Backpacking Weight Ranks

Brett,

I agree that scloding a taller/larger person for carrying more weight than some tiny female gymnist is a bit silly. But we need SOME kind of metric.

We could get more complex about it, but who'd want to figure out:

PACK MASS INDEX (PMI)

(base weight in kg) / (hiker height in meters, squared)

or something like that?

Or, perhaps more clearly:

I modeled it after Body Mass Index, but I tried to keep it metric. Using (height in meters)^2 is an extremely rough surrogate for body surface area.

For those of you who can't think in metric:

PMI Trivia:

My current summer PMI is 1.26.

A 5'8.5" person carrying the 'standard' 10-pound pack would be almost PMI=1.5 So, what say we define UL as PMI<=1.5, for simplicity's sake?

Also, a 5'8.5" person with a 5-pound pack has PMI=0.75. Again, why don't we define SUL as PMI=0.75, which makes absolute sense as half of 1.5?

Oh, and to get a PMI=1 while carrying a 10-pound pack you'd have to be almost 7 feet tall.

But, to get a PMI=1 a 5'10" person needs a base pack weight just under 6.9 pounds. A noble goal.

Thus I propose that PMI=1 be assigned as some sort of milestone, too. Especially since 1 is a nice round number.

:o)

Can you tell I'm bored?

Okay, okay, this gets even better!

How about:

Pack Weight Index (PWI) using Avoirdupois units!

PWI = ((pack weight in pounds) / ((hiker height in inches)^2)) * 500

Or:

Under this system a 5'10.7" person with a 10-pound pack has a PWI = 1 and with a 5-pound pack his PWI = 0.5.

Now, THOSE are easy numbers to remember, and correlate perfectly with the already-established definitions of UL and SUL. It is ALWAYS good to define something important as equal to 1. We just have to remember that the 'standard Avoirdupois hiker' is defined as 5'10.7", a hair taller than the 'standard metric hiker.' Which seems appropriate, somehow.

Once you calculate and memorize your PWI for a 10-pound base pack weight it is easy to calculate it for any reasonable base pack weight- it is proportional. In keeping with my medical model I will refer to that as PWI10, and it is basically an obscure way to state your height. For instance, since I am 69.5 inches tall with a 10-pound base pack weight my PWI10 = 1.035. So, if I want to know what my PWI is carrying my standard summer 8.8-pound pack, I just multiply 1.035 x 8.8 / 10 = 0.91 !

Now you sasquatches out there can compare yourselves to the rest of us in a fair manner! Thusly: "Yeah, my pack may be over 10 pounds, but my PWI is still only 0.9 whereas your PWI is 1.2, Shortstuff!"

There! I am officially abandoning the PMI in favor of the PWI!

Of course even PWI isn't perfect. It assumes, for instance, that a taller person needs a heavier stove. Likewise for other gear that isn't dependent upon body size, like compass, tent-stakes, etc. But it probably WOULD allow a group to split up communal gear in a fair way- just try to have everybody's PWI equal.

REALLY bored. :o)

Someone should check my math…

Should we break this out into:
Base Pack Weight Index (BPWI)
Total Pack Weight Index (TPWI)
Skin-Out Weight Index (SOWI)
?

SOWI might actually be the most rigorous of the three. Plus, you can pronounce it as one word. As the developer, I hereby set that as "sow we", rather than "sew we". However, SOMI will be "Sew me." Conform!

Ok, the new benchmark for the Lunatic Fringe among gram weenies is to attain a SOWI<1 !

I like it – well avoiding the avp stuff

Imperial for ya.

edited to improve range

That makes perfect sense, because a 5'9"-ish hiker carrying 20 pounds is (roughy) PMI=3 which is twice the SUL PMI=1.5, just as 20 pounds is twice 10 pounds. So, PMI=3 defines LW backpacking, as the math dictates it must.

Perfect.

How about a PWI graph? But, wait, you're in Berlin. Bummer. Well, at least I can take solace in the fact that my standard hiker is bigger than your standard hiker… :o)

Certainly, the PMI formula is more esthetically pleasing. I will admit that. That conversion factor of 500 in the PWI formula is just ugly. But it is nice to have PWI = 1 define SUL. I love it when I can set something important equal to unity!

I think it might be a little too harsh on short people / generous to tall people. A 6'5" person can carry 5lb more than a 4'11" person and still hit a PMI of 1.5 (12.6 vs 7.4 lb).

At the extreme of PMI=1 their weights are 4.95 and 8.37 lb

That's about 70% more weight for the tall person.

