X-Pac Backpack Pack v2.0 – Z-Packs Arc Blast frame conversion

The pack looks great. I've pondered making a suspension system like this and this design looks a lot easier to put together than osprey's system. I'm curious about the center strut – it must not be installed the same way as the top strut, because you don't have the webbing going over it to hold it down. Is it just the same on both ends? If so, how easy is it to get in and out?

Nicholas, thanks!

The center strut is pretty much two tubes sewn on top of another in a T shape. When I sewed them together, I made sure not to accidentally close up the perpendicular tube.

The vertical tube is open on both ends so the main frame stay can slide in and out, and the horizontal piece for the center strut is a piece of webbing folded over to close the outside end. The center strut is free floating in that it can move up, down, or off. It's kept in place by the pressure of the vertical stay and the back panel.

To remove the center strut, I have to slide out one of the vertical ones first.

AND E you are killing it. Arc blast conversion? Way to take something difficult and think your way through it for an end result that is all yours. Very nice work! Way to be inspired by the sweaty back problem that is a part of wearing a pack. Maybe we all don't have to have a drenched back from our pack. Let us know how the conversion works in the field. If indeed the sweaty back issue is even cut in half this would be a design I would be interested in making. Do you think it would be easier to start from scratch rather than do a conversion? Interesting fact on the abrasion resistance of poly vs. nylon webbing. Should I be using poly webbing for my stay sleeves? The shoulder straps look really nice. How is the Leno mesh working out? I'm getting ready to start my first X-Pack backpack. Keep up the good work! GOD BLESS

Looks like a perfect fit. Well done on a tough project, reworking the suspension/back panel of an existing pack is the definition of PITA.

Thanks Darren and David!

I'm not sure when I'll be able to head out on the trails next, we just got a 4 month old Labradoodle puppy a few days ago (already 46 lbs!)! He is a sweetheart and I'm excited to turn him into a great trail dog in the coming years.

I definitely recommend adding the frame to the pack first instead of converting it like I did. As David said, it is a PITA, but still hours of amusement. You'll end up with a neater/sturdier pack if you do the trampoline frame from the get go.

As for the polyester vs nylon, I'm just going by what the website said, but the polyester webbing is quite a bit slicker/thicker than the nylon.

Here's a picture of Toby:

Just thinking out loud here, tubular nylon would be another option for a strong webbing to use for the stay sleeves. It's also much easier to find than polyester. It's pretty durable stuff, probably at least as strong. A little heavy but you wouldn't be using too much; the only real downside I see is that it's pretty thick, so might be hard on some sewing machines.

Hi AndE

One thing I've always wondered with the Arc Blast frame is how hard it would be to increase its strength for heavier loads (along with a more substantial hipbelt of course) and also to possibly get the air gap slimmer for a closer weight distribution.

like if you had three or four vertical stays and a couple of extra horizontal ones like you have, as well as probably extra tension cords, could the arc be much narrower to reduce the space in between, and also increase load capacity?

I'm a sweaty back guy too but I also like the idea of being able to carry heavy loads for certain trips (long no resup and arid water requirements).

Any idea how much each of those carbon stays weighs???

Cheers!
Adam

Tubular nylon would work, it would look neater, but would still want to reinforce the part that folds over to keep the stay in place.

As for the frame weight, both stays and both cross struts came to ~65g IIRC. You probably couldn't use 3 stays, since a middle stay would poke you in the lumbar when it's curved.

You could double up on the outer stays, not sure how hard that would be to bend, etc, and what the actual weight load limit on each stay is.

Some tubular aluminum tent poles may work, possibly something with a larger diameter/thickness instead of the flat carbon rods.

Thanks for the reply AndE

65g really isn't much for frame parts.

Putting a stay in the middle and poking-that makes sense, didn't think of that.

Cheers!

Nice job AndE. I did a similar mod on a DIY pack last year. It does ok, but I think my carbon fiber strips are too thin and tend to lose the arc under load. Do you by chance have some calipers to determine the width and thickness of the carbon fiber strips? I think I need to go a little heavier. Well, that and lighten my load.

I never would have thought making your own pack would be so much fun. My current one is out of 1.9 PU coated ripstop with 3 different kinds of mesh just to prototype. I have the XPAC upstairs for permanent (well maybe) pack project this winter.

William,

Can I throw that question back at you and ask what size carbon fiber you used that wasn't big enough? I haven't decided whether I'm going to buy from Zpacks or make my own setup, but I'm definitely tempted to make a lighter summer pack with this design, out of Xpac D40.

William . . . I did some more research and the very link that And E posted on the top of this thread has the answer:

"The stays are a flat carbon fiber 5/16" wide by 1/8" thick. Side stays are 22 7/8" long, cross braces are 10 1/2" long."

From John Jonas's post in that thread.

Thanks, Nick.
I somehow missed that link and it has a lot of great info.
The stays I used were slightly thicker than 1/16" (.070), so I did go too thin on the first pack. I have 1/8" stays for the next one this winter, so that should work better.

A lot of people have been asking for frame pieces for DIY packs.

Here you go

Awesome Joe! Thanks so much!