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Programbo
01-13-2007, 12:16
How about a small individual sized zeppelin below which you could store all your gear and then just pull it along with you on the trail? :-?

4eyedbuzzard
01-13-2007, 12:25
How about a small individual sized zeppelin below which you could store all your gear and then just pull it along with you on the trail? :-?

Hydrogen derrigible was previously suggested in another recent thread as both weight reduction AND fuel source.

The reaction(s) was predictable: Oh, the humanity!:D

Sincerely,
Buzzard von Hindenberg

Gray Blazer
01-13-2007, 13:01
Fill the hollow tubes of your old backpack frame with Hydrogen. You would need a radio-controlled dirigible. Then your lines would not get tangled up. Do you know anybody at WB who works the mini-blimps at a major arena?

Froggy
01-13-2007, 14:39
Shouldn't need to be any longer than about forty or fifty feet, maybe less if you've cut the weight of your pack down.

After you've tried it, let us know how it worked out.

freefall
01-13-2007, 15:04
Hydrogen derrigible was previously suggested in another recent thread as both weight reduction AND fuel source.

The reaction(s) was predictable: Oh, the humanity!:D

Sincerely,
Buzzard von Hindenberg

Just don't use thermite to paint it the nice silver color. Mythbusters just covered the Hindenberg disaster. The only way they were able to get a result anyhing close to the real thing was by using 100% thermite on the skin.

buckowens
01-13-2007, 15:33
Even better, how bout a "Hoverboard" like that which was used my Michael J. Fox on "Back to the Future"... Sure would cut down on foot problems!

jrwiesz
01-13-2007, 16:28
Even better, how bout a "Hoverboard" like that which was used my Michael J. Fox on "Back to the Future"... Sure would cut down on foot problems!
Just think of the extra blue blazes one could take!

Jester2000
01-14-2007, 23:28
Billville Safety Research designer Bag o' Tricks is already working on a lighter-than-air model backpack. Hopefully he will have it ready by May.

Frolicking Dinosaurs
01-15-2007, 13:43
::: Makes note not to miss Billville homemade grear contest at TrailDays 2007 :::

Deerleg
01-15-2007, 14:29
::: Makes note not to miss Billville homemade grear contest at TrailDays 2007 :::

Miss Janet said she ran into a guy a few years ago that was working on hiking poles (tubes) that held all your gear and eliminated the traditional packÖI wonder if thatís gone anywhere or showed up at Trail Days?

The Weasel
01-15-2007, 15:09
A qualified engineer or physicist can demonstrate to you that the energy involved in pulling the dirigible behind you would be the same as carrying the same weight on your back, and a bit more to account for the friction of the air against the dirigible body and the weight of the dirigible. I think the basic formula for any energy expenditure is E = MD, where E is energy in foot-pounds, M is mass, in pounds, and D is distance in feet. I'm sure there is someone here who can be more precise.

The Weasel

rafe
01-15-2007, 15:36
A qualified engineer or physicist can demonstrate to you that the energy involved in pulling the dirigible behind you would be the same as carrying the same weight on your back, and a bit more to account for the friction of the air against the dirigible body and the weight of the dirigible. I think the basic formula for any energy expenditure is E = MD, where E is energy in foot-pounds, M is mass, in pounds, and D is distance in feet. I'm sure there is someone here who can be more precise.



Close but no cigar, Weasel. Energy is force through a distance (W=f*s). Force is mass times acceleration (F=ma.) Newtons, pounds and ounces are units of force; grams and kilograms are units of mass.

You were sorta close... but mass isn't measured in pounds.

Whatever point you're making about the dirigible makes no sense to me. It's obvious to me that if I could lighten myself with a magical "skyhook" then I could expend far less energy while hiking, on any kind of surface or terrain. Barring that, the next best thing is going light or ultra-light. :)

The Weasel
01-15-2007, 15:48
Close but no cigar, Weasel. Energy is force through a distance (W=f*s). Force is mass times acceleration (F=ma.) Newtons, pounds and ounces are units of force; grams and kilograms are units of mass.

You were sorta close... but mass isn't measured in pounds.

Whatever point you're making about the dirigible makes no sense to me. It's obvious to me that if I could lighten myself with a magical "skyhook" then I could expend far less energy while hiking, on any kind of surface or terrain. Barring that, the next best thing is going light or ultra-light. :)

Thanks for the correction. There is, however, an energy measurement known as the "foot pound" (English system), similar to joules (metric). That's the formula I was using.

As for the dirigible, while you will lighten what you have on your back at a standing moment, the dirigible will have to be moved with you as you go along the trail. Assuming that its altitude remains the same, the force to move it forward will be (thanks!) mass of the dirigible (including its cargo) times the distance it travels. The kinetic energy to allow it to rise is provided by the helium, and at the start of your day will be converted into stored (potential) energy, which stays with it as it drifts along. At the end of the day, you have to provide energy (again, mass times distance) to reel it in. Since the dirigible presumably has some mass/weight, and had friction from air as it was dragged along (both of which cause the expenditure of energy) the dirigible would be more work rather than less.

Basically, this is an example of the Second Law of Thermodynamics, i.e. every closed system ends up with less energy at the end than it started with, and is the source of the saying, "Entropy's a [miserable thing].

Glad I didn't get the cigar. Ugh!

The Weasel

c.coyle
01-15-2007, 15:52
I use an inflatable hammock. Why would anyone carry a pack?

iamscottym
01-15-2007, 16:16
Weasel, you are mistaken.

