Components for MYOG Arc Blast frame?

[Max M]

Hello all,

This is my first post on BPL (other than gear swap posts), but I’ve been lurking around and reading forums for about a year. Thanks to everyone for all the great information on here. It’s an amazing resource!

I’m starting to cut and sew a MYOG backpack, with a frame similar to the zpacks arc blast (but simpler). After begining my prototype, I decided that the stays I was using were too rigid.I would have bought stays from zpacks, but as most of you probably know they are no longer selling materials. Instead, I was using carbon hunting arrows (8.1 gpi, designed for a 60 or 70 pound bow). These are capable of bending the appropriate amount, but it requires quite alot of force, and I think that, for the longevity of the pack, it would be better for the system to be under less constant pressure.

I am wondering if anyone has suggestions for materials to use for this type of frame. I have thought of trying a lighter weight hunting arrow, a basic aluminum rod from home depot, as well as some fiberglass materials. I would definately prefer something lighter (which is why I started with carbon tubing) but am open to anything that will work well and last.

I am going to rework my design slightly after making my first prototype, but currently have a back panel completed, so am on a quest to find, cut, and insert different stay materials until I find what works. I would love to include yalls suggestions!

Thanks, Max

PS, I just thought of this, but if anyone has actual Arc Blast frame components that they want to sell, I will probably purchase them from you.

[Niels S]

I recently finished my own Arc Blast inspired pack and went through the exact same process you are about to embark on. I posted a thread with pictures on trek-lite.com if you are interested. There is a couple of close ups that may be useful. MYOG Arc Blast.

I’ll try to share what I learned in the process. I’m not a backpack pro, just sharing my experience. YMMW.

Most important finding: Don’t go with round carbon/glass fiber rods like Zpacks. I prototyped with 5 mm solid carbon fiber rods, and they were way to rigid. 4 mm works better but still provides too much tension. More importantly, round rods will make the frame warp like crazy when it’s under tension, and they are more difficult to attach to the back panel.

I managed to find 12 x 2 mm carbon fiber strips in a local RC hobby shop and they work soo much better. The tension is pretty good, maybe a tiny bit too rigid, but good enough. They are much easier/simpler to attach to the back panel and the frame will warp a lot less. There is still a bit of warp on my pack, but it’s negligible when I fill the pack. I bought two 1 m strips and it was just enough for one pack. This is the kind of strips I used. It’s a UK supplier. UK Supplier – Maybe check out this supplier if you are in the US. US supplier

A side note on the horizontal stays you can see in the pictures – I have a fourth stay going through the hip belt, but it digs into my back no matter how much foam I add to the lumbar pad, so i ended up removing it. The next version of the pack will probably only have three stays. One in the top, one in the middle and one just above the lumbar pad. I can’t figure out a better way to make it, so please do share whatever solution you end up with.

[Cheerio]

Niel S

That’s an incredible pack, especially for a first one. I hope I can try this one day and I’ll probably use yours as some inspiration as I also want to base mine off the Zpacks but with some personal touch to it.

I should start by learning how to sew….haha

[JCH]

Don’t go with round carbon/glass fiber rods like Zpacks.

Interesting fact…I purchased an Arc Haul when they first came out and all of CF rods are rectangular in cross section.  I was quite surprised to learn that ZPacks later went to round rods…seem to remember a youtube vid from Joe demonstrating how much stronger they were by bending one to nearly 180 deg.  There was also a thread on BPL by a fellow who got one of the first ones with round rods (this is how I learned of the change) and the ends of the rods were ripping out their mounting pockets.  Turned out there was a short period of production where metal reinforcements were mistakenly left out of the pockets.  Zpacks made it right with the customers who got those packs as I remember.

Nevertheless, my early Arc Haul is a thing of beauty and the rectangular structural pieces work perfectly.

[Scott G]

I know this is an old thread, but had to write to Niels S.

 

That is a fantastic MYOG pack!!

 

Importantly, it s exactly what I am after and I thank you so much for sharing your work and your pattern on treklite

 

[Author]

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