Make Mine A Miracle Of Rare Device
What Backpacks Are Made Of, Part 1: The Bag.
– General requirements. –
You may like your pack, and maybe your pack likes you (you'll never really know, but you can at least pretend that it does), but you won't agree on everything, you and your pack.
You have to live together, but living together is always a compromise. A compromise means that you can plan and scheme and fudge things and hope they always go your way but they won't. At best you'll get caught and scolded and have to give some ground. At worst, well, your pack may stop, and sit there for a little while without saying anything, and then before you know what's happened, it will die on you. Destroy itself. Unravel. Come apart at the seams. Cease to exist.
They do that.
And then you'll wish you had been smarter, easier to live with, more flexible. Less likely to perish alone in the wilderness.
But that's how life is. You need some things. Your pack needs some things. The two of you have to work it out.
What you need is a pack that is reasonably light, and strong. Besides strength you need toughness, which requires an ability to roll with the punches, take some hits, absorb some blows, and carry on. Your pack needs to be made of materials that are light, strong, and as immune to rust, corrosion, wear, rot, and insanity as they can be.
And you need a pack that is comfortable.
What your pack needs from you is respect.
Your pack needs to be treated as though you really care about it, appreciate what it can do for you, and understand how sophisticated it actually is, despite being made of simple stuff, despite being only a bag with some straps. You need to give your pack just a small bit of care, like keeping it out of the mud, away from fire, off the rocks, and giving it a good scrubby wash every now and then. Not all that often, not every day necessarily, but every now and then.
Do that, come through for your pack, and your pack will come through for you
– The pack bag (Le sac de paquet.) –
· Canvas ·
After animal hides, early on, the preferred material for pack bags was canvas, and remained so for a very long time.
Canvas is not glamorous. It is plain. No one thinks twice about canvas. It is there, waiting, like a good friend or a door mat, always ready to help out, dependable, easy to overlook, but reliable.
These qualities are rare.
You yourself may not have them.
For many centuries, when someone said canvas, what they meant was hemp. Strange but true.
The ancient Greek word kannabis, derived from even older words, meant a material that would make sturdy sails. Sails have always been important, and they require strong fabric to make them work. At one time the entire world depended on dependable sails. Sails were made of canvas and no one dared to try smoking them.
Canvas is a plain textile, whether of hemp or linen or cotton. Today we think of canvas as a cotton fabric. Fine. OK. (Yawn.) But its main purpose throughout history, after becoming sails, and avoiding being smoked, has been as a tent fabric. And if woven tightly, canvas can be nearly waterproof, at least for a while, for some uses, as in tents. As a tent material canvas serves well if it is waxed, and stretched tight, and pitched at an angle.
Whyzzat?
Because cotton fibers swell when wetted and this swelling closes the fabric's pores. Waxing and careful pitching do the rest. Canvas was the first waterproof and breathable fabric ever. Bing!
In pack bags canvas's waterproofness isn't stellar. What does matter is its other qualities. Canvas is soft, quiet, strong, durable, and feels warm to the touch. If woven properly canvas resists abrasion better than many synthetics (though less than some), but it does mildew, and will rot if left wet. And it is relatively heavy.
So now we mostly use other fabrics instead of canvas.
· Nylon ·
Like nylon.
Most pack bags today are made from the same stuff as toothbrush bristles. Nylon, the miracle of miracles of fabrics.
Developed during the 1930s, nylon is made of tiny chemical building blocks called monomers. These are like polymers but not as happy. Monomers live alone, and monomer life is monotonous. What are monomers anyway? Well, monomers consist of a few atoms stuck together by random chance working under the inevitable laws of nature, and then left that way. Unchanging. Forever. Alone.
Oh so alone.
So very alone.
Unless.
Unless?
Unless some random meddling chemist starts dinking around in the lab one day, and you are a diamine and the chemist decides to mix you up with some dicarboxylic acid and see if anything fun happens.
Sometimes.
Sometimes it does.
If there are lots of other diamines like you in a bottle, and enough dicarboxylic acid, and so on. In other words, if the chemistry is right.
Ah, chemistry.
If it is, if the chemistry is right, you mix it up. You, a diamine, and the dicarboxylic acid decide that life would be better if you were a team. And then lots of otherwise monotonous diamine bits join you and your acid partner, and more acid and more diamine bits, and pretty soon you have this really long conga line and everyone is having all kinds of fun, and you all decide hey, let's stay together. That makes you part of a polymer now. You are no longer alone. You have friends. All of you are joined together in one long line. Party on.
