Best Backpack Materials

I'd say use x pac or dyneema x for the whole thing. You don't save much weight on pack fabrics (because such a big % of total weight is hardwear, straps, etc–actual fabric is usually not much more than one square yd). x pac or dyneema is much more durable than sil. Using x pac is cheaper and more waterproof, but you don't need much material for a backpack so price is less of an issue than a quilt or tarp. Sil is kinda nice for collars though since it's a bit more flexible/rollable if you're doing a roll top.

I wonder if you could just make the whole thing out of silnylon?

The Shield from thru-hiker.com may actually be waterproof

I have a thicker fabric on the back/bottom of my pack, but I'm thinking it might not be necesary

This is assuming you don't bushwack through thorns and you can be fairly careful in order to get the lightest weight

I like to work with a combination of fabrics of thru hiker Dyeemna grid stop. I use Xpac or 500 d Cordura in place the pack can rip or I need extra strength like the bottom or shoulder straps, hipbelt.
Terry

Rob,

"…while completely adequate and usable my 4.90 ounce SUL pack was a little bit of a challenge to repack in the field. The spinnaker and silnylon shell simply doesn't have much "body" when empty. Also the material is prone to siding down as I'm trying to pack up."

I've moved away from spinnaker and silnylon shells for my packs for the reasons stated above.

XPAC is a approximately 400 Denier textured nylon with a tough waterproof laminate. The nominal fabric weight is 4.9-5.5 oz per sq yard dependent upon which "color" you choose. The grey seems to be the heavier fabric in my experience.

I used 500D Cordura on the bottom of my most recent pack for reasons of durability. In retrospect I'm not sure that the Cordura is anymore durable than the grey XPAC. Chris Zimmer seems to have used the grey XPAC material on the bottoms of all his packs.

"My requirements are the standard three: waterproof, durable and light."

We have covered waterproof and durable. How large and how light do you want your new pack? You could combine the XPAC with cuben and get light, durable and waterproof. Your wallet will be lighter also! ;-)

Take a look at Chris Zimmer's 10.5 oz Cuben Fiber / Xpac Backpack.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=41789&skip_to_post=354928#354928

There are many options to consider. How light do you want your pack and your wallet to be when the new pack is complete?

Party On,

Newton