Keeping Your Critical Gear Dry (Part 4)

Part 3 of our “Keeping Your Critical Gear Dry” series, republished with permission from Jim Wood, looked at the effectiveness of silnylon sacks and oven roasting bags for protecting your gear from the elements. In the final part of the series, Jim focuses on the combination of paddle sacks and half-pack liners as barriers against the elements…

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A Two-Part Dry System

Given the current state of technology and my near-obsession with equipment reliability, I believe that the best strategy for keeping critical gear dry is through a two-part system that uses a combination of lightweight paddle sacks, backed up with “half-pack” liners.

PART ONE:  LIGHTWEIGHT PADDLE SACKS

Paddle sacks, as the name implies, were first developed for use in canoes, kayaks and fishing boats. Because they needed to withstand the often serious punishment that accompanies such applications, they’ve traditionally been made either from thick vinyl or from heavily-coated, high-denier nylons. Conventional paddle sacks large enough to carry a backpacker’s critical gear can weigh 12 to 14 ounces or more, making them too heavy for most hikers.

In recent years, however, several companies (see Resources below) have developed lighter weight versions of these bags that are designed primarily for trail use. They’re often made from 70D coated nylons, have seams that are glued and/or taped, and sometimes have bottoms made from Cordura or other abrasion and puncture-resistant fabrics. Most also have roll-top closures that are highly water-resistant (when used properly), are convenient for accessing gear, and work equally well whether a gear bag is full or is partially empty. Rather than 12 or 14 ounces, the sack noted above can now weigh as little as 3 or 4 ounces. I’ve used these types of bags for at least five years and have never had a failure.

For most trips, especially when traveling at higher elevations or in colder climates, I now employ two of these lightweight sacks to house critical gear. Sack #1 is a 20 liter bag used to protect my down sleeping bag and dry camp clothes and is carried at the bottom of my pack. Sack #2 is a smaller, 8 to 13 liter bag that holds my filled jacket (down or synthetic), fleece hat, gloves, and possibly a 100 weight fleece jacket and is carried near the top of the pack for easy access on the trail. Together, these two bags weigh about 7½ ounces. Two comparably sized silnylon sacks, with sealed seams, would probably weigh about 3 ounces, so the incremental cost for the paddle sacks is about 4½ ounces. It’s a price that I’m happy to pay, however, since the chance of having my gear become saturated on the trail is greatly reduced.

The risk is not completely eliminated, however, especially if the pack becomes submerged. Although the bodies of these paddle sacks are not likely to leak, water can sometimes enter through the rolled tops if they’re not secured tightly enough. That’s why I also use a “half-pack” liner that both backs up the large paddle sack and protects most non-critical gear.

PART TWO:  HALF-PACK LINERS

As mentioned above, I tried plastic compactor trash bags on a couple of trips, but was not satisfied with their performance as a primary defense mechanism. When used as a backup, or for protecting non-critical items, however, I think they’re fine. As a result, I have now reverted back to compactor bags that are 2-3 mils thick and that weigh about 2½ ounces. I view these liners largely as disposable and usually replace them at the beginning of every trip. When on the trail, I simply need to remember to inspect them periodically for punctures, patching them quickly with duct tape when holes appear.

I normally place this liner in the bottom of my empty pack’s main compartment, then load paddle sack #1 containing my sleeping bag and camp clothes into it. Next, I add most of the non-critical gear described below, then seal the liner using the candy cane closure and a stout rubber band. At this point, about half the main pack compartment has been consumed. On top of the sealed liner, I finally add two silnylon food bags and paddle sack #2 containing mostly trail clothing (I should also note that this system works well from a weight distribution point of view, at least with the internal frame packs I’ve used in the recent past).

The key advantages of this system are:

– My sleeping bag and camp clothes are double-protected from water absorption. Even if the liner develops an undiscovered puncture or two, it will still keep most of the water away from both sack #1’s roll-top closure and from the non-critical gear it contains.

– The half-pack liner rarely needs to be opened on the trail, so the fact that the candy cane closure is not super-convenient is largely irrelevant.

– I don’t spend extra ounces over-protecting non-critical items.

– Having paddle sack #2 at the top of the pack makes accessing trail clothes quite convenient. It also provides an easily-accessed safe haven for camera gear or other small, water-vulnerable items when conditions warrant. In a high-risk situation (like fording a fairly deep river, for example) I usually re-seal this sack’s closure to make sure it’s tight and/or move it inside the lower liner. Alternatively, I could also carry an extra seam-sealed oven bag (at about ½ ounce) specifically to encapsulate this bag under these conditions.

