Help Us Design the Ultimate UltraLight Pack

[Luke Schmidt]

I'm working on a new pack idea with Chris Zimmer and would be interested to hear other's input, my theory is the more minds the better. Here are my requirements.

1. It needs to have a frame for up to 40 pounds of food and water for desert hiking
2. It needs to have a single stay frame because this is most comfortable to me.
3. It needs to be abrasion resistant for hikes in West Texas.
4. Water resistant for mountain hiking is nice but if I have to I'll deal with water absorption in favor of abrasion resistance.
5. It needs to be light and compress down so I can use if for weekends as well as long trips.

Here is what I came up with.

And here are pictures from David Chenault's Tamerisk pack (hope you don't mind David, if you do I'll delete). There is a single aluminum stay padded with a folded sit pad in a pocket. I'm copying the suspension but not all of the features.

Having used a similar pack (Exped Lighting) I'm sold on a single aluminum stay design. I just want to make one that is smaller and a bit burlier. Hopefully the finished product isn't too much over 2 pounds.

Questions I'm considering

Fabric Choices
Dyneema X and Xpac are out for various reasons. I'm left with DX42 from Rockywoods.com or 500 Cordura. Any thoughts on the abrasion resistance or stitch holding ability of either? I'm guessing 500 Cordura is tougher but the DX42 won't soak up water. If its adequately tough I might go with it.

Pad Design
David has the entire back of the pack padded with the hipbelt coming out from behind that. Looks great but I was thinking perhaps the hipbelt would wrap better if the pad was narrower. One idea I had was to make the pad pocket about 6 inches wide. Then the hipbelt would wrap around my hips closer and the pack might breather better. Any ideas?

[Ken Thompson]

"my theory is the more minds the better."

Pack design by committee might result in another Absaroka.

You should know by now what it is that YOU are after. Get that.

[Jerry Adams]

yeah, but often people will come up with useful ideas

or one of my stupid ideas will stimulate a good idea in someone else : )

as long as Luke makes the final decision some of the problems with committees are avoided

oh, good – thread drift – from pack design to whether committees can do anything useful : )

[Luke Schmidt]

Actually the Absaroka worked very nicely for me, unfortunately it lacked durability. I pretty much know what I want I just want to hear if anyone has a "watch out for that" idea. Weird stuff happens when you design from sctrach. I tried sewing a frame to Dyneeam X once using a webbing channel and it ripped out real fast. Bad combination of fabrics.

[Luke Schmidt]

Ah the committee jokes…

I've seen enough BPL threads to not take too much advice:) Its mostly a question of fabric choices now.

[Greg Mihalik]

There are only two questions asked –

1)Which has better abrasion resistance – DX42 or 500 Cordura ?

2)Will a 6" wide pad packet result in better airflow?

I'll put my money on the cordura – no high spots to focus the trauma.

And I'm sure narrow is always better for breatheability.

See, that's not so hard.

[Jerry Adams]

You have to include weight, if that's important to you

If the Cordura offers more abrasion resistance, but it's more than what's needed, and it's significantly heavier, then maybe the DX42 is better. Packs don't use that much fabric so weight isn't as important.

[Alister R Barnes]

You may want to put a horizontal stay across the top of the pack, or some other form of stiffening, to help it keep square. Bend to shape of back, otherwise pack will turn into a cylinder.

[William F]

Hey Luke,

I've got a new Zimmerbuilt pack coming in the mail, here are the pics if you're interested. It has the usual U-frame that Chris has been using. The dimensions are a little bigger than what you have in your drawing but pretty close. 12" wide, 8" deep, and about 32" in height. I think the way the pack is packed in the pics and the removable side pockets make it look stouter and deeper than it is in reality. Also, I asked for the angled bottom as you can see, like his ZB4 line of packs (look at Gear Deals page). This bottom is apparently stronger and more water resistant because there are less seams. Also, I hate it when a pack sags below the buttocks, it feels much better with the weight sitting above it IME. The two side pockets are removable and can be made into a lid, fanny packs or chest pockets depending. I haven't tried the design yet though so it's all in my head. I don't like things hanging on the outside of my pack in general hence the lack of permanent outer mesh pockets and the like. I have no problem stopping and taking my pack off for a drink of water. Fabric is Xpac everywhere. Similar but obviously different than what you are proposing.

