Concept idea for framed, truly UL pack using bamboo, UHMWPE fabric, cord, etc

Not bamboo, but George Frazier made a gorgeous wooden backpack frame, might give you some ideas.

Packs have reached the evolution whereby they have become very specific in form and function. I have gone through maybe 15 packs over the past 30-40 years.

Any frame is sort of a compromise between load carrying vs comfort. Here on BPL, it is difficult to say since we have many members devoted to that cusp niche between UL and Light. Base gear means what always stays in your pack: The pack itself; Your shelter; Your sleeping Kit; Your cook kit; Misc lights/batteries/first-aid/Bear line/etc;Water treatment & containers; At least one piece of insulated clothing. Often, these kits all together make up pack weights of only 5-10 pounds(or less if you are really dedicated to SUL packing) and can often fit into a largish fanny pack, or small day pack. No frame is needed.

For longer trips, you might add sleeping cloths, perhaps a change of underwear and a change of clothing, another piece of insulation gear, more fuel, spare batteries, etc. This will give you a pretty much indefinite stay out in the woods, but, it all adds weight depending on the duration of trip you expect to take. Thru hikers do the same, but most people limit themselves to weekly supply stops for fuel, batteries, etc… Now your base weight is around 10-15 pounds but extends your range. How you pack stuff starts to become important since it often determines your comfort carrying the weight.

Food is the big variable. You may leave with 1 pound per day or you may leave with 2.5 pounds per day. So, for two weeks you need 14pounds or 35pounds *just in food.*  Adding in another 2 pounds for water and you will be UL: 26pounds *or* UL:52pounds at the start! Food, within a personal range, equates directly to your range.

So, decide how far you want to travel & how well equipped you will want to be. Generally for packing on weekends up to three days or a week, you will not need a frame. Anything less than 20-25pounds doesn’t really need one. for 20-35 pounds, you can simply use a pad frame. There are several ways to configure pads, either as flat panels or inside your pack, to add stiffness and comfort. For heavier loads, *then* you need some sort of frame. What do you prefer?

Many packs have been made with simple “stays” in lieu of frames. As you describe, I think this is what you are doing. A light frame is really not useful on the trail. Too light/delicate for heavy loads, it does no more than a pad style frame, and just adds weight that is dedicated to one job. In a pinch they do add stiffness. You can drop the upper and outer members, because they do not need to be strong in this direction. Simple tension around the fabric itself will supply the enough strength. As examples: The old style Mariposa/Miniposa packs used two arrow shafts for stiffeners with a nylon web between them. This was good to about 30 pounds. And, you can remove the shafts for use as tent poles. I often use them in the rear of my tarp for added ventilation/hold up a cloths line in wet weather. But unless the weather is predicted for 5 out of 7 days of rain, I remove them as dead weight.

This sounds like one of the evolutionary steps in UL packs. A stiff, relatively rigid frame is subject to damage easily, though. While bamboo is rugged, it will likely have it’s weakness in simply being too rigid as designed. Careless handling will break either the top or bottom pieces (think airline baggage handler or tossing into a car trunk) and you wouldn’t even notice it when carrying the pack, anyway.

Good thinking though! This is where all good pack designs start!

Thanks Doug for the lead and link.  George sure made a beaut of a frame/pack.  Much fancier looking than mine will be.  Bamboo can be shaped, but it’s a pain to do.  But the nice thing about bamboo, is that it’s rather strong for it’s weight in all the main ways.  Some call it nature’s carbon fiber.

While bamboo is rugged, it will likely have it’s weakness in simply being too rigid as designed.

Possibly James, but 1/2 inch bamboo does tend to have some flex.  Plus the nylon fittings will have a little flex too.

Careless handling will break either the top or bottom pieces (think airline baggage handler or tossing into a car trunk) and you wouldn’t even notice it when carrying the pack, anyway.

  I don’t think typical careless handling would bother it over much, but i do have the concern of falling on it and possibly breaking it that way. I’m hoping that putting the closed cell foam rod in the bamboo will help a bit with it’s side compressive durability and strength. That might not be the right term though.  But the idea is that the foam core may absorb some of the force if weight is put on the sides of the bamboo tube walls.

