Hey everyone, I just got done designing and making a backpack for my heavy loads (up to 35 lbs regularly if I had to guess) and I'm pretty pleased with the results. I made it out of material I had laying around which just so happened to match my gaudy green insulated pants and bright blue MB thermawrap jacket! The back panel , bottom, straps, and hipbelt are made of 200D oxford nylon (4-5oz/sqyd) and the front panel is 70D silnylon (2.5 oz/sqyd). The frame is 2 1/8"x21"x1" bars of aluminum along with a piece of blue foam cut to fit under the shoulder straps.
I attached the shoulder straps by cutting the back panel with an angle where the straps go, putting the straps there and sewing it back where it was. The tubes where the aluminum stays go have an extra layer of oxford where the ends touch the fabric. the stay ends are padded with 6 layers of duck tape to prevent excess rubbing. I didn't have any spare ladder locks laying around so I made some out of an orange juice jug for the compression straps on the back. They are temporary, but kind of neat.
One design feature I am proud of is the bottom of the front panel (blue fabric) has a 2" deep cat curve in it so the bottom of the bag doesn't sag!
The bag weighs 9.5 oz, but I am going to have to trim up the hipbelt and shoulder straps because they are too long, so it should drop to 9 oz. The removable aluminum stays combine for 6 oz while the blue pad weighs in at 3 oz. I expect the blue pad to come in handy for a sit pad too.
I match!

I don't know if you can see it, but the cat curve is in there

Edited by willspower3 on 03/29/2008 21:23:29 MDT.

I really dig the simple lines used complexely! I also like the smooth surface. Less stuff to get snagged!
I'm a fan!

-Passionphish

That looks really great. How did you make the catenary bottom? Any interest on posting plans?

Thanks for the pat on the back. I just approximated the cat curve. I but a mark 2 inches in, in the middle of the panel and sort of drew it from there. I've heard there are cat curve generators that can make them precise, but this was just a project from scraps laying around. As far as plans go, the pack still has some minor flaws which I think I have worked out in my pattern revision, but I'll have to get motivated to see if it works :).
There are lots of patterns out there though, and they can be easily transcribed and changed to suit your needs. Get some cheap stuff and mess around for a few packs before getting the material you want the final pack made from. By that time, you will have figured out optimal sizes, attachment methods, etc. The pack on thru-hiker.com workshop is IMHO the best place to learn the best pack building techniques you can get online.