I started building an Ultralight G4 pack made out of cuben and sil. Got about half way through, and thought good god this is a lot of work for a pack that will probably fall apart during or after a thru hike.
I decided to go back to the idea of a light external pack frame, and just attach a large bag to it since the G4 is just really one big bag with attached straps.
I have been working on this thing for months, mostly thinking and procrastinating. I had replaced the heavy aluminum bar frame in my old kelty pack with something similar to this.
Thought it would work okay for a pack frame. Its made out of alum tent poles and 90d corners from quest.
It is bent in an arc on the sides and bottom and the mesh stands out to keep the bag off your back. Have not bar tacked it yet.
Weighs 11oz but it is simple. Could be lighter, with a different belt (that alone weighs almost 4 oz) and maybe a carbon fiber frame.
Dont really plan on any belt padding except it will get slip on cuben or sil belt pouches so maybe I will stuff some blue foam in those.
The shoulder straps are off my old kelty pack an on there just for testing. I plan to set it up with lighter shoulder straps and shoulder pouches big enough for water bottles and a sernum strap.
The bag part will basically be a G4 without the bottom buldge, out of cuben and sil since I already have most of it made.
I imagine it should end up at about 18-20 oz.
Its possible I might have to remake the frame at some point, but at least its a start.
I also think I might need a shelf at the bottom but not sure yet.