I've done quite a bit of experimenting to find (for my use) the lightest weight fabric that will get the job done. I started with heavy weight coated cordura nylon, then went to 1.9 ounce uncoated nylon, then 1.5 ounce uncoated nylon, then 1.1 ounce uncoated nylon, then to about .7 ounce uncoated nylon.

I figured I would eventually have a catastrophic failure and then go back up a couple notches for fabric choice. To my surprise none of the fabrics failed. The worst has been pin holes on the bottom or sometimes small tears from hooking on some sharp object. Nothing has happened that would affect the function of the pack bags on a trip, however (no big tears, no ripping at the attachment points, etc.).

All of the fabrics have been exposed to at least 30 hours of actual use with at least 30 lbs of weight. None have been exposed to abrasive rocks or serious thorns.

So I'm curious. What has been your experience? What do you consider a minimum weight of fabric for your pack bags?

Edited by lyrad1 on 01/16/2013 15:28:58 MST.

A tight 200ish denier is my minimum. I've been using heavier lately for a variety of reasons.

I see pack failures firstly with sharp things (rocks, sticks, skis, ice axes) ripping the bottom and sides. Fabric weave seems to be at least as important as mere weight here.

Second mode of failure is seam failure at stress points (harness attachments, compression straps). This is where thicker fabrics are nicer. It is possible to reinforce and distribute the load such that thinner fabrics work, but the margin for error is lower and the design fiddle factor is a lot higher. I like being able to bartack at will without worrying about failure due to fabric over-preforation.

David,

Thanks for the info. The link below (scroll down) shows some 200 denier coated oxford fabric (on sale) that weighs 4 ounces per square yard at Seattle Fabric. Is this close to what you are talking about?

here

My backpacking bags use about 1 square yard of fabric so the difference in weight between this 4 ounce fabric and the lightest I have used is about 3 ounces. Going to, say, 8 ounce per square yard fabric would add about 7 ounces to the weight of my packs. I would guess that many/most people would opt for fabric heavier than I'm using and get something closer to what you are using for the reasons that you list.

On the other hand the ocd part of me seems driven to tinker with the lighter stuff. To look at it from this distorted viewpoint I see the addition of 3 ounces or 7 ounces to my pack's current total weight of 7 ounces (frame, shoulder straps, waist belt and back bag)as increases of 40+% and 100%, respectively.

Daryl

200 denier fabrics are generally in the ballpark of 4oz/yard. It's impossible to comment on any particular fabric without seeing it, weave and coating qualities vary so much. VX-21 is 200 denier (face fabric), and the most common Gripstops are as well so it's a useful benchmark for discussing the things I mentioned in my above post.

3-7 oz for a more reliable pack which is easier to build is a price I am very willing to pay. Saving weight with pack fabric is, often, either too modest a savings to get excited about or a red herring, in that some of those ounces have to be gained back with more reinforcements.

There seems to be some confusion here.

200 denier refers to the thickness of the fibers making up the thread, or sometimes to the thread. It does not have to bear much relationship to the weight of the fabric. Quoting denier instead of grams/square metre is simply confusing. You can easily get a 2:1 range in weight with the same denier.

Cheers

Per Wikipedia, if I read it correctly, a 9000 foot thread of silk weighs 1 gram and equals 1 denier.

I've been up &down on this,but have never had a catastrophic failure with silnylon or Cuben. Super light stuff gets to looking moth eaten, but nothing falls out. For doing long trails where it is common to throw the pack into the back of a truck with a load of rock or firewood or when taking public transport, I sorta like something sturdier such as Gridstop. My preferred AT pack is Gridstop sometimes. But usually I use it as my go-to travel bag. Otherwise I just take my chances with UL fabric and wrap the UL pack in the rain cover for transport. Sticky granite ledges where you have to butt slide are the biggest danger to UL packs in my experience, so I put a more abrasion resistant layer on the bottom. It adds 3/4 oz. or less if you use garment weight Taslan. That isn't waterproof but it doesn't have to be.

Something nobody has mentioned yet is that carrying UL gear allows you to be more agile, and able to avoid rubbing up against rocks and obstructions much more easily.

You're less likely to do serious damage from setting a full pack on a sharp rock than catching the pack on sharp rock while hiking/climbing/whatever.

It depends hugely on what type of hiking you're doing. You might be more agile, but rocks/canyon walls/branches are sometimes unavoidable, and even with a light pack the occasional pack lowering/hauling up or down a short climb is necessary. If you're mostly on trails, lighter stuff is fine. I've been getting about a year out of 4-6 oz fabrics. Like Dave said, pack fabrics aren't a very efficient place to save weight.

Not sure you always have a choice between on-trail and off-trail.
Last summer I was hiking in open country above timberline until I ran into a humongous boulder slide that I might have been able to cross by myself, but not with the two Shelties who could not get across even a few feet of it. It was as if the top of mountain had broken off and slid down the mountainside in huge chunks.

So we headed down the mountain to a trail in the valley - a long nasty bushwack. The game on the steeps seems to involve always looking ahead to find a route that doesn't dead end in a box made by huge deadfalls.

Either way, it was to be an abrasive experience for my pack. The USFS attitude seems to be that trail maintenance is not apropos in wilderness areas (unless a trail club has the OK to do it).

P.S. Daryl, as you may know from prior threads, I've been looking at silcoated balloon cloths that weigh 2 to 2.75 oz/sq/yd coated. Still need to complete a HH tester though, to be sure they are water resistant enough for me.

Edited by scfhome on 01/17/2013 17:16:05 MST.

While strictly speaking denier does not directly correlate with fabric weight, given the not especially accurate weights quoted by many companies I think it's the most desirable descriptor for the time being.

Knowing the denier and the weave is enough to get a pretty good idea of weight (before any treatment, of course). One 200d oxford cloth is much like another 200d oxford cloth. There are differences, but they're nothing compared to one of a different weight, or a different construction. It's worth pointing out that you need to know it both ways; many fabrics are woven with different weight warp and weft.

"While strictly speaking denier does not directly correlate with fabric weight, given the not especially accurate weights quoted by many companies I think it's the most desirable descriptor for the time being."

Ordered a supposedly 200 den 4 oz/sq/yd nylon with 1.5 oz PU coat from Seattle Fabrics. It weighed 4.5 oz/sq/yd on my scale.
Then ordered a supposedly 140 den 4 oz/sq/yd coated nylon with 1.5 oz coat from SF. It weighed 5.4 oz/sq/yd on my scale.
(All that was posted on this forum in the recent past.)

Perhaps the denier specs from the companies are just as unreliable as the weights.
Even if there had been no hassle with SF, if i could do it over, I would have first tried to obtain samples, and used my $35 micro scale to try to get a rough idea of the weight per square yard, along with other features. Live and learn.

I've used 200D fabric from Seattle Fabrics, Outdoor Wilderness Fabrics, and from the local fabric store, the Mill End Store - all pretty much the same.

As pack it's way stronger than necesary.

I did a 1.1 oz silnylon pack with 200D bottom and back. More than a hundred days of backpacking with nothing resembling a failure. I occasionally go off trail or through brush or scrape against rocks but mostly I'm fairly careful.

Now I've done silnylon with just reinforcement of 200D for shoulder strap attachments. Used a little but I think that will be fine.

So - same conclusion as you, fabric doesn't fail no matter how lightweight.

But, on the other hand, it takes maybe 1 square yard of fabric so it doesn't matter that much which fabric, it won't weigh much total.