drawstring backpack for overnight trip

water will get in when it rains?

nice looking pack

It's fine for a few pounds of weight, but anything heavier would be painful on my shoulders.

What about flat/semi round cordage that is a bit fatter? What about a combination of cord and eg 1/2 inch webbing?

A pack this small sits a fair way down your back (like the picture of your friend). This means that with the closure closed, and in carry mode, all of the draw cord that normally is used at maximum circumference is now used to make the connection up to your shoulders.

If you get the lengths just right, at the point where the cord starts to make contact with your shoulders, change to flat webbing. When the pack closure is fully open, the webbing should stop before it enters the tube.

Subjective, but 6.5 lbs is probably reasonable for drawstring shoulder "straps". I would do something to protect the opening from rain though.

String straps wouldn't work for me, but if you add mesh straps and invert the bag (a-la Matt Kirk's design) it would work for me, and rain wouldn't come in.

A noble effort, but what a miserable way to haul stuff! The bag with a drawstring top is light and simple, but so many light packs fail on the straps. I think Gossamer Gear has the right idea with a simple pack bag and "real" shoulder straps on the Minmalist 24 pack: http://gossamergear.com/minimalist-ultralight-daypack.html

Perhaps a wide sling strap would cut weight and cost? That has been done too.

I think a haversack (aka messenger bag) design would be useful at this size and level of load. The Patagonia Lightweight Travel Courier bag is a good example, particularly with the water bottle pockets on each end. Carrying water becomes the challenge with small SUL packs. http://www.patagonia.com/us/product/lightweight-travel-courier?p=48813-0

"With hipbelt, the weight on the string could be minimum and the load capacity will be definitely much higher"

Probably not.

I honestly doubt you'd get any support from a hip belt for a pack of that size and design, whatsover.

Since you are only talking about carrying a very small amount of weight, there would not be any real "rigidity" in the bag to divert any force onto a waist belt. Any stuff the bag would simply sag, and still put the weight on your shoulders. As others have said, a wide mesh-like strap might likely be a more favorable shoulder strap for most folks to have, even if it make the design more difficult to manufacture.

Keep in mind that most hipbelts for small daypacks don't do anything toward actually diverting any force off the shoulders. They merely keep the pack from swaying right and left. If you want to create a good daypack that has utilizes a waist belt and could carry 10 lbs, design a fanny or lumbar pack instead, and forgo the shoulder straps entirely.

It might be heavier, though.

Jerry,
Actually the STEAM drawstring pack has a small removable lid for reducing the rain getting in.

Adam,
I haven’t tried flat cord since I don’t have it on hand. Nevertheless, I’ve tried to thread the “straps” through pvc soft tube to provide additional comfort. But the result is not as good as I expected.

Todd,
String straps wouldn’t work for me either. Mesh straps would definitely be more comfortable than thin strings. Actually, I still prefer padded shoulder straps and I’ve already have some minimalist padded pack. However, I still want to test if adding a hipbelt to a drawstring pack works ok.
Inverting the bag sounds good though it may reduce the convenience of open and close which benefited from a traditional drawstring backpack.

Dale,
I well reinforced most stress points of the pack with vx07. So I think the original one can probably hold up to 20lbs though I originally designed it as a summit pack which would be used to carry about 5lbs and not for long.
I agree that a messenger bag or a backpack with sling shoulder straps would be good for this size. For this project, I’m trying to figure out how minimal could shoulder straps be for a pack with simple hipbelt, since I prefer put most of the weight on my hip.

Matt,
I just tried to put 11lbs of stuff into the prototype, and I can make most of the weight on the hipbelt when I just standing straight especially when sternum strap is added to provide stability. Not sure if it works well when hiking.

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Another idea of this project is to double use it as a lumbar pack.
By tightening the shoulder straps and sternum straps. The pack would be pulled toward my back without the strap on my shoulder. But it might only works well for relatively lighter weight or when the center gravity of the pack is low.

—
Jangtian Shieh(Syoten)
HANCHOR outdoor gear design Co. Ltd.

"Besides, your sub 60 fast pack kit is really cool!"

I believe you are referring to Matt Kirk (the AT unsupported speed record holder). Either way, I feel flattered to even be remotely associated with the "other" Matt.

Regarding lumbar designs, have you looked at Mountainsmith? They've had some pretty successful designs for quite some time, imho. While there are lighter/stronger packs out nowadays, they've been at it for a while…

http://mountainsmith.com/index.php/lumbar-packs/daylight.html

@Matt,
I'm very sorry about the mistake! I'm a little embarrassed I got something so basic so wrong.

Of course I've checked mountainsmith lumbar pack. I've been using one as my EDC pack for about an year when I was a student. For the drawstring pack prototype, I'm thinking that it would be a bonus if this pack can be transformed into a lumbar pack though the 3D mesh hipbelt is too narrow and too short to provide nice support like mountainsmith's pack.

—
Jangtian Shieh(Syoten)
HANCHOR outdoor gear design Co. Ltd.

Considering that I have used my Gossamer Gear Rik Sac to go grocery shopping (California Bag Ban) and put as much as 2 quarts of yogurt, 6 mangos and assorted other produce and groceries in there and survived for a short distance, I think you'd actually be quite okay with only 6.5lbs of much more packable gear in a drawstring bag.