– The paddle sacks and liner can be removed from the pack to protect gear in camp.

– Likewise in camp, the liner can be used to temporarily store wet clothes or it can cover your empty pack when it’s stored outside of your shelter at night. It can also serve as a “washing machine” for doing laundry, or it can even be used to protect the bottom three feet or so of a sleeping bag when using an open tarp in the rain (or if your tent should develop a leak). For this last use, even though the liner is not breathable, its loose fit will normally permit moisture to escape from the air space around the sleeping bag.

Aside from their value as handy in-camp “utility players”, liners are also easy to justify from a weight perspective on the trail, at least if a pack should become soaked during the course of any given trip. That’s because the weight of the water that would probably be absorbed by the otherwise unprotected gear inside the pack would almost certainly exceed the small weight of the liner. I suppose that the same argument could be made for the pack covers that I mostly dismiss above, but at weights of 6 or 8 ounces (with seams sealed), the math becomes less appealing.

General-purpose trash compactor bags, with dimensions of approximately 24″ x 36″ make good pack liners, in part because their size is about right for the application, and in part because they’re thicker than most other plastic bags, which enhances durability. Most brands are also either white or clear, which allows more light to enter the pack than do dark-colored bags, making packing and accessing gear easier. My favorite type is currently the Safeway store brand, which is 2½ mils thick and currently costs $3.79 for 10 bags. Hefty brand bags are similar in size and weight.

Trash compactor bags can sometimes be difficult to find in retail stores, however, so it may be necessary to purchase them online from sources such as Bell Parts or Gillroy’s. As an alternative, clear poly bags of almost any size can be ordered from suppliers such as Associated Bag, Universal Plastic, or Hillas Packaging. The only catch is that it’s usually necessary to order in large quantities, so you’ll probably end up with a lifetime supply.

NON-CRITICAL GEAR

Gear that I refer to as “non-critical” either won’t be damaged by water or is already packed in smaller waterproof sacks (mostly Ziploc freezer bags). My equipment is usually modularized into “kits” (first aid kit, utility kit, personal kit, hygiene kit, kitchen kit, etc) in order to help keep it organized. Most of these kits are, in turn, loaded into one or two ultralight stuff sacks that may or may not be water-resistant. It is primarily these items that end up inside the compactor bag.

My food, unless I’m traveling somewhere that mandates the use of bear canisters, is usually carried in a pair of 16″x21″ silnylon sacks that can be easily hung from trees using the counterbalance method. My tent is usually carried in a semi-waterproof stuff sack strapped to the bottom of the pack, my sleeping pad is on the outside of the pack in a water-resistant “utility shed” bag, and shell clothing is carried in the pack’s top compartment, usually in large Ziploc or aLoksak bags.

Other Notes

DAMP CLOTHING

One trick I’ll mention at this point involves damp clothing. If you want to remove a piece of clothing on the trail that’s become only slightly wet, either from external moisture or from perspiration, you probably won’t want to return it to the same bag as your filled jacket and other dry trail clothes (sack #2 above). On the other hand, you’ll probably also want to keep it from getting even wetter, so just placing it inside a soggy pack is not a good idea either. So instead, I normally store damp clothing in one of the two silnylon food bags under these conditions. These bags won’t provide protection against immersion, but even in the worst case, the item often stored here (the 100 weight fleece jacket), will typically dry fairly quickly even if it becomes soaked. Except for the submersion hazard, however, these food sacks offer fairly good protection for such items. Alternatively, of course, one could carry a small, separate waterproof bag for damp clothing.

PURGE VALVES

Some lightweight paddle bags include one-way purge valves that allow excess air to be pushed from these sacks, but still keep water out. While this feature sounds good in theory, it doesn’t work very well with the kinds of things that backpackers are most likely to store in these sacks. What happens with sleeping bags and puffy jackets is that they create air pockets when stuffed into these bags as their own fabric presses against the sides of the sacks. Likewise, these items also tend to form seals around purge valves, effectively blocking air access. As a result, purge valves usually just add weight, complexity and potential leakage points and are therefore not recommended for most backpacking applications.

PADDLE SACK TECHNIQUES

Sometimes even a high-quality paddle sack can allow water to reach the sack’s contents. The problem is rarely with the fabric or seams, but instead is usually the result of a faulty closure. The primary key to keeping these sacks highly waterproof is to make certain that closures are tight.

