to save 2.8 oz, but dammit I was bored, and somewhat determined.
Finding the perfect shape
But just because you can make some bends doesn’t mean you are making the right ones. And it turns out, if you lay dozens of backpack stays on the same table, not a single one of them will be shaped like any other (sometimes two stays from the same pack will be different after significant use). This is both frustrating, and eye-opening. It means I’m not sure there is a “perfect curve.” More likely it means that there is a certain margin for error on a curve that fits lots of different body types. And when you consider the limitation of the radius you can bend these tubes, the shape will always be different than you can get with 6061. So that margin of error is key.
I’ve now made hundres of these stays over the last two years, and the shape works quite well. I personally can tell no difference in comfort between the custom stays and the handful of other stays (even across different manufacturers.) However there is one serious benefit – these 7075 tubular stays are much stiffer. So when you are carrying a truly heavy load, they will collapse much less and improve the overall carry.
Which begs the final question – what’s the downside? Well, the most obvious is they might not universally fit every body shape. Everyone is different. If you’ve never intentionally bent a stay to fit, these custom stays would probably work well for you. If the first thing you do when you buy a new pack is bend the stays to some irregular shape, it might be more complicated. That said, I have now built a small workflow where I can match the curve of the stays to your exact shape. All it takes is for you to send me a photo of your current stays with a tape measure next to it, taken as straight on as possible.
The other question is just how strong are they?
I have not done a truly scientific test, but based on my own experiences, normal backpacking loads are well within range, and the custom stays are easily as strong as the stock 6061 bar with one possible asterisk. If you were to say, drop your pack and it landed on a sharp object, it’s possible that impact crack the stay. It’s also possible a softer alloy might just bend or deform.
With that asterisk out of the way, I’ve now made over a hundred sets and they have performed flawlessly on some very big trips, including a 50 day traverse of the Grand Canyon with pack weights pushing 50 lbs in some stretches.
As I've built more and more of these I've adapted them to fit many types of packs from Hyperlite, Superior Wilderness Designs, and Lite AF. If you have any questions if these might work for you, send me a note and I'll get ya sorted.
Thanks for checking 'em out.