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Can treated nylon bags be waterproof when sitting in water?

On multi-day trips in my tandem canoe, I use canoe portage packs that I line with waterproof Granite Gear eVent bags (no longer available). The bags are 100 D Syl-Nylon and have an eVent bottom that allows you to purge air:

https://www.moosejaw.com/product/granite-gear-event-sil-ultra-duty-pack-liners_10093253

With a lot of bilge water---for example in rain---water gets through the bottom and/or lower sides of the liner bag (the outer bag isn't water proof to begin with). I kind of understand that with all the pressure from gear, the liner bag bottom gets pushed into a pool of water and it must be pretty difficult to keep it dry. I mean, it's just treated nylon. BTW, I did recently seal all the seams.

Can a bag like this possibly work when pressed into a pool of water for hours? Are the clear plastic liners sold by Rutabaga, Duluth Pack, Frost River the only way? They've failed me at the seam before.

I remember Glenn McGrady used the same liner bags. It's been a while since he last posted.

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  • Coated nylon will eventually lose its coat. More soaking means faster loss of the coating. Same as coated raincoats versus multi-layer stuff like Goretex. Which can also eventually lose its stuff but tends to take longer.
    So if it is the first trip with new stuff... likely better results than the 15th trip. But the three layer stuff costs a good bit more. So how hard do you need to use this gear? The less expensive coated stuff may be fine for your purposes.

  • edited October 7

    Those clear plastic liner bags naturally can't last forever, so it's a shame they usually sell them as singles, and for a rather exorbitant price too, considering what you get. I have to say I've never had a seam fail on one of them, but they do develop pinholes from wear, or bigger holes from sharp items in your gear, and these of course can be patched with a bit of duct tape. Also, since they are cheap and light, it's a good practice to use a two-layer system, knowing that the inner layer is likely to get pinholes with time.

    I bought a bunch of clear plastic liner bags from Staples Online a few years ago. I got way more of them than I'll ever need, but since the price in bulk was probably 1/100th the price on a per-bag basis from a paddling shop, I'm okay with that. From Staples or any other company that offers a huge variety of clear poly bags, you can also choose different thicknesses of material, and I chose a tougher grade of material than what you normally ever see, and I've been quite happy with them.

  • I've used the heavy white plastic trash compactor bags to wrap gear and supplies in hatches. 25" x 24" x 2 mil. I twist the top tightly then fold it over and use the drawstrings to tie off the foldover. You can get a box of 50 of them for $10 to $15.

    (Also great for disposing of heavy cat-box litter without nasty breakage on the way to the curb -- nothing worse than a ruptured sack of cat crap all over your slippers on a damp night.)

  • edited October 7

    @willowleaf said:
    I've used the heavy white plastic trash compactor bags to wrap gear and supplies in hatches. 25" x 24" x 2 mil. I twist the top tightly then fold it over and use the drawstrings to tie off the foldover. You can get a box of 50 of them for $10 to $15.

    (Also great for disposing of heavy cat-box litter without nasty breakage on the way to the curb -- nothing worse than a ruptured sack of cat crap all over your slippers on a damp night.)

    That bag size is far too small to work well in a canoe pack. A really good size for a #3 canoe pack is 28" wide and 48" long (though some are slightly shorter than that, you still need the full 28" width). That will allow the bag to expand when full of gear to fit to the actual dimensions of the pack in all directions, and you need a surprising amount of extra length to have enough left over for it to be easy to make a good seal. Using roughly four liners (in this case) which don't allow unencumbered use of the pack's full volume is less efficient, and also really slows you down in retrieving "that one piece of gear" that you need during a stop. I highly recommend using a single bag that fits the pack (I also love the side-zippered duffle bags from Cooke's Custom Sewing, which stack perfectly inside a standard canoe pack and allow you to pack/unpack with extreme speed, and to retrieve any piece of gear from anywhere in the pack in a matter of moments, but again, this is where a single pack liner has the advantage).

  • ** ...nothing worse than a ruptured sack of cat crap all over your slippers on a damp night.**

    Oh, there probably is, but that funny line just made me literally laugh out loud and shake my head.

