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

[And E]

**Firstly, a huge thanks to Joe and the whole Z-Packs team!!**

After seeing Z-Pack's creation of John Jonas's Frankenstein MLD Exodus Arc Blast , I just couldn't help myself and decided to convert my already upgraded MYOG X-Pac Internal Frame Backpack v1.1 in the never ending pursuit of that perfect pack (back literally dripping with sweat with v1.1)

I contacted Z-Packs and Joe was extremely quick and helpful with his replies and I opted to do the conversion myself and purchased the carbon fiber frame pieces and the mesh trampoline back with cord from him (I had plenty of LineLoc 3's already). I placed the order the same day and he had it already on the way later that afternoon!

This was a fun project. I got a real kick out of reverse engineering the frame based mostly on pictures on Z-Pack's website and on John's post (and some general tips from Joe at Z-Packs) and just puzzling out how to keep the frame pieces removable should they ever need to be replaced.
Anyhow…

Here's the monstrosity, complete with scars (loaded up with 18 lbs including 5 lbs of food in a BV450):

Top sleeve is open on both ends, the webbing folds over the opening, keeping it in place. You can see it open a couple pictures down.

This lil MFer was a pain to get to. I accidently sewed the side of my pack into one of the bottom stay sleeve seams and had to rip it up.

At first I made the mid cross strut sleeve with a single piece of 1.5" webbing by sewing it into a T connector, but decided to go with a two piece design so the frame pieces don't rub against each other. The cross strut overlaps behind the stays. Center strut can slide up and down, but it's trimmed down to fit here the best.

Here is the top Stay sleeve opened up. You can also see how I added the removable top cross strut. Left side (of image) is a tube closed at the end and the right side is a pouch that gets secured by the flap when the frame is engaged/taut. Both of these are one piece, i.e. a part of the webbing for the vertical stay.

Dat Gap!! Hard to get a good picture of it, but the space between the pack and back is perfect. Also, moved the load lifter straps up to where the top cross strut is so now they actually work well!

I had 24 lbs loaded up in it (actual gear + canned food in a BV450) and walked around the apartment. It actually feels much better than the internal frame and I can get almost all the weight to my hips vs what felt like 60/40 with v1.1

Managed to shave off 6g, probably a lot more, with this mod vs original, unaltered pack v1.0 (unfortunately, didn't weigh the pack after v1.1 modifications, but it gained at least .6oz more just from the hipbelt). Total weight now is 833g/1 Lb 13.38oz including all pockets and removable front pouch.

I'm gonna see if I can order a couple more cross struts so I can switch between single mid cross strut or two cross struts, depending on what I'm carrying to keep lumps away from my back/maximize gap space.

**************************************
**Some thoughts/notes/pictures on construction**

Making the modifications was a slow process. They must be saints or speed demons over at Z-Packs to be willing to add the frame for so cheap. It took me several hours and lots of seam ripping of my old frame parts. Adding the frame sleeves to the bottom of the pack was difficult since it was really hard to reach down there with my sewing machine. I accidentally sewed other parts of my backpack into the areas I was modifying a few times throughout the project. A seam ripper is a must. I also trimmed the stays an inch and also trimmed the cross struts with a hack saw as my backpack is narrower than the Arc Blast and I have the bottom of the stays mounted closer to my hipbelt attachment/center.

The stay sleeves were made with 1" polyester webbing from Strap Works . It has 5x the abrasion resistance than nylon, apparently. I already had this on hand. The LineLocs 3's are on 5/8" nylon webbing.

Removed my old internal frame sleeves and the 3D back mesh panel, except for the lumbar part.

If anybody wants to give it a try, feel free to PM me with any questions.

[Nick Smolinske]

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?

[And E]

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.

[Darren Graff]

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

[David Chenault]

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.

[And E]

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:

[Nick Smolinske]

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.

[Adam Kilpatrick]

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

[And E]

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.

[Adam Kilpatrick]

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!

[William Kerber]

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.

[Nick Smolinske]

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.

[Nick Smolinske]

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.

[William Kerber]

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.

[Joseph Valesko]

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

Here you go

[Justin T]

Awesome Joe! Thanks so much!

[Author]

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