Ultralight vs heavy duty

Cuben varies in thickness, which in turn, will determine its durability. I wouldn’t expect cuben to be as durable as cordura or dyneema. There’s a similar discussion on it here:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=52617

If you look carefully at the Backpack State of the Market Report 2011: Part 3

http://www.backpackinglight.com/cgi-bin/backpackinglight/frameless_backpacks_sotm_part3_2011.html

The durability of each backpack is rated on a scale of 1 to 5, with 5 being the most durable. It seems to map directly to the type of material used on the backpack, so here’s a quick summary:

1 – 30d Sinylon
2.5 – 70d PU Nylon
3 – Cuben 1.4 oz
4 – Cuben 1.7 oz
4 – Cuben fiber/Nylon hybrid
5 – 210d Dyneema

Again a score of 5 is the most durable.

210D dyneema gridstop is the minimum id use for rock climbing, preferably much heavier fabric … which i suspect is more the type of environment you would be using it for than walking along trails …

i dont use cuben … but i would pose the question to people here if they would drag their cuben packs through rock/concrete/rubble … throw it a few feet onto rocks … crawl with it through tight spaces … etc …

i would be quite surprised if anyone answered that they would or did … and be most interested in vids of it ;)

Dyneema is bombproof, cuben is not. Since it is apparent durability is high on your list, then go with a backpack made out of 210d Dyneema. There's a number of ultralight backpacks that use Dyneema. Look at Parts 3 and 4 of the Backpack State of the Market Report 2011.

"do you give up that durability for weight?"

Yes, in my experience. Nevertheless, I go as light as I can.

My packs, for example, are made of 1.9 ounce per square yard uncoated nylon. I bet they would get a 1 (or lower) on the scale posted here. But for my use they work and never have failed me. If I was dragging them through or against granite they wouldn't last 10 minutes.

I would put money on cuben of equal fabric weight — easy bet imo

does any manuf make such a pack of equal weight within a reasonable price range ;)

Cilogear makes their NWD (bi-axial cuben) packs from I believe 80g/sq m (I believe about 3.37 oz/ sq yd) But of course they are not cheap.

"do you give up that durability for weight?"

For any item, I determine how much durability I want. I'm not okay with disposable products, but I also don't want overbuilt and unnecessarily durable ones, since that's adding weight for nothing.

For backpacks, 1.5oz cuben is the lightest I'm willing to go. If you have a 1.5oz cuben backpack and you take pretty good care of it, it will last a very long time. I can't say the same thing for silnylon, lighter variants of cuben or other fabrics that have been used in really light backpacks (ie. G5, Terra Nova packs). Those fabrics will incur too much damage from the rigors of the trail (ie. crawling under logs, the occasional slip & fall etc) to last as long as I'd want them too. 210D nylon is a nice pack cloth and I consider this to be the upper limit of how much durability I want. 210D dyneema grid nylon is great stuff and lasts extremely long with reasonable care. I would never need something more durable for normal/off trail hiking.

For other products, I use the lightest fabrics I can for sleeping bags (ie. 7D nylon is great). For tents, 30D floors are okay although I prefer 70D. For the canopy and fly it's fine to use 15D. In cuben, a 1.5 or 1.2oz floor is good, and I prefer 0.74oz for the canopy and fly, although I can accept 0.51oz.

Zpacks released a new backpack a few weeks ago called the Exo Packs:

http://www.zpacks.com/backpacks/exo.shtml

The backpack uses a new 2.92 oz/sqyd Cuben Fiber – Nylon hybrid fabric.

“The material has the same tough Cuben Fiber as our Blast backpacks on the inside, but with a protective layer of nylon on the outside which gives it more strength, prevents fraying, and gives it a nice solid color.”

I don’t know for sure how durable it is, but I get the impression it somewhere between the Cuben 1.43 and Dyneema.

Looks like what HMG has been using to me.