i started with a list of attributes that i wanted to incorporate.
1. Symmetrical sling design with waist band that can be worn on either shoulder.
2. One piece body
3. Hammock-inspired shoulder strap made of flexible material with no padding.
4. No hardware other than a two way zipper and one s-biner
5. 20L capacity
6. Looks damn good
I first calculated the dimensions of of a conical section that would equal 20l and fit nicely across my back. Then i cut the single piece out of plastic and taped it together. When i got what i wanted, i took the tape off and traced it on a piece of cheap ripstop from Joannes. The only purchased materials were the ripstop and the zipper. The shoulder strap was made out of a pair of polyester slacks, and the rest was found or salvaged from other junk. This is how it looks.
The shoulder strap is incredibly comfortable with my sleeping bag and a jug of water in the pack. The pack hugs my back perfectly, and the paracord waistband gently holds it in place. The pack is ambidextrous and works just as well on either side and is effortless to convert.
This is just a prototype. The real deal will be made of 1oz cuben, with bunched parachute nylon shoulder strap. The rings around the top and the bottom will be daisy chains made of 1/2" webbing. 3d mesh back and a single piece of 1/4" CCF that reinforces the top, bottom and back of the pack to add structure when it is not so full.
For now i am very pleased with the prototype. The fit and function is exactly what i had in mind, and it cost me 11 dollars to make it. I would guess the weight is about 7oz, and mostly because of the heavy webbing i used (5000lb tow strap around the top lol). The goal for the finished product is 3oz.