Add an Internal Frame to a GoLite Jam - Ultralight ALICE

This article forms part of the GoLite Jam Extreme Make-over

After a lot of experimentation I discovered that the most comfortable way for me to carry my ultralight pack and ultralight kit was to dump the entire contents into a 5lb Army Surplus pack that was built 20 years ago and designed at least 40 years ago.

What is even worse is that when I'd taken the army pack for a test-drive I'd extended the hike because it was so easy to carry. It carried light.

I was seriously considering using a 5lb pack to carry a typical 15lb load. Something was clearly wrong with how I was carrying this 15lb load.

What I then did was try and work out how it was that this military pack was so much better and so much more comfortable than what I was used to. Sure, it wasn't perfect over rough ground and did bounce around a bit but I thought that such things could be fixed.

The real issue for me was how on earth I could take these ides and create an ultralight version of them. I began to wonder if adding weight to a pack might be a good investment. In fact it's been an excellent investment.

The result of all my experiments is 'Ultralight ALICE' and has been built into a Go-Lite Jam.

The total weight gain has been less than 150g and for that gain in weight my peak load carries as if it were my base load. A Carbon-fibre version would weigh even less.

Anatomy of ALICE

It's worth taking a quick look at the design features of this army pack. It is the combination of features that work together to make it so efficient.

This particular pack is one that was issued to the Swedish Army. It has design features that have been around for a very long time.. This pack has lots of similarities to packs that were created especially for the British Army when fighting in the Alps.

It looks like it should be exceedingly uncomfortable but in fact it's very comfortable.

ALICE Key Design Features

Let's now look at how this pack carries and distributes its load.

Rigid Contoured External Frame

The frame is completely solid. No matter how much you load into it the frame will not flex. Its behaviour will remain constant.

The frame has a bend in it so that it roughly matches the contour of the back. In particular it follows the contour of the shoulder blades. This is signifcant.

No Padding / Dynamic Suspension

The frame has no padding at all. Where you would expect to see pading there are in fact just two 2.75" strips of webbing. This webbing is actually lashed to itself so in practice it is springy and acts to absorb shocks and bounces.

Minimal Shoulder Straps

The straps on this pack have almost no padding in them. They consist of heavy cotton fabric with a thin bit of wadding (or something) machined between them. The straps are also quite narrow at 2.5".

Pack Shape

You can see the pack is shaped a little differently to the Alpine packs that are prevelant today. The pack is 13.5" wide at the bottom and the top and the sides taper from 9" at the top to 5" at the bottom. There is also a big gap at the bottom where other things can be strapped.

Compared with a modern pack it is upside down!

Pockets

There are no pockets. Everything either goes into the pack or is strapped to the bottom or the top of the pack. Those are your only choices.

No Compression Straps

There does not appear to be any compression straps. In fact the drawstring closure of the pack is military-strength - it locks solid - and the lid straps work very well at compressing the pack against the frame.

No Hip-belt

We've all been taught that hip-belts are really, really important. This pack doesn't have one. In fact it doesn't seem to need one.

One Internal Pocket

The pack has one internal pocket that is skinny and is about 2/3rds of the entire pack length. This pocket is designed to carry small heavy things.

Load Distribution

It should be obvious from the shape and design of this pack that it is designed to be loaded in a certain way. The best way to load it is to make it top-heavy so that most of the weight is in the top third of the pack and the lightest things are at the bottom of the pack.

Ideally you would also use the internal pocket to ensure that the really heavy stuff is carried close to your back over your shoulder-blades. When it is loaded in this way the pack feels very light.

Load Transfer

The interesting question then is how this pack actually transfers load to your body.

What seems to happen is that the load is distributed mostly through the shoulder-blades.

The top-most webbing strap transfers maybe 1/2-1/3 of the perceived pack weight and the shoulder straps and the lower webbing strap transfers the rest.

The pack basically cantilevers itself around your shoulder-blades and just sits there with the shoulder straps stabilising the pack.