Just when I thought that there was no possible way we could get dorkier….

>> I think it might be a little too harsh on short people / generous to tall people.

So is BMI. It is a harsh truth.

And, this is all a joke, brother…

But even then this might not be terribly unrealistic, as far as a measure of "effort" it takes to carry the pack for the sasquatch vs. elfin hikers in question. Consider their ideal body weights, per the MetLife tables: 4'11" female about 117 pounds, 6'5" male about 183 pounds. Thus, the "average" MetLife sasquatch also WEIGHS about 70% more than the mouse, in addition to being alloted 70% more pack weight by the PMI or PWI formulae.

And, when you're talking about such small pack weights you have to be careful about quoting percentages. 2 pounds is 100% more than 1 pound, but carrying either is trivial.

Hmm. Of course the trend holds true if you extrapolate into big weights, too, doesn't it?

Well, heck, I've already admitted that it isn't perfect. But it is probably still better than saying that 10 pounds qualifies as UL for both sasquatch and elf… :o)

"But even then this might not be terribly unrealistic, as far as a measure of "effort" it takes to carry the pack for the sasquatch vs. elfin hikers in question."

True, but we were trying to equalize the thresholds for ease of attaining a pack that light – not ease of carrying it.

"And, this is all a joke, brother…"

Of course all of this is just an intellectual exercise – riffing and jamming but with spreadsheets instead of guitars.

A geek-off.

>> True, but we were trying to equalize the thresholds for ease of attaining a pack that light – not ease of carrying it.

Well then we're talking about subtly different things. I sort of thought it would encompass a bit of both, ideally, since the whole point of going UL is to have a pack that is easier to carry. But, yes, after some thought I will agree that what you are saying is a more accurate characterization of the whining that we hear from the sasquatch people.

I will graciously concede. :o)

So, I guess we have to figure out a way to flatten the slope a bit? Any ideas on how to do that? Bearing in mind that we must have sound theory to back up whatever mechanism we come up with?

I guess that what we should do is survey 10-pound base weight packs of 5'10" individuals and see what percentage of the weight is considered "height dependent". Then we can further modify the formulae. For instance, if we decide that half of the average pack's weight is height dependent, then we can construct a formula that ignores half of the difference in height between the standard hiker and the actual hiker. (I actually think I can figure out how to do that…)

Who's up for performing the survey? :o)

Also, speaking of geek-off:

I was unhappy with the artificial origin of the 'standard Avoirdupois hiker' height, so I looked up some true average heights… Average human height worldwide is, coincidentally, 4'11" or so. But I didn't think that basing the PWI formula on that was really in the spirit of the thing since most of us are- admit it- western males.

So, ignoring extremes of age the average western male height seems to be about 5'10" or so. (The Swedish are a little taller, the French are a little shorter, etc.) With this as the height of the standard hiker the constant in the PWI formula should be 490, rather than 500, to make the average hiker's 10-pound pack result in a PWI = 1.

500 nonetheless results in a pretty good SWAG, and is easier to remember. But the "official" constant is now 490.

I could, of course, develop a similar constant for the PMI to correct for average height. As a matter of fact, if I'm going THAT far I could also make the constant such that a 5'10" hiker with a 10-pound pack produces a PMI = 1, so that it is identical to the PWI…

Do think it's worth the trouble? Or should I keep the metric formula "clean"?

EDIT—

Well, heck, it actually wasn't much trouble. The PMI constant would be 0.701, which I suppose we could round to 0.7 to make it easier to remember. We'll call that the "normalized" PMI, eh?

Actually, I guess that if I'm being intellectually honest then the PWI formula above is "normalized", too. I have adjusted the nomenclature in that first equation appropriately. Without the constant (be it 500 or 490) the Avoirdupois formula produces some very cumbersome numbers. (Even if you use feet instead of inches, UL is defines as about 0.3.) At least the non-normalized PMI formula (without the constant) produces wieldable numbers, as long as we are willing to concede the 5'8.5" 'standard metric hiker.'

I really like setting UL at unity, though! :o)

I will go further and clarify that unless otherwise specified, PWIn means BPWIn and PMIn means BPMin, and that by definition these ALWAYS factor in any item that is neither worn nor actually held in the hands while hiking, but including the weight of the actual pack, and less consumables. Thus, the gram weenies can't cheat on their BPMIn/BPWIn by having stuff in their pockets!