    We don't have pets, so I'll stick with waterproof packing uses of such bags when I

    PADDLE ON

    Frank in Miami

  • I've learned in the process of making replacement inflatable sponson tubes for my folding kayaks that making your own vinyl sacks is pretty easy. You can get the vinyl in a range of weights at Joann Fabric stores or (shudder) Walmart. H-66 vinyl glue works to bond the seams so that you can customize whatever gauge and dimensions that you want or need. You can purchase valves from outfits like DIYpackraft if you want to be able to roll-seal and then purge the air out of the bags.

  • Still curious about how waterproof nylon dry bags can be when they sit in water under pressure from the weight of the gear on top. My sylnylon CCS tarp wetted out in those areas that I accidentally touched in the rain. OK, everyone knows to never touch wet tent walls. But then how can any treated nylon bags be expected to ever stay dry?

  • edited October 9

    The warnings not to touch tent walls (or tarps) are due to the fact that warmer moist air (from the occupants' breath and evaporated sweat) condenses on those cooler surfaces. It's the same as why your glasses get wet when you get in your car or come indoors from the cold. The dripping that occurs is NOT due to more water coming through due to the touching. For coated fabric, no moisture is penetrating. For uncoated fabric you are simply consolidating the surface tension on smaller drops of condensate so that it flows together.

    If you have a tarp that actually "wets out" when you touch it (i.e., actually leaks) then the waterproofing has failed already.

    The sponsons in my folding kayaks are made from polyurethane coated nylon or dacron with glued or heat-sealed seams, the same as most lightwieght dry bags.. They not only are waterproof but airtight and can withstand pretty high pressure inflation. If air doesn't leak out of them, being immersed or even having something sitting on top of them won't force water in. Plus, the notion that items sitting on top of something submerged will increase water pressure on it makes no sense. Water flows wherever it needs to go as long as it has a path, even if it's frozen.

    Just saying, properly coated and seam sealed fabric does NOT leak.

    Condensation is not relevant to dry bags, unless you seal something damp (or breathing) in them, but that would make what is in the bag damp anyway.

  • Thank you for educating me on this, although wasn't this warning to not touch the tent wall given during rain? Maybe an old wives' tale. Maybe the rain cools down the tent walls and increases humidity, increasing condensation on the inside walls. I always assumed he water coming in was the rain water permeating through the tent walls.

    Now, tent makers rate their tent floors and rain flys with different water column pressure ratings in mm (or psi). A tent floor with a higher ratings does not leak as easily as one with a lower rating, if I understand correctly. Isn't the tent floor pressed down onto the wet ground the same situation as my liner bag being pressed down into the wet pack? Is the water coming through the tent floor just condensation?

    The sponsons in your kayaks must be a much tougher material than the flimsy GG compression dry bags that must be used inside a abrasion resistant outer pack. Aren't they more like raft tubes?

    Regarding the sysnylon tarp: I believe drops came through in an area where the water pooled and was touched. The tarp is relatively new. So no water should come through in this situation?

  • edited October 10

    The warning on not touching tent walls I believe originated when tents were made of cotton or hemp canvas (often treated with paraffin or beeswax) not urethane coated synthetics. Rain caused the outer surface of the threads in natural fiber weave to swell and the weave became more dense, so that water would roll off of it. But if you touched it the surface tension over the threads could fracture and cause the dampness to penetrate to the back of the fabric. When I was a kid we camped in an old army type dark green tent with a wooden center pole. It would keep us dry UNLESS we leaned against the wall or accidentally rolled up beside it in the night.

    Good insights on tent materials here (the British understand waterproofing -- they get a LOT of rain!)

    https://www.getoutwiththekids.co.uk/family-tents/tent-fabrics-best/

    BTW, I worked in the outdoor gear business through most of my 20's and got training on these materials from the manufacturers of product lines that we sold, like North Face, Eureka, Diamond, Jansport, Sierra Designs, Patagonia, GoreTex, etc.

    The fact is that almost all waterproof coating on nylon or dacron tents (and packs and raingear and tarps) fails. Because of wear and being often flexed with folding and being stored wrinkled up, the bond between the fabric and the coating begins to break down and micro cracks appear in it, eventually peeling or flaking off. Being stored in hot and/or damp conditions accelerates this. I suspect it is partially due to expansion and contraction of the fibers due to temperature and moisture content. Some company's products fail faster than others. Eureka tents used to be notorious for having the floor coating fail within a few years of use but I believe they eventually improved it.

