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fitting internal/external frame packs



On Mon, 15 Apr 1996, tfort wrote:

> I'd be interested in a copy, too.
> 
> t. 
> 
> 
> >Hi,
> >
> >I was reading your note about your short trip on the AT and I was wondering 
> >if you still had a copy of the information on how to adjust the External 
> >and Internal frames for the pack.  I have a new/borrowed pack and want to 
> >make sure it's properly adjusted before I go out this season.


I assume this was directed to me and the posting I did a while ago on how 
to adjust frame packs.  I don't have a copy, but I'll do it again and try 
to cover the basics.  (If this was not me, nevermind, go ahead and delete 
now)

As I've said before, pack fit, to me is one of the most important parts 
of a trip, and an often neglected one.  How can you enjoy the scenery 
when a shoulder strap is causing you to be in agony every step, or a 
misfitted hipbelt won't let you high-step over a log and all you can 
think about is making it to the next rest break?

Our objective: to get most of the weight of the pack riding on your 
hips, not your shoulders.  There are various opinions on exactly how much 
should be on which, I usually say about 80% on the hips, but that is 
really a matter of personal preference.
If you think about it, this makes sense.  The hips are the weight bearing 
bones of the body, not the shoulders.

There are 2 main components to the suspention of a backpack then: the 
hipbelt and the shoulder straps.  The hipbelt is what does the weight 
transfer and it should ride so that it is able to press onto the 
hipbones.  Don't wear it like a belt, it should be low enough to press 
onto the hips.  Generally, I wear mine a little above even with the 
points of my hipbones so it has some downward pressure onto the hips, not 
just inward pressure.

So, most of what we do is going to be with the end result to have a 
properly placed hipbelt effectively transferring the weight.  To do this, 
we have to adjust the shoulder straps.  This is where the difference 
between internal and external frame packs comes in.

Virtually all internal frame packs have an extra set of straps that go 
from the front of the shoulder strap to the top of the pack.  These are 
called "load lifters" (or sometimes "load stabilizers") they have 2 
functions (as the names imply): a) to stabilize the pack b) to make sure 
that any weight being borne by the shoulder straps is taken off and 
lifted back onto the frame of the pack (putting it back onto your hips).
We'll get back to those in a minute.

The shoulder straps on an internal frame pack should be anchored to the 
frame about 2 inches below the shoulder (sort of wrapping around the 
shoulder, almost).  The padding should cover the area of contact with the 
shoulder and extend a couple of inches down below armpit height.

On some packs, the lower edge of the load lifter straps (where it is 
attached to the shoulder strap) is adjustable with some sort of sliders so 
you can control where on the shoulder it pulls from.  It should hit the 
shoulder strap at about collarbone level.  From there, it should go up 
and back at about a 45 degree angle, and hit the frame at about earlobe 
height or so.  If the angle is really low, the strap won't lift up so 
much as back, and it won't take the weight off.  Similarly, if the angle 
is too high, it won't be able to do the job well either.

There are also straps on many internal frame packs that go from the 
middle/back of the hipbelt to the bottom of the pack on either side.  
These are usually called "hip stabilizers" playing with these adjusts how 
close the pack rides to the hips.  Also, playing with these and the 
shoulder stabilizers can vary the weight distribution (that shoulder/hip 
thing again).  

Many internal frame packs also have a sternum strap which buckles from 
one shoulder strap to the other.  Sometimes this is just a convenience to 
keep them from sliding off the shoulders but I find that it is pretty 
much necessary on my pack (a Gregory) to get the "harness" working well 
for my body.  It is meant to go across the upper chest (sternum - duh).  
Many packs have a sternum strap that can adjust up and down to get the 
right spot.  A note to women: make sure when trying on the pack that you 
can get the sternum strap to a comfortible position, I've heard/seen some 
horror stories, 'nuff said!