Hope this helps in your endeavor, it was a lot of fun working with Chris on the design. He will essentially build anything you ask him to, within reason. Great guy though, and excellent communication/customer service.

weight is 29 oz. including side pockets, w/out I have not weighed it

Edit: I guess it's kind of hard to see, but there are 3 side compression straps on each side, roughly in the same location as you have on your drawing. The side pockets have channels on the back that receive the webbing and secure them on the sides.

[Ron Moak]

Luke, the pack you're describing is quite close to our new Fusion Pack. We will be releasing details shortly, I promise. We're just waiting on final models for photography.

Anyway in dealing with the need to carry the 40 pound weight you specified, you need several components that typically aren't found on UL packs. The first and foremost is a good foundation and that starts with the hip belt. Virtually every UL hipbelt I've seen will deform and sometime severely. You need a belt that can take the load without crushing and evenly distribute the load across a wide area. This will eliminate potentially painful pressure points.

The second thing is a good connection between the hip belt and pack. It needs to be flexible enough to provide some give and rigid enough to transfer weight without collapsing.

Finally there is the stay. At 40 pounds a single small stay sewn into a channel in the back of the pack will eventually fail. It'll either be driven out the top of the pack or through the bottom. The reason is that most if not all of the force is applied to two small points at the top and bottom of the stay. Imagine a woman with high heels and all her body weight coming down on a small area. It's no wonder that even hardwood floors had a lots of dimples in the old days.

Here you're hanging 40 pound on about an eight of a square inch or a weight of 320 pounds per square inch. You need a way to transfer the weight from the top and bottom of the shaft to its length. It's doable but takes a bit of creativity.

Good Luck

[Luke Schmidt]

Uh oh, good point on the frame Ron. I'll have to think long and hard about that one. Think reinforcing patches or running a strip of webbing across the top would help spread the stress out?

Edit – Thinking outside the box a bit, what if I short piece of cappyed PVC pipe or something similar at the top of the frame channel? The would increase the surface area of the stress area a bit.

[Luke Schmidt]

Just thought of another idea. What about a piece of webbing folded over and sewn across the top. If the stay channel ended in that the stay would be pushing on an 11 inch wide piece of fabric rather then a 2 inch piece.

[William F]

You could make the stay in this form,

this shape would distribute vertical pressure points better than a rod as Ron pointed out.

Do you have a link to the page where you got the pics of Chenault's backpack? I'm interested in the stitching on the hip belt for increased rigidity. It'd be interesting to hear his experience with that element of design.

[Luke Schmidt]

The whole point of the single stay is the way it fits my lower pack. So an I shape is out.

The link to David's pack page is here

http://bedrockandparadox.com/2013/11/11/introducing-the-gossamer-gear-tamarisk/

[William F]

Luke, thanks for the link.
What about a "T", or even an upside down triangle of sorts that comes to some kind of a point at you lower back?

[K C]

I'm not sure about the single stay with traditional hip belt and shoulder harness attachment points on the back panel. The exped lightnings shoulder harness is ridgid and directly attached to the stay, not the back panel, and so is the super beefy hipbelt. I don't think the stay in a sleeve is a good idea at 30-40 pounds for transferring weight and R. Moak's point. With your design the only function of the stay is keeping the back panel ridgid. Just my thoughts….

[Luke Schmidt]

You have a point K.C. I actually have an Exped Lighting myself. For a big pack its great, I'm trying to make something a bit smaller for shorter hikes. Even with all the water I need for two days in the desert I don't come close to filling up my Lighting.

Since Lightings are going on sale I may end up buying a 45 (I have the 60). I could cut the frame off, open up the pack and shorten it to fit the frame.

[Jeffs Eleven]

Ive often thought about a "T" shape but the frame hoop horizontally at the top of the T.

Like a T with a D shaped hoop connected to the T. It would be on its side and the rotund part would be pointed away from the wearer's back.

Then you could just hang a bag from it and toss all the stuff in the bag. Like a hanging laundry basket on your back.

[Luke Schmidt]

That sounds like the old pack baskets used in the Northeast by trappers. I don't think Chris wants to build one of those though.

[David Chenault]

No problem with the photos Luke.

I assume you mean VX-42? I'd say it's a good choice for this use. Maybe not quite as straight abrasion resistant as 500d cordura, but pretty close.