A polymer is one big thing, but made from many, many smaller things, and being part of a polymer is more fun than being a monotonous monomer all by your lonesome out in the dark somewhere.
Being part of a polymer means you always have lots of friends around. There are things to do. Places to go. Fun names to try on, like nylon 6,6, or nylon 5,10, or nylon 6,12, or nylon 10,12, and so on.
Suddenly you are part of a big family, and as it is in any family, your siblings and relatives all look kind of the same but not quite, and some are better at some things than others are, and some of them are even quirky too. Like some forms of nylon are so heavy and dense that they can't even be spun into yarns, which is important because of what we talk about next.
Are ya ready?
Mostly, for the stuff we're interested in, after being invented and all, and ending up in all kinds of strange products, nylon, as most of us know it, is used in fabrics. And that's where pack bags come in.
Nylon is a synthetic, meaning that it is something that does not occur in nature. But this isn't always bad. Since nylon doesn't occur in nature, there is nothing out there that knows how to eat it or how to grow on it. Boll weevils eat cotton like popcorn but there are no nylon weevils. Corn borers bore into cobs of corn, but there aren't any nylon borers. As for mildew, it's so early in the evolution of nylon as a substance that the dew hasn't even formed yet, let alone had time to get mildy.
Nylon doesn't get its hackles up over being abraded. Bugs don't bug it. No rot rots it. It barely even absorbs water, and many chemicals, even some nasty ones, only roll off its back. Hah!
Ha! Ha! Ha!
Nylon melts rather than bursting into flames, it's comfortably stretchy, it can be shiny, lustrous, or dull. It takes dyes. Nylon fabric can be light and filmy or sturdy and stout. It is handy. Dandy-handy. 1
Nylon fabric comes in many varieties, but basically we think of only two, a solid, smooth, slippery fabric, or a ripstop.
Ripstop is a smart fabric, very smart. Ever so smart.
Ripstop can be made of various textiles other than nylon, so it's not the basic substance that's important, but the idea behind it. Ideas take smarts. Ripstop is more a concept than a thing, which is, that if you weave a fabric and then you lay in a heavier, stronger yarn every so often, you get a finished fabric made of two yarn weights. Most is the normal weight and the other is the heavy, tough stuff, but not much of it. The end result is a fabric of ordinary weight that is almost as tenacious as if it was really heavy, but without being really heavy.
Ripstop fabric is stronger overall than single-weight fabric, but the real genius inside the idea it is that ripstop stops rips. (OK, it has a pretty good name too.)
We saw the word tenacious go by a couple sentences back. Did you notice? Tenacity is actually a technical term. Tenacity is a measure of how well fabric resists tearing, if a tear does get started somewhere. Since the whole point of ripstop fabric is not to rip, ripstop fabrics are tenacious by nature. 2
How many rips would a ripstop stop if a ripstop could stop rips? Plenty, because that's what it's supposed to do. That's what it does for a living.
The ripstop fabric's pattern may be either square or diamond-shaped, or both (giving you a super anti-rippety-stoppity ripstop). The point is that the heavier yarns are too hard to tear under normal stress, so they absorb that stress, dissipate it by routing it evenly into the rest of the fabric, and then your pack stays intact and you don't die.
But how about the other option, not-ripstop?
Most packs are not actually made from ripstop fabric. They are made of relatively heavy solid fabrics of a single weave. This may be taffeta, oxford cloth, pack cloth, ballistic cloth, Cordura®, or something else again. The terminology is not exact, and there are trademarked brand names buzzing around all over. (In fact, one just flew by, right?) But you get the idea. 4
Taffeta and oxford cloth are pretty similar, with taffeta generally thought of as being a bit lighter, but maybe not. Some of the names, like pack cloth or ballistic cloth, refer more to the weight of the fabric than to the weave.
Taffeta has a plain weave, though sometimes it might have a slight ribbed appearance. Oxford cloth is pretty much the same thing except that its weave is jiggered a bit to give it a coarser, more basket-weave appearance. This looks good both in shirts and in packs, especially those for manly men. And the rest of us too.