Bamboo and CCF rod is cheap enough that i can test this before making the pack.  And bamboo at least is a highly sustainable material, so i wouldn’t feel bad “wasting” some.

The present Granite Gear load hauler (~70-80 Liters) uses some sort of maple wood board (looked straight in some pics but didn’t see the while thing) as a good chunk of the frame.  Might want to check that packs development in interviews/sales lit and scale down from that.

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Thank you HK Newman and Ken, i’ll check them out.

Some Baltic Birch in 3mm (a old door skin) would work. I doubt it would be any heavier than string, nylon and bamboo…if so not by much. Drilling some 2″ holes would lighten it up a lot.

Bamboo: 1/2″ will work, OK. I was thinking some 1/4″ stuff I got for my wife as plant stakes. Compared with tubular carbon, there isn’t a lot of strength to it. And the carbon was a bit lighter. Don’t get me wrong, I work with wood all the time as a hobby (I build boats and also spent about 20 years as a carpenter as a youngster.) Wood is a fine structural material for packs. But, there is still no need for the cross bars inside a pack body for loads up to about 30 pounds. This will also eliminate the complexity of the string and nylon joints. You really only need a couple of shorter (say 18 – 22″) bamboo sticks inside pockets sewn into the back panel of the pack. Gear wants to get out, naturally, supplying the force in the “out” direction…no sense reinforcing that area for 30 pounds.

Anyway, show us the prototype when you have one made up. Like I say, it sounds good.

Sometimes the best approach is to just do a sketch and start working, with the realization that what you envision and what you end up with will most likely be very different things.

Seems it would be possible to make some curved crossbars (and also strong vertical stays without using CF rods) with bamboo by using laminated strips, as is done with high-end flyfishing rods. Observing how bamboo furniture is made should provide some ideas.

Hi James, i understand what you’re saying.  Perhaps i should clarify some about the potential use.  Generally speaking, i would look to use this for moderate loads from like 30 to 40 lbs–especially for regular backpacking trips.

But, and this is a big but.  I do think that a major US economic collapse is a definite potentiality in my lifetime.  While i eat mostly vegetarian and often vegan now, mostly because i don’t like supporting factory farming (i do eat a little W.A. Salmon, sardines, and non cow dairy occasionally), i have no illusions that should a collapse occur, that i would be able to continue eating in that manner.  So, i know that we will be hunting should this take place.  We are set up for that already, as i have a compound bow and she has a 22 lr rifle.

Ideally the pack will be able to carry heavier loads should the need arise.  That’s why i’m a bit “stuck” on the more full frame idea/concept.

I’m quite happy with the pack i have now–a SMD Fusion, but my spouse’s current pack is not so great for even moderately heavy loads.  She has a Golite Jam.  The motivating idea is that should this event manifest, i can give her the SMD Fusion which carries moderately heavy loads quite well and comfortably, and i take the MYOG pack and carry more weight (meat, etc) if need be.  The Golite can be a back up pack should one break, wear out, etc.  (we’ll also be using something like a 3 wheel stroller or bike stroller to carry stuff in).

Completely agree Bob, often the learning is in the doing.  I don’t often do mock ups before doing a project, but i think it would probably be a good idea on this one.

A quick note about carbon fiber vs bamboo.  If you’re using both materials in a trekking pole type design where the tubes are primarily vertical, i would say the overall strength and durability per weight definitely goes to carbon fiber.

But carbon fiber hollow tubes vs bamboo if you lay them horizontally and put weight and force downwards towards the middle of the shaft, i would say the bamboo has the advantage, especially if you put the foam core in it.  Bamboo material is more elastic than carbon fiber, unless carbon fiber is specially woven to increase same.  But CF arrow shafts, golf shafts, or especially cheaper pultruded tubes–i’m definitely betting on bamboo over CF on that application.

I have wondered about placing CF tubes or rods within Bamboo or vice versa, but this would definitely increase weight and cost for me (i think a thin layer of foam, wrapped around a carbon fiber tube placed in a hollowed out piece of bamboo might be most ideal).

