A lightweight bag goes a long way to make a traveler or backpacker more flexible. The challenge is justifying the cost of carrying an additional bag. Cost in terms of money + weight.

Inspiration. The Sea2Summit bag is my favorite. I've given it as a birthday present twice since learning about it in '14. That said, I hesitate to justify the $33 (was $45, two years ago) cost for myself.

My Bag... at less than twice the weight (see note below), this generic AdventuRidge back from Aldi cost $16. Most of the added weight shows up in the seams. Both bags are made of nylon. I compare the difference in weight to that of 1" of water in a standard nalgene... not a huge difference. --we love Aldi

My Modifications. The additional weight shows up in the reinforced stitching and insulation. I'm fine with the reinforcing even though the Sea2Summit bag is better quality stitching at lower cost. The insulation is what I'm removing. Here's why:

Weight - at about .4oz it's not hugely significant... roughly the weight of a big drink of water
Heat - insulation creates more heat between my back and the pack... all hikers know sweaty it can get
Smell - that sweat means the pack starts to smell... nylon alone carries less smell and is easier to simply wash and rinse
Drying - insulation means the bag takes longer to dry. I camp in bear country and like that a lightweight bag can be lifted into a tree to store food. That said, if it rains I want it clipped to my pack so that it dries quickly.

General Note on Sewing. Sewing is the first craft I learned. Before I ever picked up a saw I had learned to operate a sewing machine (thanks mom). The sewing machine is a powerful tool. Just like carpentry a good tailor knows how to create their own tools, understand materials and use templates to be more efficient.

Step 1: The Pack

Pack details compared to the lightest weight pack I know:

My Pack - 30 Liters at only 8.8oz (3.4L/oz) (see photo)
Sea2Summit - 20L at 2.9oz (6.9L/oz) (full specs on amazon)

Materials to make modifications:

Metal Ruler (ideally with a cork back, here)
Sharpie
BBQ Lighter
Swiss Army Knife (scissors, knife) + Full Size Scissors
Singer Portable Sewing Machine - my vintage model, new model
Sewing Needle - easiest way to get started...hotel sewing kit
Polyester Thread (black)
Seam Ripper

Get Right to the Sewing? jump to Step 8
----step 7 is also a good one with a note on pins + hand stitching...

Step 2: Revealing the Insulation

Insulation. Pack is designed with two layers of nylon around an 1/8" of polyester insulation. I decided to make a single cut to open reveal the insulation.

Marking the Cut. I used the width of my ruler (1-1/8") to space from the top edge. The idea is that this cut will also be a pocket. ---I could have cut a larger pocket initially but wanted to leave myself flexibility by starting small

Step 3: First Cut

Here I used the Swiss Army scissors. I soon switched to a full size scissors.

Step 4: Finishing Edges

Heat Treating. To avoid any fraying of the nylon I used a bbq lighter. ---I was generally careful but relatively unconcerned about maintaining a perfectly straight edge. The edge will be finished with trim later.

Step 5: Remove Insulation

Removal. At first I cut the insulation. Like most insulation it is easy to simply pull apart. After a few cuts I dropped the scissors.

Step 6: Spot Stiching

Initial Connection. Like spot welding... spot stitching is my approach to getting material in place.

Two Corners. I used basic knots with an inch of stitching at each corner. I left 12" of tread after tying a final knot. I knew I'd have to return to hand stitching to finish the corners so easiest to have material in place.

General Note - Hand Stitching: the goal is to limit hand stitching as much as possible. That said, I also prefer not to use pins... I have a collection of pins but I find it tedious to arrange and rearrange. My approach is to pin material and leave thread where it can be used when needed.

Step 7: Design Decision

Here is where I made a design change midway through the project.

Initial Plan. In the first photo you can see how I planned to cut through the existing pocket. I would then create a trimmed area to pass through the smaller zipper pocket into a larger pouch where the insulation was removed.
New Plan. Instead, I would keep the existing pocket but use some extra material to trim around the top seam (step 9). From there I would enlarge the pocket (step 10) and trim (step 11).

Why Change. I knew I would never use to zippered pocket as it was designed to be a smaller carrying case for the pack itself. That is always a throw away feature for me.

Secret Pocket. With the pocket sewn in place I create a small 'secret' pocket right at the top of the pack. It's a handy place to keep a backcountry first aid stored in a cigar tube.
Isolated Zipper Pocket. I didn't want to eliminate the small designated zipper pocket. It would be annoying to have a small item move from that pocket into the insulation space and have to move it back to the zipper pocket (picture a pebble in your shoe)
Enlarged Access to Insulation Pocket. I knew I needed a larger opening to the main insulation pocket than just a narrow slice. This would make the zipper pocket even less isolated.

Step 8: Sewing Machine

Portable Singer. I had to take a minute to check + reload the bobbin and setup the portable Singer machine. I bought his machine from a salvation army in Chicago sometime in '12. It's fantastic. Know that every salvos and good will has at least one sewing machine... they are often cheap modern ones but if you check once a week for a few months you'll find a gem for ~$20. Great valued compared to the new sewing machines on amazon.

My last sewing project was The Knecky back in '15.

Step 9: Top of Pocket

Pinch Pocket. Because the zipper pocket is loose I am able to use it as trim around the upper edge of the opening.

Step 10: Trim Other Sides

Trim Material. to trim the other sides of the opening I need trim material. Fortunately I am able to use the excess material I free up when I cut the larger opening for the pocket. --see next step

Step 11: Cut Trim

Trim Pieces. The spare material is cut into strips. The trips are a little wider than 1cm... Just looking or enough material that I can get a good bite on the nylon I'm wrapping.

Step 12: Wrap Edges

My approach to stitching the trim is noted below. Photos go into a lot of detail but can be hard to follow if you're not a confident tailor.

Pinch... hold trim in place
Lower Foot... with foot lever resting on my hand I was able to maneuver material in place under the foot
Place Foot... from there I released the foot to put pressure on the material
Roll the Needle... I advanced the needle enough to pin the material in place
Align Material... using both hands I was able to secure material either ahead or behind the foot (opposite the direction of my stitching so that I could first set the stitch)
Feed Material... from there feed material and try to carefully turn the corners ---my mistake that had me pull out the seam ripper is included in the photos

----apologies to all the proper tailors/seamstresses out there!! I know I am butchering the vocab of your trade as I invent my own language to describe my process.

Step 13: Final Hand Stitching

Back to Hand Stitching.... it is important to make the final connections in the narrow spaces where the sewing machine can't access. Now that material is properly secured. Hand stitching is a much more pleasant experience.

Step 14: Reinforcing

Corners + Overlaps. I went back over the weakest sections with a few addition pieces of the material I removed to open the pocket. This material allowed me to clean up edges and reinforce corners.

Step 15: Finished Pack

Here are some shots of the finished pack.

Upgrade? At some point I may be able to justify the Sea2Summit 2.9oz pack. Until then I'm sticking with this modified version and enjoy knowing that I've made it my own. The stitching on this product is of good quality but as it wears out it provides opportunity to make further modifications!

Thanks for reading! --Jeff
Hope you enjoyed this instructable. Especially if you are new to sewing. Please consider voting in the Backpack Challenge!

Here are a few of my other backcountry instructables:

Backcountry First Aid- lightest first aid and what I've carried for 17+ years
Backcountry Blisters - best use for duct tape I know :) ---caution, foot pics
Backcountry Coffee - coming soon

As an outdoor guide for hs students while in college these were my go to sources for backcountry readings.

Introduction: Lightweight Backpack