I invented it, so I can define it however I like. So there! :o)

So, now the normalized PMIn and normalized PWIn should be equivalent, with UL defined as unity. Or, you could multiply by another factor of ten, to produce a Height Adjusted Pack Weight Equivalent (HAPWE). In such a case, UL = PWIn x 10 = 10. Get it? It will produce a number equivalent in pounds to the weight of your pack for a 5'10" person. Then you can use whatever definitions you like for UL, SUL, or whatever. HAPWE may be cumbersome to calculate, but everyone will understand the value produced intuitively.

Yeah. I think I'll run with that…

Somebody please check my math. Better yet, somebody produce a proof that the two equations are equivalent… :o)

.

>> Behold the rise of the Packweight Categorization Flame War!

Nooooooooooooooooooooooo!

Get a….

Comfortable lightweight pack.

Lightweight shelter, tent, tarp or bivy and or any combination of that will keep the bugs off and keep you and your gear dry.

Lightweight sleeping system that you can actually live with that will keep you warm.

Lightweight clothing including raingear that works for you for the appropriate season.
Lightweight water system.
Lightwieght cooking setup.

Pack it with all the other crap you want to carry, load up 2 qts of water and 5 days of food and go for a test run/hike.

If its too heavy start throwing stuff out.

Of course there is the Cody Lundin method, Barefoot, one water bottle, an old can, a stiker or a bow drill, a garbage bag, a mouse trap, a neck knife and you are good to go.

It's a JOKE, Troy.

Admittedly, it is a geek joke, but it is still a joke…

Nonetheless, if we can get the "5'10" hikers' 10-pound base pack height-dependent weight percentage survey" done, I'll figure it out. Luckily, I qualify as an (approximately) 5'10" hiker…

:o)

So, what will we define as "height dependent"?

1) Surely, any clothing, including socks and shoes, base layers, insulation layers, wind shells, rain shells, hats, gloves, etc.
2) Mosquito headnet? Kind of hard to find different sizes…
3) Sleeping system components, including bag/quilt, and pad.
4) Bivy? Shelter?
5) Stuff sack or compression sack for the bag/quilt?
6) Stuff sack for the clothes?
7) The pack itself?

What do y'all think?

What fun is that?

I agree. You guys are nuts. I love it!

Super Ultra Light “Off Set” Certificates

First message on this thread that was started on 04/01/2007.

Super Ultra Light “Off Set” Certificates-Link

===============================================.
“Super Ultra Light – “Off Set” – Certificates.



I have decided to establish a “Non – Light” Agency for the support of Pack Weight Challenged Hikers (SUL- OS – NLWPWCH). If you think Non-Profit Organizations you are close. At this time I am the only person on the Pay Roll.



If you are packing a heavier gear list than you wish for and you can not get it lighter for any of a number of reasons you can now buy SUL “Off-Set” Certificates. They are available in amounts of One Ounce up to Sixteen Ounces. You can but as many Certificates as you need or have money for. When you carry the Certificates you can reduce you real pack weight by the amount of Off-Set Certificates you buy. 



With the Off-Set Certificates you can talk about or post your gear list weight with the Off-Set amount factored into it.



When you buy SUL Off-Set Certificates I will hike X number of miles with a true SUL pack load in memory of your heavy pack. In true SUL fashion the SUL Off-Set Certificates are made of postage stamp size Cuben Fiber with the ounce weight pin stamped into the material.



SUL – OS – NLPWCH – AF07, LLC

.

Send “PM” for cost information. “

===============================================

This is one idea that is still available. Just send money.

Haha…this is awesome. It may be a joke, but it does make sense….

Personally, I don't find any need for having a number to base success on, but for those that like this going light for that aspect, your set of equations is much better than what is around now.

>>
1) Surely, any clothing, including socks and shoes, base layers, insulation layers, wind shells, rain shells, hats, gloves, etc.
2) Mosquito headnet? Kind of hard to find different sizes…
3) Sleeping system components, including bag/quilt, and pad.
4) Bivy? Shelter?
5) Stuff sack or compression sack for the bag/quilt?
6) Stuff sack for the clothes?
7) The pack itself?

Using definitions THIS liberal, my summer pack weight is roughly 70% "height dependent."

Has anybody else calculated theirs yet? (I have realized that we needn't limit this to 5'10" people and 10-pound packs, because it will average out. It should be a normal curve.)

Should I change the list?

I recall that the sasquatches always complain that they can't fit into the lightest, smallest tents, so I wanted to keep shelter on the list. But should I? Likewise, for the bivy?

Do people with different torso lengths really end up buying different-sized packs often enough that I should include the pack? Or should I go with the "main stream" and just assume that most packs are the same size and just have adjustable frames, and exclude them?

