"If you follow the tutorial on OB1's acadamy site for jet pack construction, you can't go wrong. "
Steve.... Actually, not to toot my own horn, but that PVC frame that is on Obi wans site is the one I designed and made for for my Bradley pack back in 99.
Thanks for finding it useful.
mcabrera1275.... Is it necessary? absolutly not, can you get by without it? probably.
I will tell you this however, it will give a solid place to anchor your harness straping system to and it is the main reason why I designed it the way it is. If you just use the back plastic to mount your pack harness system it will put lot of undo stress on the plastic and "possibly" fail. That would not be pretty.
It dosn't put any "real" additional weight on the pack if thats what is worrying you, my bradley pack only weighed 12lbs with it's frame, my new fiberglass pack weighs 15 lbs.
It is also really cheap and easy to make and install. too many +++++ not to use it.
Bradley put the wooden dowl in my kit when I got mine 3 years ago. I think mine was 1", you can get it any good hardware or craft store.
If you have any questions feel free to email me at email@example.com or post here, I'll be glad to help.