  • @willowleaf said:
    The warnings not to touch tent walls (or tarps) are due to the fact that warmer moist air (from the occupants' breath and evaporated sweat) condenses on those cooler surfaces. It's the same as why your glasses get wet when you get in your car or come indoors from the cold. The dripping that occurs is NOT due to more water coming through due to the touching. For coated fabric, no moisture is penetrating. For uncoated fabric you are simply consolidating the surface tension on smaller drops of condensate so that it flows together.

    If you have a tarp that actually "wets out" when you touch it (i.e., actually leaks) then the waterproofing has failed already.

    The sponsons in my folding kayaks are made from polyurethane coated nylon or dacron with glued or heat-sealed seams, the same as most lightwieght dry bags.. They not only are waterproof but airtight and can withstand pretty high pressure inflation. If air doesn't leak out of them, being immersed or even having something sitting on top of them won't force water in. Plus, the notion that items sitting on top of something submerged will increase water pressure on it makes no sense. Water flows wherever it needs to go as long as it has a path, even if it's frozen.

    Just saying, properly coated and seam sealed fabric does NOT leak.

    Condensation is not relevant to dry bags, unless you seal something damp (or breathing) in them, but that would make what is in the bag damp anyway.

    Breathing? Sounds ominous.

  • String, when I first saw that "breathing" thing, I figured that it means I shouldn't take my cat along and store him in a dry bag.

  • The ominousness was intentional. :)

  • Speaking of coating failure, I've been cleaning out and organizing my basement paddling gear storage area and came upon the PU coated cordura ripstop nylon transporting backpack that came with my Feathercraft Wisper (so it is about 10 years old) . I never actually traveled with it and it mostly just sat on a shelf with the kayak parts in in. It was kind of musty (our absurdly damp summer, which is still hanging on, has made everything in the basement soggy and with traces of mildew) so I emptied it to wash out and discovered that ALL of the waterproof coating is flaking off like a bad sunburn, in huge ragged patches. I don't really care that this has happened. Other than the mess, functionally it makes more sense for a folding kayak storage bag to be BREATHABLE. But I will have to take a stiff scrub brush to it to remove all of the nasty scraps.

  • My garage needs cleaning out if you need a break on your way South.

  • Sorry, no intention of heading south. It's damned hot enough still here in western PA. Halfway into October and I had to turn on the AC this morning due to mid 80's temps and near 100% humidity making my face sweat so much from moderate effort that it was blinding me..

  • @willowleaf said:
    Sorry, no intention of heading south. It's damned hot enough still here in western PA. Halfway into October and I had to turn on the AC this morning due to mid 80's temps and near 100% humidity making my face sweat so much from moderate effort that it was blinding me..

    Bummer

  • Tent floors are rated to waterproof resistance.. They used to be alot more waterproof in the old days where the rating was waterproof to 10.000 PSI.. Now they are down to 3000 and less. Same for waterproof dry bags.. The fabric does not care if it is in a tent or a dry bag..
    But for actual use.. That is still a lot of elephant that needs to sit on the dry bag

  • @kayamedic said:

    Tent floors are rated to waterproof resistance.. They used to be alot more waterproof in the old days where the rating was waterproof to 10.000 PSI.. Now they are down to 3000 and less. Same for waterproof dry bags.. The fabric does not care if it is in a tent or a dry bag..
    But for actual use.. That is still a lot of elephant that needs to sit on the dry bag

    Right. Materials have varying degrees of water resistance. Water can come through from the outside given enough water, time and pressure. The coating does not have to flake off before that can happen.

    You probably meant 10000mm water column, not PSI. Sure sounds like a lot. My friend's 10000mm rain hat eventually let some water through in a long, heavy rain. He did not mention an elephant sitting on his head.

  • @melenas said:
    He did not mention an elephant sitting on his head.

    No one ever mentions the elephant.

  • @Guideboatguy said:

    @melenas said:
    He did not mention an elephant sitting on his head.

    No one ever mentions the elephant.

    Even if it's in the room.

  • Regarding water permeating the tent walls vs that moisture being actually condensation that occurs due to temperature differential: I owned and heavily used two different Cannondale tents during the 70's and 80's when I was an avid year round backpacker and outfitter guide. One of the unique design features of Cannondale tents was that they did not use waterproofed material for the tent roof fly or side walls, only the floor. The tents pitched very tautly with an inside wall and outside fly separated by about 3 to 4" of consistent air gap.