Ok, here we go…

To adjust for the percentage of equipment that is "height dependent" in any of the equations above, replace the hiker height with their adjusted height.

Adjusted height is:

((( hikers true height – standard height )*R ) + standard height )

R is the "height-dependent ratio", so, for a 70% height-dependent weight, it is 0.7, get it?

Then just figure out the PMIn or PWIn as normal. And, if you want to generate a simple adjusted weight, multiply PWIn by 10 to produce the Avoirdupois HAPWE. (I've also crunched the numbers to produce a metric HAPWE.) Assuming that my 70% height-dependent weight ratio is accurate, here are some formulae:

Using these normalized PMI/PWI formulae, UL is defined as <=1. SUL is <=0.5. Etc.

The Avoirdupois HAPWE spits out a pack weight in pounds, and the metric HAPWE spits out a pack weight in kilograms.

Here is what a chart comparing Height-Adjusted Pack Weight Equivalents for people ranging in height from 4'11" to 6'5" carrying 10-pound packs:

HAPWE is, as Andrew wanted, a rough estimate of the difficulty of attaining a given pack weight if one is much smaller or larger than the "average" hiker, due to the simple fact that some of their equipment must be smaller or larger. This is NOT an adjustment for how burdensome it is for that person to carry a given pack. It is just a display of what the sasquatches have been complaining about.

For instance, according to the chart it is as hard for a 6'5" person to get his pack weight down to 10 pounds as it is for an average 5'10" person to get his pack weight down to 8.73 pounds. Fairly impressive. Likewise, a 4'11" person who gets her pack weight down to 10 pounds has overcome about the same difficulty as the average 5'10" person who got his pack weight down to 12.62 pounds. So, not quite so impressive. (Assuming, of course, that my estimate that R = 0.7 is accurate.)

And, if you crunch the numbers, a 6'5" sasquatch who gets his pack weight down to 11.45 pounds can claim to have managed his pack weight as well as a 5'10" guy who got his pack weight down into the UL range, 10 pounds.

Make sense?

As for defining how burdensome it is to carry a given pack, I maintain that PMIn or PWIn are better metrics than HAPWE. It is a harsh truth that bigger people can carry more weight more easily. I think that the steep slopes in Andrew's charts are probably pretty accurate that way. So, if we are trying to define UL as a given level of burden, then I propose a PMIn or PWIn of 1 as the definition. (After all, i developed the equations based upon a 5'10" individual with a 10-pound pack.) And thus a PMIn or PWIn of 0.5 defines SUL.

Again, somebody PLEASE check my math. It is getting late here, and I'm a little punchy.

Now we just need to agree on a value for R. Obviously, the lower this number the less that a hiker's height effects the HAPWE. I await your input…

First, I truly commend you guys and admire what kind of intellect you can put to this task.

Second, you have WAY too much time on your hands, but I guess whatever can pass the time until the next backpacking trip…

I nominate Dean as the author of the next BPL article :
backpacking light: the metrics of

Maths looks right. If I wasn't catching a plane at 6:30 in the morning i'd play around a bit more with this.

Some body call Steven Hawking, I think ya'll just solved the remaining problems in string/M-theory.

Sorry, didn't mean to open the can. Of course I am one of those nerds gone bad.

Okay, I just figured out where those constants come from mathematically! Here is an ideal formula for Height-Adjusted Pack-Weight Equivalent:

W is the pack weight
H is the hiker's height (sasquatch or mouse…)
S is the 'standard hiker' height (which I propose be about 5'10")
R is the height-dependent ratio (which in my pack is 0.7, as I mentioned). This is a measure of what percentage of the weight of a standard 10-pound pack kitted out for the 'standard hiker' is 'height-dependent'.

You can use any units that you like, as long as you are consistent. Specifically, if you input a height in inches then ALL heights must be in inches, etc.

The result will be a weight in whatever weight units you used, be it Avoirdupois or metric or whatever. You could enter weight in stone and height in hands, if one were so inclined, and it would spit out an equivalent pack weight in stone.

We'll call this the "Fellabaum-Dolman Equation". Having a hyphenated name lends it some gravitas, and I feel that I deserve top billing. Ryan, see to it that we are properly cited in the next edition of your book… :o)

Remember, HAPWE is the one that is sort of a measure of how hard it is to lighten your pack because you can't buy all size 'medium' gear like the 5'10" person can. Enter your height for H and your pack weight for W, and it will tell you what your pack weight would be if you were 5'10" and could buy standard sizes of the height-dependent gear.