As it stands, this pack will cost me around 40 to 50 dollars to make.  Most of that is the 1 meter X 1.5 meter UHMWPE fabric, which costs about 25.  The other materials i either have, or i can get quite cheaply.  Cost probably shouldn’t be a factor though, since i’m looking for long term durability in a survival scenario potentially beyond just regular backpacking.

Wood really is a damned interesting material, and so handy for so many applications. I once heard it said that “if wood didn’t already exist some materials engineer would have had to invent it.”

Agreed Dean, but i’m now looking at 7075 grade Al alloy as a potential material for the frame. It will definitely add some weight, but the rest of the pack will be so light that it should still come out fairly light and it definitely will be much, much more durable than bamboo.  Anyone know how easy or not it would be to bend .25″ thick by 1″ wide 7075 plate Al?   Or to drill it?

Be aware that there are over 1400 species of bamboo.  Picking one at random for a structural application would be a bit like picking a random fabric with which to sew your pack bag.  If they weren’t already 30-40 years old, I’d just get some old bamboo ski poles at Goodwill since they were selected for strength, durability and quality already.  It’s pretty amazing (and amusing) to see a 20-story reinforced-concrete apartment building being constructed in China with all the surrounding scaffolding made of bamboo, lashed together.

Rather than a 90-degree elbow fitting, I’d use a square lashing, a la Boy Scout monkey bridges and such.  Very light, cheap, and field-modifiable.  And diagonal lashing if you triangulate the frame for stiffness.

Another cheap, light, strong material to consider is the aluminum tubing used in crutches.  Drill out the rivets, remove the handles, and you have lengths of tubing, about 5/8″ OD that is strong enough to make a very substantial pack frame. My Salvation Army as often as not says, “Take as many as you want, for free” since EVERYONE buys $79 new ones when they sprain their ankle and NOONE thinks “the thrift store always has crutches for $2.50/pair.”  The existing bends sometimes can be worked into your design.  You can make all sorts of things from that tubing: pack frames, camp stools, Klingon disruptors, etc.

“But carbon fiber hollow tubes vs bamboo if you lay them horizontally and put weight and force downwards towards the middle of the shaft, i would say the bamboo has the advantage, especially if you put the foam core in it.”

Yes. But you want support in the vertical direction, perhaps only around 10% of the load would be horizontal.

Anyway, look at some of the aerotech designs for light weight construction for a back panel. For heavy loads, 40 pounds plus, you need to compensate for torsional twist, load carrying ability of the struts, and ways to reinforce these against the various loads should you go with Al. 1/4″ plate Al is NOT light, nor, is it very strong. I use it for making machining jigs because it is easy to work with. Under heavy loading (in the range of 2000-2500 pounds) I use it laminated over a single layer of 2×4 for stiffness.

Balance becomes important for heavy loads. Look at front packs to help there.

The internet might have some ;)

https://www.onlinemetals.com/merchant.cfm?pid=17828&step=4&showunits=inches&id=813&top_cat=60

I doubt that there is any aluminum alloy so hard that you’d have difficulty drilling through it. 7075 is what McHale uses in his stays. His website says to bend them to shape by hand, so bending is evidently not an issue.

I just re-read your performance goals and use case.

Check out the Exped Lightning: http://www.exped.com/usa/en/product-category/backpacks/lightning-45-lichen-green

I bought the 45 last summer and have been very happy with it.  They rate it to 50lbs, and I used it on a week long w/ a starting weight of 35lbs.  It uses a single center stay combined w/ a short horizontal bar at the load lifters – the T-joint is fabric, so not rigid.  The horizontal is tubular – probably aluminum, but you could use just about anything.  The vertical is an aluminum bar, but the unique thing about theirs is that it’s actually square-corrugated, making it lighter than a solid bar.  You might be able to purchase one from them as a replacement.

The pack body is just a simple, straight tube, so easy to sew, per your goal.  They have several videos explaining the design and adjustment of the frame.

Edit: that trip was the Bailey Traverse. Lots of off-trail and class IV. That pack strikes a great balance between load handling and freedom of movement.

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Thank  you for the ideas David.
Nice disruptors btw.

Thank you James.

Thank you for the info Dean.

Hi Rene, that Exped design is pretty ingenious though the pack is overall on the heavier side.  If i borrow aspects of it, i won’t have to have it as adjustable which should save some weight.