    What Cannondale had discovered in the design phase was that rain would mostly run off the outside wall (think of nylon umbrellas, which are not made of waterproof material) though the material would also absorb water and become wet. But the water that leaked through would run down the inside of the fly rather than drip onto the inside wall. Meanwhile, because the air gap created a sort of insulating zone (the fly went all the way to the ground) and the inner wall was completely breathable, water vapor from the exhalations of the tent inhabitants passed through the inner wall without condensing on it. That vapor could also pass through the outer wall on dry nights, or, if the temperature differential caused it to condense on the inner surface of the fly, it would be absorbed rather than create droplets that could fall onto the inner wall.

    Nonsensical as it may sound, these were absolutely the driest tents I ever used, year round. And I have owned tents from multiple manufacturers, including North Face, Sierra Designs, REI and Marmot, and often shared tents of every other major brand with my backpacking companions. I used the Cannondales quite often in the winter and never had any frost on the inside walls (which I always got with other conventional waterproof fly tents) which illustrates that condensation was not occurring. They had huge floor-less vestibules which were great for cooking in bad weather and for storing muddy or damp gear outside the sleeping zone.

    As for rain, used one in a pouring 10 hour deluge on Assateague Island and slept like a baby on several nights when everyone else was kept awake by the flapping and snapping of their tent flies in the gusting winds -- my Cannondale was not only dry inside but completely silent as well. I had banked sand over the bottom of the outer fly and the tension of the frame and aerodynamic shape of the tent kept the wind from getting under the nylon. The outer fly was soaking wet in the morning when it rained but as the weather cleared and the sun came out the nylon quickly dried. Uncoated nylon is breathable so air passing through it creates rapid drying.

    I still have one of the Cannondales -- they stopped making them in the 80's and just stuck to bicycles henceforth. The only drawback for backpacking was that they were heavy (7 to 8.5 pounds for a tent that held two comfortably or 3 in a pinch) but I've used that one for car camping within the past couple of decades. Despite being 40 years old, it's still usable since there is no waterproofing issue with the fly. The coated floor is probably not waterproof any more, but since I always use a tailored ground cloth, that shouldn't be a big deal.

    Another bit of more common evidence that the moisture on the inside of your tent walls is generated from the inside and not from outside is the fact that tents with mosquito netting walls (like my summer weight Marmot) don't cause you to get wet when it rains on the outer waterproof fly. If the fly was actually allowing water to penetrate, it would be falling through the mesh. Instead, because the mesh is completely breathable and there is no temperature differential on either side of the fabric, no condensation occurs there. It may condense on the inside of the fly, though the free circulation of air in the space between tent wall and fly will keep that to a minimum. Last used that Marmot during a dusk to dawn monsoon at Flamingo in the Everglades. We barely got the tent up as the storm began but slept completely dry -- zero condensation -- despite near 100% humidity.

    As to the leaking tarp, having a pool of water collecting ABOVE the tarp creates water pressure. The upper layers of water are causing more PSI pressure at the bottom, just as depth in a lake or ocean creates higher PSI. When your dry bags are sitting in water they are NOT creating higher pressure at the point of contact because, unless they are trapped in a vacuum, the water is free to flow out from under the weight of the bags. The same is true of wet ground below your tent. Water equalizes its own level. There may be more water pressure on the bag around the sides of it if the bilge is deep, but the weight of the bag itself is not causing more pressure beneath itself, nor is the tent.

    That said, the Achilles heel of most "dry" bags is generally the seams and closures, not the material itself.

    I wonder if anyone has tried those vacuum evacuation clear plastic clothing and bedding storage giant ziplock bags for canoe pack liners? They are airtight enough to maintain a vacuum for extended periods so they should be able to resist penetration of water. And they are cheap -- I've gotten 3 packs of several sizes for under $10 at places like Marshall's. Trapping air inside one rather than evacuating it would maintain some pressure that ought to help keep water from seeping in (a vacuum would just encourage moisture entry). They do make kayak flotation bags that can be used to store gear in the inflation chamber. You load the bag, seal the opening and then inflate through a valve.

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