Best Center of Gravity?

[TooOld2Hike_EP]

In the world of flying, we had to calculate the Center of Gravity for the airplane (with passengers, fuel and baggage) because CG made a big effect on how the plane flew. (Could be deadly if out of CG.)

In the world of backpacking, everyone says (correctly) that heavier items should be in the "middle" of your pack, close to your back. I could make an argument that, like an airplane, if loaded wrong (heavy items at the top) a backpack could be dangerous/cause imbalance/falling.

But is there an optimal Center of Gravity for a loaded backpack?

(Actually, there are two CG's/moments here. One is the more obvious, the weight distribution horizontally, going up the pack. But there is also the moment vertically from the weight being close (or too far) from your back. For now I'm only asking about the first.)

My intuition says that if I were to hold my arm out to balance my pack on my arm, my back should balance about a third up, about where the lumbar support ends.

(I am talking about a frame backpack.)

But perhaps it should be at the 50% point, at the midpoint of my back?

Or perhaps even 2/3's up? Because when I carry a 40 pound bag of salt pellets, that's where I usually drape the sack. Although that seems high from a "keeping your balance" perspective.

I've experimented a little. But I don't know how to quantify "comfort" or what feels right. Although I can tell when it's not right, at the extremes.

As I write this, I'm thinking that I should try strapping a bag of salt to my back to see where it feels best.

But perhaps you can save me the trouble. (And mess.) Is there a study quantifying the optimal CG for a backpack?

[Alston_Neal]

Some of our ancestors came hundreds of miles across the country with a wheelbarrow. It seems to have become passe.

[rcorfman]

@Alston_Neal
Or maybe they're illegal to use in designated Wilderness areas, just like hang-gliders.

[chumley]

@rcorfman
Technically I think the skake weight backpack is also mechanized, and subsequently also illegal.

[TooOld2Hike_EP]

@rcorfman
Tnx.

You might be right. But I don't know which matters more - weight or weight distribution.

I could make an argument that 10 pounds on your back carried the wrong way could be "harder"/less comfortable than carrying 20 pounds the right way.

(I wonder if there's a way to measure calories used? If carrying a backpack the wrong way causes you to use a bunch of extra muscles to stabilize, could that be measured to determine "tiredness"?)

Whatever the answer, one can do weight reduction and weight distribution at the same time.

So I have tried to lighten my load. So far, I've only been able to drop maybe 2 lbs. ( @azbackpackr
My cooking system. ) (Summer clothes vs winter clothes dropped another pound. But that's not a permanent change.) I seem to be stuck in the low 30's loaded with water and a little food.

My backpack is the heaviest item, weighing 4+ lbs. And I've already taken off the brain. My tent and sleeping bag are fairly light and make up for the heavy pack.

I've done the "analysis" where you ask yourself after a trip, "What didn't I use?" Aside from my med kit and some paracord/carabineers, I use everything.

(Admittedly, I have some "luxury" items, like an inflatable sleeping pad. (But not a Flextail.) But I'm a side-sleeper. So I'm not going to replace my inflatable for a foam pad because then I wouldn't be able to sleep well.)

[big_load]

But I don't know which matters more - weight or weight distribution.

Weight matters a lot, but one factor that matters a lot is suspension. You got close to that topic earlier, but I don't think you've fully considered it yet. A good suspension makes more weight easier to carry, and it helps even out imperfections in the distribution.

Since my hipbones don't stick out much and I have no rear end, I ended up going fully custom. I have a McHale pack for which I sent required measurements, and then did fittings and testing with two sample packs. Me made tweaks even after the second sample pack. (He sent me the marked-up measurement sheet, which had the notation "small !!!" by the hipbelt. It also has beefy, extendable and removable stays that are exactly contoured to my back. Besides the hipbelt design with independent upper and lower straps, his unique bypass harness design makes it easy to keep the pack fairly close to the back while keeping weight off the shoulders. Since mine is full dyneema with a bunch of bells and whistles, it was absurdly expensive. However, it allows me to comfortably carry much more weight than any other pack. That lets me get places where it's necessary to carry two days of water or more.

[TooOld2Hike_EP]

@big_load
Yes, I think that a custom (but still 'lightweight' ) backpack is part of the solution. (I am skinny and my hips aren't very prominent either.)

