MYOG D40 Arc Blast Pack
- This topic is empty.
-
So first thing's first – thank you ZPacks! Joe gave me a lot of information about how to construct this, so I didn't have to reinvent the wheel.
So anyway, my first MYOG pack has worked pretty well for me so far. In winter I'll continue to use it. But I've definitely noticed my back sweating more than with other packs I wear – the combination of the thick foam torso pad and the 3d mesh traps a lot of heat.
I love the Arc Blast frame design, and inspired by And E's awesome Arc Blast frame conversion, I decided it was time to make a new pack. I contacted Joe at ZPacks and ordered the carbon fiber frame pieces and a few other odds and ends from him. He offered me the same deal to sew the frame attachments on, but I wanted to puzzle it out myself, and besides – I had some other ideas. :) Here's what I came up with:
I wanted the pack to be durable, have very strong and direct frame connections, and be, of course, reasonably light! The pack body is made entirely from Xpac D40. The final weight is 1 lb 10 oz without the hipbelt pockets, and just under 2 pounds with the pockets. It's not quite as light as I'd hoped, but still good enough for me. The left pocket is a padded camera case, which is rather heavy, around 3 ounces empty.
The thing that I puzzled over the most was how to connect the frame to the hipbelt and shoulder straps. I wanted a very direct connection, since I have a very long torso and I was worried about the frame sagging below my shoulders. Plus, the engineer part of me just can't stand putting in a good frame and then having a lackluster connection to the pack. So I spent about a month pondering and drawing different designs before I actually started cutting.
My original plan was for the shoulder straps to come up and over the top crossbar, which would serve two purposes: it would make them pull on the very very top of the suspension, and it would change the strap attachments from being loaded in peel to being loaded in shear.
The key breakthrough was when I started playing around with using small pieces of 16oz hypalon instead of webbing. It's quite a bit thinner, so it opened up a lot of options and I ended up with this:
The idea was for the shoulder strap webbing to go behind the crossbar and fold over it. I spent so much time worrying about frame sag that I thought I'd need that extra bit of space. It turns out I didn't need it at all, and putting the shoulder straps there made them too tall! Fortunately I'd planned on having the option to make them a bit shorter by not putting them under the crossbar, so it worked out.
There are two sleeves for the crossbar which hang off of the attachments for the lineloc3's. There's also another long sleeve sewn onto the D40 itself. They are all open ended and the crossbar feeds in from the side. Friction will hold it in place once the frame is tensioned.
After putting the crossbar in, the stays are inserted from the bottom. They end up over the crossbar.
Once the frame is tensioned, the tension pulls the two pieces together, adding enough friction that I wasn't able to make the crossbar budge at all. I had hypalon tabs in case I needed to add something later to help hold it in, but I think I'll probably cut them off – the friction alone works quite well.
The stays go through sleeves on the bottom of the pack. These are open-ended, and the lineloc3 folds over them to hold them in place (with a little extra hypalon padding).
Here's the pack loaded up with 30 pounds, to show the air space. Pose blatantly stolen from And E:
So, that's the pack! I finished it early this afternoon and walked around the neighborhood with 30 pounds in it. It carries that load very well, and I bet I could push 40. Which could happen if I decide to go through with my solo Horse Thief Route trip next May (packraft + lots of water!).
Some thoughts:
-D40 is hard to cut. I didn't let my really nice scissors go near it, for fear of dulling them, so I don't know how well they would've worked. But my rotary cutter failed even with a brand new blade! The best technique I found was to use my cheaper (but still decent) Singers and squeeze repeatedly to make a sawing/sliding action happen on the fabric. This resulted in the least amount of fraying. I was kind of pulling back on the scissors each time I squeezed them, so that the fabric wasn't really getting any pressure from the blades; rather, the blades were being drawn across it repeatedly.
-I might order another crossbar piece from ZPacks, to give a bit more air space in the upper part of my back. Right now I have to be pretty careful about how I pack it so things don't bump into my shoulder blades.
-16 oz Hypalon is a really fun fabric to work with. I ended up using it for the compression straps and line loc 3's as well. I don't think it added much weight compared to webbing and it's really thin, which is nice for sewing over in seams. That said, grosgrain would be just as thin and definitely lighter. But if you're making a pack out of D40, you might as well go for durability everywhere.
-This is the first pack I've made without load lifters. And it'll be the first pack that's ever had a chance of fitting me without load lifters. So I'm interested to see how much I like it. I can always add lifters between the crossbar and the straps, so I'm not committed to the idea, but I like the simplicity of not having them. We'll see how it goes.
-Thanks again to Joe at ZPacks for coming up with this frame design, and giving me some great tips!
And the saga continues . . . I took the pack for a couple of test runs and, although the suspension system worked great, there were a couple of problems:
1) The stays would spread out, and once or twice I had the cross-piece pop out of its sleeves on me.
2) The dyneema cord in the mesh back panel was rubbing on my shoulder blades. I couldn't tell if it would become a problem or not, but it seemed like something I should try to fix if possible.
I fixed the first problem by adding two sleeves onto the pack for the stays to go through, in the middle – that way they can't spread out. I also added another cross piece while I was at it, although this is easily removable if I decide I don't need it.
I fixed the second problem by making a new mesh panel out of just leno lock mesh. So instead of cord on the sides I have hemmed mesh. This still wasn't quite good enough, so I sewed on a couple of pads where my shoulder blades touch. You can see both modifications in this picture:
I took it on a 4-day trip (got back yesterday) and it worked great! It carries better than my other packs and I love the breathability. I hiked in snow and wind and it helped my temperature regulation, keeping me from getting a sweaty back.
Unfortunately I noticed a small issue – the leno lock mesh has a slight amount of stretch. It's not noticeable when you tug on it, but it's enough that the back panel keeps loosening up on me. Joe at ZPacks warned me about this, and I'd hoped that the leno lock wouldn't be too bad, but it's definitely an issue. I might just replace the dyneema cord with thicker stuff and see if that holds in the buckles better.
It's still a great pack and I'll use it like it is, but I'd be nice if the mesh wasn't loosening on me, so I have a new solution to try today – I'll post an update when I've finished it.
- You must be logged in to reply to this topic.