Key for the top of the stay sleeve is a double layer of fabric under the whole doubled end of the channel. You end up with bartacks in the doubled areas, as can be seen in my photos above. Maybe the bartacks will eventually rip out, but I'm not too worried about it.

4" spacing between the shoulder straps seem like quite a lot. I usually use 2.75".

I put the stay slot in the back of the hipbelt, not the side against the user.

You can do quite a bit of tuning, in both load carriage and lumbar wrap, by using different foam pads. Perhaps even switch between two for different trips/loads.

[Luke Schmidt]

Yes that was a misspell, its VX42. Probably go with that then. Which one do you think has better stitch retention? We'll probably order a yard of VX 42 and a yard of 500 cordura (for the hipbelt) so we could go with either for the inside part.

I just had an idea to put a very short "top" on the pocket. If the frame channel ever wears out I could switch to using a frame sheet inside the pocket.

I've had about 4 inches of spacing on my last couple packs. I must have a thick neck. My old Jam2 caused soreness on my neck, must have been too narrow.

The slot is supposed to be on the back of the hipbelt just like yours, I'll make sure Chris understands. If its not clear to you it might not be clear to him.

Hopefully this all works out. I wish I had the time to make my own packs like I used to.

[Daryl and Daryl]

I tried a single stay pack from REI several years ago. Can't recall brand.

Bottom of single stay soon started rubbing the base of my spine. Deal breaker. Gave it away.

Design of the stay bottom and attachment to pack is, as others have said, crucial!

[David Chenault]

Stitch retention on both VX-42 and 500d is pretty darn high. 500 is probably better, but we're talking gradations that don't make much functional difference.

FWIW, I've been doing training walks around town with the Tamarisk pack (above) and a 55 pound load of water and climbing hardware. Once I got the stay bent just perfectly load transfer has been excellent. The foliage hipbelt shown above is a hacked down Kifaru Wraptech Plus. 500d on inner and outer, and a single payer of dense but pliable 3/8" CCF. Hipbelt is not a limiting factor at 55 pounds. I'm coming to believe that any plastic nonsense in a belt is indicative of a design shortcoming elsewhere.

[Paul McLaughlin]

At the weight range that you are aiming for – in the 40's – I have come to the conclusion that sewing the hipbelt directly to the bag is not the best way to do it. I have a pack I made about 30 years ago on which I used three velcro straps to attach the belt – two at the bottom of the stays (strap sewn to the belt, looped through a looploc and velcro to the belt) and one at center top of the belt. That pack is more comfortable once the weight gets up than any of my sewn-on belts. All belts are conically cut.
My guess as to why this works better is that you maintain a very direct connection of the belt to the base of the stays – for excellent weight transfer – and yet you have more flexibility in the connection. I do have sidepull straps running from near teh belt buckle back to the lower corners of the pack, which I will tighten when I'm skiing downhill to keep the pack under more control – I put those on any pack I plan to ski with.

As to stays wearing through the pockets – I've had to do a number of repairs on that pack over the years but no issues at all with the stay sleeves. The two stays are 1/2" wide by 1/8" thick aluminum; the bottoms of the sleeves are 1" wide nylon webbing; the ends of the stays were eased with a file and wrapped with a couple layers of electrical tape. The pack has seen a lot of use by myself and my son, with many loads over 40 lbs at the start of ski trips

Also – I would strongly recommend a crossbar at the top of the stay or stays to help avoid the pack rounding out. Keeps the load closer to the body. And with a single stay pack, it gives you a place to attach lifter straps that has some connection to the frame so they will work much better. I have used both flat bar stock and aluminum tent pole tubing as crossbars on my packs – both work.

[Nick Smolinske]

So if durability is a huge concern, you should think about 1000d cordura as well. Seems crazy, 1000 is twice as big a number as 500! But the difference in weight is 8 oz/yd for 500d versus 10.8 oz/yd for 1000d. A pack uses a yard, plus or minus half. So if it's a small pack you could be talking 2 oz difference in weight, for double the tear strength.

See http://milspecmonkey.com/customize/materials for strength info.

1000d is still probably overkill for you, but I just wanted to point out it's not as heavy as people think, compared to 500d. I make my bikepacking gear out of 1000d because all of my gear uses just a couple of yards, and the strength is worth it for that application.

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