If I were more into backpacking and if I had more time to live, a custom pack is something that I might consider. But I'm not ***that*** into backpacking. (And will probably be out of backpacking after my first bad fall.) And I only have a few more years to live, and less to backpack. So no point for me to spend the money.

I have a pre-2021 model year Gregory Baltoro. While it fits me fairly well (I think), I have hacked it to fine tune it more.

One thing that I noticed a few weeks ago at the end of my first ever 3-day trip is that I needed more lumbar support.

I didn't used to. Or maybe it takes a few days to feel the lack of support? Or maybe my spinal curve is changing from backpacking? (Hopefully for the better. I have been trying to backpack with my "ears over my shoulders" and I've noticed that I'm standing taller as my core strength increases.)

Anyway, my pack came with a removable, adjustable (?) wedge to add to the lumbar curve already in the frame. I put it in halfway up and am eager to go on a two-day to see if I made the fit better or worse.

[rcorfman]

@TooOld2HikeQ
I think one thing to consider is that, unless you pack your bag in a completely asinine manner, weight matters much more than any minor changes in CoG. There're some obvious things to avoid, such as hanging stuff high off the back of the pack, or having an unbalanced pack. Really, just keep the pack balanced and that's it.

I used to have a 4+ pound pack, now I have a 10oz pack with no belt nor frame. With that setup, it's imperative that my pack is balanced, but that's easy enough to do. I suppose having a big backpack with lots of space might make CoG and how it's packed more of a concern. For me balancing the pack extends past packing the bag to things like how the water is distributed in four bottles on the two side pockets or maybe even what side of my front pocket I place my umbrella. This isn't rocket-science, and for my two cents, it isn't worth making scientific.

I will add that weight matters more the longer you are out and the farther you go. Over a weekend with lots of camp time, it really doesn't matter much, but over a couple of weeks, walking all day, it does.

I tend to go for the all-day walking, farther distance, type backpacking, so my kit is fairly light. Last weekend, I hiked the southern half of the Black Canyon trail home and had a pretty minimal kit. See the last paragraph of my trip report for what I carried.

[TooOld2Hike_EP]

@rcorfman
I met a few thru-hikers on the AZT with Hyperlight brand packs. And loaded to the gills for the Superior to Pine run.

1) Their packs looked heavy. And 2) their packs looked like they were digging in/pulling on their shoulders a lot.

I can tell when my back pulls on my shoulders because it isn't cinched tight enough around my hips or because it slips down an inch. It makes my neck muscles hurt instantly. (And the pain goes away immediately after I hike up my pack.)

So I don't think that I could wear a frameless pack. I certainly couldn't wear a beltless one.

I can see how the lighter the backpack, the more sensitive it will be to load, since the load becomes a larger percentage of total weight.

So then I suppose that one unspoken advantage of a heavier pack is that its weight reduces this sensitivity.

I can see how a heavy pack would wear one down on a long hike. Fortunately for me, I am just a "casual" backpacker, not really going anywhere. The longest hike that I ever expect to make (maybe) is from Flag to Pine on the AZT.

[azbackpackr]

I could not wear a pack with no hip belt. I even use a hip belt on my day pack. But we are all made differently, and that's probably a good thing, haha!

[RedRoxx44]

I am lucky enough to have the room to store several packs. For dayhiking depends. Mystery Ranch for off trail tough hiking and where I might have a pack weight go from a few pounds to 40 if I find pretty rocks in an old mining area. Regular day hiking hot temps a mesh panel small Gregory I've had for years. Slightly larger is a Camelback fourteener I've also had for years. It's a clean profile I like for light scrambling, nothing to get caught on on the outside.
Backpacks currently using a North Face with a full side zip, I also have a Dueter I like. I have a new/old "journeyed North" pack from ebay that I will probably use for the first time in a day or so. It is the lightest base weight backpack I have right now. I do like a good suspension and a good hip belt. The only frameless pack I liked was an old Osprey, it could carry a lot but loaded had a bulbous profile and not great for off trail backpacking.

[xsproutx]

1) Their packs looked heavy. And 2) their packs looked like they were digging in/pulling on their shoulders a lot.

Most thru hikers using an HMG pack are using one that has a frame and that is going to be in the "not heavy" category, typically. You may interpret a pack hugging the body well as not fitting correctly, but you generally want it that way: close to your body. Without pictures, I can't say for sure, but I'm going to go out on a limb as someone who has done multiple thru hikes and say they probably have a bit more experience and know what they're doing than the guy trying to use research papers to pack a bag. You may see "loaded to the gills" but the content of those litres may be much lighter than you think for the volume.

