Jul 15, 2023


This article originally appeared on Backpacker

In the past several years, fabrics from a sailcloth maker called Challenge Sailcloth have taken over the ultralight world. Though Challenge has a range of fabrics available, two in particular have the ultralight community abuzz: Ultraweave and UltraTNT. Ultraweave, often just called Ultra, has become a top choice for durable, lightweight packs. Thanks to its strength, Ultra has largely supplanted Dyneema as the premium choice for backpacks. UltraTNT, meanwhile, is gaining traction as an alternative tarp and tent fabric. Rather than using traditional materials like nylon or polyester, Ultra fabrics are made with strands of ultra-high-molecular-weight polyethylene (UHMWPE), a type of plastic that is stronger than steel by weight. In the past year, I've written stories about Ultraweave and UltraTNT that explain the technical details of both fabrics.

This summer, I've been testing gear that uses both products: an Outdoor Vitals CS40 Ultra backpack and an Etowah Outfitters UltraTNT tarp. I've put them through their paces to see if the fabrics live up to Challenge's claims of next-level strength, durability, and abrasion resistance.

In person, the first thing you'll notice is that Ultra has a lot in common with its main competitor, Dyneema Composite Fabric. Like Dyneema, Ultra is stiff and crinkly, and has a kind of uneven, wrinkled appearance. It doesn't look or feel particularly strong, but Challenge's in-house tear and abrasion tests allegedly show that Ultra is stronger than any other lightweight backpack fabric, including X-Pac and Dyneema. Ultra's claim to fame isn't that it's the lightest fabric, but rather the most durable option that's still light enough to be used in ultralight gear.

The Outdoor Vitals CS40, which is currently on presale (shipping around the end of August), is made of Ultra 200, the most popular version of the fabric and a good balance of weight and durability. To me, the 40-liter, 27-ounce CS40 feels like a perfect use case for the fabric--a versatile, do-it-all pack built with some of the toughest material available. There are a few smart design choices I appreciated during testing. The side pockets are big enough to fit two 20-ounce bottles, and low enough to reach without removing the pack. The foam back panel is plush and U-shaped (with no padding down the center), which helps prevent the classic ultralight pack bulge. This pack carries weight exceptionally well thanks to two .9-ounce carbon fiber stays that extend above the shoulder straps. That means that the load lifters (which attach to the top of the stay) can actually take weight off the shoulders. That suspension system, which Outdoor Vitals rates with a 35-pound capacity, is capable of hauling a few extra days of food or withstanding a long water carry.

I do have a few small gripes. I'd like to see a modular system for straps: If Ultra is as durable as it’s cracked up to be, it'll long outlive the more fragile foam and mesh used in shoulder straps and hip belts. The side compression cords aren’t substantial enough to actually compress much. This pack also isn’t seam-sealed. Since Ultra is a 100-percent waterproof, watertight seams could essentially turn the CS40 into a dry bag. That said, seam-sealing would probably raise the price of the pack, and enterprising hikers can do it themselves.

One of the biggest complaints about Ultra as a fabric is the risk of delamination, or having the layers peel apart--I have a friend who saw delamination after thru-hiking with an Ultra pack from another brand. Delamination is a potential risk for any laminated fabric, whether it's an Ultra backpack or a polyurethane-coated nylon drybag. If PU-coated nylon delaminates, the nylon's woven fabric is unaffected. But in Ultra, the PU coating is structural: the UHMWPE fibers are so slippery that they can--in theory--work themselves loose without the support of the coating.

So far, I haven't seen any indication of delamination on the CS40. I haven't had the chance to test my pack for a full thru-hike, but it has been put through the wringer. In addition to several backpacking trips, I've used the CS40 to haul all sorts of tools and materials, including pruning shears, fencing materials, and even a small chainsaw. I've taken it on hiking trips and bike rides on trails overgrown with rose bushes, and used it as a seat every time I've taken a break or eaten a meal on-trail. While I've managed to obscure its shiny white fabric under a layer of grime and dirt, I haven't seen any pinholes, delamination, or seam failure. Delamination seems to be of special concern in areas with consistent friction, like the panel that sits against your back. With the CS40, no part of the pack that's regularly in contact with your body is made of Ultra.

UltraTNT is essentially two layers of PET (polyethylene terephthalate) film that sandwich a grid of Ultra fibers. Like Ultraweave, it will probably strike anyone who's used to nylon or polyester tents as a bit strange. In-hand, my Etowah Outfitters UltraTNT tarp feels like a sheet of plastic, which doesn't bring strength and durability to mind. It doesn't pack down particularly well (a folded UltraTNT tarp is bigger than either a silnylon or Dyneema alternative) and is nearly as reflective as a mylar emergency blanket. Like with my Ultra backpack, though, I've found the tarp to be far stronger than expected.

The Etowah tarp is a flat 6×10 rectangle--a very simple design that leaves little to review besides the fabric itself. The seams, which are both taped and sewn, are uniform and straight. The tie outs are made of half-inch webbing and make trekking pole setups quick and painless.

During setup, the near total lack of stretch and sag is immediately evident. I'm a longtime silnylon tarp owner, which practically feels like a trampoline in comparison, and generally requires at least one round of readjustment during the night. The lack of stretch does have its drawbacks, though. I winced the first time I tripped over one of the tarp's guylines, because without any elastic in the system, all of that force is put directly on the fabric and stitching. Still, I didn't manage to damage the fabric or the tie outs, which are all reinforced with Ultra100 fabric. I also switched to using shock cord guylines, to keep a bit of stretch in the system.

One of the bigger concerns with UltraTNT is its lack of puncture-resistance, which, after testing, I think is overstated. In between the grid of Ultra strands, the bare PET film does seem pretty exposed. But in everyday use, I didn't managed to poke any holes in the fabric, so I manufactured a scenario with a sharp stick. The Ultra grid, which measures about a fifth of an inch wide, stopped the hole in its tracks (even trying to tear the hole larger with my hands proved fruitless), and all sorts of repair tapes stick readily to the tarp surface.

Just like a plastic bag, UltraTNT is essentially fully waterproof, far beyond what you might experience in real-world rainstorms. The plastic film also makes UltraTNT hot in direct sunlight, just like Dyneema. If you're the type to set up a shelter for afternoon naps, composite fabrics probably aren't for you.

The one true drawback of UltraTNT is its weight, which is roughly double that of the lightest version of Dyneema--a favorite tarp material for ultralighters. In my opinion, UltraTNT functions more like a premium version of silpoly or silnylon. Luckily, the price matches that reality. Tarptent recently unveiled three new models in UltraTNT. The new TNT Scarp 1 costs just $120 more than the silnylon model. Dyneema models, in comparison, are usually double the price.

So, do Ultra products live up to the hype? In terms of durability, absolutely. That extra strength is accompanied by a few quirks. With Ultraweave, there's little doubt that the fabric can withstand abrasion or blunt force trauma, but there are still lingering questions about delamination and how it affects the fabric's integrity. With UltraTNT, the look and feel of the fabric might dissuade some customers. For both Ultraweave and UltraTNT, I'm still on the fence as to whether the extra tear and abrasion strength is truly worth the price. In my own experience, I've found cheaper alternatives, like silpoly tents or robic nylon packs, to be able to withstand the rigors of daily hiking with a weight penalty of just a few ounces. And, if I’m being completely honest, my personal opinion is that Ultra fabrics and Dyneema both look like they belong on spacesuits, rather than outdoor gear. Still, it's hard to argue with the results.

For exclusive access to all of our fitness, gear, adventure, and travel stories, plus discounts on trips, events, and gear, sign up for Outside+ today.