Pack cloth is basically only a heavier fabric of whatever kind, and generally has a waterproof, urethane coating on one side. (Urethane is the stuff that peels off like sunburned skin after a couple of years.) Ballistic cloth is about the same thing, just very heavy, and with a kinkier name. 3
Weights for fabric used in pack bags range from about 200 to 500 denier, or around three to eight ounces per square yard of fabric (85 to 225 grams per square meter). In light and ultralight packs heavy fabric might be skipped altogether, or used only on the bottom, with an intermediate weight fabric going into the shoulder straps and waist belt for a tad more abrasion resistance there.
· Extra Tough Fabrics ·
Ballistic cloth sounds tough. It is.
It is because it is nylon, and because it has a thick and heavy weave. The yarn weights for ballistic cloth range from about 1000 to 2000 denier. (Denier is the weight in grams of 9000 meters of a single yarn. This sounds excessive — single yarn, 9000 meters — but the French are like that. Denier belongs to them in case you hadn't guessed.) Common yarn weights for clothing run from maybe 50 to 150 denier, to give you some perspective.
Ballistic cloth is used in luggage, computer cases, and sports bags as well as packs, and in a few clothing items as well. It gets its name because it looks like it might be bulletproof, and early on it was, in a way, if you were not all that fussy about exactly which bullets you might stop on a given day. Overall, ballistic cloth is decent — strong, puncture resistant, and tear resistant.
Cordura® is a brand name, though there are similar products under different names. Cordura® is nylon, and the process used to manufacture it gives it a rough but fuzzy texture that is especially good at resisting abrasion, though it may not be so puncture proof as flat weaves like oxford cloth. Like ballistic cloth, Cordura® is used in luggage, hunting equipment, heavy footwear and some clothing as well as in packs.
Aramids. Who? Aramids.
These are forms of nylon from outer space. They are super strong, just about indestructible, not normally made into sheets of fabric, but as with Kevlar®, a proprietary form produced by DuPont™, they are generally used as a reinforcing fiber. Various versions are used in actual body armor, and even as substitutes for asbestos.
Exemplifying how amazing this aramid stuff is, it won't burn or even support combustion. Get it hot enough (800° F to 900° F, or 427° C to 482° C) and it will break down, but it won't even melt first. It performs this act while remaining flexible, and twice as resistant to cuts as cotton is. 5
Spectra® — like Kevlar® but different. Not an aramid but good old polyethylene, like the stuff clear plastic bags are made of, but tweaked a bit. It is High Modulus Polyethylene or HMPE. A bit gnarly though — it is currently the strongest synthetic fiber in existence, at eight to 10 times the strength of steel (40 percent stronger than those aramids, and having twice the cut resistance. It is also known as Dyneema®, which is the same stuff but made by a different company, and also stronger somehow, at up to 15 times the strength of steel instead of 10 times.
Spectra, unlike steel, is light enough to float, while exhibiting a resistance to chemicals (like water) that is way beyond steel's as well. Rot, micro-critters, and ultra-violet light don't affect it either. In packs it, like Kevlar and Dyneema, is used mostly as a reinforcing fiber. Elsewhere in the fabric world it finds its way into climbing equipment, shoes and luggage. 6
The High Modulus Polyethylenes have a lot of strength for little weight but they do melt at relatively low temperatures, somewhere between 145° F and 155° F (152° C). While they could be fashioned into a wider range of clothing fabrics, their chemical makeup is one of extremely long molecules (the high modulus part) of almost inert materials, which contributes to a slippery feel that people don't like in clothes, for example. (Although with HMPE you could have bullet proof underwear.) 7
· Super Light Fabrics: Silnylon ·
Now we get to pop over the opposite half of the lunatic universe. We won't be comparing the next set of fabrics to slabs of steel, but to the gossamer-thin, silvery unobtanium wings of hyperintelligent cyborg butterflies capable of sailing on the faintest of solar winds. Not that long ago nylon itself was a strange mystery material, and even more recently nylon soaked in a silicone oil was too. (It was then and still is now called silnylon.)
Then came spinnaker cloth, and after it, Cuben Fiber (now known as "Dyneema Composite Fabric").
Silnylon. Spinnaker. Cuben. Dyneema Composite Fabric. Sound exotic? They are, but you might already be using some of them.
Silnylon is now used extensively in stuff sacks, tarps, single wall tents, and packs. Depending on which variety you encounter it may feel light, dry and crinkly, or still light but slippery, or yet again light, but almost oily. The samples you find in high quality items from big-name manufacturers look better and feel drier than the stuff you may get to make your own gear from, but the latter is still fine.