Frameless packs, of course, aren't for everyone and I think are generally kind of silly for most but I still have one for certain kinds of trips. The extra pound of my framed packs is generally worth it with the only real exception being trips where I'm having to do some bouldering/climbing in a more extreme fashion; at that point, the lack of hip belt and frame give me a lot of extra flexibility/agility that's nice. I have to pay more attention to how I pack it but it's still not a huge deal.

Similar to biking where the number of bikes you need are n+1, packs aren't toooooooooooo different....

[big_load]

Frameless packs, of course, aren't for everyone

Yeah, it all depends on having a light enough load and specific ways of packing. I used to carry frameless in conducive environments (warm weather only, plentiful water, not too many days of food). The old-school frameless packs essentially used the sleeping pad as a frame, but they were generally using hard foam pads, not today's more comfortable air pads. Among more modern light packs, something like ULA is a good option for many people. A lot of my hiking partners use them comfortably even with what they consider fairly heavy loads (up to 35 lbs).

Anyway, I can remove the stays from my pack, remove the lid pocket and other extras and be pretty down to the same thing, only a bit heavier, but with a rock-solid suspension.

[TooOld2Hike_EP]

@xsproutx
(I tried the Quote feature on this forum. But it didn't work for me.)

Similar to biking where the number of bikes you need are n+1, packs aren't toooooooooooo different....

LOL at the n+1. (Especially after dinging me about research papers.)

[TooOld2Hike_EP]

I visited a Professional Guide the other day as a "Sanity Check" regarding my pack. She had me take everything out of my pack and then she packed it.

Although she started with some light stuff at the bottom, it seemed to me that she was more focused on cramming as much into my pack as she could. (I.e. focused on using every nook & cranny.)

This resulted in a more dense pack than I usually pack, which consequently resulted in more room at the top. It also resulted in a bottom heavy pack. (With some heavier things levering more away from my back too.)

I took it as she packed it and went on a one hour training hike.

Ouch, my shoulders.

The pack felt heavier, even though it weighed the same.

(BTW, she said that my pack fit me well. So that's not the problem.)

So I unpacked my pack and repacked it with more of a focus on CG. (E.g., I packed my two 1L water bottles higher in the stack.)

When on a 1.5 hour, 4.5 6 mile training hike today.

Wow, what a difference.

I don't have as much room at the top as when she packed it. But I'm willing to trade that off. (More room means I could pack more things. Which means more weight. Don't need that.)

In the end, I think that this is like sleeping on a "bad" mattress most of your life. Since it's the only mattress you've known, you think it's as comfortable as a mattress can be, and that aches and pains are normal. Until you sleep on a "perfect" mattress and learn how good things can be.

[chumley]

When on a 1.5 hour, 6 mile training hike today.

I call that a training run!.

[The_Eagle]

@chumley
It helps to have Fresh Tips

[chumley]

I think that this is like sleeping on a "bad" mattress most of your life. Since it's the only mattress you've known, you think it's as comfortable as a mattress can be, and that aches and pains are normal. Until you sleep on a "perfect" mattress and learn how good things can be.

This is also true with hiking shoes. Until you've experienced true GREATNESS, you really just don't know any better.

[TooOld2Hike_EP]

@chumley
Oops. Guess I was telling a fish story. It felt like 6 poun... err, miles.

I didn't have my GPS tracker operating. But I traced out the track after the fact. 4.5 miles. So 3 mph.

I will set my tracker next time I'm out to confirm.

[TooOld2Hike_EP]

I've been experimenting more with (vertical) Center of Gravity. I think I've found the sweet spot for me. (At 6 ft tall.)

After that, I read some more about optimal CG in the literature.

One guy (from bushwackingnsw.org.au), who thinks out of the box, submits that the best way to carry a heavy load on the human body is on the head. It's best for CG - No change. It's best for shock absorption - through your (bent) spine. No weight on your shoulders.

He cites porters in other countries who routinely carry 90 lbs on their heads. (More if you pay them more.) He cites women in (so-called) 3rd world countries who carry pitchers of well water on their heads.

Not that I'm advocating this. Nor would I do it.

But I was surprised to see it being done in a recent video of an Influencer on a backpack trip on the West Highland Way. (Scotland.)