[jdietrich]

For anyone interested in a serious DIY ultralight backpack, I'd suggest taking a look at Ray Jardine's "Ray-Way Backpack Kit". Jardine was a pivotal figure in the modern ultralight backpacking movement; his designs have been used successfully by countless AT and PCT through-hikers.

http://www.rayjardine.com/ray-way/Backpack-Kit/index.htm

[chrisseaton]

Do all those backpacks have umbrellas on them? Do people hike with umbrellas? Why does every single bag have them? Are they part of some kind of system for something specific?

[ClifReeder]

Indeed - I've hiked almost 3k miles carrying an umbrella. Worn rain gear is a compromise between breathability and waterproofness - even if you keep the rain out, you'll sweat and it's trapped inside. Umbrellas keep rain off you, are very breathable, and double as sun protection when it's really hot. Only downside is when it's windy and rainy, so it's nice to have a poncho too.