An early silnylon tarp I bought from a major retailer came with a somewhat oily feel that didn't dissipate even after years, though the fabric was impeccable otherwise, and the oily feeling never became an oily stain anywhere, nor did anything peel from the fabric or rub off.
Still, the fabric you buy already professionally made into stuff sacks or packs seems nicer all around.
Silnylon isn't really fancy except for a couple of things. The basic fabric weighs 1.1 ounces per square yard, which would be around 35 grams per square meter if we ever calculated such things. The silicone coating, which permeates the fabric (and is not just painted on one side) adds 0.35 ounces (10 g) to give a total weight of 1.45 ounces per square yard (50 grams per square meter).
Considering that some of the usual pack materials weigh five to 10 ounces per yard, this seems nuts. And it is nuts for some people, for some loads. No, scratch that. Make it most people, most of the time. Normal people won't go near an extremely light pack, even if tempted by the possibility of carrying extremely light loads. It takes time to catch on.
But if you have caught on, and if your loaded pack weighs 15 to 20 pounds (seven to nine kg), and it's made well, and you are reasonably smart, this fabric can handle it. A pack made with silnylon won't stand abuse. As in: you can't sit on it and expect it to come through for you. You don't throw it into the back of a gritty pickup truck and pretend that everything will be fine, especially if 10 other people dump their packs and boots in after you, and your pack is on the bottom of it all.
But this fabric is tough. Silicone-impregnated fabric has good abrasion resistance, and it is a lot more tear proof than the plain version of the same fabric. And silnylon is automatically waterproof. Sewn-through seams leak but the fabric won't.
And another thing.
This coating of silicone oil actually becomes part of the fabric. It doesn't peel off like the polyurethane coating on regular nylon. It is there for the duration. Make a frameless pack from silnylon and make it well and you don't really have to worry about the fabric as long as you take reasonable care of the pack. The pack will hold as much weight as you can stand to carry in it, and you will give up before the pack does.
Want a light pack? Use this fabric and make one that weighs from 10 to 16 ounces (285 to 450 g), depending on size, design, and features. Or which weighs less, sometimes much less. And always more, if you want, but that's not the goal, is it?
· Super Light(er) Fabrics: Spinnaker Cloth ·
Lighter yet, there is (was) spinnaker cloth.
Kinky-doodle.
This is a concept rather than a type of fabric, the same way that ripstop is. The idea comes from cloth used in spinnaker sails on racing boats. You've heard about sailboat fuel. Well, this is the stuff that sailors use to fill their tanks.
Some spinnaker cloth is nylon. Some spinnaker cloth is polyester. People also use spinnaker cloth for making kites. Some is uncoated. Most (as used in backpacking) is coated. Weight (per square yard) ranges from 0.5 ounces up to 1.5 ounces (15 to 50 grams per square meter). The stuff that the cottage super ultra light backpacking manufacturers use (or once used) ranges from 0.7 to 0.99 ounces per square yard.
Spinnaker cloth is extremely delicate and for use only by the most accomplished super ultra light backpackers who aren't afraid to feel a little tingle of fear all day long, lest their packs suddenly explode and dump goodies all over the trail. Commercial packs of spinnaker cloth weighed from seven to 10 ounces, and used to be available from a couple of manufacturers, if you had a note from your mother, but they all seem to have been replaced now by Cuben/Dyneema Fiber packs. Oh, well. Never mind.
Why is spinnaker cloth a concept rather than a type of fabric? Because spinnaker cloth is any cloth used to make spinnakers, and that fabric can be anything you want. A spinnaker is a type of sail. Nuff said there.
For packs and tarps, the preferred spinnaker cloth was SpinnTex, made somewhere deep underground in secret caves by high tech gnomes with six-fingered hands and strange-looking tools. SpinnTex is silicone impregnated polyester ripstop, not nylon. It weighs 0.97 ounces per square yard. Next year, or even this year, or last year, you may see, or may have seen, a different brand, made of a different base fabric. Technology marches on. Don't fret so much.
· Super Light(est) Fabrics: ·
· Cuben Fiber/Dyneema Composite Fabric ·
Yeah, fiber. And that's Cuben, not Cuban. Fidel never stirred this pot. But we are still sailing.
Cuben Fiber came to us by way of the 1992 America's Cup race, and the boat America3 (pronounced America Cubed), that used sails made of a new material called America Cube Carbon Fiber Hybrid. The news media could not handle it (too many syllables, took too long to say, grammar checkers went nuts) and so they shortened this to Cuben Fiber and that's what we all called it until the huge Dutch company DSM Dyneema acquired Cubic Technologies, the original U.S. manufacturer, in May of 2015.