Effect on Balance

This is the biggest surprise The pack has almost no effect on how you stand, walk or clamber over rough ground. It seems to work very well with your body and have little effect on your centre-of-gravity. It feels more like you have gained 25lbs than strapped a 25lb pack to your back.

ALICE in the field

Even though ALICE is more comfortable than any pack I had ever previously worn it is not perfect.

If you travel over very rough ground you can feel the pack shift around slightly. This can be a little disconcerting but doesn't have that much effect in practice.

The webbing straps tend to transfer load a little unevenly - they can bounce a little if you are walking on a rough surface.

The shoulder straps are not wonderful although they do work.

ALICE DNA Transplant - JAMICE

The challenge then is to take all the good points from this old pack and transfer them to a GoLite Jam donor pack without the addition of 4lbs of weight.

These photos show how the DNA transfer has worked.

Note: This JAM pack has been modified in other ways but those changes are incidental.

Let's now look at what design features have been blended into the JAM.

External/Internal Frame

These photos show the first workable prototype. The total weight of the new internal frame is just 105g and even so is deliberately over-engineered.

The bulk of the frame is constructed from 10mm Aluminium tubing that has been bent to shape. The rest of the frame is constructed from 10mm plastic tubing.

The plastic tubing has been introduced into the frame so that the frame can flex naturally if the hip-belt is used.

The frame has been designed to be totally rigid at the main load-bearing area around the shoulders with the lower part of the frame being allowed to flex for comfort reasons alone.

The frame is fitted into two tube pockets that have been machined onto the pack seams. These tube pockets mean that the Jam pack and its load work with the frame to provide a rigid structure.

Shoulder and Hip Pads

The Shoulder and Hip pads mimic the action of the webbing straps on the ALICE pack. They transfer load onto the shoulder-blades and the hips.

The use of foam and 3D mesh allows the pack to transfer load to the whole contact surface and work to eliminate pack-bounce.

The pads also work to move the pack away from the back a little and create really good airflow. The pads are not absolutely essential but they do make a worthwhile contribution to efficient load transfer

Chest Strap

The chest strap doesn't get used much anymore. The shoulder straps now seem to sit naturally in the right place and stay there. The cross-bar of the frame mean that the straps cannot move around without a lot of help.

Hip Belt

When I made the changes to the Hip belt I was expecting that it would see a lot of use. In practice I use the hip-belt only rarely and when used it only tends to be for load stabilisation rather than load transfer.

Load Distribution and Transfer

I've had to radically alter the way that the Jam is packed. I've adopted a traffic-light system of stuff sacks.

The bottom third of the pack is used to carry only very light things - a sleeping bag is placed in an over-sized Silnylon GREEN stuff sack.

The middle third of the pack is used for medium-density things such as spare clothing and hygiene items. This is packed in an over-size 'AMBER' SilNylon stuff-sack.

The top third of the pack is reserved for heavy dense items such as water, food and shelter. This is a RED stuff-sack.

This topmost stuff sack is tied to the frame so that it more-or-less hangs from the frame and transfers load to the top rather than the bottom of the pack.

There is a 2L bladder fitted to the back of this red stuff-sack and a 1L Platypus stored directly in front of it. The red stuff-sack has an internal divider (blue spinnaker) so that heavy items can be placed next to the back and kept there.

The total weight of the three stuff sacks is 150g. They have replaced the manufacturer's sleeping bag stuff-sack (110g) and an 8L SilNylon stuff sack (30g!!!) and so there has been basically no change in weight.

The pocket on the JAM is now only used for light-n-fluffy things such as hat and gloves. The side-pockets are used for trail snacks and a windshirt.

The stuff-sacks help to allow me to pack the JAM to be top-heavy despite it's pear-drop shape.

When fully loaded the pack's centre-of gravity is just on the lower-edge of the shoulder pad, and very close to the spine. On my back that means it is just below the shoulder-blades and so the pack naturally transfers load onto the shoulder blades thanks to the rigid frame and soft pad.

The hip pad thus transfers any load not picked up by the shoulder pads and straps.