The energy that allows the derigible to float is not provided by the helium, but rather by the atmosphere, and thus has a limitless supply. The forces at work here are atmospheric air pressure pushing up on the balloon, and gravity pulling down. Just like a boat in water, a balloon is displacing a certain amount of air. If the balloon is less dense than the air it is displacing, it will rise.

Granted, at higher altitudes atmospheric pressure is lower, so the balloons are heavier relative to the air they displace, and thus don't have as much lift. Negating the varying lift of the balloons and the possible solutions to maintain a balanced ship (~neutral avg weight between balloon and pack), the only work involved on the hiker's part is to pull the derigible along, which works out to fighting air friction.

Air friction (drag) is proportional to v^2, so unless you're trying to pull it at 100mph, the work involved is nothing compared to carrying the pack (m*g*delta h). This also brings up another point- work in the physics sense is different than what people consider work. The classic example is a person pushing on a wall. Does it make you tired, sure, but you aren't doing any true work because the wall's not going anywhere (W=f*d). If you're standing around with a pack on, you aren't doing any true work either, but you are making yourself tired.

While it takes the same amount of true work to climb a mountain no matter how fast you walk (negating efficiencies of different gaits), the faster you walk the less "work" you'll do fighting gravity. With a derigible, this point is moot because you're not carrying your pack, and since you're only fighting air resistance, you do work only when you're moving.

The Weasel
01-15-2007, 16:42
Weasel, you are mistaken.

The energy that allows the derigible to float is not provided by the helium, but rather by the atmosphere, and thus has a limitless supply. The forces at work here are atmospheric air pressure pushing up on the balloon, and gravity pulling down. Just like a boat in water, a balloon is displacing a certain amount of air. If the balloon is less dense than the air it is displacing, it will rise.

Granted, at higher altitudes atmospheric pressure is lower, so the balloons are heavier relative to the air they displace, and thus don't have as much lift. Negating the varying lift of the balloons and the possible solutions to maintain a balanced ship (~neutral avg weight between balloon and pack), the only work involved on the hiker's part is to pull the derigible along, which works out to fighting air friction.

Air friction (drag) is proportional to v^2, so unless you're trying to pull it at 100mph, the work involved is nothing compared to carrying the pack (m*g*delta h). This also brings up another point- work in the physics sense is different than what people consider work. The classic example is a person pushing on a wall. Does it make you tired, sure, but you aren't doing any true work because the wall's not going anywhere (W=f*d). If you're standing around with a pack on, you aren't doing any true work either, but you are making yourself tired.

While it takes the same amount of true work to climb a mountain no matter how fast you walk (negating efficiencies of different gaits), the faster you walk the less "work" you'll do fighting gravity. With a derigible, this point is moot because you're not carrying your pack, and since you're only fighting air resistance, you do work only when you're moving.

Well, this is why I defer to current engineers; it's been a long time since I blew out of engin school.

But I'm still pretty sure that the dirigible is using the same energy, which is why the Goodrich Blimps seem to have motors for propulsion. The "work formula" is for precisely that (and assumes a frictionless movement), and yes, moves mass through distance. (Correct, that "work" isn't the same as "effort".) As for "lift", well, yeah, we're both wrong, and both right: The atmosphere "lifts" the blimp through the same "high pressure/low pressure" aspect that causes lift for an airfoil, too. So one could say the same thing for tying your gear to a kite that had sufficient "lift" (thank you, Wilbur; thank you, Orville). But to move it forward is "work" since it constitutes mass moved through distance. You can't cheat the laws of thermodynamics. At least I don't think so.

The Weasel

rafe
01-15-2007, 17:12
You can't cheat the laws of thermodynamics. At least I don't think so.

I really don't think thermodynamics has much to do with it. Most of the "work" that we do while hiking on level (or quasi-level) ground involves a conversion from kinetic energy to heat, or simple displacement of matter. If gravity were reduced to X percent of its current value, the "work" done hiking would be reduced by roughly the same amount -- and I think that's as true for the flat sections as for the climbs and descents. Reducing body weight and pack weight would have roughly the same effect as reducing gravity.

The climbs and ascents really bring home the wasted energy issue; we feel the extra work on the ascents, but we get no "credit" for that work on the descents. Bummer.

The Weasel
01-15-2007, 17:29
I really don't think thermodynamics has much to do with it.

You can't escape them. If something moves, it uses energy. If it doesn't move, it has energy. If it doesn't have energy, it doesn't exist.

http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookEner1.html

The Weasel

The Weasel
01-15-2007, 17:33
***If it doesn't have energy, it doesn't exist. ***
The Weasel

Quantum physicists are free to tell me I'm wrong, at subatomic levels. My mistake.

The Weasel

rafe
01-15-2007, 19:46
You can't escape them. If something moves, it uses energy. If it doesn't move, it has energy. If it doesn't have energy, it doesn't exist.


All I'm saying, Weasel, is that that's all very deep and all, but for hiking and backpacking the tiredness you feel at the end of the day comes from F=ma. You can't do much about "a" but you have a fair amount of control over "m." That's what the gram weenies (and speed hikers) understand.

The Weasel
01-15-2007, 20:16
All I'm saying, Weasel, is that that's all very deep and all, but for hiking and backpacking the tiredness you feel at the end of the day comes from F=ma. You can't do much about "a" but you have a fair amount of control over "m." That's what the gram weenies (and speed hikers) understand.

You're right there!

The Weasel

Jester2000
01-18-2007, 18:38
So, anyone care to have a physics discussion about my BSR Refrigerator Backpack?