material/form factor of aluminum stays and framesheet

Hi Sarah. Also interested in this topic. There's an interesting discussion in a current thread about replacement frame sheets for the GG Crown VC in the gear section. See end of that thread. I am supplementing my floppy HDPE frame sheet with a piece of CC foam right now but looking to upgrade the HDPE frame sheet at some point. GG just put out a new pack where the frame sheet is…maple!!!

Btw, an aluminum tube will resist deflection in 360 degrees whereas a flat stay will readily flex fore and aft. I asked a similar question about which is most desirable in the thread ref'd above, but no answer. I always thought you wanted the sheet/stays to conform to, and flex with, your back so I don't know why the interest in round stays.

The air beam-type frame sheets which are basically small air pads seem popular. Another thing to puncture, though. It absolutely blows my mind that an air bladder could be stiffer than a plastic frame sheet, but it seems there's widespread agreement on this.

One other idea: Seems to me the pocket for the stay or sheet is just as important as the stay or sheet itself. The fabric pocket, if it's nice and tight, can take a lightweight, floppy material and make it behave as if it were much stiffer than on its own. I've noticed a tendency by people to evaluate the frame material out of the pack and on its own…I think that's only half the equation.

del

I made a backpack with an HDPE sheet and Easton tent poles for stays. I bent the poles to the profile I wanted against my back and attached them to the frame sheet by sewing sleeves of 1 inch grosgrain. You can sew the sheet using a heavy-weight needle and an ordinary sewing machine(slowly!). It took a while to get the thread tension right of course.
The poles are incredibly rigid and much lighter than flat bar of the appropriate strength.
The ends of the poles stand proud from the top and bottom edges of the framesheet and into webbing slings stitched to the inside back panel of the backpack. At the same point on the outside I attached my load-lifter straps and waistbelt loops, so the whole thing is rigid and the load transfers well to the hips.
You can get the HDPE from signage/plastics supply merchants in various thicknesses and colours/opacities (I used 0.7mm).
Its cheap and useful for other things like flexy cutting boards or as an outer layer to rigidify your hipbelt wings.
Nothing will stick to it however…
I found the Nanolite Easton poles at Quest Outfitters (http://www.questoutfitters.com/tent_poles.htm#.344%22).
As a guide my Dyneema X-grid pack with framesheet, top lid (I like a decent pocket on the top of my pack) and all the extras weighs about 700 grams.
The best part is the rigid back profile keeps the pack off my back. I'm a heavy sweater and having air flow around the back keeps me sane in hot and humid Australian conditions. Of course if you prefer full contact its simply about how you bend the stays/poles!

Tubing – stiffer for the same weight of metal, but harder to bend to suit your back.
Flat bar stock – more flexible, more easily bent to suit your back.

I have used flat bar stock for all my stays in all my many myog packs, and I've never had an issue with either the flexibility affecting weight transfer, or with any of the stays bending out of shape. And I sue pretty skinny stays – 5/16" wide by 1/8" for my lighter packs and 1/2" by 1/8" for packs intended for heavier (like over 30 lb) loads. Personally I don't do framesheets, I've never felt a need for one. But I did have a Marmot pack from the 80's that had a framesheet and single stay. That framesheet was polyethylene, I'd say about 1/16" thick, and that thickness seemed about right in terms of flexibility and stiffness

Did you see this post from thread 52274? (Quote:)

So here's the skinny on how to make a pretty sweet, UL frame sheet:

First, go to Lowe's and buy a piece of corrugated plastic board – it is located in the windows department next to the acrylic and Lexan sheets, even though it's commonly used for signs – Cost: $7 and you can get two+ frame sheets out of it.

Second, cut the frame sheet to size – I did it with the ribs running vertically so as to keep it stiffer in that direction. That's what she said. A box cutter works nicely.

Third, sew two strips of 1" webbing directly to the frame sheet to create two "sleeves" (open at the top). Most sewing machines should penetrate the plastic just fine! That's what she said.

Fourth, procure some aluminum stays – the kind I used from my brace were the "ribbed" variety (pictured second from the left on http://www.higginssupply.com/products/alumstays.html); the flat variety were not stiff enough. That's what she said.

Finally, bend the stays to the contours of your back and slide them into the sleeves (not… gonna… say it), the back panel now takes on the nice, curved shape of the stays.

Works great though a small amount of care must be used to not crush the corrugation of the plastic.

(End quote.)

I thought the ribbed stays he mentioned were nifty. The URL is different now:

http://www.higginssupply.com/en/stays/aluminum-stays.html