A new molecule-bonded polyethylene laminate construction and stripped-down design allow Arc’teryx to raise the bar (and lower the weight) of what’s possible with an ultra-light, waterproof day pack for fast alpine missions and beyond.
words :: Feet Banks
The Full Story
The future has arrived.
Or, more accurately, it has evolved.
The new Arc’teryx Alpha SL 30-litre backpack weighs in at just 444 grams—essentially the same as an inflated soccer ball. This makes the Alpha SL up to 30% lighter than many top 30L packs, and still lighter than the competition’s “stripped down” mode (no waistbelt, etc).
And it’s all thanks to this crazy new material called Graflyte™.
“We’ve partnered with ALUULA, a BC-based kite surfing company who developed the Graflyte™ fabric,” says Chris Hodgetts, Arc’teryx Senior Design Director—Hard Goods & Accessories. “They’re working with ultra-high (UH) molecular weight polyethylene and they figured out a way to bond the fabric directly to itself to build lighter and lighter kites. That caught our attention.”
While the UH fabric showed promise, Chris says they played around with it for years trying to find an application that would work. “It was always stiff material,” he says, “It didn’t rip but it wasn’t that durable, and with those UH fabrics, you can’t attach stuff to them. We saw and opportunity though, and it became a bit of a loop—we’d build stuff, test it, wreck it, and come back to them to tweak the design. I bet we did that for over a year and a half.”
In the end, Arc’teryx and ALUULA were able to create a laminate of the UH polyethylene, that solved durability issues, maintained waterproofness and—importantly—did away with the need for adhesives and (weighty) excess stitching.
“It became a bit of a loop—we’d build stuff, test it, wreck it, and come back to them to tweak the design.”
“Laminating the fabric to itself,” Chris says. “We were able to develop techniques that got stronger bonds than sewing, without adding adhesives. That was a first.”
No adhesive, no tape, no stitches…it all adds up to weight savings.
The waterproofing is also noteworthy because rather than treating a pack fabric with a film (which peels off over time), the ALUULA fabric is inherently waterproof, without the addition of “forever chemicals” (and it feels like super strong wax paper).
“There is nothing in this pack from the current list of ‘forever chemicals,’” Chris says. “Polyethylene is pretty inert and the way this pack is constructed, it doesn’t require the DWR (durable water-resistant) treatments that are often responsible for those chemicals.”
Similar to previous Alpha FL 30 models, the SL has a drawcord-open top for quick and easy access, but with a new triangular flap—made of the same UH polyethylene—that adds extra weather protection for the top of the pack and makes for a much more secure system when carrying a rope.
“This pack is designed simple and minimal,” Chris says. “The idea was to make a pack where the performance advantage of this new fabric and construction, would actually make a difference for the sports being done. Mainly alpine climbing, day trips and super big missions where people are pushing the limits and every gram counts.”
Six front lashing loops create endless attachment options. Climber/guide Sam Hennessey helped develop two molecular-bonded loops on the front of the pack so he could better attach skis with boots clicked in, and a new “pick sleeve” makes for a more secure fit for one or two ice axes of a variety of sizes.
“Our team and athletes tested this pack hard,” Chris says, “and they’re reporting this pack is exceeding the durability of the previous Alpha FL packs. One benefit of this material is if you do happen to get a nick, it won’t propagate. It’ doesn’t tear open. And it doesn’t catch—you can bang through a grove of devil’s club and the spikes will just skate off.”
“The idea was to make a pack where the performance advantage of this new fabric and construction, would actually make a difference for the sports being done.”
For our tests, the pack carries well—the minimalist, unpadded waist belt keeps it snug (but can be removed to reduce weight) and the shoulder straps ride comfortably. A watertight internal pocket with key loop protects the real valuables while an easy-zip front pocket will hold enough trail mix energy gels to keep you going all day (a folded route map will fit in their nicely too).
The pack ships with two removable webbing straps and a self-adhesive patch kit, which you hopefully will never need because the ALUULA Graflyte material apparently boasts eight times the strength-to-weight ratio of steel.
A pack that works for solo missions or as the go-to choice for whoever is leading that multipitch, the Alpha SL only comes in one colour (crinkled white), but that only makes it more of a head turner at the crag.
Specs: Length: 55cm, Width: 27cm, Depth: 17cm, Volume: 30L Weight: 444g / 15.7 oz
Price: $500
