Enough ideas from the last ~year of hiking have coalesced to that point where I'll be building another large pack soon. I'm confident enough in my design to consider using a heavier weight cuben for the vast majority of it. Having never worked with the stuff, I have some big questions about construction technique, especially seams and strap reinforcements.

Is there a preferred thread and needle diameter, and stitch length? I use a thinner thread and needle when sewing sil v. something like VX-21, and I'm curious if something similar is a good idea here.

With long seams for a big pack, is a single layer of cuben sufficient or should reinforcements be bonded along the length of the seam prior to sewing to enhance long-term strength? Bear in mind this will be a ~70 liter pack which will at least occasionally see 40 pound loads. My though is to bond (with tape?) a strip of cuben oriented at a different angle along the main seams before sewing them, so that the stitch will go through four layers and the differently oriented fibers will enhance longevity.

Similar question to the above w/r/t compression straps. Reinforcement a good idea? The attachment of harness components will have sufficient surface area so that I'm less worried there.

Thoughts appreciated.

I use a thin needle and a long stich length. I use tex 40 or 50, one problem is that the tape starts going in the eyelet in the needle and impeed the thread sometimes so have a bunch of needles ready to swap out then clean them later.

I make a bunch of cuben 1/2 inch tape oriented at 45 degrees. I place the tape on all major seams then tape again to adhere the panels together then sew.

So each sewn seam is reinforced with 3 layers, one at 45 degrees and two layers of tape.

Using a cutting mat and mini razor blades like an exacto knife and a carpenters square helped me out a lot.

Hey Dave,
I did a little cuben pack experiment last summer and knowing the kind of trips you do (maybe this is intended for something else?) I kinda think you should reconsider. I used 1.5 oz cuben and put a decent sized hole in it on it's first day out in Death Hollow due to a (not very hard) bump on the canyon wall. I later put another hole in it on the same trip after walking through some willows. On the other hand, I've used a VX07 pack (which I didn't expect to be strong enough...thought I'd need vx21) for well over a year now and beat the hell out of it in the mountains and canyon country with no apparent wear. Unless you're using one of the laminates with a nylon face, the lack of abrasion strength is significant unless it's going to be strictly for (wide) trail use.

If you're going to go for it:
-I used v46 bonded nylon thread. I like nylon thread for packs and v46 seems like a good strength/hole size compromise.
-An extra strip to sew through is good, but I think it'd be a good idea to also tape seams AFTER they're sewn. This way, the tape is taking most of the stress, rather than the needle holes (which will take all the stress, regardless of # of layers, if not taped). I'd go all out here. Something like a compression strap can be a lot of stress on a seam.

I think taping after sewing is the way to go if possible. I had a lot of trouble keeping a needle gunk free for any length of time on my rain jacket project. I ended up with too many skipped stitches because the eye of the needle would get gunked up. On the other hand. It was nice to have the Cuben already taped in place when I went to sew. There may be other benefits to taping first that I am missing. The Sail makers surely tape first.

Maybe you should put tape on both sides, but no tape where the seam is?

Thanks for the feedback everyone. Brendan, that's the sort of concern I had. I've found VX-21 to be a good fabric for me, so something with significantly less abrasion resistance wouldn't last long.

I may just buy a Cilogear 60L. Material and time add up quickly.

+1 on VX07. Have made on small and one big pack out of it and I have had no problems at all with durability. Think it strikes a very good balance!

On cuben fiber. I'm kind of skeptic about it for packs. Yes the sandwiched fibers are plenty strong, but the face fabric, mylar, isn't. If the pack is otherwise well made, reinforced at stress-points and adequately designed for the intended load, abrasion will be the no.1 issue. In other words it'll be susceptible to abrasion damage.

On the other hand, I actually don't own a cuben pack. Only experience is a myog tarp (CT2K.08).