The Ursack is a bear-resistant backpacking food storage bag that's both light and more packable than typical hard sided bear canisters - like the BearVault BV450 we reviewed in Issue 30. The Ursack has been around a while, and the latest version, the Ursack Major (previously referred to as the Ursack Allwhite S29.3), features a tighter more tear-resistant weave than previous models and is IGBC certified.
The Major comes in a standard, 650 cubic inch model that holds about 5 days of food for one person and weighs 7.6 ounces, while the larger Ursack Major XL holds 925 cubic inches of storage at 8.8 ounces. The Ursack Major models aren't designed to thwart rodents and other small critters, so if bears don't frequent the area you're hiking in, Ursack also offers rodent specific food bags like the Ursack Minor that would be a better choice, or if you’re looking for the best of both worlds Ursack also offers the AllMitey.
Ursack Major XL (left) and standard size (right)
The Major is best utilized in conjunction with an Opsak liner, purchased separately, that perfectly fits the standard model and is essentially a heavy duty Ziploc bag. 2 of these would be required for the Ursack Major XL. The Opsak waterproofs your food when the Ursack is tied off during the night hours out in the elements, and helps to reduce food odors that could attract wildlife. While Opsaks are fairly durable, I usually get one or two longer trips out of mine before the bag develops holes or the seal starts to break down; it's a good idea to always have a few stocked in the gear stash.
To use the Ursack one seals the Opsak with your food inside (after sealing, gently compress the Opsak to verify no air is leaking), cross the drawstrings at the top of the bag, cinch these tight, then tie a double overhand knot tightly at the top. At this point there are several ways to complete the process. One way is then to hang the bag with an otherwise proper hang from a tree branch, or (more conveniently and the most common way to use the Ursack) tie it off above the ground to a secure tree branch or trunk with branches to keep it elevated and with a figure eight knot. You're looking for a branch or part of a trunk that the Ursack cannot be pulled off of and one that's quite sturdy. You could tie off at ground level, but tying off above ground helps limit any possible stomping and crushing of your food.
Once properly secured and hung, any pulling on the bag only closes the top more securely, and when properly tied off even after a lot of tension the knots are easily untied in the morning – by a person – as Ursack states, bears don’t have thumbs. The Spectra fabric, weave, and construction of the Ursack is designed to be both strong enough and dense enough to withstand Ursine investigation. If you're above treeline, it is suggested to tie additional knots and either hang over a boulder / cliff or leave on the ground. If crush resistance is desired, an aluminum liner is also offered. For any method, well away from camp and downwind of your campsite is a great idea.
Over the past 10 years or so, I've used multiple versions of the Ursack in several areas of the country, and on one occasion, it has even successfully kept my food safe during a black bear investigation at the hang site. I find that the standard model is indeed about right (at first tightly) for about 5 days of food solo and fits great horizontally in my ULA Circuit, and you can either hang a separate food bag the first few days if this isn't enough space, take another Ursack or more than one on group trips, or look at the Ursack Major XL which offers more space at not much of a weight penalty. The Major XL also offers more room for cookware at the end of the day, at the cost (perhaps) of packing ease when full and depending on your pack.
Compared to hanging a silnylon food bag / dry sack or similar every night and retrieving each morning, using the Ursack is much more convenient, albeit with a little weight increase. Over time some failures have been reported, although many times the Ursack may not have been secured and used properly and as instructed. On the flip side, some canisters have been compromised on occasion as well. Compared to a canister however, the Ursack is lighter and more packable while being more convenient than a typical food bag hang, and thus hits the sweet spot for me and is my nightly food storage system of choice on every excursion I take.
The Ursack is best utilized when combined with an Opsak, retailing at about $12 for a pack of 2 - find them here.