Moving along to external frame packs:
many of the principles are the same, and in some of the high end 
externals you get all of the neat-o adjustments that the internals have.  
With or without them, you should be able to get an equally (or often 
more) comfortible fit.  While the basic principles are the same, there 
are some differences.  The biggest one is the shoulder straps.  Most 
don't have load lifters.  If this is the case, then the shoulder straps 
themselves should be going up at a 45 degree angle from your shoulder to the
pack frame.  Even if it does have the load lifters, the shoulder strap 
should anchor to the frame straight back, not down like an internal.

I'll mention buying tips is a minute but to interject here, be warned, 
that it is more complicated to make these adjustments on an external 
frame than an internal, usually it involves taking out a pin and moving 
some plastic spacers (it is usually much easier on an internal).
For this reason, sometimes salespeople are resistant to doing this (or 
even don't know how!).  If they don't want to and you feel like you need a 
better fit, tell the guy to piss off and go somewhere else.  Don't let 
them bully you into thinking that it will be OK when you get it on the 
trail (more on that later).

An adjustment that many external frame packs have that many internals 
don't is a floating hipbelt.  You can change where on the pack the 
hipbelt in anchored (actually, it is vice versa, but it is simpler to 
think of it that way) and adjust for height that way.

Which brings me to my next point: adjusting for height (on both internals 
and externals)
Just because you and your friend are the same height does not mean that 
your pack size will be the same.  Pack (frame) sizes are determined by 
TORSO LENGTH, not height.  You can be the same height as your friend but 
have longer legs and a shorter torso.  You can measure your torso by 
using a soft tape measure (like the fabric kinds tailors use) and having 
a friend measure your spine from the 7th vertibre (the bump at the base 
of your neck) to the point on your spine in between the points of your 
hipbones (usually around to top of your back pocket on your jeans).  
Generally speaking an extra small torso is around 16 inches and a very 
large one around 21 inches.  (I'm about 18 inches, a medium in most cases).
Often manufacturer specs will say which sizes are for what torso ranges.

When putting on packs, don't worry if your internal rides lower than your 
buddy's external, externals ride higher, you are not carrying more weight
*do not adjust your set* (or pack)

Also, before you take off your pack loosen the important buckles: 
shoulder stabilizers, shoulder strap, and hipbelt in that order.  This 
will do a couple of things: a) make it easier to take off because it fits 
looser, b) put less stress on the hipbelt buckle when you unsnap it (so 
it doesn't spring back and wear down) and c) make it _much_ easier to put 
back on.  It is soooo much easier to aim for a big loose shoulder strap 
than a super tight one and try to wriggle into it.
When you get the pack on, shrug it up to the right position and tighten 
in the opposite order (hipbelt, shoulder strap, shoulder stabilizer).

OK, almost home.  A quick word about buying a pack.  The choice between 
internal and external frames is a tough one, and we can discuss that 
another time.  
But I would like to say something about shopping for a pack.  You are 
buying something that you will have to wear for a long time.  Think how 
much effort you put into buying a car and you only spend a couple of 
hours a day in that.  Don't let a salesman bully you into getting a pack 
that he things is best for you.  If he/she thinks this is the case, then 
ask him to explain the rationale for thinking so.  
Also, try on the pack WITH WEIGHT IN IT!!!  Every pack feels good empty.  
If possible, bring your stuff in (packed neatly in stuff sacks) and 
actually pack the pack there (I would do this on second or third trip, 
once you have narrowed it down to 2 or 3 packs).
Keep the pack on for a while, walk around the store in it for at least 
1/2 hour.  See if anything starts to chafe.

Remember that on most internal frame packs, the 2 stays (which provide 
the frame) casually be custom bent to fit your back.  You can do this 
or have the salesman do it (usually they come pre-bent to general back 
shape, you can customize it, but remember when taking the stay out, to 
mark it so you remember which way it goes back in!)

Also, most internal frame packs have a break in period, it should feel 
better after a week or two on the trail.

Well, I think that's it.  I'm sure I'm forgetting stuff, if you have any 
specifics, feel free to ask.

-jeff
-----------------------------------------------------------------------------
Jeff Mosenkis,                                                   
University at Albany - Psych, Anthro, Judaic Studies             
                   							 	
jm1360@cnsvax.albany.edu                   

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