The shoulder straps are carrying a little more load than they perhaps did before but are doing so in a way that's very comfortable - more load is carried on the chest.

The load is transferred mainly through the body and the spine so that when you are moving over rough ground there is no shock-loading of the hips.

Because the hips are not actually being used to control the load but balance it they are allowed to move in a much more natural way.

This is the first pack that I have ever worn that allows me to walk and stand naturally. The only noticeable difference is a very slight forward lean from the hips. This seems to be just enough to realign the pack's C-of-G with my own.

JAMICE - Construction

The construction is split into two styles. The first part is easy and requires only minimal changes to your Jam pack. The second part requires major surgery.

My Jam pack is a Large. The text will explain how to measure and cut so that it can be adapted for use with the smaller packs.

Construction Style #1 - Just a Frame

Materials

• 60cm of 10mm aluminium tubing

• 70cm of 10mm plastic tubing

• 35cm of 8mm aluminium tubing

• Epoxy glue

• Some scrap Silnylon/Rip-Stop nylon and some scrap Cordura

• 10cm of 25mm Velcro
  

Note 1. You could probably get away with 8mm tubing instead of 10mm. It might flex a little or bend under extreme loading but that's all. It would save perhaps 20g.

Note 2. When you buy the tubing make sure that the 8mm tubing will slide inside the 10mm tubing. Quality control can vary. Drilling out tubing to make it fit is a little technical and griding tubing down to fit is equally problematic.

Note 3. If you wanted to use Carbon Fibre tubing then of course you could but it will be expensive and will save maybe 50g. You could save much more than that by replacing the 40mm hip belt with a 25mm for a fraction of the cost....

Construction - Frame (105g+10g SilNylon)

1. Cut the 10mm Aluminium tubing into two 30cm lengths.

2. Cut the plastic tubing into two 25cm lengths and one 20cm length. Adjust to fit YOUR pack (see below).

3. Cut the 8mm tubing into two 12cm lengths and two 5cm lengths. [It may be safer to cut it AFTER you have applied the bends to the tubing.

4. Bend the 10mm tubing approximately 7cm from one end and apply a 15° bend. (see picture)
   
   

5. Bend the 10mm tubing approximately 5cm from the other end and apply around a7° bend. (see picture). [This just adds a little extra contouring to the shoulder area.
   
   

6. Join the 10mm plastic and aluminium tubes by using the epoxy glue and the 5cm lengths of 8mm tubing as an internal sleeve. This should be at the end where you have the 15° bend.
   
   
   
   
   
   [I wrapped the joints in Sellotape so that I could carry on working...]
   
   
7. Insert the two bent 8cm tubing into the other ends of the 10mm aluminium tubing and glue them in place using epoxy. Make sure that they mirror each other. If you are in any doubt then dry-fit them into the plastic cross-member before gluing in place.
   
   [I've drilled these tubes to fit a 2.5mm bolt but this is overkill. It's not necessary and if you want to do something similar just drill a 1mm hole and use a fragment of paperclip and some glue...]

Note: I use a professional set of pipe-benders like these:

Construction - Pack Modifications

This is the basic version of the pack modifications that is easiest to do and does minimal damage to the pack. It doesn't quite match the pictures because I went for the extreme version.

1. Cut two lengths of scrap fabric that are as tall as your pack and about 5-6cm wide (you can always trim them later).
   
   
2. Onto one end of these scraps sew a bit of cordura or other heavy fabric. This will act as a pocket and stop the tubes poking a hole in your pack.
   
   
3. Turn your empty pack inside out.
   
   
4. Sew the two strips of folded fabric onto your pack's rear seams using a #16/Denim needle so that the cordura base is at the lowest pack seam. Make the pocket bigger than you think it needs to be. The seam should be at least 1.5cm from the fabric fold. (see picture).
   
   
   
   
5. Fold the cordura over to create a triangular corner pocket and machine it onto the lowest pack seam (see picture). [You may also want to add a cordura reinforcing tube at the bend - this can be under a lot of stress]
   
   
   
   
6. Test-fit your frame into the tube pockets and ensure that your horizontal top-tube is roughly where you want it to be. Mine is set to be by the (redundant) H2O outlets.
   