(Obviously the real world doesn't quite work this way. There is a pretty broad range of body habitus that will fit into the same medium-sized shirt, for example, so there really isn't a weight penalty. HAPWE is most appropriate at the extremes of body size.)

So, say you are a 6'5" sasquatch, but you can't seem to get your pack weight below 11 pounds. Punch that into the formula and you will note that if you weren't stuck buying (heavier) super-sized gear your pack would only weigh 9.6 pounds! Feel good about that 11 pound pack, Sasquatch!

And of course you could produce a HASOWE by inputting your skin-out weight instead of your pack weight, too. But, obviously, R would have to be larger, because a greater proportion of the weight we are measure is clothing…

P.S. Nobody has other ideas for a value for R ??? Or am I the only guy here with a well enough developed sense of geek humor to run with this?

I'm currently thinking about how to express ideal formulae for the PMI/PWI, but that's going to be sticky. The units won't cancel out as they do in the Fellabaum-Dolman equation, so the output of those formulae will be in odd compound units and will differ greatly from one another. I may be stuck with separate metric and Avoirdupois systems, and resort to a conversion factor between them. Bummer.

Craig,

Your outfit, with tarp, seems safe but barely "OK" when it comes to "pack comfort" or "comfort food". My REI Cruse UL 60 is the lower limit I'll go on pack comfort. I absolutly insist on an internal frame for load transfer to a decently padded hipbelt.

So much do I insist on an internal frame that I'm in the process of modifying a 2,300 cu. in. Camelbak "Commander" pack for backcountry skiing. Yesterday I cut off the cloth belt and slid an REI padded belt behind the pack's lumbar padding. Next step is installing 1" wide aluminum frame slats, precurved and bolted into the plastic so-called frame sheet W/ s.s. bolts, washers and nuts. Did it before on a smaller pack.

So it's all in our perceptions of comfort. Yeah, my WM Megalite bag, TT Contrail, Ultra Lite Thermarest mattress (hey, I'm 66 & deserve it) and Vargo Jet-Ti canister stove (or Vargo Triad base & ESBIT tabs) W/single 1 L. pot, plastic cup & Cool Whip[ bowl & Lexan spoon are what I consider basic UL gear. I carry a Steripen often and sometimes a Garmin Colorado GPS. Always Micropur chlorine dioxide tabs come along (never, ever liquid Aqua Mira).

Going lighter is not worth a tighter bag, a less comfortable pack, a tarp or eating cold food. So you and I part ways in the comfort area but not the safety area.

Living in the dry southwest requires me to often carry my 3 L. hydration bladder full and my 1 L. bike bottle W/ its electrolytes as well. Do I want to carry base weight, fuel, food and all that water in a no-frame pack? Heck no. Why shun real advances in pack design and comfort to save some ounces that will result in DIScomfort?

Eric

Hi Eric,
I'm amazed you actually found my 5 lb. gear list in the midst of all this craziness!

I guess it is a personal comfort thing. But I'm coming from the opposite end of the spectrum: carrying a five pound base has never impacted my comfort level; in many ways it improves it. I sleep perfectly well without a cushy pad and pillow. I eat what I like. I'm not cold. And as a bonus, I enjoy the simplicity.
As for hot food: hot trail food usually equals something dehydrated. I'm not into it. I'd just as soon carry fresh food on short trips- I like tomatoes, salads, bread, bananas, sandwiches/wraps, etc. No hot food is hardly a drawback to me (unless we're talking COLD weather or long trips). In fact, I think I end up eating better without it. Long trips are a different story…

As for pack comfort, my experience has been that the most comfortable packs are the ones that barely weigh anything. High technology, hip belts, suspension, frames, etc. are nothing but devices to make the discomfort of a bunch of weight more bearable- not needed if you're not carrying any substantial weight! If you can walk comfortably carrying it by only one shoulder strap you're in business!

"Why shun real advances in pack design and comfort to save some ounces that will result in DIScomfort?"

These advances in pack design mean nothing to me if I don't have anything substantial to put in the pack in the first place. With the exception of mountaineering/climbing trips involving rope and gear, I have a very hard time seeing myself ever needing more than a frameless Jam…and even it's begun to look heavy to me.

But whatever floats yer boat, right?

And for the record, I think this weight rank thread is getting a bit WIERD. UL, SUL, they're all just descriptors. To my knowledge nobody gets points awarded or docked for how little/much they carry. I've got WAY more respect for the person that simply gets out ALOT. 5 pounds or 50, who gives a hoot?