Anyhow, Cuben Fiber or Dyneema Composite Fabric, whichever you prefer, is light. It is tough. It is waterproof.
But.
It can't stand much abrasion, so its use in packs, clothing, or anything else that contacts the ground or is involved in rubbing activities is problematic.
This non-fabric fabric is a composite.
A composite is assembled, not woven on a loom. Cuben/Dyneema Composite Fiber has two outer layers of clear plastic that sandwich a layer of fibers between them. The fibers can be laid in randomly or can be loosely woven. These fibers provide the strength and the outer layers hold them together and provide waterproofness. (Or if you are still interested in sails, windproofness.)
The middle layer, the fibers, may be carbon fiber as it was early on, but this layer is more likely strands of Ultra High Molecular Weight Polyethylene (UHMWPE), basically the same stuff that Spectra and Dyneema are made of. The two outer layers are polyester film (clear, non-woven polyester sheets).
Got it?
Cubic Tech, the manufacturer, sells to companies that use this material in "parachutes, kites, balloons, airships, tension structures, tubes and tube reinforcements, flexible pressure vessels, tarps, backpacking, medical devices, protective clothing, aerospace equipment", and so on.
Airships. Sure. Gimme two. 8
Since 1992 Cuben/Dyneema Composite Fiber has been refined, and now you can buy it in quantities small enough for the home hobbyist who can afford it. Note that. Who can afford it.
One retailer had this truly insanely light and insanely expensive fabric available by the yard or by the roll in January, 2017, at the following prices.
| Weight (oz/yd2) | Weight (g/m2) | Cost/yard | Cost/36 m roll |
|---|---|---|---|
| 0.34 | 11.4 | $25 | $ 899 |
| 0.51 | 17.4 | $28 | $ 999 |
| 0.67 | 22.7 | $34 | $ 615 |
| 0.74 | 25.4 | $29 | $1050 |
| 1.00 | 34.0 | $28 | $ 999 |
| 1.43 | 48.4 | $31 | $1095 |
The short interpretation of this is that Cuben/Dyneema Composite Fiber is really light and really expensive material. An experimentally-minded hiker named Bill Fornshell made a 1.5 ounce (42.5 gram) pack and seven ounce (198 gram) hammock out of Cuben. Light. Srsly. And given those prices, expensive too, even if you make your own.
So you may not want to.
– Conclusion (Zusammenfassung). –
Lighter than this we can't go yet. Does anyone want to go lighter? Sure. Always. You betcha.
Should anyone go lighter? Your call.
Silnylon is extremely light as these things go, and surprisingly tough due to its silicone coating. A small pack made from silnylon is naturally abrasion resistant, easy to clean (no open weave for dust and grit to lodge in), waterproof (aside from the seams), and strong enough to do the job.
Move to spinnaker cloth, or something similar, or to Cuben Fiber and you are immediately inside a world where your pack can function admirably, as long as it's really small and your load is especially light. And as long as you don't fall on the pack or scrape it against thorns.
It is hard to imagine a fabric being much lighter than half an ounce per square yard, or what real advantage a person would get. Is a four ounce pack noticeably lighter than a seven ounce pack? (Or in terms of tarps, would a six ounce tarp really beat out a nine-ouncer?) This is a question only you can answer.
Weights will go down, eventually, but don't expect anything radical soon. What is more likely is that strength and durability will go up. Things like puncture resistance, abrasion resistance, tear strength, ability to hold stitches. (Or better tapes and adhesives for those fabrics that should not be sewn.) These things will improve. And they they will be more practical improvements than absolute cuts in absolute weight. But they won't be here this afternoon. Maybe tomorrow afternoon.
Next up — what the rest of the pack is made from.
– Footsie Notes –
1: Nylon properties: http://bit.ly/12oFsXf
2: Tenacity: http://bit.ly/1sg3WZi
3: Ballistic cloth: http://bit.ly/1GaRBxX
4: Cordura, etc.: http://bit.ly/1sg3WZi
5: Aramid: http://bit.ly/1Bx3Jtg and http://bit.ly/12Kejhg
6: Spectra: http://bit.ly/1ww3VaM and http://bit.ly/1IvU2NA
7: HMPE: http://bit.ly/1waulNb and http://bit.ly/1vLyHuj
8: Cuben: https://bit.ly/3mLEKh7