   
   
7. Sew some velcro onto the pack by the H2O outlets.
   
   
8. Sew the other half of the velcro onto the edge of a 12cmx5cm scrap of Cordura
   
   
9. Sew the strip of cordura with a single seam below the velcro that you've sewn so that if forms a flap AND the two pieces of velcro can be folded to meet. The idea is to create a cordura tube through which the top tube will fit.
   
   
   
   Note: My pack has been heavily modified and so you cannot exactly copy what I did.
   
   
10. Fit the two vertical tubes into the tube pockets.
    
    
11. Fit the horizontal tube (see above).
    
    
12. Trim the vertical plastic tubes so that the top tube will fit through your velcro and cordura 'tube'.
    
    
13. Trim the top tube so that it does not over-stretch your pack.
    
    
14. You are done!

Construction #2 - Frame (105g) - Old Inner (28) + New Inner (23g) + Pads (36g) =161g

This version is a little more technical. It will give you two very comfortable pads for carrying the pack.

In order to do this you will need to cut out the inner foam pocket and re-sew it later. The only sensible way to do this is to replace the foam pocket with a new one out of scrap SilNylon or PU-coated nylon. There will not be enough fabric to cut and re-sew the existing pocket.

I tried to sew the pads without removing this pocket and failed 4 times before giving up. I always managed to machine through the pocket as well at some point. Save yourself the trouble and cut it out before you start.

The frame should be constructed as above. This section just describes the extra bits of how to create the pads.

Materials

• An old 8-10mm foam camping mat (or a very cheap new one). You will only need a piece of foam approximately 15cm x 50cm. (see below).

• Some 3D mesh Foam or similar wicking mesh.

• A piece of SilNylon or PU-coated fabric that is at least 50cm tall and at least your-pack-width + 15cm. This will be used to replace the foam pocket and form the frame pockets.

Construction

1. Create the frame as outlined above.

2. Carefully remove the foam pocket by running a pair of scissors or a seam-ripper down the side of the PU Nylon seam. Remember to keep the velcro safe.

3. Cut two pieces of the 3d Mesh to fit your pack:
   • Hip pad: 13cm x 29cm
   • Shoulder pad: 14cm x 24c.
     [The shoulder pad will be fitted approx. 8cm below the highest seam of the shoulder straps]
4. Sew the upper and lower mesh into position using a narrow-spaced zig-zag stitch. The mesh should be sewn along the two longest seams. There needs to be about 1cm of slack so that a foam pad can be slid in later.
   
   
   
   
5. Cut two identical pieces of foam for each pad. The foam should be cut slightly smaller than the mesh.
6. Test the fit of the foam in the pockets. It should be a tight fit but not too tight. For best results you can cut the top layer of foam to be slightly smaller than the bottom layer and use crimping shears.
7. Partially remove the foam from each pocket and sew one vertical seam on each of the pokets.
8. Stuff the foam into the pocket so that it is clear of where you need to sew the final vertical seams.
9. Sew the last two vertical seams again using a narrow zig-zag stitch.
10. Adjust the foam so that it lies flat inside the pocket.
11. You should now have something that looks like the picture above.
12. Turn the pack inside out
13. Take your SilNylon and fold over about 3cm from the longest side and machine one pocket. Make sure it is big enough!!!
14. Sew the fabric onto seam with the pocket running parallel to the seam and outside of it.
    
    
    
    
15. Fold over the fabric on the far edge and carefull sew it onto the other seam. Make sure the pocket is large enough and make sure that the fabric is at least as the pack. If the fabric is machined too narrow then the foam will not fit and the pack will not sit properly. You can use the original foam pocket for guidance.
16. Test fit the foam into the pocket and test fit the tubes. The pack should look like a pack again.
17. Sew the velcro from the old tube pocket onto the new one.
18. Turn the pack right-side out; fill with gear and take it for a test drive....