When sealing a sack of the style that uses a single side-release buckle at the top edge (i.e., most paddle sacks), first push as much air as possible out of the bag. Then, carefully align the two sides of the top lip, which probably contains either a single or a double sewn-in stiffener. Next, fold the top of the bag over the stiffener at least three or four times, trying to keep the fabric flat and wrinkle-free. Continue folding until you think you can’t go any further, then fold the top one more time and fasten the buckle. Either the contents of the sack and/or the air pressure inside the sack should now be exerting enough force on the closure to enable it to maintain a tight seal.

Even this closure probably won’t be perfect, however, which can be a good thing if you’re changing elevations to any significant degree over the course of your day. A bag sealed, for example, at 5,000 feet elevation could become much like an over-inflated balloon at 10,000 feet, possibly bursting if some of the air inside wasn’t allowed to escape. That’s never happened to me, however, probably because enough air leaked out through the roll-tops that pressures could be equalized.

COMPRESSION SACKS

Many of the same companies that sell paddle bags also sell compression sacks, which allow a hiker to squeeze the load down even further than normal. These sacks typically employ heavier fabrics and multiple straps, usually attached with side-release buckles, to compress their contents. Unless you’re carrying a very low volume pack and can’t get your gear in any other way, I think that compression sacks are generally a bad idea. They add a fair amount of weight, but more importantly, can damage expensive sleeping bags and puffy jackets.

The kinds of items you need to protect most usually provide warmth through the lofting of either natural fill materials such as goose down, or synthetic fibers such as Polarguard or PrimaLoft. The ability of any of these fills to keep you warm can decrease quickly if they’re over-compressed, since they lose part of their ability to “puff up”. Synthetics are usually damaged most quickly, but even high-quality down, though generally more resilient than synthetics, can become permanently “squished” with too much compression.

The paddle sacks recommended here already provide a measure of compression for sleeping bags and filled clothing. In fact, if you’re particularly sensitive to this issue, or if you routinely use synthetic filled gear, you may want to use slightly larger sacks than those mentioned above. So rather than a 20 liter size for your sleeping bag and dry camp clothes, you might want to use a 30 or 35 liter sack, which usually weighs only slightly more.

PERSPIRATION AND HUMIDITY

Two other potential sources of moisture that can be absorbed by critical gear are perspiration and humidity. Though neither is likely to create problems as serious as those caused by rain, snow or submersions, each can nonetheless reduce the ability of insulated clothing and sleeping bags to keep you warm. Though a detailed discussion of these problems is beyond the scope of this article, I will include a few brief comments:

– When hiking in cold weather, be careful not to overdress. If you’re perspiring heavily into a jacket, take it off and replace it with a lighter piece if possible. Damp clothing should, as noted above, be stored in such a way that it doesn’t get even wetter.

– Even at night, your body continues to perspire, often imperceptively. A down sleeping bag, it is said, can absorb up to a pint of moisture during a single night, so it’s important to air your sleeping bag every morning if possible. If the bag is opened so that the inside is exposed to the maximum airflow, much of the accumulated moisture will evaporate fairly quickly, even under chilly or cloudy conditions.

– If you’re camping in very cold weather, where moisture that collects in a sleeping bag won’t evaporate (or might even freeze inside the bag), the use of a vapor barrier, such as the one sold by Western Mountaineering is highly recommended. Such a liner will keep you warmer, since it helps prevent evaporative heat loss, and will also keep the insulation from degrading.

– High humidity levels can sometimes induce insulated gear to absorb moisture, though rarely with notable consequences. While affected gear might feel clammy, even down garments and sleeping bags usually won’t lose a substantial amount of loft from humidity absorption alone. Some people worry a lot about down’s capacity to absorb water, but as Chris Townsend writes in the third edition of The Backpacker’s Handbook: “…keeping down dry need not be difficult or a chore and it’s harder to get down wet than many people think. I use down bags most of the time, including in wet places, and I haven’t yet had one get more than a little damp. Packing a down bag in a waterproof stuff sack and sleeping in a tent or under a tarp when it rains are the best ways to keep it dry.”

MAINTENANCE

Even though a paddle sack may start out waterproof, its performance can deteriorate with use, so it’s important to check your bags periodically for leaks. As noted above, probably the best way to test gear sacks is to turn them inside out, then fill them with water. Minor cracks in polyurethane coatings can usually be repaired with an adhesive such as McNett’s Seam Grip.

Punctures that occur in the field, though fairly rare with nylon paddle sacks, can often be temporarily repaired with duct tape. Unfortunately, duct tape won’t stick to silnylon bags, so you’d need to carry a tube of SilNet, and perhaps a needle and thread and/or an extra piece of silnylon if you wanted to repair these bags on the trail.

NEW DEVELOPMENTS

Last year, DuPont introduced a silicone impregnated Cordura fabric that is said to be both stronger and lighter than standard weight silnylon. This new fabric is now being used by companies such as Granite Gear in a line of ultralight stuff sacks that I’m now testing. Preliminary results suggest that its water resistance is about the same as standard silnylon, though the fabric does appear to be a little less “stretchy”, so it may be slightly better suited to gear sack construction.

Sea to Summit, an Australian company, is also using Sil Cordura in a new line of ultralight gear sacks. Perhaps even more noteworthy, they have found a way to add a thin polyurethane coating to the inside surface of the silicone impregnated fabric that is said to improve the water resistance of the fabric over standard weight silnylon. The PU coating also allows the seams to be factory taped.

The new line of “Ultra-Sil” sacks are also the first commercially-produced silicone impregnated bags that I’m aware of to offer a roll-top, paddle-style closure (previously, as far as I know, only my own silnylon sacks incorporated this feature). All of this at an average weight of less than half of their already lightweight sacks. A 20 liter version of this new sack, for example, weighs only 1.8 oz versus 4.2 oz for their older sack. Likewise, a 13 liter version of the new sack weighs only 1.4 oz versus 3.7 oz for their old sack (See Ultra-Sil update below).

Outdoor Research has also updated their line of dry bags with the recent introduction of the HydroLite and Hydroseal sacks. While both offer roll-top closures and taped seams, the Hydroseals seem to use slightly heavier fabrics and coatings and include daisy chain webbing for lashing purposes. Both bags, however, are still very light, with the HydroLites weighing in at not much more than the new Sea to Summit Sil Cordura bags.

ULTRA-SIL UPDATE, May 2006

I recently tested one of the new Sea to Summit Ultra-Sil sacks, an 8-liter model purchased from a local REI store. The good news is that the advertised weight of 1.1 ounces was dead-on, at least according to my scale. The bad news is that the new polyurethane coating seems to have added little incremental water resistance to the fabric over standard weight silnylon / Sil Cordura. When the bag was turned inside out (to simulate real world conditions) and filled about 2/3 with water, the bag leaked extensively, especially through the bottom panel (see picture below).

It was difficult to determine if there was also leakage around the seam tape, but I suppose it really didn’t matter since the fabric leakage was so substantial. Hoping to shave a few more ounces of pack weight with these bags, my test results were disappointing, especially knowing that the stresses of real-world trail usage would probably induce even greater leakage in the future.

My current take on the Ultra-Sils is that even though some preliminary reviews by others have been favorable, I would not entrust critical gear to these bags. For a couple of additional ounces, it’s possible to get a much more substantial sack that has welded seams (versus the sewn and taped seams in the Ultra-Sils) and better waterproof fabric coatings. The Camp Inn sacks discussed herein are still among my favorites since they offer excellent protection at reasonable weights. I should also note that I returned my test Ultra-Sil sack to REI along with a copy of the picture above, predicting that they would probably see a high rate of customer returns on this product.

Resources

While there are several companies that offer paddle sacks designed for marine sports, most of their products are too heavy (in my opinion) for trail use. The following companies currently offer lighter weight versions of these sacks that I believe are more attractive for backpackers:

Sea to Summit offers two lines of lightweight paddle sacks, including the new Sil Cordura models mentioned above.

Outdoor Research has now added lightweight, roll-top sacks to its lineup.

Camp Inn offers lightweight nylon gear sacks that I’ve used with good success. Their model # 7912 is a great size (about 20 liters) for a sleeping bag and camp clothes and weighs 4.5 ounces. They’re available at a number of retail outlets nationwide.

Granite Gear offers a lightweight dry sack that features dual latch straps.

Montbell America sells two lines of paddle sacks. One is fairly heavy and is designed for use primarily in water sports. The other, however (the “Protection Aquapel” series), includes four bags that weigh from 2 to 5 ounces, lightweight enough for trail use. (Thanks to “WildMan” from the Lightweight Backpacker forum for the alert about these bags).

Seattle Sports offers the Cyclone Round Camp Sack, which in the 20 liter version is a bit heavy at 6.9 ounces. It includes, however, a daisy chain for lashing, as well as an autopurge valve that some may like. I currently have several of their older Camper Hydro sacks, which lacked the valve, are slightly lighter and were available in more sizes, but which have been dropped from their current lineup.